Building Services System Evaluation And Development Coursework Presentation

Andreea DUMITRESCU

BARC0167 Environmentally Responsible Building Systems

Rennae DU

Building Specifications

• purpose: a multi-use exhibition centre

• location: Longsdale Road, Oban, UK (coordinates 56°25'11.1" N 5°28'11.0" W)

• can host launches, special exhibitions and demonstrations and will also be available for lectures, conferences and other events for local organisations and professional bodies as well as the general public

• expected to accommodate a maximum of 150 people per day

• good quality and flexible internal environment for all the potential range of uses is required

Performance specificationsCriteria Period Indoor Building Space Requirements

TemperatureWinter 20 Celsius

Summer 23 Celsius

Humidity 40-70%

Ventilation rate 10 L/s per person

CO2 <1000 ppm

NO21-hour mean 200 µg/m3 not to be exceeded more than 18 times a year

Annual mean 40 µg/m3

PM2.5 Annual mean 10 µg/m3

PM1024-hour mean 50 µg/m3, not to be exceeded more than 7 times a year

Annual mean 18 µg/m3

Filtration grade G3-G4

Illuminance (lux) 500

Noise (dBA) 45

Reverberation Time (s) 0.6-1.3

Surface Material Colour

Walls Gypsum plaster White

Floor 25mm wood block flooring Brown

Ceiling Mineral wool tiles white

External design conditions for Oban at 99.6% criteria

Dry Bulb Temperature:

• min 2.6 Celsius

• max 25.6 Celsius

Humidity:

• min 50%

• max 95%

External Design Condition

Winter Internal Design Condition

Summer Internal Design Condition

Design Conditions

The heat losses per square metre: • 50.72 W/m2

Compared to relevant benchmarks (BSRIA, 2011) - non-domestic buildings:• educational buildings: 87 W/m2

• offices: 70 W/m2

The calculated values are significantly lower than the benchmarks.

Surface U-value (W/(m2K))

Area (m2)

Calculated losses (kW)

DB losses (kW)

Floor 0.61 170.35 -2.35 0.138

Roof 0.38 65.41 -1.48 -1.48

Walls 0.52 11.037 -1.30 -1.19

Glazing 1.96 47.70 -2.11 -1.75

Infiltration - - -1.40 -1.54

TOTAL -8.64 -5.82

Heating Loads

Type Gain (kW)

Solar 4.85

Occupancy 11.25

Light 0.17

Equipment 0.34

Infiltration -0.03

Roof -0.39

Wall -0.25

Floor -1.25

Glazing 1.56

Sensible 15.91

Latent 7.52

TOTAL 23.43

The solar gains followed by the occupancy gains represent most of the load.The occupancy loads cannot be modified as the occupancy is specified by the client.The solar gains can be modified by adding external shading to the glazing.

The cooling loads are 137.54 W/m2.

The BSRIA benchmark for office:• 87 W/m2

Cooling Loads

Potential Environmental SystemsSystem Type Constant Volume Chilled Beams Chilled Ceilings

Displacement ventilation

Heat Pumps

FunctionalityVarying temperature and

relative humidity to meet comfort demands

Long rectangular units containing finned tube

chilled water

Chilled water pipe attached to a thin

metallic ceiling panel provides radiative and

convective cooling

Provides good indoor air quality

Localised heat pumps

Syst

em p

erfo

rman

ce

Control good but limited good good good very good

Noise Level low none none very low or none can be high

Air Distribution very good depends on ventilation depends on ventilation good good

Energy Efficiency good to average very good very good very good very good

Maintenance Costs low to average low to average low average average to high

Spac

e Re

quire

men

ts

Plant Room high low low low low

Occupied Area none none none none or moderate none or moderate

Ductwork high none (separate ventilation) none (separate ventilation) moderate none

Observations

minimum ceiling void depth around 300 mm;

cooling outputs ~ 100-160 W/m2

risk of condensation;cooling outputs ~ 70 W/m2

not suitable when ceiling is low

The criteria on which the choice is to be based is, in order:• Energy efficiency: the building is to have a sustainable servicing system

• Control: the multi-use nature of the building demands for good control of the environment to suit thedifferent purposes it might serve in time

• Noise level: the space in all its potential uses needs a low noise environment to not disturb the events takingplace inside

• Air distribution: the moderately large space of the exhibition zone demands a good air distribution

The space occupied by the systems is not a key issue in the choice, as there is plenty of room for the plant roomaround the building or underground, as well as a rather deep void (500 mm) in the ceiling for ductwork or otherrequired systems. The filtration level of the air is also not problematic, as the air quality in Oban is good.

The system chosen for the exhibition area is a chilled beam system supplemented by a displacement ventilationsystem. The reason is that chilled beams can be fitted in the large ceiling void and provide the required coolingload when supplemented by the ventilation system. The low noise levels requirements are also met by thissystem.

Potential Environmental Systems

Chilled beams + DOAS + displacement ventilation System• Cooling: water-based vapour

compression cycle chillers with an EER of 3.9 using electricity

• Heating: natural gas-fired single boiler of seasonal efficiency of 91%

• Mechanical ventilation• Thermal wheel of 65% dry heat

recovery efficiency

The chosen environmental system significantly outperforms the benchmarks

Energy Electricity (kWh) Gas (kWh) CO2 emissions (kg)

Design Value 4125.21 3744.03 2949.70

Design Value over area ( ./m2) 24.22 21.98 17.32

Benchmark ( ./m2)(CIBSE TM46, 2008)

Offices 95 120 75.1

Museums 70 200 76.5

Energy Performance

An “all air” CAV system that supplied the environmental requirements of the exhibition area is designed in the following.

The volume flowrate of air is either the flowrate of fresh air or the supply for the sensible cooling load (qs):

𝑄𝑄𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓𝑓 𝑎𝑎𝑎𝑎𝑓𝑓 = 𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣𝑣 𝑟𝑟𝑣𝑣𝑣𝑣𝑣𝑣 ⋅ 𝑣𝑣𝑣𝑣. 𝑣𝑣𝑜𝑜 𝑣𝑣𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑣𝑣𝑣𝑣𝑣𝑣𝑜𝑜 = 10 ⋅ 150 �𝑣𝑣 𝑜𝑜 = 1500 �𝑣𝑣 𝑜𝑜 = 1.5 �𝑚𝑚3𝑜𝑜

𝑄𝑄𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑎𝑎𝑎𝑎𝑓𝑓 =1𝜌𝜌 ⋅ 𝑚𝑚𝑐𝑐𝑐𝑐𝑐𝑐𝑐𝑐 𝑎𝑎𝑎𝑎𝑓𝑓 =

1𝜌𝜌 ⋅

𝑞𝑞𝑓𝑓𝑜𝑜𝑝𝑝 ⋅ Δ𝜃𝜃

=1

1.2 ⋅15.91

1.02 ⋅ 8 =1

1.2 ⋅ 1.95 = 1.62 �𝑚𝑚3𝑜𝑜

Therefore, the required flowrate is 1.62 m3/s.

All-air Ducted System Design

Unit sized according to Swegon General Sizing Chart

AHU placed outside at North side of building• Protected from wind and

excessive solar radiation• Easy Accessibility• Limits noise in exhibition area

Thermal Wheel for heat recovery• Compact and energy efficient

Bag filter• Assuming worst case scenario• Good air quality in Oban

All-air System: Air Handling Unit Sizing

Summer Design Conditions(Without thermal wheel recirculation)• Cooling coil load 45.83kW• Heating coil load 8.78kW• Total load 54.61kW

(With thermal wheel recirculation)• 7% return air recirculation• Flow rate and fresh air requirements are

similar• Cooling coil load 44.85kW

Winter Design Conditions(Full fresh air)• Heating coil load 40.76kW• Humidifier load 18.72kW• Total load 59.48kW

(Mixed air)• Heating coil load 14.63kW• Humidifier -0.98kW• Needs dehumidifying

Mixed air & thermal wheel component only provides significant advantages in Winter

All-air System:Coil Loads

• Rectangular ducts that are adjusted to have only one dimension changed at connections (it was managed to keep the height constant) and a 1:1 aspect ratio at the end branches

• Waterloo Louvred Diffusers Model DF41/375x375 (max supply rate 282 l/s; min – max throw 2 – 4.5 m; noise level NC24).

The highest index run is found on circuit 1-2-3-4, 291.72 Pa.

Extractor Fans

AHU

Diffusers

Supply Ducts

Extract Ducts

All-air System:Duct Sizing

A centrifugal fan with forward curved blades is chosen, as it has high efficiency and it is relatively quiet.

The system operating point is 2.4 m3/s, higher than the required one. Using the fan cube law:𝑊𝑊𝑟𝑟𝑊𝑊𝑖𝑖

= 𝑁𝑁𝑟𝑟𝑁𝑁𝑖𝑖

3= 𝑄𝑄𝑟𝑟

𝑄𝑄𝑖𝑖

3= 1.62

2.4

3=

0.31The fan speed change reduces the fan power by 69%, close to the minimum allowable speed. Demand-controlled ventilation is, in this case, not available.

0

200

400

600

800

1000

1200

0 0.5 1 1.5 2 2.5 3 3.5

Pres

sure

(Pa)

Flowrate (m3/s)

Fan Curve System Curve

All-air System:Choosing the Fan

Reverberation time specifications (s)0.6-1.3 (Exhibition hall, lecture theatre)1.2-1.9 (Recital hall)

Calculated reverberation time (s)2.34 (original building, no modifications)0.86 (acoustic paneling across entire ceiling)

Other measures• Spacing out acoustic paneling to

increase reverberation time• Carpeting to further lower

reverberation time

Acoustic Evaluation Surface Material Surface Area (m^2) Absorption Coefficient (at 500Hz)

Total Absorption (at 500Hz)

Wall 1

Gypsum

21.36 0.02 0.43

Wall 2 53.70 0.02 1.07

Wall 3 24.09 0.02 0.48

Wall 4 6.15 0.02 0.12

Ground Wood 170.35 0.10 17.04

Ceiling Mineral Wool Tile 170.35 0.08 13.63

Doors Wood 12.90 0.10 1.29

Glazing Glass 47.70 0.04 1.91

Reverberation Time (s) 2.34

Surface Material Surface Area (m2)

Absorption Coeff. (at 500Hz)

Total Absorption (at 500Hz)

Reverberation Time (s)

Alt. Ceiling

Acoustic Panels 170.35 0.44 74.95 0.86

PurposesLighting scheme minimum 500 luxRecitals recommended illuminance 150 lux

Illuminance uniformity• Recommendation 0.8• Activities may take place anywhere in the

exhibition area• Even distribution for occupant comfort

Measures & controls• Warm tone/natural colour - welcoming

atmosphere• Dimmers – low light events• Photosensors – automatic detection,

minimise manual handling, prevent energy waste when lighting unnecessary

LED Lighting• Higher efficiency than normal halogen

lighting• Reduces costs• May cause glare depending on surface (as

with other light sources)

Lighting Design

SLL Lighting Handbook

Work Plan

Green – initial plan

Orange – realistic work progress

Red highlight – initial and final deadline (respectively)

• The discussed systems are chosen to maximise energy performance while still allowing for flexibility

• Ventilation can be optimised to cater for the current pandemic situation (ieby using high efficiency filters like molecular filters and UVGI filters)

• The performance can be controlled via demand control ventilation• The recirculation rate in the all-air system is low and does not have a

significant impact in reducing the coil loads• Lighting scheme can be sized and designed based on the presented

suggestions• Current acoustic design does not fully suit the requested conditions but can

be improved by modifying surfaces either before or after the building stage

Conclusions & Next Steps

Building Services System Evaluation And Development Coursework Presentation

Andreea DUMITRESCU

BARC0167 Environmentally Responsible Building Systems

Rennae DU