Polesworth Abbey Energy Options Report Prepared for and Design … · 2018-03-06 · 1. Introduction 8 2. Current energy use 9 2.1 The Gatehouse 9 2.1.1 Current energy use 10 2.1.2

Encraft Limited Perseus House, 3 Chapel Court, Holly Walk, Leamington Spa CV32 4YS T: 01926 312 159 | F:01926 882 636 | E: [email protected]

Polesworth Abbey Energy Options

Polesworth Abbey Energy Options Report and Design Review

Prepared for Father Philip Wells Polesworth Abbey, High Street, Polesworth B781DU

Author Paul White

Date 23rd March 2012

Reference P2353

Polesworth Abbey Energy Options | Father Philip Wells 2

Copyright © Encraft Ltd 2012 23rd March 2012 Document reference: P2353

Document History

Role Name Date

Author Paul White 17/3/2012

Checked Graham Eastwick 19/3/2012

Authorised Ed Kenny-Levick 23/3/2012

Author Paul White 27/4/2012

Checked Graham Eastwick 27/4/2012

Authorised Graham Eastwick 27/4/2012

Legal Note

The information which we provide is by way of general guidance only to your situation (so for example we do not provide any assurance that particular savings will be realisable, as they typically depend on user behaviour).

Design recommendations and specifications provided in this report are based on the best professional endeavours of the authors. All calculations are based on the best information available to us at the time of report production. Where third party equipment is referred to we rely on manufacturer performance statements, guarantees and warranties. We are not liable for any errors in calculations or omissions resulting from data provided by the customer or third parties.

Encraft works to all relevant professional standards and is accredited to ISO9001 and ISO14001 by Lloyds Register. We hold professional indemnity insurance as consulting engineers for design to the sum of £5 million.



Contents Executive summary 5

1. Introduction 8

2. Current energy use 9

2.1 The Gatehouse 9

2.1.1 Current energy use 10

2.1.2 Existing energy system 11

2.1.3 Building development plans 14

2.2 The Church and Refectory 15




2.3 The Vicarage 23




2.4 Existing building summary 27

2.5 The Memorial Hall 28

3. Energy Efficiency 29

3.1 The Gatehouse 30

3.2 The Church 32

3.3 The Refectory and Reception area 35

3.4 The Vicarage 38

3.5 Energy Efficiency Summary 43

4. Heating and renewable energy options 44

4.1 The Gatehouse 44

4.2 The Church 45

4.3 The Refectory and Reception area 49

4.4 The Vicarage (original building) 51

4.5 Summary 53

5. New building review 54

5.1 The new Refectory 54

5.2 The new Vicarage 55

5.3 Heating Options 56

5.4 Building Regulation Options 62

6. Polesworth Abbey Low Carbon Strategy 63

6.1 Introduction 63



6.2 Energy Efficiency Strategy 64

6.3 Heating Strategy 65

6.4 Renewable Energy 71

6.5 Summary 72

Appendices 73

7. Appendix A – Renewable energy descriptions not suitable for this site 74

7.1 Solar Thermal 74

7.2 Wind Energy 74

7.3 Hydro Energy 75

8. Appendix B – The Church Solar PV system images 76



Executive summary

The Low Carbon Strategy, if completely implemented will give the site savings of over £2,000 per year. Combining the heating of the new buildings, the Church and Vicarage (which are in need of new heating systems), using a gas CHP unit gives these buildings an annual heating bill of just £2,854 and a total site heating bill of £4,119. The proposed PV system gives the site an annual income of £914 which can be used to reduce the overall site energy bill.

The Low Carbon Strategy comprises three sections;

Energy Efficiency Strategy – to reduce primary energy demand

Heating Strategy – to install efficient heating systems across the site

Renewable Energy Strategy – to install renewable energy generation on the site to offset onsite use

The energy efficiency strategy results are shown below. The installation of a range of technologies including secondary glazing, internal insulation and roof insulation have raised no major objections with the local conservation officer and will provide the site with significant savings.

Table 1: Executive summary - Energy efficiency savings

Energy saving measures proposed

Cost Annual savings Carbon savings (tonnes per year)

Energy efficiency measures

£88,470 £2,000 12 tonnes

Lighting measures £2,898 £367 1.5 tonnes

Total £91,368 £2,367 13.5 tonnes

The savings above are based on the installation of all of the energy efficiency measures identified for each property. In total they would cost over £90,000 and realise savings of over £2,200 annually.

The site heating strategy covers all of the buildings on the site. The Gatehouse building and Reception and Refectory heating systems are deemed adequate and not recommended for replacement at this time.

The Church and Vicarage systems are recommended for replacement during the development of the two new buildings proposed. Combining these buildings’ heating systems into a common system gives better overall system efficiency and saves on installation and maintenance costs. These sites are combined in the new heating strategy described below.



The heating strategy proposed is made up of a single Baxi Dachs CHP unit to provide the hot water demand and a gas boiler to provide the heating demand.

Table 2: Executive summary - Site heating strategy

CHP Gas

CHP unit spec 5.5kWe, 12.5kWth

Gas boiler spec 158.5 kW 171 kW

Capital cost £32,680 £13,680

Total annual cost £5,263 £4,698

Net annual cost £2,854 £4,698

Net annual CO2 production 10.75 tonnes 19.88 tonnes

The lower annual cost of the CHP system can be used to pay back the higher capital cost of the system.

Table 3: Executive summary - CHP system payback

Payback period

Additional capital cost £19,000

Annual cost saving £1,844

Payback 10.30 years

Based on this information we would recommend the CHP system for installation as it provides an excellent, sustainable foundation for the future of the site. This combined with the energy efficiency measures, gives the Church, Vicarage, new Vicarage and new Refectory buildings an estimated heating and hot water bill of just £2,854 per year.

As the site is Grade II* listed there are limitations on the renewable energy options on the site. A wind turbine would not be suitable due to the local topography and obstructions. A hydro scheme would not be suitable as the river section the Abbey owns has a very low flow and head.

The only viable renewable technology for the site is Solar PV. A system has been proposed for the Church and designed in such a way as to minimise its visual impact in accordance with the conservation officer’s recommendation.



Figure 1: Executive summary - PV system

The image above shows the Church PV system and Appendix B shows various viewpoints of the building to illustrate how the system has been designed to minimise its impact. The table below shows the benefits of the system shown above.

Table 4: Executive summary - PV system

Proposed system assumptions and outputs

System System size (kW) 4

Annual energy produced (kWh) 3,272

Cost £9,000

25 Year income/benefit streams

Feed in Tariff income £21,221

Export income £1,566

Savings £7,831

25 Year CO2 savings

Tonnes of CO2 saved through generation 40

Project returns Rate of return (pre finance) 10.00%

NPV £5,674

Payback period (years) 10



1. Introduction

This report is based on a visit and survey of the Polesworth Abbey complex on 17th February 2012. This provided us with a general overview of your building and data on overall energy and fuel consumption. The objective of this report is to provide an overall energy strategy which will enable you to decide which options are most suitable for the site and which should be prioritised as well as what approach Polesworth Abbey should take to future development. The existing buildings surveyed were:

The Gatehouse

The Church

The Refectory

The Vicarage Alongside the existing buildings, this strategy incorporates buildings which are included in the new development:

new Refectory

new Vicarage Father Philip has also asked for comment on the adjacent Memorial Hall.

The report is structured as follows:

Section 2 summarises the site visit, current energy use of the existing buildings and the building descriptions.

Section 3 sets out the opportunities for energy demand reductions and efficiency improvements in the existing buildings.

Section 4 explores using renewable energy resources for heating and electrical generation for a sustainable future for the site.

Section 5 reviews the plans for the new buildings being considered for the site.

Section 6 summarises the report and develops the overall energy strategy recommended for the site and the future development of the Abbey.

This report has been prepared and delivered by Encraft Ltd, an independent low carbon technology consultancy.



2. Current energy use

Polesworth Abbey is a Grade II* listed site, including Scheduled Monument areas; the Gatehouse, the former Abbey Cloister and areas of new building locations. The site is located in the village of Polesworth. The site is split into 4 main buildings with different usage patterns and heating characteristics. The four sites will be dealt with in turn.

2.1 The Gatehouse

The current Gatehouse was constructed in the 14th century and was refurbished in 2010. It is split into two holiday lets, a History Room and the Gatekeeper’s Lodge.

Fabric Description The building is stone construction with a timber framed roof. The ground floor is a concrete slab with under floor heating in the larger of the two residential areas. Space heating throughout the upper floors of the accomodation is provided by a gas boiler and cast iron radiators. The teaching room is heated with three electric tube heaters located beneath the seating. During the site visit access to the Gatekeeper’s Lodge was not possible.

Figure 2: The Gatehouse

Usage The Gatehouse is split into four sections; one single bedroom residential property, one two bedroom property, a History Room and Gatekeeper’s Lodge. The two accommodation areas are rented out throughout the year as holiday homes, while the History Room and lodge are used for teaching local school children and tours.



Services The accommodation has mains gas and electricity. Gas is supplied by British Gas and electricity is supplied by Eon on the Eon EnergyPlan.

Building Dimensions From drawings supplied and measurements taken on the site visit the total heated floor area of both flats is around 221m2 with a total heated volume of approximately 565m3. The History Room and Gatekeeper’s Lodge has a floor area of 24m2 and volume of 44m3.

2.1.1 Current energy use

The energy use is split between the two refurbished flats and the teaching rooms. The low use of the History Room and Gatekeeper’s Lodge makes the energy use in this portion of the building negligible. It has been assumed that energy use is just for the flats and the teaching rooms have been ignored.

The total energy cost for the smaller, single bedroom accommodation (No24) is £824 per year (based on 2011 electricity and gas consumption). The building uses gas for hot water and space heating. The total energy requirement is around 12,888kWh for hot water and space heating and 1,880kWh for lighting and appliances. This level of energy usage is responsible for carbon dioxide (CO2) emissions of approximately 3.52 tonnes per year.

The table shows this energy consumption split between fuels and its associated costs and CO2 emissions.

Table 5: Current energy use in the Gatehouse, No 24

Fuel type Annual usage (kWh)

Annual cost (£)

Annual CO2 emissions (tonnes)

Source of data

Electricity - First units - Second

untis

885 955

£187 £104

0.45 0.49

2011 energy bills

Gas 12,888 £533 2.58 2011 energy bills (Jul 11 – Oct 11 estimated)

Total 14,728 £824 3.52

The total energy cost for the larger, two bedroom house (No22) is £1,083 per year (based on 2011 electricity and gas consumption). The flats use gas for hot water and space heating. The total energy requirement is around 22,026kWh for hot water and space heating and 2,118kWh for lighting and appliances. This level of energy usage is responsible for carbon dioxide CO2 emissions of approximately 4.92 tonnes per year.




Table 6: Current energy use for the Gatehouse, No 24


Annual cost (£)


Source of data

Electricity - First units - Second units

673 1,445

£144 £155

0.45 0.49

2011 energy bills

Gas 19,908 £784 3.98 2011 energy bills (Jul 11 – Oct 11 estimated)

22,026 £1,083 4.92

The annual gas fuel cost is based on the existing British Gas supply contract which applies a two tier tariff. The latest price is 8.262p/kWh for the first 698kWh and 3.767p/kWh thereafter.

The annual electricity fuel cost is based on your Eon, EnergyPlan tariff which applies a rate of 24.07p/kWh for the first 224 units and 12.67p/kWh for remaining units. This tariff is extremely high and may not be the most cost effective plan for these units.

We would recommend you check with the current providers to see if you are under contract. Note any expiry dates and notice periods so that contracts can be renegotiated or supplies changed in good time. Energy companies often roll you onto new contracts at a higher price if you do nothing.

2.1.2 Existing energy system

Space Heating and Hot Water Space and hot water heating is supplied by a Valiant Ecotec plus combi boiler in each flat with Sedbuk ‘A’ rating. The specification is unknown; however these are supplied in two versions; 24kW and 31kW. Number 22 is heated via an under floor heating system on the ground floor and cast iron radiators on the upper floors. Number 24 is heated via cast iron radiators. The boilers were both new during the refurbishment in 2010.

The heating is controlled by 7 day digital controllers in both flats. The system is generally switched off, only used when the flats are in use by customers and instructions are provided.



Figure 3: Cast iron radiator example from upper floors of the Gatehouse

Secondary heating is supplied to both living areas by log burning stoves. This is especially helpful in No 22 as the under floor heating can take some time to heat up from cold.

Figure 4: Wood burning stove from No 22

Lighting Lighting is predominantly via halogen spot lights and wall mounted CFLs. The level of installed lighting is relatively low considering the general provision for over lighting in most modern properties. We observed there are no automatic lighting controls in the internal areas.

Existing insulation Insulation is measured with u-values. The u-value is a measure of the energy transmitted by a square metre of material, given a one degree difference in temperature between its two sides. A better insulator will have a lower u-value. U-values are measured in W/m2k. Our estimation of the existing u-values for the Gate house flats using the plans provided are summarised below.

Table 7: U-values for the Gatehouse properties

Area Construction Assumed u-value (W/m2k)

Walls Solid stone with plaster

0.8




Roofs Pitched tile roof with insulation between the rafters

0.2

Floors Ground floor Suspended floor

Solid floor with under floor heating Insulated suspended floor

0.22 0.22

Windows Standard windows Roof light

Single glazed metal frames Double glazed

5.5 3.3

Doors Mixture of solid wood, wooden with double glazing

3.0

As the property has been recently refurbished the u-values for the floors and roof are very good for a building of this age. The walls and windows are as originally intended due to restrictions on work that can be completed in relation to the outward appearance of the buildings.

Air tightness As well as heat loss through the building fabric, heat loss due to the air flow through the building caused by natural means (i.e. because of cracks and small openings in the structure) has to be included in the heat loss calculation.

Air tightness is measured in terms of air permeability (q50) at a given pressure (50Pa). This is a measure of how much air leaks from the building envelope when the building is pressurised. For our calculation we have taken appropriate values from the CIBSE guide A.

The pie chart shows the percentage of calculated heat loss due to heat losses from the main building elements (walls, roof, floors etc) and due to ventilation.



Figure 5: The Gatehouse heat loss chart

Boiler sizing The combined heating requirement of both flats is around 19kW. Assuming a 3-4kW allowance per flat for hot water demand, this is below the rated output of the Ecotech plus boilers.

2.1.3 Building development plans

The Gatehouse building was refurbished in 2010 and there are no immediate plans to carry out any work on this building.

12%

37%

9%

8%

35% Windows and doors

Walls

Floors

Roof

Ventilation



2.2 The Church and Refectory

The earliest Church on the site is believed to date from 827. The Church after many alterations has existed in its current format since 1869. The Refectory was constructed along with the Vicarage in 1881 after the demolition of the original Hall. Some parts of the Hall were reused in the construction of the Refectory including the roof and fire place.

In 2004 a modern entrance way to the Church and Refectory was constructed and contained the boilers for both the Refectory and Church.

Fabric Description The Church is stone built with a wooden framed roof and solid floor. Space heating is provided by cast iron radiators and radiant heat pipework and via vented pipe work in the floor.

The Refectory has a brick and timber construction with the roof constructed from timbers taken from the original Hall. The room has a solid floor with single glazed windows in metal frames with stone framework. Heating is provided via two air blowers connected to the boiler that supplies the Reception area with heating and hot water.

The Reception area was constructed in 2004 and contains a main Reception area and toilets for users of the Church and Refectory. The building is timber framed with double glazed window and wall areas. The heating is provided by under floor heating.

Figure 6: The Church



Usage The Church is used and heated on average two days a week plus Sundays. It is open most days for people to use but not heated on these days.

The Refectory and Reception is open 6 days a week for use by Church groups, meetings and general visitors.

Services The Church contains the main site gas meter and has electricity. Electricity is supplied by Eon on a three year Flexirate2 plan. Gas is supplied by British Gas.

Building Dimensions From drawings supplied and measurements taken on the site visit the total heated floor area of the Church around 404m2 with a total heated volume of approximately 3,470m3. The Refectory has a floor area of 75m2 and volume of 381m3 and the Reception area has a floor area of 19m2 and volume of 43m3.


The energy bills for the Church and Refectory are combined. The total energy cost for the Church and Refectory is £3,029 per year (based on 2010/11 electricity and gas consumption). The buildings use gas for hot water and space heating. The total energy requirement is around 44,414kWh for hot water and space heating and 11,374kWh for lighting and appliances. This level of energy usage is responsible for carbon dioxide (CO2) emissions of approximately 14.71 tonnes per year.


Table 8: Current energy use for the Church and Refectory


Annual cost (£)


Source of data

Electricity - Normal - Weekend - Standing

charge

2,605 8,770

£273 £603 £113

5.82

2010/11 energy bills

Gas - Rate 1 - Standing

charge

44,414

£1,868 £171

8.88

2010/11 energy bills

Total 55,788 £3,028 14.70

The annual gas fuel cost is based on the existing British Gas supply contract which applies a single tariff for use and a standing charge. The latest price is 4.182p/kWh for the energy use and 61.93p/day for the standing charge.



The annual electricity fuel cost is based on your Eon, 3 year flexirate2 plan which applies a rate of 10.50p/kWh for normal units and 6.878p/kWh for weekend units.

The rates are very reasonable however we would recommend you check contract closing date so that contracts can be renegotiated or supplies changed in good time. Energy companies often roll you onto new contracts at a higher price if you do nothing.


The existing energy system was put in place in 2004 during the construction of the Reception area and this serves both the Church and Refectory.

Space Heating and Hot Water Space heating in the Church is supplied by an Ideal Imax W60, 60kW boiler connected to the original cast iron heating system. The boiler was replaced during the construction of the Reception area in 2004 and is rated at over 90%. This boiler was specifically chosen to provide a low pressure output to the existing wet heating system as the system is very old and would leak under high pressure. This means the 90% efficiency is not met. The aging system and low pressure input means that heat control is difficult with the heating having to go on in plenty of time to heat the building.

Figure 7: The Church boiler



Figure 8: The Church heating distribution system

The heating is controlled by switching the thermostat on and off; the 7 day mechanical timer is not used. The system is adjusted as required due to the weather conditions.

Some supplementary heating is supplied by some electric bar radiators in Church Chancel. These are used during the winter and for short services.

The Refectory is heated with two Biddle heat fans which are supplied by a Potterton Gold combi, 28kW boiler. This boiler also supplies heating to the Reception room under floor heating and hot water for the toilets. The heating in the Refectory can be insufficient on cold days. This is partially ascribed to the heating from one of the fans being obstructed by a storage cabinet.

Figure 9: The Refectory boiler



Figure 10: The Refectory heating distribution system

This heating system is controlled via the thermostat in the Refectory and the inbuilt timer on the unit is used to ensure the heating does not stay on over night.

Lighting The main Church lighting is provided by metal halide lamps (size unknown) which are quite efficient and are left on when the church is open. There are a number of decorative halogen lamps only used 1-2hours per week. The lighting is controlled via manual on/off switches, which are marked telling users what they are and if they are decorative and therefore only for use in services.

The lighting in the Refectory is supplied by six, 300W lights used around 30 hours per week.

The Reception area is lit by halogen spot lights with on/off manual controls. The toilets are lit by CFLs again with on/off controls.

Existing insulation Our estimations of the existing u-values for the Church are summarised below.

Table 9: U-values for the Church


Walls Stone walls 1.0

Roofs Wooden roof - un-insulated

2.7

Floors Various areas with a range of building methods

Solid stone – un-insulated Suspended timber – un insulated

0.45

Windows Stained glass 5.5

Doors Solid timber 3.0



As we would expect, these u-values compare poorly to those stipulated under modern building standards (particularly for the roof and windows) and consequently the Church experiences high levels of heat loss.

Our estimations of the existing u-values for the Refectory are summarised below.

Table 10: U-values for the Refectory


Walls Solid brick 2.1

Roofs Wooden roof - un-insulated

2.3

Floors Solid floor 1.2

Windows Single glazed metal framed

4.8

Doors Door are internal

Again as expected the u-values compare poorly to those stipulated under modern building standards (particularly for the roof and windows) and consequently the Refectory experiences high levels of heat loss.

Our estimations of the existing u-values for the Reception area are summarised below.

Table 11: U-values for the Reception area


Walls Toilets Front and rear hallway

Brick, with filled cavity Timber frame

0.35 0.35

Roofs 0.2

Floors Solid floor 0.25

Windows Front and rear hallway Roof light

Double glazed, wooden frame

2.7 3.0

Doors Double glazed wooden frame Solid timber

2.7 3.0



The Reception area built in 2004 has relatively good u-values.

Air tightness The pie chart shows the percentage of calculated heat loss due to heat losses from the main building elements (walls, roof, floors etc) and due to ventilation for the Church.

Figure 11: The Church heat loss chart

The pie chart shows the percentage of calculated heat loss due to heat losses from the main building elements (walls, roof, floors etc) and due to ventilation for the Refectory and Reception area.

Figure 12: The Refectory heat loss chart

11%

18%

8%

4%

59%

Windows and doors

Walls

Floors

Roof

Ventilation

10%

37%

19%

4%


Walls

Floors

Roof

Ventilation



Boiler sizing

The Church

The heating of the Church poses a number of challenges. The buildings are of historic interest and are normally poorly insulated. This is complicated by the intermittent use of the building that only requires a warm building for relatively short periods of time.

Typically heating systems are sized to meet a peak heating load (kW). Calculation of the peak heating load is based on the temperature rise or “uplift” that would be required to bring your building up to temperature from cold on a cold day. For the purpose of this study we have calculated the peak heating load to maintain the building at 19°C when the outside temperature is -3°C.

With intermittent heating additional heating is necessary to warm up the fabric and therefore consideration should be given to provide additional boiler capacity to enable room design temperatures to be achieved in a reasonable period of time. The rate at which different building fabrics heat up depends primarily on the thermal mass of the material. Old Churches have a high thermal mass and therefore require a loner time to heat up than buildings constructed from more lightweight materials. Our recommendation is that the boiler capacity should be increased by an additional 40% to address this and this has been included in our calculations.

Based on the current fabric condition of the building and high air change rate the boiler sizing required would be 162kW. This is significantly higher than the current boiler. This is due to the boiler being undersized to ensure the heating system does not cause any leakage within the aging distribution system.

The Refectory

The Refectory poses fewer problems than the Church for its heating. Its high use means that the heating is on almost every day which means the building fabric is kept warm and does not require heating up every time the heating is required. The Refectory is heated via the same boiler as the Reception area.

For the purpose of this study we have calculated the peak heating load to maintain the building at 19°C when the outside temperature is -3°C.

Based on the current fabric condition of the building and high air change rate the boiler sizing required would be 21kW. This is lower than the boiler currently installed, confirming the suitability of the current boiler for the building given its current configuration. Assuming a hot water demand of 2kW gives a total boiler size of 23kW.


There are no short term plans for the Church but long term, the heating distribution system will need replacing due to its age.

The Refectory is planned for refurbishment with the development of the current Vicarage. Improvements to the roof insulation and possible heating upgrades are expected.



2.3 The Vicarage

The building is part of a plan for the Abbey development. It is planned to turn the current Vicarage into accommodation with a new Vicarage being developed on the site. As such the building will be significantly upgraded during the refurbishments. This section describes the building as it is currently used.

Fabric Description The building is Victorian brick and timber frame construction heated via a large gas boiler in the kitchen. It is known that the building is suffering from damp problems and an infestation of Death Watch Beetle which will need to be treated during the refurbishment.

Figure 13: The Vicarage

Usage The building is currently only in use by Father Philip, with a main living area heated via a log burning stove and an office area between the Refectory and this main living space. The upstairs bedrooms are sometimes used for visitors and the main heating system is only used when this is the case. The majority of the time the wood burning stove is used as the primary heating system.

Services The building has both mains gas and electricity supplied by British Gas, the tariffs for which are unknown.

Building Dimensions From drawings supplied and measurements taken on the site visit the total heated floor area of the Vicarage is around 457m2 with a total heated volume of approximately 1,238m3. With the modifications proposed in the new layout drawings



the Vicarage floor area and volume will reduce to 436m2 and 1,178m3 respectively with the removal of the lean-to section of the building.


The building is currently significantly under used with the Vicar only using a small proportion of the property as his living quarters. It is therefore important to note at this point that even with the refurbishment of the building the energy bills may increase significantly. The Vicarage heating and lighting includes that of the Parish Office which has a small gas heater which uses the majority of the gas for around 24 hours a week.

The table shows this energy consumption split between fuels and its associated costs and CO2 emissions. The actual energy tariffs are unknown but because of the buildings expected change of use they are not relevant for this piece of work.

Table 12: Current energy use for the Vicarage


Annual cost (£)


Source of data

Electricity 2,960 £385 1.53 2010/11 Energy bills

Gas 8,842 £531 1.75 2010/11 Energy bills

Total 11,802 £916 3.28


The existing heating system was put in place over 15 years ago and is not utilised because of the low occupancy of the property and its unsuitability.

Space Heating and Hot Water Primary space heating and hot water are provided by a Clyde, 55kW combi boiler located in the kitchen. To install the boiler in this area 9 additional vents had to be fitted meaning that when the boiler is in use this room does not heat up due to the excessive air changes that occur. The system is zoned for the upstairs portion of the property and the downstairs section with the kitchen being common to both zones. The heating distribution system is panel radiators with TRVs fitted to some of the radiators. The heating system is currently only used when guests are using the bedrooms upstairs. At all other times the wood burning stove is used as the primary heating system.

Lighting Lighting is predominantly provided by energy saving bulbs, with some additional lamps to provide extra lighting.



Existing insulation Our estimations of the existing u-values for the Church are summarised below.

Table 13: U-values for the current Vicarage


Walls Basement Ground floor First floor

Solid brick Solid brick Timber frame

2.1 2.1 2.5

Roofs Wooden frame tiled, insulated to rafter level

2.3

Floors Basement floor Suspended floors

Solid stone Timber joists

1.2 1.2

Windows Single glazed metal frame

5.5

Doors Solid timber 3

As we would expect, these u-values compare poorly to those stipulated under modern building standards (particularly for the roof and windows) and consequently the Vicarage experiences high levels of heat loss.

Air tightness The pie chart shows the percentage of calculated heat loss due to heat losses from the main building elements (walls, roof, floors etc) and due to ventilation.



Figure 14: The Vicarage heat loss chart

Boiler sizing

The Vicarage is currently not used a great deal, however along with the planned development of the site this occupation is expected to increase to a higher level with the building being occupied the majority of the time. Given this, the boiler size has been calculated for the building as it currently is and also for the building given its reduced floor area but with its current fabric configuration. This will provide a baseline against which various fabric improvements can be assessed. The most appropriate fabric improvements for the building can then be included in the refurbishment of the Vicarage.

For the purpose of this study we have calculated the peak heating load to maintain the building at 19°C when the outside temperature is -3°C.

Based on the current fabric condition of the building and high air change rate the boiler sizing required would be 77kW. This is greater than the boiler currently installed, confirming the unsuitability of the current boiler.

Based on the new building plans the baseline for the original portion of the Vicarage property that remains requires a 68.5kW boiler. Assuming a hot water demand of 6kW this brings the boiler size required to 74.5kW. This will be used in the calculation of savings made for this property in the next section.


The Vicarage is expected to undergo significant refurbishment works with the development of the new Refectory. Plans for the new Vicarage and Refectory have been reviewed and the energy efficiency measures described in the next section are based on the Vicarage development plans supplied.

11%

14%

13%

4%

59%

Windows and doors

Walls

Floors

Roof

Ventilation



2.4 Existing building summary

The current installed boiler sizes and calculated boiler sizes are shown below to show how appropriate the current installed boilers are. As expected the Church and Vicarage boilers are under sized, while the Refectory and Gatehouse boilers are sized correctly.

Table 14: Current building boiler summary

Building Installed boiler capacity

Calculated boiler size required

Hot water demand estimation

Total boiler size required

Gatehouse 48-58 kW 19 kW 8 kW 27 kW

Church 60 kW 162 kW N/A 162 kW

Refectory 28 kW 21 kW 2 kW 23 kW

Vicarage 55 kW 68.5 kW 6 kW 74.5 kW

The average weekly occupancy for the buildings has been estimated for use in the baseline calculations in the remainder of the report (see note). The annual heat requirement has been calculated based on the heat required to heat the buildings for the given occupancy levels and the estimated hot water demand for each building.

Table 15: Current building heat loss summary

Building Occupancy assumption (hrs/week)

Calculated annual heat requirement (kWh)

Estimated hot water requirement (kWh)

Estimated annual cost

Actual energy cost

Gatehouse 70 12507 5190 £740 £784

Church 20 19575 N/A £1023

Refectory 70 13633 789 £772 £1795

Church and Refectory

39360 789 £2111 £2039

Vicarage 841 56234 12878 £2887 £531

The calculations reflect the current energy bills very well confirming the current energy use profiles and equipment. The Vicarage calculation is based on the expected occupancy after the renovation works and is therefore significantly higher.

The tables above represent the base line data used in the next section.

1 While the current Vicarage occupancy is much lower than this the renovation of the building is assumed to provide a

space for overnight visitors and the occupancy estimation reflects this increase and will be used in later calculations



2.5 The Memorial Hall

During the site visit Father Philip asked for comment on the adjacent Memorial Hall. The building is shown below. It is brick built with a large south facing roof and is assumed to be 40-50 years old.

Figure 15: Memorial Hall

Many of the energy efficiency measures described in the report would be applicable to the hall. With its large south facing roof and non-listed status it would also be suitable for a large Solar PV system. The income from such a system could be used to implement other savings projects for the building, such as:

New windows or secondary glazing

Internal or external wall insulation

Roof insulation



3. Energy Efficiency

This section discusses the different approaches to improving the building’s energy performance. It is recommended that options to reduce the overall energy consumption of the building are considered first. Improving building insulation, using more efficient lighting and heating technologies with proper control systems are often more cost effective.

Proposed fabric improvements are based on target u-values. Example materials are specified for each measure but similar products made by other manufacturers are available. The quoted thicknesses and costs are material and u-value specific. All energy savings calculated have been adjusted to reflect your actual energy consumption used for space heating (according to actual billing information supplied by you).

All of the buildings on the Abbey site are Grade II listed, this places many restrictions on modifications to the building fabric that can be carried out.



3.1 The Gatehouse

The Gatehouse was refurbished in 2010 and the survey revealed a limited amount of improvements that could be made to the building. There are a number of high energy use lights in both buildings which could be replaced with energy efficient bulbs. No additional work is recommended for the History Room or Gatekeeper’s Lodge.

Calculation details The main assumptions and results from the heat loss calculations used in the energy efficiency calculations are shown below:

Occupancy - The Gatehouse is used as holiday flats and it is assumed the occupancy is around 70 hours per week.

Baseline heat demand – Based on the heat loss calculation the properties require a 19kW boiler to provide 12,507 kWh of energy per year.

Baseline hot water demand – Based on the Gatehouse floor area (222m2), the occupancy and CIBSE guide F the hot water demand is 5,190 kWh per year. Any additional 3-4kW allowance, per boiler, is required for the hot water demand giving a boiler size requirement of 27kW.

Windows The windows are all single glazed metal framed units in both properties. Replacement of windows for modern efficient ones is not acceptable due to the Gatehouse listed building status. Secondary glazing could be fitted to the property to reduce heat loss through the windows. Listed building consent would be required to install such a measure.

The expected costs and benefits for this measure are given below.

Table 16: The Gatehouse - secondary glazing savings

Secondary glazing

Current u-value 5.5 W/m2K

Target u-value 2.3 W/m2K

Suggested specification/product Bespoke secondary glazing units

Budget installation cost £4,959 @ £250/m2

Annual cost saving £52

Annual CO2 saving 0.27 tonnes

Financial payback 96 years

Heating System and Heating Controls The current heating system and controls are appropriate for the use of the building and no significant savings could be made by changing them.



Roof The roof was insulated during the refurbishment and the method used has been held up as an example by the local conservation officer as an example of sympathetic improvement that can be used in other buildings on the site.

Walls The walls cannot be externally insulated as this would be detrimental to the look of the building. Internally as the building has undergone an extensive refurbishment dry lining would cause significant disruption to the building and is not recommended.

Floors From the drawings provided it is believe the majority of the floors were insulated during the refurbishment so no further action is recommended.

Lighting The single bedroom flat living area contained a number of halogen lamps which could be replaced with LED lamps which can be fitted to halogen lamp transformers. There are 8 lamps which could be replaced.


Table 17: The Gatehouse - lighting savings

LED lights

Number of lights to be replaced 8

Budget installation cost [£] £192

Annual cost saving [£/year] £77.00

Annual CO2 saving [tonnes] 0.32

Financial payback [years] 2.5

This shows significant savings can be made on just 35 hours of use per week given a product cost of £24 each.

Summary

Table 18: The Gatehouse energy efficiency summary

Measure Pre energy efficiency measure Post energy efficiency measure

Boiler size

Total demand

Annual energy cost

Boiler size

Total demand

Annual energy cost

Secondary glazing

27kW 17697kWh £740 25.5kW 16451kWh £688

Combined 27kW 17697kWh £740 25.5kW 16451kWh £688



3.2 The Church

The Church short term development plans are limited. In the long term however there are some energy efficiency measures that could be implemented.


Occupancy - The Church is used intermittently during the week and on a Sunday for approximately 20 hours per week.

Baseline heat demand – Based on the heat loss calculation the building require a 162kW boiler to provide 19,575 kWh of energy per year.

Baseline hot water demand – The Church has no hot water demand.

Windows Stained glass windows have a very high u-value of around 5W/m2K. This can be improved by around 50% by fitting of secondary glazing unit. A number of old Churches have successfully completed this improvement without any detrimental impact to its appearance or on-going preservation. It is fitted on the inside of the window with the frame following the pattern of the original window. A downside is the considerable cost involved, as units have to be made bespoke for each window.

Figure 16: The Church - secondary glazing example

One company with experience in this kind of installation are Selectaglaze2. They are able to supply custom made units for historic buildings like this one.

2 www.selectaglaze.co.uk




Table 19: The Church - secondary glazing savings

Secondary glazing








It is estimated that the fuel savings achieved by fitting secondary glazing would amount to approximately 7% per year. Secondary glazing could also help to improve air tightness around frames which is not accounted for in this calculation.

Heating System and Heating Controls The current distribution system is old and showing the signs of its age, with the current boiler purposefully undersized to avoid causing leaks in the system. A new distribution system is required and it would be recommended that this be installed during the renovation and building works on the site. The supplementary heating provided by the electric bar heaters should be retained in case additional heating is required, but does not have to be used.

Details of a recommended heating system are included in the next section.

Roof Heat loss through the roof can represent more than 20% of the total heat lost from a building. The roof above the Church has a pitched roof with no insulation. It has already been indicated by Father Philip that the insulation solution used in the Gatehouse is planned for the Refectory with the conservation officer’s approval. It is proposed that the same solution could again be used in the Church roof to improve the thermal characteristics of the Church.

The insulation used in the Gatehouse was Triso-Super 10 produced by Actis, with a u-value of 0.19W/m2K.

Installing this insulation would be time consuming given the number of roof trusses, gaps to be filled and the height of the roof.




Table 20: The Church - roof insulation savings

Roof insulation



Suggested specification/product Triso-Super 10





Installation of this would also help with air tightness.

Walls The walls cannot be externally insulated as this would be detrimental to the look of the building and in contravention of the Grade II listing of the building.

Floors Insulation of the floor ground slab is not recommended due to the high level of disturbance this would cause to the Church.

Lighting During the site visit a large number of decorative halogen floodlight fittings were noted. Replacing these with LED lights would achieve energy savings, however as they are only operated 1-2 hours a week the payback period would be too long to make this viable.

The main Church lighting is supplied via metal halide lamps. The table below shows the savings made by replacing gone of these lamps with an equivalent 150W LED lamp based on 30 hours operation a week.

Table 21: The Church - lighting savings

LED lights


Budget installation cost [£] 40

Annual cost saving [£/year] 28





Summary

Table 22: The Church energy efficiency summary


Boiler size

Total demand per year

Annual energy cost

Boiler size per year

Total demand

Annual energy cost

Secondary glazing

162kW 19,575kWh £1,023 150kW 17,910kWh £936

Roof insulation

162kW 19,575kWh £1,023 120kW 13,908kWh £727

Combined 162kW 19,575kWh £1,023 108kW 12,243kWh £750

3.3 The Refectory and Reception area

The Refectory adjoins the new Reception area built in 2004. During the building of the Reception area a new boiler and distribution system were installed for the Refectory. The Reception area, Refectory and Church are billed for their energy together.


Occupancy - The Refectory is used 6 days a week for approximately 35 hours a week (although the heating may be on for longer).


Baseline hot water demand – Based on the Refectory and Reception floor area (222m2), the occupancy and CIBSE guide F the hot water demand is 789 kWh per year. Given the low hot water use an additional 2kW would be required for hot water giving a total boiler sixe requirement of 23kW.

Windows Old single glazed windows have a very high u-value of around 5W/m2K. This can be improved by around 50% by the fitting of secondary glazing unit.




Table 23: The Refectory - secondary glazing savings

Secondary glazing








Heating System and Heating Controls Father Philip requested that the type of heating distribution system in use be reviewed to see if more traditional and in-keeping radiators could be used to heat the Refectory room. This has been addressed in the next section.

Roof Father Philip has already had discussions with the local conservation officer who has giving outline approval for the installation of roof insulation as per the specification in the Gatehouse refurbishment. This would reduce the roof u-value significantly to around 0.2 W/m2k.

The insulation used in the Gatehouse was Triso-Super 10 produced by Actis, with a u-value of 0.19W/m2K.


Table 24: The Refectory - roof insulation

Roof insulation



Suggested specification/product Triso-Super 10

Budget installation cost £1836 @ £25/m2






Walls The walls cannot be externally insulated as this would be detrimental to the look of the building. Internally the additional of dry lining would potentially cover some of the internal detailing which would retract from the current look of the building.

Floors As this is a high use facility the removal and insulation of the floor is not recommended at this time.

Lighting The lighting in the Refectory is supplied by 6, 300W halogen lights, used for around 30 hours a week. Replacement with similar output LED lights would yield significant savings.

Table 25: The Refectory - lighting upgrade

LED lights


Budget installation cost [£] 720

Annual cost saving [£/year] 296



Summary

Table 26: The Refectory energy efficiency summary


Boiler size


Annual energy cost

Boiler size per year

Total demand

Annual energy cost

Secondary glazing

23kW 14,422kWh £772 22kW 13,810kWh £739

Roof insulation

23kW 14,422kWh £772 19kW 11,398kWh £610

Combined 23kW 14,422kWh £772 18kW 10,786kWh £577



3.4 The Vicarage

The current Vicarage is planned to undergo an extensive renovation in the Abbey development plan. This section of the report aims to shows the different improvements that can be made in terms of energy efficiency at an early stage so they can be incorporated into the building design.

Calculations for the Vicarage are based on the new building layout and represent the savings that could be made on improving the current building fabric during the renovation of the building. The calculations have also been based on an increased site usage as per the Abbey development plan.


Occupancy - The Vicarage will be used for approximately 84 hours a week.


Baseline hot water demand – Based on the Vicarage floor area (457m2), the occupancy and CIBSE guide F the hot water demand is 12,878 kWh per year. As the building is to be used as accommodation with a number of rooms and en-suite showers a high hot water boiler allowance of 6kW has been estimated giving a total boiler size of 74kW before any energy efficiency reductions.

Windows Old single glazed windows have a very high u-value of around 5.5W/m2K. This can be improved by around 50% by fitting of secondary glazing unit.

Initial discussion with the local planning officer has determined that this measure would not be objected and Listed Building Consent may be depending on the type proposed.


Table 27: The Vicarage - secondary glazing savings

Secondary glazing








Secondary glazing



Heating System and Heating Controls The Vicarage is due to undergo a full refurbishment during the building of the new Refectory and Vicarage. At this stage we would recommend installing a new boiler as the current one is not providing the required heat output and is badly installed. The size of boiler will depend on the number of energy efficiency measures implemented during the renovation.

The different boiler options available are discussed later in the report.

Roof The roof currently has insulation to the joist level in the cold attic sections of the roof. The recommended depth of mineral insulation for a cold roof space to achieve the recommended thermal performance is now 270mm: this would achieve a heat loss reduction of around 75%.

To meet this specification a further layer of insulation (typically 200mm thick) is added across the joists. As the insulation will hide the joists, you will need a boarded passage to enable you to enter the loft safely.

Is it important to ensure that ventilation levels are maintained to avoid the risk of condensation occurring in the loft. Care should therefore be taken to ensure that the insulation does not block the ventilation in the eaves.


Table 28: The Vicarage - roof insulation savings

Roof insulation



Suggested specification/product 200mm mineral wool insulation quit/roll



Annual CO2 saving 2 tonnes




Walls Insulation or dry lining of the internal walls is the addition of insulated boards to the internal sections of the walls. This method of insulation was preferred over external cladding as the building is a heritage building and a dramatic change in its appearance would not have been acceptable. The walls in the Vicarage are solid brick and could be improved in this way. If this measure was carried out then it would potentially reduce heat loss here by over 80%.

Initial discussion with the local planning officer has highlighted that this measure may receive some objection and Listed Building Consent would be required. Further discussions will be required to determine the basis for objections and a suitable solution found.

Thermal laminate dry lining board consists of plasterboard with a backing of insulation. The rigid insulation backing can be specified in a variety of types and thicknesses and is usually fixed to the wall surface using continuous ribbons of plaster or adhesive, plus additional mechanical fixings, or onto 25mm thick softwood battens.

Most types of thermal laminate plasterboard provide better insulation than comparable thicknesses of fibre-based insulation (such as mineral wool). It is therefore possible to achieve the same thermal performance using thinner insulation (and therefore ensuring that the loss of room area is kept to a minimum. Examples of such products include Kingspan K18 or K17, Knauf Phenolic laminate and Gyproc Thermaline Super.

Testing will have to be carried out before installation to ensure that the interstitial condensation conditions are suitable for the property, as per the English Heritage guidelines.3

An indicative cost benefit analysis for this measure is presented below.

Table 29: The Vicarage - internal wall insulation savings

Dry-line external walls



Suggested specification/product Solid wall internal cladding using 62.5mm Kingspan K17 Kooltherm (or similar) laminate plasterboard.

Budget installation cost £18,811 @ £65 per m2




3 www.english-heritage.org.uk/publications/energy-efficiency-historic-buildings-partl/

http://www.english-heritage.org.uk/publications/energy-efficiency-historic-buildings-partl/



Floors During the refurbishment it is assumed that the floor and ceilings will be stripped to ensure that the timbers within the building are in an adequate condition for continued use. At this stage it would be possible to insulate the suspended floors in line with current regulations to achieve a u-value of 0.22W/m2K.

An indicative cost benefit analysis for this measure is presented below.

Table 30: The Vicarage - suspended floor insulation savings

Insulate suspended floors



Suggested specification/product Mineral wool





Lighting As previously shown with the Gatehouse lighting example LED lights have significant savings over traditional lighting and should be installed as a matter of course during the refurbishment of this building. Where this may not be possible low energy CFLs should be used.



Summary

Table 31: The Vicarage energy efficiency summary


Boiler size


Annual energy cost

Boiler size

Total demand

Annual energy cost

Secondary glazing

74.5kW 69,112kWh £2,887 71.5kW 66,316kWh £2,770

Roof insulation

74.5kW 69,112kWh £2,887 64kW 59,998kWh £2,506

Dry-lining 74.5kW 69,112kWh £2,887 56kW 58,833kWh £2,207

Floor insulation

74.5kW 69,112kWh £2,887 69.5kW 64,842kWh £2,708

Combined 74.5kW 69,112kWh £2,887 30.5kW 30,847kWh £1,288



3.5 Energy Efficiency Summary

The table below summaries the current annual energy use and cost against the predicted use and cost based on the implementation of all of the energy efficiency measures in ach building. The cost of all of the measures is around £90,000.

Table 32: Energy efficiency summary – Boiler sizing

Building Pre energy efficiency measure Post energy efficiency measure

Boiler size


Annual energy cost

Boiler size

Total demand

Annual energy cost

The Gatehouse

27kW 17,697kWh £740 25.5kW 16,451kWh £688

The Church

162kW 19,575kWh £1,023 108kW 12,243kWh £750

The Refectory

23kW 14,422kWh £722 18kW 10,786kWh £577

The Vicarage

74.5kW 69,112kWh £2,887 30.5kW 30,847kWh £1,288

Total 286.5kW 120,806kWh £5,372 182kW 70,327kWh £3,303

The tables show that implementing the measures suggested would save Polesworth Abbey over £2,000 per year on its predicted energy bills and over 12 tonnes of CO2.

Table 33: Energy efficiency summary - CO2


Annual energy cost

CO2 emissions (tonnes)


Annual energy cost


The Gatehouse

17,697kWh £740 3.89 16,451kWh £688 3.61

The Church

19,575kWh £1,023 4.84 12,243kWh £750 3.03

The Refectory

14,422kWh £722 3.17 10,786kWh £577 2.37

The Vicarage

69,112kWh £2,887 15.2 30,847kWh £1,288 6.78

Total 120,806kWh £5,372 27.1 70,327kWh £3,303 15.79



4. Heating and renewable energy options

This section looks at the heating options for each building based on the boiler sizes and demands calculated in the previous sections. This includes options for gas boilers, biomass boilers and heat pumps.

This section also reviews the potential of other renewable generation on each building. This includes Solar PV and Solar Thermal.

Upon reviewing the site the use of a wind turbine or a hydro system has been discounted. There is no clear area where a wind turbine would not be adversely affected by turbulence from trees or buildings. Although half of the river adjoining to the Abbey land is owned by the Abbey there is a limited head available along the portion of river owned by the Abbey making a hydro scheme unviable.

Appendix A contains information on the renewable energy options not considered for the site.

Each building is dealt with in turn examining the heating technologies and their benefits, as well as the renewable potential.

4.1 The Gatehouse

Heating The Gatehouse refurbishment in 2010 makes the replacement of the current heating system unviable.

Table 34: The Gatehouse - Annual heat demand


Boiler size


Annual energy cost

Boiler size

Total demand

Annual energy cost

The Gatehouse

27kW 17,697kWh £740 25.5kW 16,451kWh £688

The energy efficiency measures reduce the annual heating bill from £740 to £688 per year.

Renewable energy The Gatehouse does have a section of south facing roof that could be used for Solar PV or Solar Thermal. However large trees to the south of the building would provide significant shading. This combined with the fact that this is a Grade II listed structure makes any kind of visible system unviable.



4.2 The Church

Heating The current boiler that supplies the Church was installed in 2004 and has been sized to cope with the distribution system in its current condition and is not recommended for immediate replacement.

However long term the Church heating system will need to be replaced. It is recommended that the work be carried out with the rest of the renovation and building work planned for the site. At this time a biomass boiler or new gas boiler could be fitted along with a new distribution system. These boilers are recommended because they are designed to produce a high temperature heat which is suited to rapid heating which is required in a building with such an intermittent use.

As previously calculated a new heating system would have to be sized according to the fabric condition of the building at the time. The table below shows the boiler size required in a new heating system, based on the recommendations made in this report.

Table 35: The Church boiler sizing

Fabric improvements Boiler size required

Current fabric condition 162kW

Secondary glazing 150kW

Roof insulation 120kW

Combined installation 108kW

This table assumes no improvement to the air tightness of the building with the improvements.

The different boiler options for the Church are a traditional gas boiler or a biomass boiler. These both generate high temperature heat suitable for buildings with intermittent heat demand. The boiler options for the Church have been reviewed based on the installation of the energy efficiency measures recommended, using the information below.

Table 36: The Church - Annual heat demand


Boiler size


Annual energy cost

Boiler size

Total demand

Annual energy cost

The Church

162kW 19,575kWh £1023 108kW 16,451kWh £750

The energy efficiency measures reduce the annual heating bill from £1,023 to £750 per year.



Biomass Boiler A biomass boiler burns wood pellets or chips to create heat. The amount of heat that can be generated depends on the amount of fuel the boiler can burn at any one time. A higher heat demand will require a larger sized boiler. Boilers and heating systems are rated in kilowatts (kW) and this is a measure of the maximum output power they can produce. Biomass boilers have a modulated output which varies the firing rate from a peak capacity down to a minimum rate. They can deliver heat to your heat distribution system with 80% efficiency.

Biomass boilers can either burn wood chips or wood pellets. Pellets are a denser form of fuel and therefore stores can be smaller. There is also less maintenance required as there is less ash to remove and they tend to get stuck less frequently in the automatic feeding mechanism. The processing required to make pellets mean there are more expensive than wood chips. The current price is in the range of £170 to £214 per tonne delivered @ 5% moisture content. This equates to around 3.5p/kWh to 4.2p/kWh respectively.

Biomass boilers usually have an automatic fuel feeding mechanism to take chips or pellets as needed from an integrated hopper. Filling of the hopper can be done automatically or manually from a nearby fuel store. Any automated feed system will be powered by electricity. Smaller systems are generally manually fed, with frequent removal of waste as also required.

Figure 17: Biomass boiler diagram

Modern biomass heating systems can be operated as an independent standalone system, can be installed in series with a gas boiler(s) or installed in parallel with a gas boiler(s) to operate as a lead boiler. However, there are features that make them different from gas boilers that need to be considered. The main ones are as follows:

Wood-fuel boilers are larger and heavier and require a larger plant room.

Wood-fuel boilers are more expensive than gas boilers (for the same output) and therefore it is important to ensure that they are correctly sized.

Although output can be modulated, wood-fuelled boiler reaction times are much slower than gas boiler reaction times, and so it is better to operate them close to



full capacity and for longer periods of time to optimise efficiency. It is therefore advisable to size the boiler such that is operates on a continual basis i.e. to meet the base load. Thermal storage or gas back-up can be used to meet peak loads.

Modern wood boilers are designed to be automated, nevertheless there will need to be someone available to help with deliveries and provide basic maintenance to the boiler on a regular basis.

The table below shows the summary of costs associated with a biomass boiler to serve the Church heat demand. The income derived from the system is based on the Renewable Heat Incentive (RHI) scheme. This is a government initiative to provide incentives to businesses to use renewable energy to produce heat and operates in a similar way to the Feed in Tariff scheme. Phase I of the RHI for non-domestic sectors commenced on 28th November 2011. A number of renewable heating technologies are eligible under the scheme: namely biomass, solar thermal and ground and water source heat pumps. The tariff paid depends on the type of technology used and the size of the system. The tariff levels are adjusted annually for inflation and are guaranteed for 20 years.

The savings below are calculated when compared to a gas boiler of the same output.

Table 37: The Church - biomass boiler summary

System size 108 kW

Annual pellet consumption 3 tonnes

Recommended storage volume for fuel

5 m3

Budget installation cost £ 85,128

Annual heating bill after installation

£ 715

Annual fuel cost savings £ -44

Potential income from RHI £ 1,098

Annual savings (including RHI) £ 1,053

Annual CO2 emissions after installation

0.42 tonnes

Annual CO2 savings 2.85 tonnes

Financial payback (including RHI)

80.8 years

The table shows that the low occupancy would result in a very long payback period. Installation of this system would not be suitable for this building. The table below shows the summary costs for a new gas condensing boiler.



Table 38: The Church - gas boiler summary

Gas boiler

System size 108 kW

Annual energy consumption 16,047 kWh



£ 671


3.27 tonnes

Based on this information we would recommend a gas boiler for the Church heating system if the building is treated individually.

Renewable Energy The large south facing areas of roof on the Church lend themselves to Solar PV or Solar Thermal systems. As the Church has no hot water requirement solar thermal is not applicable for this building. Solar PV however is a possibility for this site.

Given the Grade II listed status of the site a PV system has been confined to the hidden northern section of roof space between the roof apexes. A single row of panels could be placed along this section with limited shading from the southern roof section and the tower. It would be effectively hidden by the southern roof section and the tower, only visible from a very limited location to the south west of the Church. The inverter could be placed above the flat section of roof in a specially constructed cabinet attached to the tower.

The image below shows the PV system proposed with viewpoints marked around the building approximately 10m away from the Church. Appendix B shows several ground level viewpoints to illustrate how the system has been placed to limit its visibility.

Figure 18: The Church - Solar PV system sketch



The table below shows the potential outputs of the system proposed with savings based on saving electricity across all of the Abbey site buildings.

Table 39: The Church - Solar PV system outputs

This shows that a PV system on the roof could generate significant savings for the site and also save 40 tonnes of CO2 over 25 years.


System System size (kWp) 4


Cost £9,000

Annual income/benefit streams (1st Year)

Feed in Tariff income @ 21p per kWh £687

Export income (50% deemed) £51

Displaced energy savings (70% onsite use) £183

CO2 savings Tonnes of CO2 saved through generation 1.77




Savings £7,831

25 Year CO2 savings Tonnes of CO2 saved through generation 40


NPV £5,674


Preliminary discussions with the local conservation officer have shown no objections to a PV system as long as it is hidden from public view. It should also be noted that the FIT level used in the report is taken from the Consultation into tariffs post July 2012, scenario B. Once the consultation has been reported on this financial output may need to be revisited to ensure the figures are up to date.

4.3 The Refectory and Reception area

Heating The current heating system was installed in 2004 and is deemed suitable. The table below shows the current heat and hot water demand supplied by the current boiler.



Table 40: The Refectory - Annual heat demand


Boiler size


Annual energy cost

Boiler size

Total demand

Annual energy cost

The Refectory

23kW 14,422kWh £722 18kW 10,786kWh £577

The energy efficiency measures reduce the annual heating bill from £722 to £577 per year.

The suitability of the distribution system has been queried by Father Philip. The current distribution system consists of two Biddle hot air blowers fed by the boiler located in the Reception area. One of the heating units is located above a storage area and it is thought that this impacts on the flow of air from the unit.

Father Philip asked if a radiator system could be sized for the room to estimate the cost and size of radiators required. To do this cast iron radiators4 have been used in the specification to mirror the recent refurbishment of the Gatehouse. Radiator sizing has been completed for both the current fabric conditions and the suggested, combined energy efficiency measures.

Table 41: The Refectory - Radiator sizing

Heat demand Radiator Specification

Radiator output

Total radiator output

Pre energy efficiency measures

19,200 W Insufficient wall space to fit the required radiators

Post energy efficiency measures

14,096 W 3 x 4C813 3 x 4C460

3 x 1660W 3 x 3034W

14,082 W

The current heat loss through the Refectory is very high requiring a large number of radiators to be fitted. The low windows, hearth and storage cupboard restrict the wall space available for radiators making a switch to them given the current fabric conditions unsuitable. It should be noted that with just the roof insulation the addition of another small radiator would cover the heat demand of the building as well.

Renewable energy The current Refectory does not have any available roof space and already has adequate heating capacity from an existing modern boiler. So no renewable energy options are recommended for this building.

4 http://www.21stcenturyradiators.com/default.cfm

http://www.21stcenturyradiators.com/default.cfm



4.4 The Vicarage (original building)

Heating The current boiler is not suitable for the heating of this building. Its location, age and size are not suitable for the future development of the site. The boiler will need replacing and the distribution system should be reviewed as part of the refurbishment plan. The summary table below shows the heat demand and system size requirements for the building given the expected increase in use with the planned development of the site.

Table 42: The Vicarage - Annual heat demand


Boiler size


Annual energy cost

Boiler size

Total demand

Annual energy cost

The Vicarage

74.5kW 69,112kWh £2,887 30.5kW 30,847kWh £1,288

The energy efficiency measures reduce the annual heating bill from £2,995 to £1,500 per year.

As the building is undergoing a major refurbishment there is the opportunity for installing a range of heating systems. Treating this building individually there is limited room for a heat pump; however a biomass boiler and gas boiler could be fitted into the Vicarage basement. Given the biomass boilers relative small size (1.6mx0.8mx1.5m) the feed store for this could be located in the basement. As this site also has some hot water demand it may be possible to fit a small gas combined heat and power unit to produce the hot water demand and a portion of the electrical demand.

The table below summarises the cost and benefits of a biomass boiler compared to a gas boiler for the Vicarage. It is assumed that the site will be deemed a commercial site rather than domestic as the sustainable future of the site depends on income generated by the site and buildings on it.

Table 43: The Vicarage - Biomass boiler summary

System size 31 kW

Annual pellet consumption 8 Pellets


12 m3





£ 1,687

Annual fuel cost savings £ -105

Potential income from RHI £ 2,588

Annual savings (including RHI) £ 2,483


0.98 tonnes

Annual CO2 savings 6.72 tonnes


10.3 years

The table above shows a very high capital cost for the biomass boiler. The location of the boiler in the basement of the property would make deliveries of pellets and removal of ash waste an issue. The table below shows the summary costs for a installing a new gas condensing boiler.

Table 44: The Vicarage - Gas boiler summary

System size 31 kW

Annual energy consumption 37,832 kWh



£ 1,582


7.71 tonnes

Based on the difficulty of operating the system and high capital cost we would recommend an individual gas boiler for the Vicarage heating system if the building is treated individually.

Renewable energy Unfortunately all the parts of the roof that would be suitable for solar suffer significant shading problems due to other roof sections. This makes this building unsuitable for Solar PV and Solar Thermal technologies



4.5 Summary

The tables below summarise the heating and renewable energy recommendations made in this section.

Table 45: Recommended heating systems

Building Heating system recommended

Capital cost

The Church Gas boiler £9,720

The Vicarage Gas boiler £2,790

Total £12,510

Table 46: Recommended Church PV System


System System size (kWp) 4


Cost £9,000









Savings £7,831



NPV £5,674




5. New building review

The two new buildings will have to comply with current building regulations as well as being in keeping with the existing structures on the site. Using the u-values from current regulations, and the information available in the Abbey development plan, the heat loss has been estimated for the two new buildings. It should be noted that depending on the proposed development timeframe, the current building regulations may be amended requiring even greater energy efficiency requirements.

The table shows the current building regulation u-values used in the calculations below.

Table 47: New building u-values

Assumed u-value (W/m2k)

Walls 0.2

Roofs 0.13

Floors 0.15

Windows 1.5

Doors 1.5

Using this information and the floor areas provided in the Conservation Management Plan the baseline heat demand has been calculated for both buildings.

5.1 The new Refectory

The new Refectory building is described in the Conservation Management Plan as, ‘c.40m long by 8-12m wide, two-storeyed to the west, with an open dining hall to the east and storage rooms beyond’. Based on this information the heat demand for the building has been calculated.

Air tightness The pie chart shows the percentage of calculated heat loss due to heat losses from the main building elements (walls, roof, floors etc) and due to ventilation.



Figure 19: The new Refectory heat loss chart

Boiler sizing

Based on the calculations the boiler size required for heating building is estimated to be around 12.5kW. An additional hot water allowance of 6kW has been added to give a total boiler size of 18.5kW.

5.2 The new Vicarage

The new Vicarage building is described in the Conservation Management Plan as, ‘ c.21m x 6m north-south with a wing projecting to the east (c.8mx6m) and a single-storey lean-to extension (c.10mx3m) on its south-west corner’. Based on this information the heat demand for the building has been calculated.

The pie chart shows the percentage of calculated heat loss due to heat losses from the main building elements (walls, roof, floors etc) and due to ventilation.

12%

18%

14%

12%

44%

Windows and doors

Walls

Floors

Roof

Ventilation



Figure 20: The new Vicarage heat loss chart

Boiler sizing

Based on the calculations the boiler size required for this building is estimated to be around 8kW. An additional hot water allowance of 6kW has been added to give a total boiler size of 14kW.

5.3 Heating Options

As these are new buildings there is the opportunity to explore different heating options for the new buildings. The standard heating option for the buildings would be a gas condensing boiler and wet distribution system. However, it would also be possible to heat the building with a ground source or air source heat pump, a biomass boiler or even a combined heat and power unit.

Each of these options has been reviewed against a standard gas system to show the difference in cost and the savings achievable from each. Costs shown are estimates for boiler only as the distribution system costs will be very similar.

The new Refectory

The new Refectory as a new building has a range of heating options available to it. The land it is going to occupy is currently undergoing a thorough archaeological investigation. The investigation will ultimately clear some of the remains in anticipation of the services required for the new building and potential heating systems. This section reviews the use of heat pumps, biomass boilers and standard gas boiler.

The new Refectory heating and hot water demand are based on an occupancy rate of 84 hours per week. The table below shows the heat demand and boiler size for the new building.

16%

24%

11% 10%


Walls

Floors

Roof

Ventilation



Table 48: The new Refectory - Annual heat demand

Building Heating and Hot water demand

Boiler size (heat demand/heat and hot

water demand)

The new Refectory Heat –10,060 kWh/yr Hot water – 19,951kWh/yr

12.5 kW / 18.5 kW

Based on the heat and hot water demand for the new Refectory an 18.5kW system has been sized for each technology and compared against the cost of running a gas boiler on the same site.

The new Vicarage

The new Vicarage as a new building has a range of heating options available to it. The land it is going to occupy is currently undergoing a thorough archaeological investigation. The investigation will ultimately clear some of the remains in anticipation of the services required for the new building and potential heating systems. This section reviews the use of heat pumps, biomass boilers and standard gas boiler.

The new Vicarage heating and hot water demand are based on an occupancy rate of 84 hours per week. The table below shows the heat demand and boiler size for the new building.

Table 49: The new Vicarage - Annual heat demand

Building Heating and Hot water demand

Boiler size (heat demand/heat and hot

water demand)

The new Vicarage Heat –6,342 kWh/yr Hot water – 10,905 kWh/yr

8 kW / 14 kW

Based on the heat and hot water demand for the new Vicarage a 14kW system has been sized for each technology and compared against the cost of running a gas boiler on the same site.



Gas boiler The table below shows the capital cost and annual heating bill for a new 90% efficient gas boilers providing both hot water and heating to the new buildings.

Table 50: Gas boiler baseline cost

The new Refectory The new Vicarage

System size 19 kW 14 kW

Annual energy consumption 33,346 kWh 19,163 kWh

Budget installation cost £ 1,710 £ 1,260


£ 1,395 £ 801


6.79 tonnes 3.90 tonnes

GSHP Ground source heat pumps (GSHPs) utilise the ground as a store of energy. This energy is amplified in the heat pump to provide space and water heating. Heat pumps take advantage of the fact that at a depth of a few metres, the temperature of the ground remains at a constant 10-12°C throughout the year.

Ground source heat pump systems absorb energy from the earth and transfer it into the building using highly efficient heat pumps. The effectiveness of heat pumps is measured by the ratio of the heating capacity to the power input, referred to as the Coefficient of Performance (COP). Typically, manufactures state that for every 1 unit of electrical energy used to drive the pump, around 3 to 4 units of thermal energy can be produced.

The ground loops can be installed either vertically in boreholes (typically 50m–100m deep), or horizontally in trenches at a depth of 1.5m–2.0m. Either method is dependent upon local geology conditions and horizontal space available.

Heat pumps are ideally suited for buildings which have good levels of insulation and are reasonably airtight and ideally have under floor heating; for example, a new building or an existing building that has undergone a complete refurbishment.

Standard LTHW heating systems are designed to operate at high flow and return temperatures. Due to the lower flow and return temperature of a heat pump system the larger model radiators are required that provide more surface area and can deliver the required heating. Alternatively, an underfloor heating system could be installed throughout the building. In addition, the ground collector for a system of this size would require several hundred square meters (m2) of land area to bury the collector pipes. This space is not available at the site. An alternative would be the installation of vertical collectors in boreholes in the spaces cleared by the archaeological surveys currently planned at the site.



The table below shows the financial returns of a GSHP, with the savings based on a comparison to a gas boiler. The COP used for the GSHP is 3. This shows an increased capital cost, annual fuel cost and a greater annual CO2 production for both sites.

Table 51: GSHP – Gas boiler comparison






£ 1,200 £ 690

Annual fuel cost savings £ -10 £ -6

Potential income from RHI £ 1,350 £ 776

Annual savings (including RHI) £ 1,340 £ 770



Annual CO2 savings 1.39 tonnes 0.80 tonnes


16.3 years 22.7 years



ASHP An ASHP works in a similar way to the GSHP but only requires a small unit which resembles an air conditioning system. These can be unsightly and given the nature of the site would have to be hidden from view. Unlike the GSHPs, Air Source Heat Pumps are not eligible for RHI payments.

The table below shows the financial returns of a ASHP, with the savings based on a comparison to a gas boiler. The COP used for the ASHP is 2.5. This shows an increased capital cost, annual fuel cost and a greater annual CO2 production.

Table 52: The new Refectory – ASHP






£ 1,441 £ 828


Annual savings £ -250 £ -144




Financial payback N/A N/A



Biomass boiler The table below shows the cost and comparison of a biomass boiler to the gas boiler. The biomass boiler has been designed to run on pellets at £214/tonne. This shows an increased capital cost, annual fuel cost and a significant annual CO2 production saving.

Table 53: The new Refectory - Biomass boiler



Annual pellet consumption 7 tonnes 4 tonnes


11 m3 6 m3



£ 1,487 £ 854


Potential income from RHI £ 1,956 £1,311

Annual savings (including RHI) £ 1,660 £ 1,141




Financial payback (including RHI) 9.5 years 10.8 years

Review and Recommendations Based on the tables above it can be seen that where gas is a potential fuel source heat pumps do not compare very favourably. They have significantly higher capital costs, higher fuel bills and generate more CO2.

The gas boilers also have a lower fuel cost than the biomass boilers but the RHI payments offset the fuel price. The operation and maintenance of a gas boiler requires an annual inspection. The biomass boiler requires a significant amount of time for its operation and requires very regular servicing and maintenance which can be expensive. The biomass boilers also require storage for the fuel close to the unit and daily filling.

Given the Abbey’s sustainable future requirement we would recommend the gas boilers for their lower capital cost, low operational and maintenance cost.



5.4 Building Regulation Options

During the site visit Father Philip explained that due to the excavation works on the site of the new Vicarage that this building would probably be re-designed to incorporate the archaeology in some way. This gives the designers the opportunity to consider designing a building to exceed the current building regulations by designing a PassivHaus standard building.

The PassivHaus standard has three basic rules:

The heat demand must not exceed 15kWh/m2

The primary energy requirement must not exceed 120kWh/m2

The building air change rate must be less than 0.6

By achieving these requirements the building ongoing energy demand would be very low, helping contribute towards the Abbey site sustainable future. We would recommend this option be investigated during the design of this building to determine the additional cost involved and the potential energy savings it would achieve.



6. Polesworth Abbey Low Carbon Strategy

6.1 Introduction

The Polesworth Abbey estate is currently made up of four buildings:

The Church,

the Refectory and adjoining Reception area,

the Gatehouse

and the Vicarage

As part of the Abbey development plan two new buildings are proposed; a new Vicarage and new Refectory. The original Refectory will operate as it does now while the original Vicarage is turned into an accommodation block. Other work included will be a new insulated roof in the Refectory and stabilisation of the Coach House building.

As part of the development plan a Low Carbon Strategy is required to help the Abbey evolve into a more sustainable site to help secure its future. By creating a strategy we can set out a plan for reducing on site energy demand, use and even incorporate generation on site to provide an income.

The Low Carbon Strategy comprises three sections;

Energy Efficiency Strategy – to reduce primary energy demand

Heating Strategy – to install efficient heating systems across the site

Renewable Energy Strategy – to install renewable energy generation on the site to offset onsite use

Energy demand on the site is split into; space heating, hot water and electricity. The use of energy efficient measures and behavioural learning can reduce electrical use, while energy efficient building fabric measures and heating technologies can be used to reduce onsite demand.

To achieve this, the four existing buildings have been assessed to show the current energy demand and the potential energy efficiency and renewable technologies that could be installed and the benefits of doing this. The two new buildings have also been assessed based on current building regulations to determine an overall site energy demand.

The Low Carbon Strategy reviews the current and predicted use on site and determines the best possible method for meeting this demand.



6.2 Energy Efficiency Strategy

The energy efficiency proposals based on building fabric improvements are outlined in the table below. The total demand is made up of the heating and hot water requirements for each building.

Table 54: Low Carbon Strategy – Fabric improvements

Building Pre -energy efficiency measure Post energy efficiency measure


(kWh)

Annual energy

cost


Total demand per year (kWh)

Annual energy

cost


The Gatehouse

17,697 £740 3.89 16,451 £688 3.61

The Church

19,575 £1,023 4.84 12,243 £750 3.03

The Refectory

14,422 £722 3.17 10,786 £577 2.37

The Vicarage

69,112 £2,887 15.2 30,847 £1,288 6.78

Total 120,806 £5,372 27.1 70,327 £3,303 15.79

Implementing all of the measures above would save the Abbey site over £2,000 annually and save almost 11 tonnes of CO2 every year.

Table 55: Low Carbon Strategy - Lighting savings

Building Energy Efficiency measures proposed

Cost Annual savings

Carbon savings

(tonnes per year)

Payback period (years)

The Church Lighting £2,700 £77 1.19 9.3 years

The Gatehouse

Lighting £198 £290 0.32 2.5 years

Total £2,898 £367 1.51

Implementing all of the measures above would save the Abbey site £367 annually and save almost 1.5 tonnes of CO2 every year.



6.3 Heating Strategy

The table below shows the buildings’ expected heat demand and hot water demand before and after the proposed energy efficiency measures are installed.

Table 56: Heating system summary

Building Pre energy efficiency measures Post energy efficiency measures

Boiler size

Total heat

demand per year

(kWh)

Total hot water

demand per year

(kWh)

Boiler size

Total heat

demand per year

(kWh)

Total hot water

demand per year

(kWh)

The Gatehouse

27kW 12,507 5,190 25.5kW 11,262 5,190

The Church 162kW 19,575 N/A 108kW 12,243 N/A

The Refectory

23kW 13,633 789 18kW 9,997 789

The Vicarage

74.5kW 56,234 12,878 30.5kW 17,969 12,878

The new Vicarage

14kW 6,342 10,905

The new Refectory

18.5kW 10,060 19,951

Total 286.5kW 101,949 18,857 214.5kW 67,873 49,713

The table shows that if all of the energy efficiency measures proposed are implemented then the total annual space heating and hot water demand is 117,586 kWh requiring a 214kW boiler of boiler capacity.

The current Refectory and Reception area have an adequate heating system (installed in 2004) and replacement of this system is not recommended. Replacement of the heating systems is also not recommended in the Gatehouse flats after their 2010 refurbishment which included new boilers.



The Church requires a new distribution system and boiler. The current Vicarage is due for refurbishment including a new boiler and the new Vicarage and Refectory will both require primary heating systems. Different heating options have been reviewed for these buildings and it has been recommended that the most cost effective solution is for gas boilers to be fitted.

Table 57: Low Carbon Strategy - boiler replacement summary

Building Pre energy efficiency measures Post energy efficiency measures

Boiler size

Total heat

demand per year

(kWh)

Total hot water

demand per year

(kWh)

Boiler size

Total heat

demand per year

(kWh)

Total hot water

demand per year

(kWh)

The Church 162kW 19,575 N/A 108kW 12,243 N/A

The Vicarage

74.5kW 56,234 12,878 30.5kW 17,969 12878

The new Vicarage

14kW 6,342 10,905

The new Refectory

18.5kW 10,060 19,951

Total 236.5kW 75,809 12,8778 171kW 46,614 43,734

Heating these four buildings across the site individually would require the installation of a number of boilers, all requiring maintenance and individual controls. To save on capital and running costs a centralised ‘energy centre’ could be installed to heat a number of the buildings on the site. The basement in the Vicarage offers options for heating a number of buildings from one central location. Installing a central energy centre here would save on space requirements in the individual buildings and capital installation costs.

It has been shown in the study that the use of heat pumps where a gas supply is present is not a viable option in terms of cost or carbon dioxide savings. As such the options remaining are for a gas powered unit or a biomass unit. The biomass unit would require a large fuel store ideally with an automatic feed system. However, this would require the construction of a new building with vehicle access. Upon reviewing the site plan it is difficult to see where such a building could be placed without compromising the current site. This leaves a gas powered unit as the most appropriate technology for the site.

Gas can be used to power traditional boilers or a combination of gas boilers and Combined Heat and Power (CHP) units. A CHP unit uses gas to generate both electricity and heat. The electricity can be used to offset the electricity used on site and the heat used to meet the heat demand of the site. The units are typically 80% efficient and generate twice as much heat as electricity. The units use internal



combustion engines to generate the electricity and the waste heat is captured and transferred to the building heating system.

In this case a Baxi Dachs unit has been specified to provide the hot water requirement of the four buildings considered. This will allow long running periods to gain greater unit efficiency. The remaining peak load can be generated via a traditional gas boiler.

Based on this assumption a gas powered centre comprising a small CHP unit and gas boiler, as per figure 20, has been reviewed for installation.



The Vicarage – 30.5 kW

The Refectory – 18kW

The Church – 108kW

The new Refectory – 18.5kW

The new Vicarage – 14kW

Vicarage basement energy centre –

1 x Baxi Dachs CHP plant, 12.5kWth to provide base load and hot water

1 x 158.5kW boiler to provide peak load

Figure 21: Proposed heating system - low carbon strategy



The table below shows the comparison of the CHP unit system and the Gas only system.

Table 58: Low carbon strategy comparison

CHP Gas

Total demand 90,348 kWh 90,348 kWh

CHP unit spec 5.5kWe, 12.5kWth

Gas boiler spec 158.5 kW 171 kW

Capital cost £32,680 £13,680

CHP efficiency 80%

Gas boiler efficiency 90% 90%

Demand met by CHP 45,625 kWh

Demand met by gas boiler 44,723 kWh 90,348 kWh

CHP unit input 57,031 kWh

Gas input 49,692 kWh 100,387 kWh

Gas cost £4,463 £4,198

CO2 production 21.13 tonnes 19.88 tonnes

Electricity production 20,075 kWh

Electricity offset income £2,409

CO2 offset 10.38 tonnes

O&M £800 £500

Total annual cost £5,263 £4,698

Net annual cost £2,854 £4,698

Net annual CO2 production 10.75 tonnes 19.88 tonnes

The lower annual cost of the CHP system will reduce the payback period of the higher capital cost, CHP system. Table 58 shows the payback for installing this system over a standard gas boiler is around 10 years.



Table 59: Low carbon strategy - payback period

Payback period

Additional capital cost £19,000

Annual cost saving £1,844

Payback 10.30 years

The table below shows the total capital cost and annual cost associated with installing gas boilers in all of the buildings. This shows an increased capital cost and annual heating cost. It should also be noted that the annual operational and maintenance cost would be increased with a larger number of boilers to service and maintain.

Table 60: Individual gas boiler comparison

The new Refectory

The new Vicarage

The Vicarage

The Church

Total

System size 19 kW 14 kW 31 kW 108 kW 172 kW

Annual energy consumption

33,346 kWh 19,163 kWh

37,832 kWh

16,047 kWh

106,388 kWh

Budget installation cost

£1,710 £1,260 £2,790 £9,720 £15,480


£1,395 £801 £1,582 £671 £4,449



7.71 tonnes

3.27 tonnes

21.67 tonnes

The CHP unit has an annual running cost of £2,854, compare to £4,698 for the single large gas boiler. The individual gas boilers running costs are £4,449 (excluding annual maintenance and servicing). The capital cost for the individual boilers and CHP system are higher than for the single gas boiler; however the savings generated through the electrical production mean the additional cost of the CHP plant can be repaid in around 10 years. The savings made also extend to CO2 production which is reduced by around 9 tonnes through the use of the CHP unit.

It has been shown that if the annual hot water demand for the four buildings can be met with a small CHP unit, then there are significant advantages of using this system over a large single gas boiler, as well as over the use of individual gas boilers in each building.



6.4 Renewable Energy

The only renewable energy deemed suitable for the site is a Solar PV system for the Church roof.

Given the Grade II listed status of the site a PV system has been confined to the hidden northern section of roof space between the roof apexes. A single row of panels could be placed along this section with limited shading from the southern roof section and the tower. It would be effectively hidden by the southern roof section and the tower, only visible from a very limited location to the south west of the Church. The inverter could be placed above the flat section of roof in a specially constructed cabinet attached to the tower.

The image below shows the PV system proposed. Appendix B shows several ground level viewpoints to illustrate how the system has been placed to limit its visibility.

Figure 22: The Church - Solar PV system sketch

The table below shows the potential outputs of the system proposed.

Table 61: The Church - Solar PV system outputs


System System size (kW) 4


Cost £9,000












Savings £7,831



NPV £5,674


This shows that a PV system on the roof could generate significant savings for the site and also save 40 tonnes of CO2 over 25 years.

Preliminary discussions with the local conservation officer have shown no objections to a PV system as long as it is hidden from public view. It should also be noted that the FIT level used in the report is taken from the Consultation into tariffs post July 2012, scenario B. Once the consultation has been reported on this financial output may need to be revisited to ensure the figures are up to date.

6.5 Summary

The energy efficiency measures recommended for the site could save the Abbey, if implemented, the Abbey site over £2,000 annually and save almost 11 tonnes of CO2 every year.

It has been shown that if the annual hot water demand for two new buildings, the Church and the Refectory can be met with a small CHP unit, then there are significant advantages of using this system over a large single gas boiler, as well as over the use if individual gas boilers in each building.

Combining the heating for the two new buildings, the Church and the Refectory gives an annual heating and hot water cost of just £2,854. With the additional £1,265 for the Gatehouse and Refectory the total site heating and hot water cost could be reduced to just £4,119.

The proposed PV system gives the site an annual income of £914 which can be used to reduce the overall site energy bill.



Appendices



7. Appendix A – Renewable energy descriptions not suitable for this site

7.1 Solar Thermal

These systems like Solar PV require clear, south facing roof sections. Gvien the Grade II listed nature of the site there is only one roof section where a system could be fitted and not visible to the public and this has been used to fit a PV system as this is more economically viable for the site.

7.2 Wind Energy

The government’s NOABL database for national wind speed shows a wind resource of 4.8m/s at 10m above ground level for your site (although this figure can vary by 25% from year to year). The national database is based on a topographical mathematical model of the UK, effectively modelling the wind as fluid flow over a smooth contoured surface driven by known weather patterns. This means it can be wrong, as local trees and buildings and detailed topography can have significant impacts. Taking the actual built environment into account the actual wind speed is therefore likely to be considerably lower than 4.9 m/s. To ensure that a wind turbine operates effectively it needs to be located away from any nearby buildings and trees. Typically, the turbine should be located at a distance of around ten times the height of nearby buildings and trees to avoid turbulence (see below). Turbulence has the effect of reducing the energy generated by the turbine and can also put additional mechanical stress on the turbine reducing its lifetime.

Figure 23: Reference distance for wind turbine installations near buildings and large objects

The viability of wind turbines is strongly related to wind speed and thus we would not normally consider a wind speed below 5 m/s as suitable. A wind speed of 4.8m/s is marginal but as already mentioned the likelihood is that the actual wind speed will be lower than this due to the local topography. For this reason we would not recommend installing a wind turbine on your site.



7.3 Hydro Energy

This is the production of energy through the movement of water through a turbine. The site does in fact own a section of the river; however the river has a very low head and flow making it unsuitable for a hydro scheme.



8. Appendix B – The Church Solar PV system images

Viewpoint Image

West

South west

South

South east

East

Documents

Polesworth Abbey Energy Options Report Prepared for and Design … · 2018-03-06 · 1. Introduction 8 2. Current energy use 9 2.1 The Gatehouse 9 2.1.1 Current energy use 10 2.1.2