Energy Conservation Opportunities (ECOs) for Air ... · Energy Conservation Opportunities (ECOs) for Air Conditioning ... interest of a renovation project or to compare different

Technical guides for owner/manager of an air conditioning system: volume 5

Energy Conservation Opportunities (ECOs) for Air Conditioning auditors

uthors of this volume itecnico di Torino, Italy)

The sole responsibility for the content of this publication lies with the authors. It does not represent the opinion of

AustriaAustrian Energy Agency

BelgiumUniversité de Liège

ItalyPolitecnico di Torino

PortugalUniversity of Porto









SloveniaUniversity of Ljubljana

UKAssociation of Building

Engineers

BRE (Building Research Establishment Ltd)

Welsh School of Architecture




Engineers


Engineers





Eurovent-CertificationEurovent-Certification

Team

France (Project coordinator)Armines - Mines de Paris

France (Project coordinator)Armines - Mines de Paris

AMarco MASOERO (PolChiara SILVI (Politecnico di Torino, Italy) �

the European Communities. The European Commission is not responsible for any use that may be made of the information contained therein.

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Objectives of the guide The objectives of that guide are mainly to help building owners detecting drifts in energy consumptions of their air-conditioning plant. However, building owners have to be conscious of energy consumptions of their plants and even require reference indicators allowing them to launch actions. These actions can then be of several kinds: behavioral changes, operational changes (adjustments), investments in punctual replacements or in a complete retrofit. Finally, as soon as actions have been carried out, checking energy savings generated can be useful to judge about the payback time of these investments. In this document finally we have a detailed look at some actions proposed in the ECOs list and in Annex we report most common economic methods to evaluate the economic interest of a renovation project or to compare different project in order to choose the most interesting following different criteria.

1. Structure of the ECO List

The main purpose of an Energy Audit is to identify a suitable set of actions that should lead to significant energy savings, within the specified operational and financial constraints. In the Preliminary Audit phase, a set of candidate ECOs is identified The ECOs are selected from a list in which they are grouped into the following categories and subcategories:

E. ENVELOPE AND LOADS E.1 Solar gain reduction / Daylight control improvement E.2 Ventilation / Air movement / Air leakage improvement E.3 Envelope insulation E.4 Other actions aimed at load reduction

P. PLANT

P.1 BEMS and controls / Miscellaneous P.2 Cooling equipment / Free cooling P.3 Air handling / Heat recovery / Air distribution P.4 Water handling / Water distribution P.5 Terminal units P.6 System replacement (in specific limited zones)

O. OPERATION AND MAINTENANCE (O&M)

O.1 Facility management O.2 General HVAC system O.3 Cooling equipment O.4 Fluid (air and water) handling and distribution

In the “Envelope and Loads” categories, ECOs aimed at reducing the building cooling load are listed. These ECOs may be either of the operational type, or may involve renovation work on the building envelope. Therefore, the evaluation methods may be similar to those normally applied either to category “O&M” or “Plant”.

“Plant” ECOs involve more or less radical intervention on the HVAC system. Their applicability should therefore be carefully assessed both from the technical and economical standpoint.

The “O&M” ECOs include all actions that may in general be implemented in a building, HVAC system, or facility management scheme. The costs involved by such ECOs are generally limited

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if not negligible: application is therefore normally recommended, provided their technical feasibility is assessed.

Several of the ECOs of each of the above categories may be effectively implemented with the aid of a Building Energy Management System (BEMS). Such circumstance is highlighted in a specific column of the ECO list.

ENVELOPE AND LOADS

CODE ECO BEMS control

SOLAR GAIN REDUCTION / DAYLIGHT CONTROL IMPROVEMENT E1.1 Install window film or tinted glass E1.2 Install shutters, blinds, shades, screens or drapes E1.3 Operate shutters, blinds, shades, screens or drapes Y E1.4 Replace internal blinds with external systems E1.5 Close off balconies to make sunspace/greenhouse E1.6 Modify vegetation to save energy E1.7 Maintain windows and doors

VENTILATION / AIR MOVEMENT / AIR LEAKAGE IMPROVEMENT E2.1 Generate possibility to close/open windows and doors to match climate Y/N E2.2 Ensure proper ventilation of attic spaces Y E2.3 Optimise air convective paths in shafts and stairwells E2.4 Correct excessive envelope air leakage E2.5 Roll shutter cases: insulate and seal air leaks E2.6 Generate possibility of night time overventilation E2.7 Add automatic door closing system between cooled and uncooled space E2.8 Replace doors with improved design in order to reduce air leakage

ENVELOPE INSULATION IMPROVEMENT E3.1 Upgrade insulation of flat roofs externally E3.2 Upgrade attic insulation E3.3 Add insulation to exterior walls by filling cavities E3.4 Add insulation to exterior wall externally E3.5 Add insulation to basement wall externally E3.6 Upgrade insulation of ground floor above crawl space E3.7 Locate and minimize the effect of thermal bridges E3.8 Cover, insulate or convert unnecessary windows and doors E3.9 Use double or triple glaze replacement

OTHER ACTIONS AIMED AT LOAD REDUCTION E4.1 Reduce effective height of room E4.2 Use appropriate colour exterior E4.3 Employ evaporative cooling roof spray E4.4 Provide means of reducing electrical peak demand through load shedding Y E4.5 Replace electrical equipment with Energy Star or low consumption types E4.6 Replace lighting equipment with low consumption types E4.7 Modify lighting switches according to daylight contribution to different areas E4.8 Introduce daylight / occupation sensors to operate lighting switches Y

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E4.9 Move equipments (copiers, printers, etc.) to non conditioned zones

PLANT


BEMS AND CONTROLS / MISCELLANEOUS P1.1 Install BEMS system P1.2 Define best location for new electrical and cooling energy meters P1.3 Modify controls in order to sequence heating and cooling Y P1.4 Modify control system in order to adjust internal set point values to external

climatic conditions Y

P1.5 Generate the possibility to adopt variable speed control strategy Y P1.6 Use class 1 electrical motors P1.7 Reduce power consumption of auxiliary equipment Y/N

COOLING EQUIPMENT / FREE COOLING P2.1 Minimise adverse external influences (direct sunlight, air flow obstructions,

etc.) on cooling tower and air cooled condenser (AHU, packaged, split, VRF systems)

Y

P2.2 Reduce compressor power or fit a smaller compressor P2.3 Split the load among various chillers P2.4 Repipe chillers or compressors in series or parallel to optimise circuiting P2.5 Improve central chiller / refrigeration control Y P2.6 Replace or upgrade cooling equipment and heat pumps P2.7 Consider feeding condenser with natural water sources Y P2.8 Apply evaporative cooling Y P2.9 Consider using ground water for cooling Y

P2.10 Consider indirect free cooling using the existing cooling tower (free chilling) Y P2.11 Consider Indirect free cooling using outdoor air-to-water heat exchangers Y P2.12 Consider the possibility of using waste heat for absorption system Y P2.13 Consider cool storage applications (chilled water, water ice, other phase

changing materials) Y

P2.14 Consider using condenser rejection heat for air reheating Y

AIR HANDLING / HEAT RECOVERY / AIR DISTRIBUTION P3.1 Reduce motor size (fan power) when oversized P3.2 Relocate motor out of air stream P3.3 Use the best EUROVENT class of fans P3.4 Use the best class of AHU P3.5 Consider applying chemical de-humidification P3.6 Apply variable flow rate fan control P3.7 Consider conversion to VAV P3.8 Exhaust (cool) conditioned air over condensers and through cooling towers Y P3.9 Introduce exhaust air heat recovery Y

P3.10 Consider applying demand-controlled ventilation Y P3.11 Generate possibility to increase outdoor air flow rate (direct free cooling) P3.12 Replace ducts when leaking P3.13 Modify ductwork to reduce pressure losses P3.14 Install back-draught or positive closure damper in ventilation exhaust

system Y

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WATER HANDLING / WATER DISTRIBUTION P4.1 Use the best class of pumps P4.2 Modify pipework to reduce pressure losses P4.3 Convert 3-pipe system to 2-pipe or 4-pipe system P4.4 Install separate pumping to match zone requirements Y P4.5 Install variable volume pumping Y

TERMINAL UNITS P5.1 Consider applying chilled ceilings or chilled beams P5.2 Consider introducing re-cool coils in zones with high cooling loads P5.3 Increase heat exchanger surface areas P5.4 Consider displacement ventilation P5.5 Install localised HVAC system (in case of local discomfort) Y

SYSTEM REPLACEMENT (IN SPECIFIC LIMITED ZONES) P6.1 Consider water loop heat pump systems Y P6.2 Consider VRF (Variable Refrigerant Flow) systems

O&M


FACILITY MANAGEMENT O1.1 Generate instructions (“user guide”) targeted to the occupants O1.2 Hire or appoint an energy manager O1.3 Train building operators in energy – efficient O&M activities O1.4 Introduce an energy – efficient objective as a clause in each O&M contract O1.5 Introduce benchmarks, metering and tracking as a clause in each O&M

contract, with indication of values in graphs and tables

O1.6 Update documentation on system / building and O&M procedures to maintain continuity and reduce troubleshooting costs

O1.7 Check if O&M staff are equipped with state – of – the – art diagnostic tools

GENERAL HVAC SYSTEM O2.1 Use an energy accounting system to locate savings opportunities and to

track and measure the success of energy – efficient strategies Y

O2.2 Shut off A/C equipments when not needed Y O2.3 Shut off auxiliaries when not required Y/N O2.4 Maintain proper system control set points Y O2.5 Adjust internal set point values to external climatic conditions Y O2.6 Implement pre-occupancy cycle Y O2.7 Sequence heating and cooling Y O2.8 Adopt variable speed control strategy Y

COOLING EQUIPMENT O3.1 Shut chiller plant off when not required Y O3.2 Sequence operation of multiple units Y O3.3 Operate chillers or compressors in series or parallel

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O3.4 Track and optimize chillers operation schedule Y O3.5 Maintain proper starting frequency and running time of (reversible) chillers Y O3.6 Improve part load operation control Y O3.7 Maintain proper evaporating and condensing temperatures Y O3.8 Raise chilled water temperature and suction gas pressure Y O3.9 Lower condensing water temperature and pressures Y O3.10 Check sensor functioning and placement for (reversible) chillers Y O3.11 Maintain efficient defrosting (reversible chillers) Y O3.12 Maintain proper heat source/sink flow rates Y O3.13 Maintain functioning of (reversible) chiller expansion device Y O3.14 Check (reversible) chiller stand-by losses Y O3.15 Maintain full charge of refrigerant Y/N O3.16 Clean finned tube evaporator / condenser air side and straighten damaged

fins

O3.17 Clean condenser tubes periodically O3.18 Repair or upgrade insulation on chiller O3.19 Clean and maintain cooling tower circuits and heat exchanger surfaces O3.20 Apply indirect free cooling using the existing cooling tower (free chilling) Y

FLUID (AIR AND WATER) HANDLING AND DISTRIBUTION O4.1 Consider modifying the supply air temperature (all–air and air–and–water

systems) Y

O4.2 Perform night time overventilation Y O4.3 Shut off coil circulators when not required Y O4.4 Replace mixing dampers O4.5 Adjust fan belts (AHU, packaged systems) O4.6 Eliminate air leaks (AHU, packaged systems) O4.7 Increase outdoor air flow rate (direct free cooling) Y O4.8 Adjust/balance ventilation system Y O4.9 Reduce air flow rate to actual needs Y/N O4.10 Check maintenance protocol in order to reduce pressure losses O4.11 Reduce air leakage in ducts O4.12 Clean fan blades O4.13 Maintain drives O4.14 Clean or replace filters regularly O4.15 Repair/upgrade duct, pipe and tank insulation O4.16 Consider the possibility to increase the water outlet – inlet temperature

difference and reduce the flow rate for pumping power reduction

O4.17 Balance hydronic distribution system Y O4.18 Bleed air from hydronic distribution system Y O4.19 Switch off circulation pumps when not required Y O4.20 Maintain proper water level in expansion tank Y O4.21 Repair water leaks O4.22 Reduce water flow rates to actual needs Y/N

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2. Improvement through actions aimed at Envelope and Loads

Significant energy savings may be achieved by implementing actions aimed at reducing the building cooling load through an improvement of the envelope performance or a better management of the internal heat gains. Such ECOs cover a broad variety of actions, including purely operational / maintenance measures, as well as partial or total replacement of components and systems.

Solar gain reduction / Daylight control improvement

One of the main contributions to the cooling load of a building, particularly in the commercial sector, is the solar radiation gain through glazed envelope components. The adoption of largely glazed external envelopes in commercial buildings is justified both by architectural reasons and by daylighting. The optimal selection of the solar-optical properties of glazing, as well as the provision and use of effective shading devices (ECOs E1.1 to E1.4), is the key factor in achieving a satisfactory balance between the potentially conflicting goals of limiting summer solar gains without penalising the availability of daylight. A reduction in day light availability, in fact, not only determines a direct increase in lighting energy consumption, but may also indirectly increase the space cooling load, since the luminous efficacy of most artificial lighting systems is usually lower than that of natural light.

ECO 1.5 “Close off balconies to make sunspace/greenhouse” modifies the usable floor area and the natural ventilation of the dwelling. Its applicability is therefore subject to local regulations.

Solar control may also be achieved by acting on landscaping, i.e. through the use of vegetation (ECO E1.6); seasonal variation of solar radiation patterns and presence of leaves should be considered.

Ventilation / Air movement / Air leakage improvement

Natural ventilation in buildings may be an effective energy conservation strategy, based on the proper interaction between building envelope characteristics (air permeability, presence of operable windows, etc.) and internal layout of the building (presence of convective paths).

It is important to control natural ventilation by proper operation of windows and doors (ECO 2.1), by controlling convective paths through which significant airflow may occur (ECOs 2.3, 2.7) and envelope air leakage: excessive envelope air leakage in fact may be detrimental - both in winter and summer - when it implies excessive infiltration of untreated outdoor air (ECOs E2.4, E2.5, E2.8); on the other hand, natural ventilation of buffer spaces such as attics is an effective way of removing solar heat gains before they enter the air conditioned space (ECO 2.2). Free cooling strategies, such as night time overventilation (ECO 2.6), is another typical application of this concept since it helps reducing the cooling load in the morning hours.

Envelope insulation improvement

This group of ECOs concern actions aimed at increasing the thermal resistance of the building envelope by adding proper insulating material to opaque components - such as roofs (ECOs 3.1, 3.2), external walls (ECOs 3.3, 3.4), floors and basement walls (ECOs 3.5, 3.6) - or by installing low-U-value glazing (double, triple, low-emittance, low conductivity gas cavity, etc.) – ECO E3.9. Thermal bridges, if present, should be corrected by adding external insulation (E3.7). When practicable, unnecessary windows and doors should be covered, insulated or converted (ECO E3.8).

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Such actions have a significant impact on winter heat losses, due to the high indoor-outdoor temperature difference, but may also be beneficial in terms of cooling load reduction, provided that the insulation position does not negatively alter the transient response of the structure, which is a crucial factor in the summer energy balance of the building.

Similarly to the discussion of point 3.1, the economical attractiveness of these ECOs greatly depends on the possibility of application in conjunction with major building renovation work (e.g. roof or facade refurbishment, window substitution, etc.).

Other actions aimed at load reduction

Under this generic heading, miscellaneous ECOs are listed that do not fall into the previous categories. Most of these ECOs are related to the use of lighting - high efficiency lighting sources (E4.6), optimised lighting management based on effective occupancy or daylight availability (E4.7, 4.8) - and electrical equipment - electric load management (E4.4), use of high efficiency equipment (E4.5), positioning of office equipment in unconditioned spaces (E4.9). These ECOs have dual energy efficiency significance: they contribute to cooling load reduction, and directly reduce the electrical energy use of the building.

The other ECOs in this category - reduced volume of conditioned space (E4.1), exterior colour selection (E4.2), evaporative cooling to reduce roof heat gain (E4.3) - are building-related.

3. Performance enhancement through adequate improvement works

The ECOs of the “Plant” type always imply some modification or replacement work on the HVAC system; they are subdivided into six sub-categories:

• BEMS and Controls / Miscellaneous: ECOs implying an improvement in control strategies at the hardware level.

• Cooling equipment / Free cooling: ECOs concerning chillers and cooling towers; energy-efficient cooling strategies (such as free cooling, cold storage, use of ground eater, etc.)

• Air handling / Heat recovery / Air distribution: ECOs concerning air handling and distribution equipment; energy-efficient air treatment strategies.

• Water handling / Water distribution: ECOs concerning water handling and distribution equipment; energy-efficient water distribution strategies.

• Terminal units. • System replacement (in specific limited zones)

The possibility of BEMS implementation is indicated with a Y in the ECO list third column.

BEMS and Controls / Miscellaneous

Building Energy Management Systems (BEMS) are more and more becoming a standard in new buildings, thanks to the availability of digital controls and powerful, low-cost computers – ECO P1.1. BEMS make it possible to monitor from a remote location the main building and HVAC system operation parameters (occupancy, indoor temperatures, system components on-off status, fluid flow rates and temperatures, etc.) and to modify the HVAC system control parameters (set-points, component operation timing, etc.). BEMS can monitor energy consumption, provided electrical and thermal energy meters are installed (ECO P1.2). BEMS also make it possible to implement advanced control strategies, such as optimal equipment

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start-stop, free cooling, demand controlled ventilation, variable speed pumping and air flow, sunshades operation, artificial light trimming based on occupancy and daylight. To take full advantage of such features, the existing controls and HVAC hardware may require some modification (ECOs P1.3 – 1.5).

The auditor should not overlook the energy consumption of electrical motors (ECO P1.6) and auxiliary equipment (ECO P1.7) present in HVAC systems that should be replaced when inefficient.

Cooling equipment / Free cooling

The generation of a cooling effect is probably the single major cause of energy consumption in air conditioning. With this respect, several energy conservation options area available that may be implemented by optimisation of the existing equipment, or by system upgrading / replacement. The efficiency of the cooling equipment may be increased by different actions that are listed below:

• The optimal placement of cooling towers, air-cooled water chillers, air handling units, packaged, split or VRF systems should be considered by taking into account the negative effects that may derive from impinging solar radiation, obstructions to air flow, etc. (ECO P2.1).

• The efficiency of chillers and heat pumps can be increased by reducing the power if oversized (ECO P2.2), or by splitting the load among multiple chillers of smaller size (ECO P2.3): the latter ECO enhances the regulation capabilities by increasing the number of possible power steps.

• Multiple chillers can be hydraulically connected in series or parallel, with effects the overall performance of the system; the auditor is advised to verify the hydraulics of the cooling plant, check the water flow rates and inlet / outlet temperatures, and make a judgment if such values are optimally matched with the equipment characteristics and load profiles (ECO P2.4). The auditor should also check that the control strategies of the refrigeration equipment are adequate, or if improvements can be implemented (ECO P2.5). If feasible from the technical and legal standpoint, chiller (heat pump) efficiency may be increased by feeding the condenser (evaporator) with a constant temperature natural water sources, such as the water table, a river, a lake or the sea (ECO P2.7). As a more radical alternative, equipment replacement may be considered (ECO P2.6); such decision may be influenced by maintenance conditions, type of refrigerant fluid employed (it is not unlikely to encounter refrigeration units employing CFC’s that are no longer produced), excessive noise or vibration emissions, etc.

• A significant cooling effect may sometimes be obtained by directly exploiting free sources of cooling, such as the outdoor air, ground water, or the soil. Evaporative cooling (ECO P2.8) is particularly effective in dry climates. Ground water – local regulations permitting – is an excellent source of cooling (ECO P2.9) for HVAC systems that may be fed with relatively high temperature cold water (e.g. radiant panels, chilled beams, etc.). Free chilling / cooling using the existing cooling tower (ECO P2.10) or air-to-water heat exchanger (P2.11) is practicable when the outdoor air enthalpy is low enough.

• If relatively high temperature waste heat is available – a common circumstance in industry – the auditor should evaluate the option of installing absorption-cycle refrigeration equipment (P2.12). It is important to point out that, compared with vapour compression-cycle

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equipment, absorption chillers have normally lower efficiencies and higher initial costs: therefore, the economical feasibility of such option strongly depends on the cost differential between the thermal and electrical energy input.

• Short-term storage of cooling energy in chilled water, water ice, or other phase-changing materials, may be an effective way of reducing electricity costs (by shifting the peak power demand to the night time), or equipment sizing (a smaller chiller running for more hours + storage may substitute a larger chiller running only when cooling is needed, e.g. in buildings with non continuous occupancy, such as offices, shopping centres, etc.) – ECO P2.13. Due consideration should be paid to high initial costs, space requirements, and to the fact that this solution – albeit being a cost saver - may actually increase the energy consumption, particularly if the temperature of the storage medium is significantly lower than the required chilled water temperature.

• It is well known that any refrigeration process implies the rejection of heat to a suitable heat sink (outdoor air, cooling tower water, ground water, etc.). Since the air conditioning process often implies reheating for humidity control, the possibility arises to recover condensation heat for air reheating (ECO P2.14). Most refrigeration equipment manufacturers offer condensation heat recovery as a standard option for their water chillers.

Air handling / Heat recovery / Air distribution

A significant source of electrical and thermal energy demand in HVAC systems is air handling and distribution: air filtration, heating, cooling, humidification, dehumidification are the processes taking place in the air handling unit (AHU), which normally incorporates one or two fans for air movement. Normally a hot heat carrier fluid is needed for air preheating, reheating and humidification (indirect steam production); a cold heat carrier fluid is needed for air cooling and dehumidification, electricity for direct steam production, air and water movement, and occasionally for air reheating. For most of the above processes the auditor may consider the ECOs that are discussed below:

• Fan electrical input may be reduced by correct motor sizing (ECO P3.1) and selection of high performance components according to Eurovent classification (ECO P3.3); such classification applies to the AHU as well (ECO P3.4). If feasible, the fan motor should also be placed outside the air stream, to avoid air heating in the air cooling regime (ECO P3.2).

• Chemical de-humidification (ECO P3.5) may be considered as an alternative to the conventional process based on reducing the air temperature below its dew-point. This approach reduces the chiller consumption, but implies the availability of heat (possibly recovered without extra consumption) in order to regenerate the dehumidifier.

• Variable flow rate systems have become very popular with the diffusion of low-cost inverters (solid state electronic devices that allow motor speed control by varying the AC supply frequency). Such options may be considered as retrofits of existing constant air flow systems (ECO P3.6, P3.7).

• Energy may be recovered from exhaust air by using a heat recuperator giving up heat (and possibly water vapour) from the warm / humid outdoor air and the cool / dry exhaust indoor air (ECO P3.9). Alternatively, the indoor air may be exhausted to heat-rejection equipments such as condensers and cooling towers (ECO P3.8).

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• Demand-controlled ventilation (DCV) is particularly suited for variable occupancy buildings, such as theatres, auditoria, conference rooms, classrooms, etc. (ECO P3.10). DCV techniques imply variable fan speed control, adjustable outdoor / recirculated air dampers, and sensors estimating occupancy by measuring a suitable tracer pollutant (e.g. CO2, VOCs, etc.). A similar system concept applies to direct free cooling (ECO P3.11): the percentage of outdoor air is automatically increased, thus reducing recirculation, to take advantage of suitable climatic conditions for space cooling.

• An inspection of the ductwork and measurements of fan flow rate and pressure may help in identifying and eliminating excessive duct leakage (ECO P3.12) and pressure loss (ECO P3.13). Back-draught or positive closure dampers may be installed to reduce unwanted ventilation losses in exhaust systems (ECO P3.14).

Water handling / Water distribution

Considerations similar to those in the above section apply to water handling and distribution:

• As for fans, pumps of the best quality class should be selected (ECO P4.1). Variable flow pumping is achieved with inverter-driven electric motors (ECO P4.5), a solution particularly suited when two-way regulation valves are present in the fluid network.

• If feasible the pipework layout should be modified to correct excessive pressure losses (ECO P4.2), reduce mixing losses in 3-pipe systems (conversion to 2-pipe or 4-pipe – ECO P4.3), match zone requirements by installing separate pumping (ECO P4.4).

Terminal units

Older HVAC systems normally adopt a limited range of terminal units (e.g., fan coils, induction units, complete mixing air diffusers, etc.). When such terminals are obsolete, too noisy, or causing discomfort, their replacement may be advisable. Under such circumstances and if technically feasible, switching to more innovative terminals may be evaluated:

• Chilled ceilings or cold beams (ECO P5.1) provide excellent comfort, and can be nicely integrated in the room architecture; as any low-temperature heating / high-temperature cooling units, they help increasing the heating / cooling generating equipment performance.

• Displacement ventilation (ECO P5.4) increases the ventilation and pollutant removal efficiency; this technique is applicable in the cooling mode only in spaces with significant internal loads from people or equipment.

• Introducing re-cool coils in zones with high cooling loads (ECO P5.2), increase heat exchanger cooling areas (ECO P5.3), install localised HVAC systems in case of local discomfort (ECO P5.5) are other possible retrofits on existing plants.

System replacement (in specific limited zones)

When more radical renovation work on existing HVAC systems is needed, options such as the water loop heat pump system (ECO P6.1) or the variable refrigerant flow (VRF) system (ECO P6.2) may be considered. The former system is indicated when, in a large building, different zones simultaneously require either heating or cooling. The latter system uses the refrigerant as the heat carrying fluid, and therefore eliminates the need for producing and distributing chilled

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water; the presence of large quantities of refrigerant inside inhabited areas may however pose a safety problem, and may not be compatible with present or future regulations.

Methods for the cost-effectiveness evaluation of ECOs

To evaluate the cost – effectiveness of energy retrofit projects, several evaluation tools can be considered. The basic concept of all these tools is to compare among the alternatives the net cash flow that results during the entire lifetime of the project. The common evaluation methods in engineering projects are:

• Net Present Worth • Rate of Return • Benefit – Cost Ratio • Payback Period • Life – Cycle Cost analysis

A description of the above methods may be downloaded from the AUDITAC website as an appendix to this Technical Guide.

4. Improvement through O&M

O&M diagnosis and assessments

Building Operation and Maintenance (O&M) is the ongoing process of sustaining the performance of building systems according to design intent, the owner’s or occupants’ changing needs, and optimum efficiency levels. The O&M process helps sustain a building’s overall profitability by addressing tenant comfort, equipment reliability, and efficient operation. Efficient operation, in the context of O&M, refers to activities such as scheduling equipment and optimizing energy and comfort-control strategies so that equipment operates only to the degree needed to fulfill its intended function. Maintenance activities involve physically inspecting and caring for equipment. These O&M tasks, when performed systematically, increase reliability, reduce equipment degradation, and sustain energy efficiency. Building operation and maintenance programs specifically designed to enhance operating efficiency of HVAC can save 5 to 20 percent of the energy bills without significant capital investment.

An O&M assessment is a systematic method for identifying ways to optimize the performance of an existing building. It involves gathering, analyzing, and presenting information based on the building owner or manager’s requirements. Owners generally perform an O&M assessment for the following reasons:

• To identify low-cost O&M solutions for improving energy efficiency, comfort, and indoor air quality (IAQ);

• To reduce premature equipment failure; • To insure optimal equipment performance; • To obtain an understanding of current O&M practices and documentation.

O&M assessments may be performed as a stand-alone activity that results in a set of O&M recommendations or as part of a more comprehensive approach to improving existing-building performance. The goal of the assessment is to gain an understanding of how building systems and equipment are currently operated and maintained, why these O&M strategies were chosen,

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and what the most significant problems are for building staff and occupants. Implementing O&M changes without fully understanding the owner’s operational needs can have disappointing and even disastrous effects. Most projects require the development of a formal assessment instrument in order to obtain all the necessary O&M information. This instrument includes a detailed interview with the facility manager, building operators and maintenance service contractors who are responsible for the administration and implementation of the O&M program. Depending on the scope of the project, it may also include an in-depth site survey of equipment condition and gathering of nameplate information. An O&M assessment can take from a few days to several weeks to complete depending on the objectives and scope of the project.

The assessment identifies the best opportunities for optimizing the energy-using systems and improving O&M practices. It provides the starting point for evaluating the present O&M program and a basis for understanding which O&M improvements are most cost effective to implement.

O&M assessments identify low-cost changes in O&M practices that can improve building operation. The O&M assessment may be performed first of all as part of an energy audit because it offers ways to optimize the existing building systems, reducing the need for potentially expensive retrofit solutions, besides because implementing the low-cost savings identified in the assessment can improve the payback schedule for capital improvements resulting from the energy audit.

The greatest benefit of performing a building O&M assessment is informational. The information resulting from an O&M assessment can be used to help prioritize both financial and policy issues regarding the management and budget for the facility. It presents a clear picture of where and what improvements may be most cost effective to implement first. The assessment process, depending on the owner’s or manager’s requirements, can also provide direct training and documentation benefits for O&M staff. Depending on the goals for performing the assessment, typical benefits may include:

• Identifying operational improvements that capture energy and demand savings; • Identifying operational improvements that positively affect comfort and IAQ; • Improving building control; • Developing a baseline report on the condition of major HVAC equipment; • Developing an updated and complete equipment list (nameplate data); • Identifying issues contributing to premature equipment failure; • Identifying ways to reduce staff time spent on emergencies; • Increasing O&M staff capabilities and expertise; • Determining whether staff require additional training; • Identifying and gathering any missing critical system documentation; • Developing a complete set of sequences of operation for the major HVAC systems; • Evaluating the BEMS for opportunities to optimize control strategies; • Recommending energy-efficiency measures for further investigation; • Determining original design intent and the cost to bring the building back to original

design; • Providing a cost/benefit analysis of implementing the recommended O&M improvements; • Developing an operating plan and policy to maintain optimal building performance over

time.

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The best benefits keep on giving long after the process is completed. For example, the final master log of recommended improvements along with the estimated savings allows an owner or building manager to prioritize and budget accurately for the implementation process. Also, minor problems that could be solved during the assessment may begin to reduce energy costs and improve comfort immediately; equipment life may be extended for equipment that may have failed prematurely due to hidden problems, short-cycling, or excessive run time.

How much an O&M assessment costs is influenced by several factors: • The number and complexity of the buildings, systems, and equipment involved; • The number and type of assessment objectives; • The availability and completeness of building documentation; • The availability and expertise of the O&M staff.

A project with several objectives will naturally cost more than a project with fewer objectives. Also, a project with complicated controls and numerous pieces of equipment will cost more than a simple building with only a few pieces of equipment. Scoping the project to obtain the most benefit at the least cost can be challenging. The owner must have a clear vision for what the assessment needs to accomplish and impart that vision to the O&M consultant. In some cases the owner may want to hire an O&M consultant to help scope the project.

Inclusion of proper clauses in O&M service contracts

Frequently, building owners and managers outsource most if not all of the O&M services for their building systems. Several factors contribute to increasing business opportunities for O&M service providers in commercial buildings. These include:

• Growing interest in indoor air quality (IAQ) issues; • Phase-out of CFC refrigerants; • Building owners’ and managers’ desire to reduce operating costs and assure reliability; • Building owners’ and managers’ desire to be environmentally responsible.

The research required to design and obtain a good O&M service contract is often too confusing and time-consuming for the typical owner or manager to pursue. The purpose of this section is to provide clear information on service contract options and trends to building owners, facility managers, property managers, and chief building engineers.

In the service companies, there is no standard or set of definitions for the various kinds of service contracts. Each mechanical or maintenance service contractor puts together a unique package of contracts. The package often consists of three or four types of contracts, each presenting a different level of comprehensiveness. In this document, four fundamental types of contract are defined: full-coverage, full-labor, preventive-maintenance, and inspection contracts. The newer concept of an end-use or end-results contract is also briefly discussed. There can be many variations within a contract type, depending on owner needs and contractor willingness to modify or customize service offerings. Most of the contract types discussed below can encompass either the entire mechanical system or just one piece of major equipment such as a chiller. Also, owners may have more than one type of contract in place at any given time. Full-Coverage Service Contract

A full-coverage service contract provides 100% coverage of labor, parts, and materials as well as emergency service. Owners may purchase this type of contract for all of their building

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equipment or for only the most critical equipment, depending on their needs. This type of contract should always include comprehensive preventive maintenance for the covered equipment and systems. If it is not already included in the contract, for an additional fee the owner can purchase repair and replacement coverage (sometimes called a “breakdown” insurance policy) for the covered equipment. This makes the contractor completely responsible for the equipment. When repair and replacement coverage is part of the agreement, it is to the contractor’s advantage to perform rigorous preventive maintenance on schedule, since they must replace the equipment if it fails prematurely. Full-coverage contracts are usually the most comprehensive and the most expensive type of agreement in the short term. In the long term, however, such a contract may prove to be the most cost-effective, depending on the owner’s overall O&M objectives. Major advantages of full-coverage contracts are ease of budgeting and the fact that most if not all of the risk are carried by the contractor. However, if the contractor is not reputable or underestimates the requirements of the equipment to be insured, they may do only enough preventive maintenance to keep the equipment barely running until the end of the contract period. Also, if a company underbids the work in order to win the contract, they may attempt to break the contract early if they foresee a high probability of one or more catastrophic failures occurring before the end of the contract. Full-Labour Service Contract

A full-labour service contract covers 100% of the labour to repair, replace, and maintain most mechanical equipment. The owner is required to purchase all equipment and parts. Although preventive maintenance and operation may be part of the agreement, actual installation of major plant equipment such as a centrifugal chillers, boilers, and large air compressors is typically excluded from the contract. Risk and warranty issues usually preclude anyone but the manufacturer installing these types of equipment. Methods of dealing with emergency calls may also vary. The cost of emergency calls may be factored into the original contract, or the contractor may agree to respond to an emergency within a set number of hours with the owner paying for the emergency labour as a separate item. Some preventive maintenance services are often included in the agreement along with minor materials such as belts, grease, and filters. This is the second most expensive contract regarding short-term impact on the maintenance budget. This type of contract is usually advantageous only for owners of very large buildings or multiple properties who can buy in bulk and therefore obtain equipment, parts, and materials at reduced cost. For owners of small to medium-size buildings, cost control and budgeting becomes more complicated with this type of contract, in which labour is the only constant. Because they are responsible only for providing labour, the contractor’s risk is less with this type of contract than with a full-coverage contract. Preventive-Maintenance Service Contract

The preventive-maintenance (PM) contract is generally purchased for a fixed fee and includes a number of scheduled and rigorous activities such as changing belts and filters, cleaning indoor and outdoor coils, lubricating motors and bearings, cleaning and maintaining cooling towers, testing control functions and calibration, and painting for corrosion control. Generally the contractor provides the materials as part of the contract. This type contract is popular with owners and is widely sold. The contract may or may not include arrangements regarding repairs or emergency calls. The main advantage of this type of contract is that it is initially less expensive than either the full-service or full-labour contract and provides the owner with an agreement that focuses on quality preventive maintenance. However, budgeting and cost control regarding emergencies, repairs, and replacements is more difficult because these activities are often done on a time-and-materials basis. With this type of contract the owner takes on most of the risk. Without a clear understanding of PM requirements, an owner could end up with a contract that provides either too much or too little. For example, if the building is in a particularly

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dirty environment, the outdoor cooling coils may need to be cleaned two or three times during the cooling season instead of just once at the beginning of the season. It is important to understand how much preventive maintenance is enough to realize the full benefit of this type of contract. Inspection Service Contract

An inspection contract is purchased by the owner for a fixed annual fee and includes a fixed number of periodic inspections. Inspection activities are much less rigorous than preventive maintenance. Simple tasks such as changing a dirty filter or replacing a broken belt are performed routinely, but for the most part inspection means looking to see if anything is broken or is about to break and reporting it to the owner. The contract may or may not require that a limited number of materials (belts, grease, filters, etc.) be provided by the contractor, and it may or may not include an agreement regarding other service or emergency calls. In the short-term perspective, this is the least expensive type of contract. It may also be the least effective—it’s not always a moneymaker for the contractor but is viewed as a way to maintain a relationship with the customer. A contractor who has this “foot in the door” arrangement is more likely to be called when a breakdown or emergency arises. They can then bill on a time-and-materials basis. Low cost is the main advantage to this contract, which is most appropriate for smaller buildings with simple mechanical systems. End-Results Contracting

End-results or end-use contracting is the newest concept in service contracting and is not yet widely available. The outside contractor takes over all of the operational risk for a particular end result, such as comfort. In this case, comfort is the product being bought and sold. The owner and contractor agree on a definition for comfort and a way to measure the results. For example, comfort might be defined as maintaining the space temperature throughout the building within a fixed range for 95% of the annual occupied hours. The contract payment schedule is based on how well the contractor achieves the agreed-upon objectives. This type of contract may be appropriate for owners who have sensitive customers or critical operational needs that depend on maintaining a certain level of comfort or environmental quality for optimum productivity. How risk is shared between the owner and contractor depends on the type or number of end results purchased. If comfort defined by dry-bulb temperature is the only end result required, then the owner takes on the risk for ameliorating other problems such as indoor air quality, humidity, and energy use issues. Maximum contract price is tied to the amount and complexity of the end results purchased. Energy Performance Contract

An Energy Performance Contract (EPC) is an agreement by an Energy Service Company (ESCO) for the provision of energy services in which energy systems are installed, maintained, or managed to improve the energy efficiency of, or produce energy for, a facility in exchange for a portion of the energy savings. A preliminary project scope should be included in the Request For Proposals so that a more effective comparison can be made of proposals used in selecting an ESCO. The project scope must be directly related to energy savings. Projects that do not reduce energy use are not appropriate. Projects that replace, repair, or maintain systems and equipment that are covered by previous EPCs are not acceptable. For example, repair or replacement of lighting fixtures or temperature control systems that were installed by a previous EPC, water conservation plumbing fixture replacement, replacement of paper towels in toilet rooms with electric hand dryers, fire alarm systems, security systems, telephone systems, technology cabling, etc. and any work in new construction are not appropriate for EPCs.

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The EPC project scope must be complete and designed to be independent of any and all other projects that may be proposed or underway and all construction and administrative costs necessary to install EPC work must be the responsibility of the ESCO.

Classification of O&M ECOs

The ECOs of the O&M type have been subdivided into four sub-categories: • Facility Management: general, energy-related recommendations to building owner or

manager. • General HVAC system: ECOs of a general type, that may be implemented irrespectively

of the type of HVAC system or subsystem being addressed. • Cooling equipment: ECOs concerning chillers and cooling towers, as well as their

components • Fluid handling and distribution: ECOs concerning Air Handling Units, fans, ductwork,

pumps, piping, etc.

As for other ECOs categories, the possibility of BEMS implementation is indicated with a Y in the ECO list third column.

6. Improvement through BEMS1

Methods usually programmed in BEMS

Once a Building Energy Management System (BEMS) is in place and fully operational, the facility manager who will supervise its operation may look toward optimization. Before trying to optimize a system, it is important to understand basic BEMS capabilities. Features may vary widely from model to model, but some basic capabilities are almost universal. In this document the interest is focused upon energy management. The standard BEMS capabilities are:

• Scheduling • Set-points • Alarms • Safeties • Basic monitoring and trending

With each of these features, there are opportunities to move beyond minimal utilization without significant effort or complexity. Selected control strategies that can save energy or reduce demand are listed in the following table; a detailed description may be downloaded from the AUDITAC website as an appendix to this Technical Guide.

1 For a more detailed description of BEMS capabilities look at AuditAC Technical guide n°12: Building Energy Management Systems (BEMS) control strategies for air conditioning efficiency on http://www.eva.ac.at/projekte/auditac_publ.htm

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Scheduling Lockouts Miscellaneous • Holiday scheduling • Zonal scheduling • Override control and tenant billing • Night setup/setback • Optimum start • Optimum stop • Morning warm-up/cool-down

• Boiler system • Chiller system • Direct expansion compressor cooling • Resistance heat

• Simultaneous heating/cooling control • Zone-based HVAC control • Dual duct deck control • Chiller staging • Boiler control • Building space pressure • Variable speed drive control • Heat recovery

Ventilation Control Energy Monitoring Lighting • Carbon dioxide • Occupancy sensors • Supply air volume/OSA damper compensation routines • Exhaust fans

• Whole building or end-use • kWh or demand

• Lighting sweep • Occupancy sensors • Daylight dimming • Zonal lighting control

Air-Side Economizers Resets Demand Control • Typical air-side • Night ventilation purge

• Supply air/discharge air temperature • Hot deck and cold deck temperature • Mixed air temperature • Heating water temperature • Entering condenser water temperature • Chilled water supply temperature • VAV fan duct pressure / flow • Chilled water pressure

• Demand limiting or load shedding • Sequential startup of equipment • Duty cycling

Evaluating the current Building Energy Management System

In addition to clearly defining a building’s BEMS needs, an owner or facility manager must also evaluate the state of the current system. Determining whether an existing system can and should be upgraded is even more complex than the specification of a new system and requires an honest and complete analysis of the current system. The BEMS operator may be the most appropriate person to answer questions and provide insight. If sufficient expertise is not available in-house, consult with a knowledgeable engineer other than the vendor. With the help of the system operator, put together a list of negative and positive aspects of the current system. In addition to a thorough technical evaluation, consider other factors, such as ease of operation, required training level of the BEMS operator, customer (occupant) comfort and controllability. Determine whether the BEMS vendor has an upgrade path for the existing BEMS. If he does, compare the cost to system replacement and review the relative benefits of an upgrade versus a replacement. Some further points to consider when evaluating your BEMS are:

1. Is the current system operating to its maximum capability? If not, why not?

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• Are any BEMS problems due inadequately trained operating personnel? If this is the case, would replacement of the system solve the problem, or will the same problem exist after the system has been replaced?

• Are problems due to lack of maintenance of the EMS, including software, firmware, and hardware upgrades?

• Are there a number of points that are being operated in “hand” condition, overridden by the operators, non-operational, or completely bypassed? Why? If so, will upgrading the system really solve these problems?

2. Consider these broad management and financial issues: Are there energy management strategies the current system cannot perform? For example, a BEMS may not be able to implement strategies because it cannot interface with DDC terminal equipment controllers (VAV boxes, fan coil units, unit ventilators, etc.).

• Has the existing system met your expectations from the time it was installed? • Have you documented any savings accomplished by the existing system? • Will the proposed changes allow greater energy, and/or cost savings than the existing

BEMS system?

3. If the system has been serviced by the vendor (either by contract or casual labor calls), has the service been up to expectations and have the costs seemed appropriate? If there is a service contract, is it fully understood? Inadequate service could account for poor performance.

4. Do you have one BEMS system or several different systems consisting, in some cases, of only one field panel? If there are systems from more than one manufacturer or separate incompatible systems from one vendor, would both systems be upgraded?

5. Are you preparing to expand the facility or perform major system improvements that will result in adding points and functions to the existing BEMS? Is the existing BEMS worth including in these plans? Does it have the capacity to handle these changes?

6. If a replacement is being considered, do the system components have any resale value? Some companies purchase the BEMS components of older systems for sale to facilities still using those systems. Will the vendor of the existing BEMS offer any kind of trade-in allowance for the old equipment? After considering all the relevant factors, the facility manager, with the help of a consultant or vendor, can begin to formulate options for BEMS upgrade or replacement. The development of very detailed options is usually done by the consultant or vendor, although the facility manager may specify the inclusion of certain features.

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ANNEX- ECONOMICAL ANALYSIS METHODS

Net Present Worth

The present worth of the cash flows that occur during the lifetime of the project is calculated as follows:

∑=

+−=N

kk kdSPPWCFCFNPW

10 ),(*

where: SPPW (d,k) [Single Payment Present Worth after N years] = P/F = (1+d)-k = value of the cash flow P needed to attain a needed cash flow F after k years N = lifetime d = discount rate CF = cash flow

The initial cash flow is negative (a capital cost for the project), while the cash flows for the other years are generally positive (revenues). For the project to be economically viable, the net present worth has to be positive or at worst zero (NPW ≥ 0). Obviously, the higher the is the NPW, the more economically sound is the project. This method is often called the net savings method since the revenues are often due to the cost savings from implementing the project.

Rate of Return

In this method the first step is to determine the specific value of the discount rate, d’, that reduces the net present worth to zero. This specific discount rate, called the rate of return (ROR), is the solution of the following equation:

∑=

=+−N

kk kdSPPWCFCF

10 0),'(*

Once the rate of return is obtained for a given alternative of the project, the actual market discount rate or the minimum acceptable rate of return is compared to the ROR value. If the value of ROR is larger (d’>d), the project is cost – effective.

Benefit – Cost Ratio

The benefit – cost ratio (BCR) method is also called the savings – to investment ratio (SIR) and provides a measure of the net benefits (or savings) of the project relative to its net cost. The net values of both benefits (Bk) and costs (Ck) are computed relative to a base case. The present worth of all the cash flows are typically used in this method. The BCR is computed as follows:

∑

∑

=

== N

kk

N

kk

kdSPPWC

kdSPPWBBCR

0

0

),(*

),(*

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The alternative option for the project is considered economically viable relative to the base case when BCR > 1.0.

Payback Period

In this evaluation method, the period Y (years) required to recover an initial investment is determined. Y is the solution of the following equation:

∑=

=Y

kk kdSPPWCFCF

10 ),'(*

If the payback period Y is less than the lifetime of the project (Y<N), then the project is economically viable and the obtained value of Y is called discounted payback period (DBP) since it includes the value of money. If, as in the majority of applications, the time value of money is neglected, y is called simple payback period (SBP) and is solution of the following equation:

∑=

=Y

kkCFCF

10

The methods described above provide an indication of whether or not a single alternative of a retrofit project is cost – effective. However, these methods cannot be used or relied on to compare and rank various alternatives for a given retrofit project. Only the life – cycle cost (LCC) analysis method is appropriate for such endeavour.

Life – Cycle Cost analysis method

The Life-Cycle Cost (LCC) analysis method is the most commonly accepted method used to assess the economic benefits of energy conservation projects over their lifetime. The method is used to compare at least two alternatives of a given project. The basic procedure of the LCC method is simple since it seeks to determine the relative cost effectiveness of the various alternatives. The cost is determined using one of two approaches (the present worth or the annualized cost estimate). The alternative with the lowest LCC is typically selected.

1. One single present value amount:

∑=

=N

kk kdSPPWCFLCC

0),(*

2. Multiple annualized costs over the lifetime of the project:

⎥⎦

⎤⎢⎣

⎡= ∑

=

N

kka kdSPPWCFNdUSCRLCC

1),(**),(

where: USCR [Uniform Series Capital Recovery Factor] = A/P = d/(1-(1+d)-N) = cost savings due to the retrofit project (A)/initial investment (P)

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A LCC analysis can be performed a variety of ways without compromising the results if the assumptions that shape the LCC analysis employ reasonable and consistent judgement.

The LCC analysis of each project alternative should include: • A brief description of the project alternative • A brief explanation as to why the project alternative was selected • A brief explanation of the assumptions made during the LCC analysis • Conceptual or schematic documentation indicating design intent of the alternative • A site plan showing the integration of the proposed facility on the site and necessary site

improvements (for projects involving additions or new construction) • A detailed LCC analysis of the project alternative • A summary table that compares the total life cycle costs of Initial Investment, Operations,

Maintenance & Repair, Replacement, Residual Value of all the project alternatives The first step in the completion of the LCCA of a project alternative is to define all the initial investment costs of the alternative. Initial investment costs are costs that will be incurred prior to the occupation of the facility.

The second step is to define all the future operation costs of the alternative. The operation costs are annual costs, excluding maintenance and repair costs, involved in the operation of the facility. All operation costs are to be discounted to their present value prior to addition to the LCC analysis total.

The third step is to define all the future maintenance and repair costs of the alternative. Maintenance costs are scheduled costs associated with the upkeep of the facility. Repair costs are unanticipated expenditures that are required to prolong the life of a building system without replacing the system.

The fourth step is to define all the future replacement costs of the alternative. Replacement costs are anticipated expenditures to major building system components that are required to maintain the operation of a facility. All replacement costs are to be discounted to their present value prior to addition to the LCC total analysis.

The fifth step is to define the residual value of the alternative. Residual value is the net worth of a building or building system at the end of the LCC analysis study period.

Once all pertinent costs have been established and discounted to their present value, the costs can be summed to generate the total life cycle cost of the project alternative.

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