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The Illustrated Guide to

Mechanical Building Services

By Tom de Saulles

A P P L I C A T I O N G

U

I D E

A G

1 5 / 2 0 0 2

Written in association with



Introduction Heating Ventilation Air-conditioning Controls

ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES

© BSRIA AG 15/2002

ACKNOWLEDGEMENTS

This work was part-funded by the former Department of the Environment, Transport andthe Regions (DETR), under the Partners in Innovation collaborative research programme.BSRIA acknowledges the financial support of the DETR, and would also like to thank theChartered Institution of Building Services Engineers (CIBSE) for its financial contribution.

The project was undertaken under the guidance of an industry steering group.representatives. BSRIA would like to thank those on the steering group for their help andguidance. The members of the group were:

Andrew Ford Fulcrum Consulting (Representing DETR)Dr Hywel Davies CIBSE (Representing CIBSE & CCC) John Killey Citibank (Representing CIBSE) John Deal CIBSE (Representing CIBSE)Nicholas Rowe Gardiner & Theobald (Representing BCO)Hans Haenlein Hans Haenlein Architects John Armstrong Ove Arup & Partners

Special acknowledgement is given to Gay Lawrence Race (BSRIA), for her considerable

contribution to this publication.

BSRIA would also like to thank the following organisations who kindly provided thephotographs and additional information which have made this illustrated guide possible:

Airedale International Air Conditioning Ltd FFwd Precision MarketingAmbi-Rad Limited Hudevad LtdAtlantic 2000 Ledger Bennett Advertising LimitedBluesky Communications Mitsubishi ElectricCaradon Gent Limited Monodraught Limited

Carrier Air Conditioning Powrmatic LimitedClockwork Marketing Co Ltd Royston Simpson PublicityColt International Ltd Taylor Alden LimitedCovrad Heat Transfer Limited Temperature LimitedDaikin Europe NV Toshiba Carrier UK LtdDE-VI Electroheat Ltd Trox TechnikDisplacement Design Ltd Trox (U.K.) LtdDravo Environmental Services Ltd

The views expressed in this document are not necessarily those of the former Department ofthe Environment, Transport and the Regions. Final editorial control of this documentrested with BSRIA.

B R I T I S H

C O U N C I L

f o r

O F F I C E S

©BSRIA 70290 August 2002 ISBN 0 86022 606 9 Printed by The Chameleon Press Ltd.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,

or transmitted in any form or by any means electronic or mechanical including photocopying,recording or otherwise without prior written permission of the publisher.

Royal Institute ofBritish Architects

(RIBA)




ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES

© BSRIA AG 15/2002

CONTENTS Page

GLOSSARY iv

INTRODUCTION

Building design and building services 1Location of building services 2Thermal comfort 3

HEATING

Radiators 5Convectors 6Underfloor heating 7Radiant heating 8Warm-air unit heaters 10Boilers 11

VENTILATION

Natural ventilation - The use of windows 13

Natural ventilation - Powered window actuators 15Natural ventilation - Single-sided and cross ventilation 16Natural ventilation - Stack ventilation 17Natural ventilation - Stack/wind ventilators 18Mechanical ventilation - Extract only 19Mechanical ventilation - Supply only 20Mechanical ventilation - Supply and extract systems 21

AIR-CONDITIONING

Introduction to air-conditioning systems 23Constant volume (CV) 26

Variable air volume (VAV) 27Displacement ventilation 29

Fan coils 30Chilled beams 32Chilled ceilings 33Room-based heat pumps (Versatemp systems) 34Split systems 35Variable refrigerant flow systems (VRF) 36Chillers, dry coolers and cooling towers 37Air diffusers 38

CONTROLS

Introduction to control systems and components 39

Analogue and direct digital control (DCC) systems 41Building management systems (BMS) 42Integrated control systems 43

ALPHABETICAL LIST OF SYSTEMS AND EQUIPMENT 44




ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES 1© BSRIA AG 15/2002

INTRODUCTION - BUILDING DESIGN AND BUILDING SERVICES

Building design can determine many of the costs which anoperator will encounter during the life of a building. Thebuilding services can account for around 30% of the capitalcost and 50% of the operating cost for a typical office. It istherefore important that the services form an integral part ofthe overall building concept to help ensure they will operateefficiently. Involving the specialist building services engineerat an early stage in the design process can help achieve thisobjective.

If the services are not considered until a later stage, problemswhich could have been overcome by simple measures mayrequire a more complex technical solution. A well-designedbuilding may cost a little more initially, but the overall cost ofownership should be reduced. Whole-life costs of buildingservices systems should be considered as the cost-in-useelement can form a large proportion of the total cost,outweighing the initial capital cost.

It is not always possible to design a building that can utilise allpossible energy and environmentally friendly measures.Urban noise and pollution may dictate the need for sealedbuildings incorporating a mechanical ventilation or air-conditioning system. The activities in some buildings canalso necessitate air-conditioning to offset a high internal heatgain.

Some basic energy efficient strategies relevant to mostbuilding types are:

• During cold weather useful heat gains should be

maximised and heat losses minimised while ensuringadequate ventilation.

• Heat gains during warm weather should be minimised toavoid overheating. Correct orientation, external shadingand fenestration can all reduce heat gains.

• Natural ventilation should be used wherever practicable.Deep-plan depths and substantial partitioning can precludethis. Where natural ventilation alone is not adequate for

cooling, a mixed-mode system (combined natural andmechanical ventilation) may be sufficient as opposed to anair-conditioning system.

• Wherever possible, maximum use of daylight should be

made to reduce the energy used by artificial lighting.

High internal heat gains and/or the need to have sealed windows

to keep out external noise and pollution means that somebuildings cannot avoid the use of mechanical ventilation or air-

conditioning.

If internal heat gains are sufficiently low and the externalenvironment is suitable, natural ventilation can provide a low

energy solution to cooling and ventilating a building.




2 ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES

© BSRIA AG 15/2002

INTRODUCTION - LOCATION OF BUILDING SERVICES

The amount of space taken up by the services is among themany criteria upon which a well designed building can be judged. Project specific factors, such as the amount ofservicing required, means that it is not possible to lay downspecific guidelines on the spatial requirements for buildingservices. However, as a rough guide, the space taken up bythe services in a conventional office will be in the order of6 – 10% while for a high-tech building it will be around

15 – 30%.

An example of a building with minimal mechanical services isillustrated opposite. A radiator heating system is suppliedwith hot water from a basement plant room. A vertical riserlinks the radiator circuit on each floor with the boiler plant.The building is naturally ventilated and consequently there isno ductwork or related air handling plant.

The illustration at the bottom of the page is an example of amore highly serviced building, typical of many air-conditionedoffices. Each floor has a ceiling void containing a range ofservices which might include hot/chilled water pipes,ventilation ductwork, fan coil units and luminaires (seeintroduction to air-conditioning). The riser contains pipeworklinking boiler plant in a basement plant room with the ceilingvoids on each floor and the rooftop plant room. The riser alsocontains ductwork to link air handling and refrigeration plantin the roof top plant room with the ceiling void on each floor.

Although not shown in the illustration, it is not uncommonfor there to be a perimeter area on each floor which is takenup with equipment such as radiators and convectors. These

provide additional heating adjacent to glazing to offset colddowndraughts during the cooler months.

Centralised air systems generally require the most space fordistribution, as air is a relatively poor carrier of heat comparedto water (see introduction to air-conditioning).

Large and/or highly serviced buildings often require severalplant rooms, one or more of which may be on anintermediate floor or located separately from the building or agroup of buildings.

Boiler plant is often located in a basement or ground floor

plant room, while air handling and refrigeration plant islocated at high level to ensure a clean fresh air supply andgood heat rejection for the refrigeration plant (see chillers, drycoolers and cooling towers). In addition to heating andcooling plant, central plant areas can also contain a variety ofother equipment such as electrical transformers and standbygenerators.

Riser for pipes,drainage stacks,cables, etc.

Basementplant room for

boilers etc.

Example of a simple heating system distribution layout.

R

a i s e

d f l o

o r z o n

e 1 5

0 m m

S t r u c t u r a l

s l a b

( d e p t h

v a r i e

s )

S t r u c t u r

a l b e a

m ( d e p t h

v a r i e

s )

S e r v i c e

s z o n e

( d e p t h

v a r i e

s )

L i g h t

i n g z o

n e 1 5 0

m m

Basementplant room forboilers etc.

Riser for pipes,drainage stacks,ductwork &cables etc.

Plant room forchillers & ventilationequipment

Ceiling void for services eg ducts, pipes, fan coils etc.

Example of an air-conditioned building showing the additional

plant and distribution space that is required.




ILLUSTRATED GUIDE TO MECHANICAL BUILDING SERVICES 3© BSRIA AG 15/2002

INTRODUCTION - THERMAL COMFORT

Creating an internal environment in which all the occupantsfeel comfortable can be difficult to achieve, as the factorswhich determine comfort affect each of us in varying ways.There are seven parameters that determine thermal comfort.These can be grouped in the following way:

Personal factors

• Metabolism

• Clothing

• Skin temperature.

Environmental factors

• Air temperature

• Surface temperature of walls and partitions

• Air velocity

•Relative humidity.

While personal factors are dependant on the individual, theenvironmental factors relate to the weather, building type anduse and the operation of any mechanical services that may beinstalled. Design conditions for a space usually specify the

environmental factors, with air temperature, surfacetemperature and air velocity often combined into a singleindex called resultant temperature.

For critical applications, such as for the production ofpharmaceuticals, it may be essential to maintain relativelyconstant temperature and humidity levels. This requires a

high degree of servicing and is consequently expensive.

For the majority of building types it is acceptable for internalconditions to vary within limits, without having a significanteffect on the comfort of the occupants. Therefore, forbuildings such as offices, the internal conditions may be

specified as requiring a resultant temperature of 22°C ±2.

If humidity control is required, such as in a fully air-conditioned building, it is typically specified as needing tomaintain a level of relative humidity (RH) between an upperand lower limit, for example 40% – 60%RH. For buildingswithout a full air-conditioning system, control of the

humidity level is either limited or non-existent and it is ableto float in response to internal and external conditions.However, humidity levels in buildings with only a comfortcooling system (in other words, without humidity control –

see introduction to air-conditioning) will generally staywithin the limits of comfort which are approximatelybetween 30% – 70%RH.

Heat exchange between people and their surroundings.

Typical temperature variation in a space heated by radiators.

Conditions, particularly air temperature and velocity, willfluctuate within a space due to buoyancy effects, thermalresponse of the building and its services, localised heat gainsand type of heating/cooling system used. For example, thetemperature gradient within a space heated by radiators canvary considerably between floor and ceiling level as shownabove.

18oC

21oC

26oC

35oC

-1oC

We lose some heat by

radiation to coolsurfaces and spaces...

When we are hot, over 50% of

body heat is lost by convection and evaporation.

...and receive radiant

heat from warm

surfaces and spaces.

We are warmed

by convection ifthe air around

us is warmer

than our skin.



A BSRIA Guide www.bsria.co.uk

The Illustrated Guide to

Electrical Building Services

Second edition

Revised by Paddy Hastings

BG 5/2005



ii ILLUSTRATED GUIDE TO ELECTRICAL BUILDING SERVICES

© BSRIA BG 5/2005

INTRODUCTION

Providing basic reference information on electrical building servicessystems for construction clients and professionals, this guide has beengreatly updated to incorporate latest electrical technology.

This guide will assist technical dialogue between the client and designteam during the briefing process, and help clients to identify and raisetechnical questions that they feel are relevant to their organisation’sspecific needs. For construction professionals, the guide provides aquick reference to electrical building services systems and cancomplement their working knowledge of the subject.

While a design team’s role includes assessing and recommendingappropriate design solutions, this guide makes no attempt to providea route for system selection other than pointing out typicalapplications for many of the systems covered. Readers should refer

to BS 7671:2001, Requirements for Electrical Installations. IEE Wiring

Regulations (Incorporating Amendment 1 and 2:2004), The WasteElectrical and Electronic Equipment (WEEE) Directive and otherappropriate standards for detailed design information. Unless

otherwise stated, any reference to the requirements of the Building

Regulations refers to the regulations for England and Wales. Readersin Scotland and Northern Ireland should refer to local buildingregulations.

BSRIA has also published a companion guide: An Illustrated Guide to

Mechanical Building Services. This provides information on mechanicalsystems including heating, ventilation and air conditioning systems.

Also available is How to Choose Building Services – A Clients’ Guide to

System Selection, a guide that provides a basic understanding ofbuilding services.

All three guides are available from the BSRIA Bookshopwww.bsria.co.uk/bookshop or Tel: +44 (0) 1344 465529.

Forthcoming

legislation

Waste Electrical and

Electronic Equipment

(WEEE)

Directive 2002/95/EC on the restriction of

the use of certain hazardous substances in

electrical and electronic equipment andDirective 2002/96/EC on waste electrical and

electronic equipment are designed to tackle

the fast increasing waste stream of electrical

and electronic equipment. The Directives

complement EU measures on landfill and

incineration of waste.

Producers will be responsible for taking

back and recycling electrical and electronic

equipment. It is intended that this will

provide incentives to design electrical and

electronic equipment in an environmentally

efficient way, which takes waste

management aspects into account. The

proposed implementation date is June 2006.



ILLUSTRATED GUIDE TO ELECTRICAL BUILDING SERVICES iii© BSRIA BG 5/2005

CONTENTS Page

ALPHABETICAL LIST OF SYSTEMS AND EQUIPMENT iv

POWER SUPPLIES AND CONTROLLow voltage supplies 1High voltage supplies 4

Electric shock 6Earthing 7Bonding 8Earthing arrangements 10Power quality 10Metering and power factor 11Switchgear and circuit protection 12Busbar systems (low voltage) 15Cable management (low voltage) 16

FIRE DETECTION AND ALARM SYSTEMSFire detection and alarm system categories and terminology 17Zones/system layout 20Detectors 21

Sounders 23Call points and fire-resistant cables 25Asset protection systems 26Regulations and standards 27

SECURITY SYSTEMSAn introduction to security systems 29Intruder detection 30Closed circuit television (CCTV) 32Access control 34Access control entry devices 35Regulations and standards 36

LIGHTING SYSTEMSAn introduction to lighting 37

Glare 38Luminaires for use with display screens 40Luminaires – general 41Lighting systems for work areas 43Lighting systems – design considerations and control systems 44Emergency lighting 46Light-emitting diodes 49Summary of lamp characteristics 51Incandescent lamps 52Tungsten halogen lamps 53Tubular fluorescent lamps 54Compact fluorescent lamps 55High pressure mercury lamps 56Sodium lamps 57

Metal halide lamps 58UNINTERRUPTIBLE POWER SUPPLY

Uninterruptible power supplies (UPS) 59Static UPS – off-line systems 60Static UPS – on-line systems 61Rotary diesel UPS systems 62Hybrid rotary UPS systems 63Photovoltaics 64

STRUCTURED CABLINGStructured cabling 65Key components of structured cabling systems 66Unshielded and shielded data cabling 67Wireless LAN 68

SOURCES OF INFORMATION 69

FURTHER READING 70

GLOSSARY 71



iv ILLUSTRATED GUIDE TO ELECTRICAL BUILDING SERVICES

© BSRIA BG 5/2005

ALPHABETICAL LIST OF SYSTEMS AND EQUIPMENT

Access control 29Active motion sensors 31Addressable systems 18Argonite 26Aspirating smoke detectors 23Automatic blinds 39Backbone cable 67Batten with industrial reflector 41Battens with opal diffuser 41Biometric access control 35Bonding 8, 9Busbars 15Cable basket 16Cable clips 16Cable tray 16Cabling systems 65Carbon dioxide 26CCD cameras 32

CCTV 29, 32Central battery systems 48Charged coupled device cameras 32Circuit breakers 13Closed circuit television 32Colour rendering 37, 49Colour temperature 37Combined direct and indirect luminaires 40Combined PIR and microwave sensors 31Compact fluorescent lamps 55Conduit 16Data protection 36Digital codes 35Disability glare 38

Discomfort glare 38Display lighting 42Distribution board 2, 16Downlighters 42Earth clamps 9Earth fault 12Earthing 7-10Efficacy 44, 49Fixed temperature heat detectors 22Fire Precautions Act 27Flame detectors 22Flywheel system 64Foil screened twisted pair (FTP) 67Fuses 12General lighting systems 43Glare 38, 39Glass-break detector 30Harmonics 10High bay luminaires 40High pressure mercury lamps 56High voltage distribution 4Horizontal cabling 66Hybrid rotary UPS 63Hybrid system 64Illuminance 37Incandescent lamps 52Inergen 26Intruder detection 29Ionisation smoke detectors 22

Kilowatt-hour metering 11Leading and lagging power factors 11Lenses 33Light-emitting diodes 49Lighting control 45

Line interactive 60Linear heat detection cable 21Local lighting systems 43Localised lighting systems 43Low bay luminaires 40Luminous flux 37Magnetic contact switch 30Magnetic stripe cards 35Main switch 1Maintained emergency luminaires 47Maximum demand metering 11Mechanical-reed switch 30Metal halide lamps 58Miniature circuit breakers 13Modular luminaire 41Modular wiring 16Monitors 33Multiplexers 33

Non-maintained emergency luminaires 47On-line systems 34Optical beam smoke detectors 22, 23Overcurrent fault 12Packaged sub-station 4Pan and tilt camera mountings 33Passive infrared sensors 31Patch panel 66Photoelectric sensors 31Photovoltaics 64Point detectors 21Power factor 11Proof fluorescent luminaires 41Proximity cards and tags 36

Radio-linked systems 19Rate of rise heat detectors 22Repeater panels 19Residual current device 13Resolution 32Rotary UPS 62Sags 10Self-contained emergency luminaires 47Shielded twisted pair (STP) 67Short-circuit fault 12Single-phase supply 1Sodium lamps 57Sounders 23-24Spikes 10Stand-alone systems 34Standby generators 61Static inverter 48Static UPS 59Sub-stations 4Surges 10, 62, 63Switchers 33Three-phase supply 1TN-C-S 10TN-S 10Transformers 5Trunking 16TT 10Tubular fluorescent lamps 54Tungsten halogen lamps 53

Unshielded twisted pair (UTP) 67Video recording 33Weigand effect cards 35Wireless LAN 68Zones 20



ILLUSTRATED GUIDE TO ELECTRICAL BUILDING SERVICES 1© BSRIA BG 5/2005

LOW VOLTAGE SUPPLIES TO

BUILDINGS

Low voltage is a term used to describe 400 V three-phase and 230 Vsingle-phase supplies. These are nominal voltages, the actual voltage mayvary by ± 10%. The intake to buildings that have a low voltage supply is

usually provided by the electricity supplier in the form of anunderground cable that emerges at a suitable point within the building.The cable is connected directly to the supplier’s cut-out. This is a fusedunit that protects the consumer’s installation up to the main switch.

In turn the cut-out is connected to an electricity meter. Both the cut-outand the meter are provided by the electricity supplier and remains itsproperty. In some cases, the supplier may also provide a main switchbetween the meter and the consumer’s installation. This provides analternative means to isolate the supply other than the removal of the fusein the supplier’s cut-out, which is sealed by the supplier to preventtampering by unauthorised persons.

The main switch is capable of handling the full load of the installation. Inmany smaller installations the main switch is an integral part of the maindistribution board/consumer unit. The diagram opposite shows the basiccomponents of a low voltage system. In small installations, sub-distribution boards may not be required.

Single-phase supplyThe supply to most domestic and small commercial buildings is single-phase, 230 V. All electrical equipment within the property is powered bythis phase. Other properties of a similar size in the immediate area arealso likely to have a single-phase supply, but not necessarily the samephase. This is because each of the three phases supplied by the local sub-station are divided, as evenly as possible, between the properties to

ensure that the overall load between phases is balanced.

Three-phase supplyFor larger buildings the electricity supplier may determine that a three-phase supply (400 V) is required, as the loading on a single-phase supplywould be too high. Typically, a building can be divided up into threezones, each of which has approximately the same load. Each zone isserved by one of the three phases, L1, L2 and L3 (in most existingbuildings are coloured red, yellow and blue) such that a red zone isserved by the red phase, and, blue and yellow zones are served by theblue and yellow phases respectively. Buildings may be zoned by floor asin the example, or distributed throughout to achieve equal loading oneach phase.

Although the incoming supply is at 400 V, the voltage in each zone isonly 230 V, as this is the voltage between any one of the three-phasesand the neutral conductor. While the majority of electrical equipment inthe building is likely to require a single-phase, 230 V supply, there mayalso be heavy-duty equipment, such as air conditioning plant and liftmotors, that require a three-phase supply. Equipment such as this willtypically be connected to the main distribution board by separate three-phase circuits. Buildings with loads greater than around 1000 kVA(depending on the supplier) require a high voltage three-phase supply(see next section on high voltage supplies to buildings).

Example of basic low voltage system components.

Example of zoning arrangement to ensure even loading

of a low voltage three-phase supply within a building.



ILLUSTRATED GUIDE TO ELECTRICAL BUILDING SERVICES 5© BSRIA BG 5/2005

incoming high voltage supply and sub-station can be located in a singlearea. Larger commercial buildings and industrial applications may haveseveral load centres and will require a high voltage distribution system toserve multiple sub-stations. Two systems can be used, ring main or radialfeeder, each of which have advantages and disadvantages.

Ring main

The high voltage distribution circuit is arranged in the form of a ringwhich starts and finishes at the high voltage intake. The load centres areconnected through suitable circuit protection at convenient pointsaround the ring main. The benefit of this system is that each load centrehas a high voltage supply from either side of the ring main. If a faultoccurs with one of the supplies the load centres can still operate.

Radial feeder

In a radial feeder system each load centre is fed separately from theconsumer’s main high voltage switchboard through suitable circuitprotection. The main benefit of this system is that a fault in the supply toone of the load centres should not affect the others.

TransformersDifferent types of transformers can be used, all of which fall into twobasic categories: dry and liquid-filled. The most widely used liquid-filledtransformer contains mineral oil. They are usually located outside due tothe fire hazard potential from oil leaks (see section on liquid-filledtransformers).

Liquid-filled transformers

The most common type of liquid-filled transformer contains a mineral-based oil which, in addition to providing a cooling medium, alsoelectrically insulates the internal windings. The heat generated by thetransformer is taken away by means of natural convection of the ambientair around the multiple oil-filled panels located on both sides of the unit.

The cylinder mounted on top of some units is called a conservator andacts as an expansion vessel for the oil under varying operatingtemperatures; other types of unit are hermetically sealed. Theconservator also contains a sump which traps air-borne contaminants thatcan enter the unit through its breather.

As mineral oil is inflammable there is a slight fire risk. Consequently, thistype of transformer is often located outside in a special enclosure or smallbuilding. If the transformer is located internally, a soak-away is oftenbuilt to deal with any oil spillage. Automatic fire extinguishers may alsobe installed.

As an alternative to mineral oil, non-flammable substances such assilicone and synthetic ester can be used. These tend to be moreexpensive but are better suited to high-occupancy buildings such asoffices where it is particularly important to minimise fire hazards.Another option is to use a dry transformer which is available with high-grade insulation that renders it fire resistant.

Dry transformers

There are two basic types of dry transformers: those in which thewindings are encapsulated within cast-resin and those in which thewindings are directly exposed to the ambient air. In both types it is theambient air which provides direct cooling. This is usually by naturalconvection but in some cases mechanical ventilation is used to boost

performance of the transformer. The cast-resin option has the advantagethat the windings are protected from moisture and the ingress of dirt, butare not quite as good at dissipating heat as the resin acts like a thin layerof thermal insulation.

Oil-filled 1000 kVA transformer.

Dry, cast-resin transformer.

Dry transformersBenefits

Available with high-grade insulation that

renders them fire resistant enabling them to

be used in locations where an oil-filled

transformer may not be suitable

Transformer performance can be boosted by

using mechanical ventilation to enhance

cooling.

Limitations

More expensive than oil-filled transformers,

especially the cast-resin type

Dry transformers tend to be significantly

heavier and larger than oil-filled transformers,

which can be a problem where space is

restricted

At low to medium loads, dry-type

transformers tend to be less efficient, which

results in more electrical energy being

converted to heat and lost to the

atmosphere. This wasted energy must be paid

for by the consumer and represents a

significant operating cost.

Oil-filled 1000 kVA transformer.




The Illustrated Guide toRenewable Technologies

By Kevin Pennycook

BG 1/2008



2 ILLUSTRATED GUIDE TO RENEWABLE TECHNOLOGIES

©BSRIA BG 1/2008

INTRODUCTION

Welcome to a new BSRIA illustrated guide to low energy andrenewable technologies. The publication is the ideal primer forunderstanding the wide variety of innovative systems that providecleaner and less environmentally damaging ways of heating,cooling and powering buildings.

This guide covers the majority of technologies that derive all orsome of their power from renewable sources of energy, such aswind and biofuel. However biomass boilers can be used inconjunction with combined heat and power (CHP) andabsorption refrigeration. As it’s vital that clients and designersunderstand the relationships between conventional low energysystems and emerging renewable energy systems, the guide coversboth types (although, for reasons of brevity, not all low energysystems were able to be included).

Renewable energy describes power obtained from sources that areessentially inexhaustible. This covers energy supplies such as windpower, geothermal power, biomass, and solar power includingphotovoltaics. Some renewable supplies can also be used to createsecondary fuels, such as hydrogen for use in fuel cells.

Whether the motivation comes from tighter energy regulation,higher fuel prices, or greater corporate responsibility, clients andtheir design teams will be required to consider using suchrenewable forms of energy to partially or wholly offset the use offossil fuels and mains electricity.

Some renewable energy sources are able to absorb naturally anycarbon dioxide emitted as a consequence of their use orcombustion. Biofuels, derived from plant crops, are a goodexample. The carbon dioxide emitted from burning wood chipsor plant oils is absorbed very quickly by new growth. It stands toreason that burning oak is not as sustainable as burning coppicedwood, as the growth cycle is longer and the carbon dioxideemitted will hang around longer in the Earth’s atmosphericsystems to play its role in increasing the greenhouse effect.

Other systems, such as wind turbines and solar panels, emit no

carbon dioxide when generating electricity. However, aconsiderable amount of carbon dioxide will have been emittedduring product manufacture.

The distinction is important for designers who take a whole-lifecosting approach to construction. Embodied energy shouldinfluence both the basis of a building’s design and the selection ofproducts – including renewables. Photovoltaics, for example,contain precious materials that require considerable energy tomanufacture and transport. Depending on their contribution tothe building’s energy needs, it might take 20 years or more for thephotovoltaics to redeem the energy used in their manufacture.

This needs to be considered during the specification stage.



ILLUSTRATED GUIDE TO RENEWABLE TECHNOLOGIES 3©BSRIA BG 1/2008

There is also a mistaken belief that buildings will automaticallybenefit from improved efficiency and lower carbon-dioxideemissions by being kitted-out with renewables technologies. Thisis a fallacy. Few technologies are truly fit-and-forget and work in alow energy mode straight out of the box. Renewable

technologies, by and large, require greater attention at design, andcan be demanding to manage and maintain. So when clients arebeing asked to invest in renewables technology, they need toknow under what conditions the systems will perform, and whatlevels of diligence and expertise will be required in their facilitiesmanagement. Fine-tuning of the renewables systems afteroccupation is also vital to ensure sustainable performance over thelong-term.

So while renewable energy systems are certainly desirablecompared with conventional fossil-fuel energy sources, the startingpoint is not a supplier’s catalogue of gleaming solar panels or

rooftop-mounted wind turbines.

The starting point is to reduce the loads in the building first, andthen increase the efficiency of the heating, ventilating, cooling andlighting systems. This can be achieved by investing in passivedesign, building it properly, and through discerning productspecification. The third step is to halve the carbon in the mainsfuel supplies, perhaps by taking power from off-site wind turbinesor district biomass-CHP. Community energy schemes using large-scale wind power, co or tri-generation and district heating makemore environmental and economic sense than lots of separate,smaller renewable systems serving single buildings.

By following this process, designers can cut carbon-dioxideemissions to one-eighth of what they would otherwise be beforeneed arises for specifying renewables technology.

As we head into a changing world where carbon neutrality willsoon become a government objective, the mantra is this: keep itsimple, do it well, finish things off properly, and only get cleverwith renewables where they are truly justified. And when you do,use this guide as your design primer.

Roderic BunnBSRIA, March 2008




©BSRIA BG 1/2008

SUMMARY

Technology Characteristics Functionality Costeffectiveness

Reliability Maintenancerequirement

CO2 saving Overall

rating

Absorption

cooling

Requires nomechanicalvapourcompression.Activated byexternal heatsource

High. Wasteheat from CHPsource used toprovide coolingsource for airconditioning

Medium. Moreexpensive thanconventionalchillers butuses waste heat

High. Fewmoving parts

Low Medium –high

***

Biomass Uses plant-derived organicmaterial(relatively carbonneutral). Canproduce heat orbiogas dependingon the type of

technology

High. Directcombustionsystems canreplace gas/oil-fired boilers.Requires largefuel storagefacility

Medium. Moreexpensive thanconventionalboilers

High for directcombustionsystems.Anaerobicdigestion andgasificationsystems can beproblematic

Medium. Directcombustionsystems arepartially selfcleaning

High *****

CHP Generates bothelectricity andheat using fossilor renewablefuels

High. Requirespredictable andrelativelyconstant loadsfor bestperformance

Medium.Requires fullutilisation ofwaste heat

Medium.Proventechnology

Medium.Requiresregular plannedmaintenance

Medium. Canbe improvedif biomass fuelis used

****

Fuel cells Electrochemicaldevice thatproduceselectricity andheat on-site

High. Same asCHP

Low. Limitedrange ofcommerciallyavailable fuelcells, andexpensive

Medium. Long-term reliabilitydata not yetavailable.Expected to bereliable

Medium. Fewmoving parts.Fuel cell stackhas finite life

Medium.Depends onfull utilisationof generatedheat and fuelsource

**

Greywater

recovery

Reuses wastewater (bathing,washing, laundry)for toilet flushing,irrigation, andother non-potable uses

Medium.Requires matchbetween wastewater sourceand use

Low.Installation andon-going costsmay not justifysavings

Medium.Pumps, filters,and sensorscan presentproblems

Medium.Requiresplannedmaintenanceregime tocover healthrisks

Low **

Ground

source

systems – air

Uses heat fromthe ground topre-condition thesupply air to abuilding

High. Can pre-cool air insummer andpre-heat it inwinter

Medium.Depends oncost of drillingor excavationto install pipes

High. Nomoving parts

Low. Providingsteps are takento pre-filter airand avoidwater ingress

Medium ***

Ground

source

systems – water

Makes use ofwater fromaquifers (eitherdirectly orindirectly) toprovide cooling insummer

High. Can becombined withheat pumptechnology.Heat sourcecan pre-heatventilation air

Medium.Depends oncost ofboreholes

High. However,open-loopsystems aresusceptible toblockages andbiologicalfouling

Low for closed-loop systems

Medium ***

Ground

source heat

pumps

Takes up heatfrom ground andreleases it athighertemperatures.

Heat can be usedfor space heatingand domestic hotwater

High. Systemscan be run incooling mode

Medium High. Relativelyfew movingparts. Proventechnology

Low Medium. HighCOPs aredependant onrelatively lowsupply

temperaturesin heatingmode

****




Technology Characteristics Functionality Costeffectiveness

Reliability Maintenancerequirement

CO2 saving Overall

rating

Photovoltaics Converts sunlightdirectly to DCelectrical power.Requires inverter

to convert to AC

Medium.Requires carefulpositioning foroptimum

performance.Wide range ofinstallationoptions

Low. However,costs arepredicted toimprove

Medium.Associatedinverters cancause problems

Low, butspecialist

Low. Relativeto high cost

***

Rainwater

recovery

Collects andstores rainwaterfrom roofs andother catchmentareas for toiletflushing

Medium.Requires abalancebetweencollected waterand its use.Large storagetanks may berequired

Low.Installation andon-going costsmay not justifysavings

Medium.Pumps, filters,and sensorscan presentproblems

Medium.Requiresinclusion in aplannedmaintenanceregime

Low **

Solar airheating

Collects solarenergy to heatsupply air. Canalso heat re-circulated air

Medium.Relatively largenumber oftechniques.Can also pre-heat domestichot water

Medium. Solarcollectors canbe an integralpart of thebuilding fabric

High Low. Systemcleaningrequired, soaccess can bean issue

Low –medium.Requires fanpower,however thiscould beprovided byphotovoltaics

***

Solar cooling Solar thermalenergy used todrive absorption,adsorption ordesiccant cooling

Medium.Requiresmatching ofsolar collectortemperaturewith chiller

operatingtemperature.

Low. Relativelyhigh cost ofabsorptionchillers andsolar collectors

High Low.Absorptionchiller is lowmaintenance

Low –medium

*

Solar wat er

heating

Solar energy usedto heat water,usually fordomestic hotwater purposes

Medium.Proventechnologywith a range ofcollectors fordifferentoperationalrequirements

Medium Medium – high.Circulationpump andvalves arerelativelyreliable

Low Medium.Circulatingpumps can bePV powered

****

Surface

water

cooling

Uses pumpedwater from thesea, lakes or

rivers to providea cooling medium

Low. Relativelyfew buildingsclose to

suitable watersources

Low – medium.Depends onthe length of

piping required

Medium – high.Filtrationrequired to

prevent heatexchangerfouling

Low Medium.Depends onthe pumping

powerrequired

***

Water

conservation

Range of devicesused to limitwaterconsumption

Can be used ina wide range ofapplicationsand buildingtypes

Medium.Depends ondevice

Generallyreliable, butsome devicesmay besusceptible tohard water

Low – medium.Waterlessurinals requireregular andcorrectmaintenance

Low ****

Wind Turbine/generatorconverts windenergy to

electrical power

Bestperformance inopen, non-urban

locations. Canbe installed on,or integratedinto, a building

Low. Dependsgreatly onavailable windconditions.

Actual poweroutput likely tobe much lessthan the ratedoutput

Medium. Turbulent airconditionsassociated with

urban locationsmay reducelifespan ofcomponents

Medium.Requiresregularmaintenance.

Access may bean issue

Low –medium.Large sizedturbines in

non-urban oroff-shorelocations willbe moreeffective

**




©BSRIA BG 1/2008




CONTENTS Page

SUMMARY 4


ABSORPTION COOLING 9

BIOMASS 13

COMBINED HEAT AND POWER 20

FUEL CELLS 27

GREYWATER 32

GROUND SOURCE SYSTEMS 36

Ground source systems – air 36Ground source systems – water 39Ground source heat pumps 42

PHOTOVOLTAICS 47

RAINWATER RECOVERY 53

SOLAR 59

Solar air heating 59

Solar cooling 63Solar water heating 66

SURFACE WATER COOLING 73

WATER CONSERVATION 75

WIND POWER 80




©BSRIA BG 1/2008


Absorption chillers 9-10, 12 Lithium bromide 10

Absorption cooling 63 Membrane filters 33

Adsorption cooling 64 Micro CHP 20, 22

Ammonia refrigeration 10 Open-loop systems 39, 41, 60-61, 68, 73

Anaerobic digestion 15 Perforated air-collectors 61

Back-pressure steam turbine systems 21 Photovoltaics 47, 52

Biofuel 13 Pitched roofs 48-49, 70

Biological treatment 33, 56 Plate heat-exchanger 21

Biomass CHP 22 Pressurised systems 68

Biomass storage 17 Rainwater 34-35, 53-56, 58

Biomass system 18 Reciprocating engine CHP 11

Building façade 48-49, 51, 59, 71, 82 Reed beds 33, 57

Cavity collector 60 Sand filters 33

Closed-loop collector 60 Seawater cooling system 74

Closed-loop systems 40 Shell and tube heat-exchanger 21

Collection tanks 55 Showers and baths 77

Combined heat and power 17, 18 Sloping roofs 48, 49, 70

Condenser 9-10, 12, 39 Soakaway 35, 58

Dehumidification 45 Solar air systems 59

Desiccant cooling 65 Solar collectors 60

Direct combustion 13, 18 Solar heating of ventilation air 59

Directly pumped systems 53 Solar shading devices 48, 50

Disinfection 57-58 Solar water heating systems 66, 70

Domestic hot water heating 45 Space cooling 23, 45

Drainback systems 69 Space heating 44

Dry air-coolers 12 Steam turbines 21

Evacuated-tube collectors 67 Surface water cooling 73

Evaporator 9-10, 42 Tri-generation 22

Flat roofs 48-49, 51 Unglazed plastic collectors 68

Flat-plate collectors 59 Urinals 75

Foul drainage 35, 58 Vapour-compression chiller 12

Fuel cells 27-31 Vertical-axis turbines 80

Gas turbines 11, 20-21 Water conservation 75, 79

Gasification 16 Water storage 34

Glazed flat-plate collectors 67 Water treatment 33

Gravity systems 53 Water-efficient WCs 76

Greywater systems 32 Waterless and vacuum toilets 77

Ground-coupled systems 36 Wet cooling towers 12

Ground source heat pumps 40, 42-46 Wind turbines 80-84

Heat exchangers 21, 39, 43-46, 60, 66-70, 73-74 Woodchip fuel 13




ABSORPTION COOLING

System description

In a conventional vapour-compression chiller an electric motor is used todrive a compressor. In an absorption chiller a heat source drives the

cooling process. Heat sources can include hot water, steam, hot air orhot products of combustion (exhaust gases) from the burning of fuel.

In a conventional mechanical vapour-compression chiller the refrigerantevaporates at a low pressure and produces a cooling effect. A compressoris then used to compress the vapour to a higher pressure where itcondenses and releases heat. In an absorption chiller the compressor isreplaced by a chemical absorber, generator and a pump. The pumpconsumes much less electricity than a comparable compressor(approximately nine percent of that for a vapour compression plant). The majority of the energy required to drive the cooling process isprovided by the external supply of heat.

Absorption cycles use two fluids: the refrigerant and the absorbent. Themost common fluids are water for the refrigerant and lithium bromidefor the absorbent. These fluids are separated and re-combined in theabsorption cycle. The low-pressure refrigerant vapour is absorbed intothe absorbent releasing heat. The liquid refrigerant/absorbent solution ispumped to a generator with high operating pressure. Heat is then addedat the high-pressure generator which causes the refrigerant to desorbfrom the absorbent and vaporise. The vapours flow to a condenser,where heat is rejected and condensed to a high-pressure liquid. Theliquid is then throttled through an expansion valve to the lower pressurein the evaporator where it evaporates by absorbing heat. This absorbingof heat is used to provide a useful cooling effect. The remaining liquidabsorbent in the generator passes through a valve where its pressure is

reduced and is then re-combined with the low-pressure refrigerantvapours returning from the evaporator. The cycle is then repeated.

Schematic of absorption chiller.

Benefits Can make use of waste heat

Refrigerants used have no global warmingpotential

Quiet and vibration-free

Reliable

Relatively low maintenance costs

Limitations Low efficiency, and low coefficient of

performance compared to conventionalchillers

Relatively high cost compared to vapourcompressors

Larger heat-rejection plant than conventionalchillers

Slower to start up and slower to respond tochanging loads




©BSRIA BG 1/2008

Absorption chillers have a number of advantages:

They are activated by heat

No mechanical vapour-compression is required

The refrigerants used do not damage the atmosphere and have

no global warming potential (some refrigerants used in vapourcompression chillers have very high global-warming potential)

Require no lubricants

Quiet and vibration free.

System typesAbsorption chillers can be classified based on the type of heat source,the number of effects and the chemicals used in the absorption process.Indirect-fired absorption chillers use waste/rejected heat from anotherprocess to drive the absorption process. Typical heat sources includesteam, hot water or hot gases. Direct-fired chillers include an integralburner, usually operating on natural gas.

In a single-effect absorption chiller the heat released during thechemical process of absorbing refrigerant vapour into the liquid streamis rejected as waste heat. In a double-effect absorption chiller some ofthis energy is used to generate high-pressure refrigerant vapour. Usingthis heat of absorption reduces the demand for heat and boosts thechiller system efficiency.

Double-effect chillers use two generators paired with a singlecondenser, absorber and evaporator. Although they operate with agreater efficiency they require a higher temperature heat inputcompared with a single-effect chiller. The minimum heat sourcetemperature for a double-effect chiller is 140

oC. Double-effect chillers

are more expensive than single-effect chillers. Triple-effect chillers areunder development.

Two absorbent-refrigerant mixtures are widely used. These are lithiumbromide water mixture and ammonia refrigeration mixture. In a lithiumbromide water mixture the lithium bromide (a salt) is the absorbent andthe water is the refrigerant. Lithium bromide systems are the mostcommonly used absorption system, particularly for commercial cooling.In an ammonia system the water is the absorbent and the ammonia is therefrigerant. Ammonia systems are typically used when low temperaturecooling or freezing is required.

Lithium bromide water systems are widely available as packaged units with

capacities ranging from 100 kW to several thousands of kilowatts. Apractical limitation associated with this type of system is that the minimumchilled water temperature that can be produced is approximately 5

oC.

Ammonia refrigeration systems are available in small (30-100 kW),medium (100-1000 kW) and large (>1000 kW) sizes. Coolingtemperatures down to -60

oC are possible.

Allied technologies

CHP

Industrial processes producing waste heat

Renewable sources producing heat.

Table 1:Absorption chiller range.

Chiller type Heat source

Hot water(80-130

oC)

or steam(0·2-1·0

bar)

Steam (3-9bar)

Engineexhaust

gases (280-800

oC)

Single-effect

Refrigerant Water - -

Condenser type Watercooled

- -

Co-efficient of

performance0·7 - -

Double-effect

Refrigerant - Water Water

Condenser type

- Watercooled Watercooled

Co-efficient of

performance- 1·2 1·1

Source: CIBSE Guide B4




Where to useAbsorption cooling can be considered as an alternative to traditionalchillers if one of the following factors applies:

An existing combined heat and power (CHP) unit is present andnot all of the waste heat is being used

A new CHP installation is being considered

Waste heat is available from a process

Renewable fuel sources can be used such as landfill gas.

The available heat source will determine the type of absorption chillerthat is suitable for a specific application. Typical sources of heat include:

Gas turbine CHP

Reciprocating engine CHP

Waste heat

Hot water and steam.

With a gas turbine CHP, the exhaust gas from the gas turbine is used toraise steam in a waste heat boiler. The high-pressure steam available issuitable for supplying a double-effect absorption unit. The overallefficiency of the CHP can be enhanced if second stage heat recoveryusing the exhaust gases is used to heat water for domestic hot waterand/or space heating uses.

Reciprocating engine CHP units typically provide hot water at 85-90oC.

This can be used for a single-effect absorption chiller, although theperformance of the chiller will have to be down-rated (single-effectabsorption chillers normally work on a heat source at 102

oC and above).

Some CHP engines can produce water at higher temperatures, in whichcase the performance of the absorption chiller will be improved.

Waste heat from other sources such as industrial processes can also beused to drive absorption chillers. Low-pressure steam and water can beused with single-effect absorption chillers while higher pressure steam (7-9 bar) can be used to drive double-effect chillers.

In instances where boilers provide space heating and are required tosupply a small load in summer, or where a large ring-main is used tosupply a few users, the efficiency of the boiler system can be improvedby using the heated water/steam to drive an absorption chiller. Inpractice, however, it may be more efficient to reconsider the heating

strategy and install a number of small local boilers.

Application considerations The factors that determine whether a heat source is suitable for anabsorption cooling application are:

Temperature of the source heat-stream

Flow rate of the recovered heat-stream

Chemical composition of the source heat-stream

Intermittency of the recovered heat stream temperature andflow.




©BSRIA BG 1/2008

The performance of an absorption chiller is dependent on the following:

A higher chilled water temperature gives a higher coefficient ofperformance (COP) and cooling capacity

A lower cooling water temperature gives a higher COP and

cooling capacity A higher temperature heat source gives a similar COP but

increases cooling capacity.

Using a lower heat source temperature, higher condenser watertemperature or lower chiller water temperature will reduce the coolingoutput. This means that a larger, more expensive machine will berequired.

The heat rejection from an absorption chiller will be greater than aconventional chiller with the same cooling capacity. This will requirelarger heat rejection units (such as dry air-coolers or wet cooling towers)for absorption chillers. The associated space and weight constraints on

some sites may be an issue.

Absorption chillers are slower to start-up than mechanical vapourcompression chillers. They are also slower to respond to changing loads.For large systems a buffer tank may be required to increase the inertia forthe chilled water circuit. The frequent starting and stopping ofabsorption chillers should be avoided.

Absorption chillers have few moving parts and have correspondinglylower maintenance requirements compared to conventional chillers.Maintenance costs can be lower than conventional chillers.

An absorption chiller can be used to meet the base-load cooling demand

in a building, while peak cooling loads can be met by a conventionalchiller. This approach can be advantageous because conventional chillersusually cost less than the equivalent absorption chiller. Their use istherefore more cost-effective for limited running hours.

Designers should consider the requirements for a standby heat sourceshould the normal heat source (such as a CHP unit) not be available. The requirement for standby capacity will depend on the criticality ofthe business function associated with the building. Designers should alsoconsider whether it is more appropriate to size the absorption chiller onthe available heat source or on the building’s cooling demand. Thetemperature of the heat source will determine whether a single ordouble-effect chiller is appropriate.

An absorption chiller used in conjunction with a CHP unit will raise theviability and cost effectiveness of the CHP unit. Most CHP installationsare sized on the basis of heat demand. This usually means that thebuilding’s electrical base load is higher than the CHP’s electrical output.By using an absorption chiller the additional heat load allows increasedrunning hours while reducing the electricity demand associated withconventional chillers.

.

GlossaryVapour-compression chiller A refrigeration device that uses mechanicalmeans (usually driven by an electric motor) toraise the pressure of a refrigerant

Combined heat and power system A system that simultaneously generateselectricity and heat in a single integrated unit.

The heat (usually in the form of heated water or

steam) can be used for building services-relatedprocesses. Also referred to as cogeneration

Dry-air coolers A device used to reject heat from a refrigerationsystem. Air is passed over a heat exchanger(condenser)

Wet cooling towers A heat-rejection device that extracts heat from arefrigeration system to the atmosphere throughthe cooling of a water stream to a lowertemperature. Heat is lost through evaporation ofsome of the water. Also referred to as anevaporative cooling tower

Evaporator A part of a refrigeration system in which therefrigerant evaporates and in so doing takes upexternal heat in its vicinity

Condenser A part of a refrigeration system, which enablesthe refrigerant to condense, and in so doing givesup heat

StandardsNone identified

References and further reading An Introduction to Absorption Cooling , GoodPractice Guide 256, Energy Efficiency Bestpractice Programme 2001

Application Guide for Absorption

Cooling/Refrigeration using Recovered Heat,ASHRAE 1995, ISBN 1 88341326 5

ASHRAE Handbook – Refrigeration ASHRAE

Refrigeration and Heat Rejection, CIBSE Guide B4

Small-Scale Combined Heat and Power for Buildings,CIBSE AM12, 1999




The Illustrated Guide

to Ventilation

Compiled by Kevin Pennycook

BG 2/2009



2 ILLUSTRATED GUIDE TO VENTILATION

© BSRIA BG 2/2009

INTRODUCTION

Effective ventilation, whether provided by mechanical or naturalmeans, is crucial to provide a comfortable, healthy and ultimatelyproductive working environment. This new guide addresses thedesign and performance issues of the three main types of

ventilation:

Natural ventilation

Mechanical ventilation

Mixed-mode ventilation.

The effective ventilation of buildings has always been a primarydesign requirement. But in recent times more stringent energyconservation standards have sought to improve the thermalperformance of building fabric and reduce levels of uncontrolled

infiltration. Among other things this has put greater emphasis onthe correct design of windows and mechanical ventilation systems.

No longer can designers expect natural infiltration to helpmaintain air quality. What you specify and what you procure willalmost wholly determine what you’ll get.

Correct specification, careful detailing, accurate installation,thorough commissioning and diligent post-handover fine-tuningare now of equal importance in order to achieve a satisfactoryventilation system. They are all of equal ranking. Skimp on anyone, and a ventilation design can be fatally compromised.

This guide therefore not only describes the basics of ventilation,with copious pictures and illustrations to show how things workand the often subtle differences between components, but also

points out key design checks that are necessary to achieve a highquality system. Inevitably, the guide is often more geared to theskilled designer than the lay client, but such guidance is rarely readin isolation from other members of the project team. BSRIA isalso available to help its Members understand the more complexissues that the Guide sometimes raises. It’s BSRIA’s view that it’sbetter to provide too much information than leave readers withbegged questions.

Note that while the information in this Guide relates primarily tonon-domestic buildings, the basic information is relevant to alltypes of buildings, particularly in terms of the usability andmaintainability of ventilation systems.

It is not desirable for readers to consider the various forms ofventilation in isolation from allied subjects, such as passive design,use of thermal mass, and controls. Inevitably these subjects are co-related and often co-dependent. The guide therefore touchesupon the minimising of cooling loads, the contribution fromthermal massing, the control of ventilation, the commissioning of

systems, and the maintenance and upkeep of ventilation systems.



ILLUSTRATED GUIDE TO VENTILATION 3© BSRIA BG 2/2009

The best example one can give is the humble window handle. It isnot unusual for far more design attention to be paid to the glazed

element than to the window handle and the friction stays that areneeded to keep window open. Clients and designers thereforeneed to keep a very watchful eye on the specification of ancillaryitems. They may be small, but they are not trivial. A few pennies

shaved during the value engineering exercise can result in less thanrobust handles and stays, premature failure of which will seriouslyweaken the performance of a ventilation strategy.

Controls can also ultimately dictate the success or failure of a

ventilation system. Like the window handle, the issue of controls(particularly override controls for occupants) is often lost in thebigger picture.

For example, motorised windows are often a packaged subcontractitem, which includes the suppliers’ dedicated wall-mountedoverride controls. These are often generic controls that are rarely

tailored to a specific context. Result: the controls are not discussedby the architect’s or services engineer, and end up being put in bythe specialist sub-contractor, as part of the package subcontract,without anyone on the design side overseeing their usability.Subsequently, the building’s users may not know what thecontrols do, and when to use them. Even the building’s architectsand designers can be flummoxed, which will be embarrassing. By

that time, it’s too late to do anything about it.

It follows that ease of commissioning and maintenance becomevital to the performance of any ventilation system, whether naturalor mechanical or a mix of the two. In the end it comes down todesigning for managability and maintainability. There are a host ofBSRIA guides that give advice on these issues, and the relevantones are given in the bibliography. BSRIA Members candownload these guides in PDF from the BSRIA Bookshop, while

non-members can purchase printed versions on-line.

In conclusion it is worth quoting the old adage: build tight,ventilate right. Do that – and provide well-designed and fully-commissioned controls – and you won’t go far wrong.

Roderic BunnBSRIA January 2009




CONTENTS Page


NATURAL VENTILATION

Types of natural ventilation 7

Design and application issues 13

MECHANICAL VENTILATION

Types of mechanical ventilation 19

Design and application issues 21

Supply air terminal devices 26

Use with low carbon technologies 30

Control of mechanical ventilation 32

Key design and application checks 34

MIXED-MODE VENTILATION 38

MINIMISING COOLING LOADS 41

THERMAL MASS 42

Night cooling 43

CONTROL STRATEGIES 45

COMMISSIONING 47

MAINTENANCE AND UPKEEP 50

VENTILATION STANDARDS AND REQUIREMENTS 52

STANDARDS 53

REFERENCES/BIBLIOGRAPHY 54




© BSRIA BG 2/2009


Activated carbon filters 25

Actuators 16

Air distribution system 21

Air filtration 23

anemometer) 46

Carbon dioxide control 45

Carbon dioxide sensor 46

Ceiling-mounted systems 28

Charged-media non-ionising filters 24

Circular, square and rectangular diffusers 26

Commercial kitchens 19

Constant supply air temperature 32

Control strategies 45Controls 39

Cooling loads 41

Cross ventilation 9

Dampers 15

Demand-controlled ventilation 22

Design solutions 39

Displacement ventilation 28

Ducted systems 49

Earth ducts 30Electrostatic filters 24

External air temperature sensor 46

Extract ventilation 19

Fabric energy Storage 42

Fabric socks 27

Factories or industrial buildings 19

Fan motors 21

Fans 21

Floor mounted units 27

Floor-mounted systems 29

Free-standing units 27

Grilles 26

Ground-coupled air systems 30

Heat recovery 22

High efficiency filters 23

Linear and slot diffusers 26

Local supply systems 29

Localised industrial extraction 19

Mechanical ventilation 19, 47

Mixed ventilation 28

Mixed-mode ventilation 38

Natural ventilation 7, 48

Natural ventilation components 13

Nozzles and drum-louvres 26

Perforated face diffusers 26

Photocatalytic filters 25

Pre-cooling control 45

Primary filters 23

Rain sensors 46

Re-usable filters 24

Roll filters 24

Roof-mounted ventilation 11

Room air cleaners 25Secondary filters 23

Side-wall mounted grilles 29

Sill-mounted grilles 29

Single-sided ventilation 8

Slab temperature sensors 46

Solar gain sensor 46

Space temperature sensors 45

Stack ventilation 10

Summer ventilation: 14Supply and extract systems 20

Supply ventilation 19

Swirl diffusers 26

System configuration 28

Thermal capacity 42

Thermolabyrinths 30

Toilets and bathrooms 19

Trickle ventilation 15

Ultraviolet irradiation systems 25

Underground car parks 19

Variable air flow rate 32

Variable supply air temperature 33

Ventilated ceilings 29

Ventilation and ground water cooling 31

Ventilators and louvres 15

Wall mounted units 27

Wind direction sensor 46

Wind speed sensor 46

Windows 13

Winter ventilation 14




TYPES OF NATURAL VENTILATION

Natural ventilation makes use of the forces of wind and differences in airto move air through a building. There are a number of different naturalventilation air flow paths in buildings, the three main ones being:

Cross ventilation

Single-sided ventilation

Passive stack ventilation.

The latter relies on the temperature difference between the outside andinside of a building to drive air movement.

Natural ventilation enables occupants to make their own decisions ontrade-offs between ventilation rate, external noise, draught and viewsout. It is often better and more energy efficient to provide people withtolerable conditions, and the means to change them, than with betterconditions with no means of control.

A schematic showing the various natural ventilation strategies described in the chapter on natural ventilation systems.




© BSRIA BG 2/2009

NATURAL VENTILATION KEY DESIGN AND

APPLICATION CHECKS Natural ventilation is unlikely to cope with heat gains exceeding 40 W/m

2.

Reduce heat gains where possible or consider the use of exposedconcrete ceiling slabs and/or night ventilation/cooling or mixed-modestrategies

Be realistic about system performance and achievable internal conditions.

A naturally ventilated open-plan office cannot be controlled in summer tostable temperatures typical of a mechanically, air-conditioned space

Check that the air-change rate will be sufficient to provide satisfactoryoutside ventilation air and internal temperatures for occupants. Naturalventilation is intrinsically variable – always check performance under aworst-case scenario, such as on a warm day with no wind, as part of thedesign assessment

Check room air distribution patterns and air velocities in the occupiedzone for both summer and winter

Check external noise and pollution levels to assess whether natural

ventilation is feasible. Consider noise attenuation strategies

Assess the security arrangements and risks associated with openingwindows

With a building depth of over 15 m, the ventilation strategy can be verycomplex, with a 6 m depth often the limit for single-sided ventilation

The effective depth for natural ventilation systems varies from twice thefloor to ceiling height for single-sided openings, to five times the floor toceiling height for cross-flow or stack ventilation. However, occupiersatisfaction may be dependent on other factors, such as the degree ofcontrol occupants can exert over ventilation devices. The use of anatrium can allow greater floor depth depending on design

Driving pressures for natural ventilation can be very low. As a result,natural ventilation will not be efficient where there are obstructions tothe flow path or resistance to airflow, such as partitions, furnishing, andchanges of direction

Cross ventilation is most effective with an open plan. Any partitionsshould be kept low, preferably under 1·2 m in height. Tall furniture shouldbe placed perpendicular to the perimeter wall to present the leastresistance to airflow in the room

For cross ventilation with full-height partitions, such as central corridorand perimeter rooms, windows in the internal walls or transfer grilles in

walls or doors can be used, although the resistance of these to air flowmust be considered

Tall windows, or windows with top openings can promote crossventilation at high level without inducing draughts at desk heights

Passive stack-ventilation can be used when cross ventilation and single-sided ventilation cannot provide a sufficient air-change rate

Consider the use of trickle ventilators for permanent backgroundventilation in winter



The Illustrated Guide toMechanical Cooling

By Kevin Pennycook

BG 1/2010




ILLUSTRATED GUIDE TO MECHANICAL COOLING 1© BSRIA BG 1/2010

ACKNOWLEDGEMENTS

The guide has been compiled by

BSRIA’s Kevin Pennycook withadditions from Roderic Bunn, designed by Ruth Radburn and

produced by Alex Goddard.

BSRIA would like to thank the following organisations whokindly provided photographs, diagrams and information:

TROX UK Ltd

Clivet Air Conditioning LtdToshiba Air Conditioning

Mitsubishi Electric JS Humidifiers plc

Voyant SolutionsDravo Environmental Services

Max Fordham

We would also like to thank the reviewers of the document:

Les Smith, Cudd BentleyNick Cullen, Hoare Lea

Richard Tudor, WSP

Their input has been invaluable but the responsibility of the finaldocument remains entirely that of BSRIA.

©BSRIA 2010 May 2010 ISBN 978 0 86022 675 8 Printed by ImageData Ltd.

All rights reserved. No part of this publication may be reproduced, stored in a

retrieval system, or transmitted in any form or by any means electronic ormechanical including photocopying, recording or otherwise without prior written

permission of the publisher.

This publication has been printed on Nine Lives Silk recycled paper, which is

manufactured from 100% recycled fibre.



2 ILLUSTRATED GUIDE TO MECHANICAL COOLING

© BSRIA BG 1/2010

INTRODUCTION

BG 1/2010 The Illustrated Guide to Mechanical Cooling starts with ageneral overview of the various cooling systems and their purpose

in maintaining comfortable conditions in buildings. It thendescribes the main refrigeration systems and their application

principles, the types of refrigerants available, and the various waysin which renewable forms of cooling energy can be used. The

guide goes on to explain the various ways in which cooling can bedelivered to an occupied space.

The use of buildings is intensifying. More people are using more

IT equipment and the internal heat loads are growing. In addition,expectations are increasing with almost every new car being sold

with air conditioning. And climate change is resulting in moreextremes of weather. Hardly surprising that the demand for

cooling our buildings is also growing.

As concerns over our impact on the environment escalate, weneed to maximise every opportunity to reduce cooling loads

before we consider how to remove the remaining unwanted heat.

Traditionally we have used refrigeration based cooling but for the

lay person, what is it?

Essentially, it’s where the water in hydraulic circuits or the air inventilation systems is cooled by some form of powered

refrigeration cycle. It can either be gas-powered or electrically-powered, and some or all of the cooling work can be done by

recourse to natural resources, such as the use of ground water. At

the more complex end, equipment known as absorption chillerscan utilise hot water to create cold water. The absorption cycleenables waste heat from combined heat and power machines or

any other source of high grade waste heat such as exhaust steam

from a laundry to be used to produce cooling. But all that, ofcourse, just begs another question: “what is combined heat and

power”?

Non-technical people struggle with these concepts on a regular

basis. Even technical people can have difficulty with explaininghow systems work – the absorption refrigeration cycle being a

classic example. This is why BSRIA has created a series of

illustrated guides that explain and demystify complexenvironmental engineering systems. The various technologies are

described in straightforward language that non-technical peoplecan understand. Simple illustrations also provide a deeper insight

to the workings of often arcane concepts.

It’s important to appreciate that cooling systems can be both

augmented and/or boosted by passive design measures, such asthermally heavyweight and well-insulated building structures.

Some systems, such as ground-coupling, can provide what isknown as free cooling. This can significantly reduce or even

eliminate the electrical energy required to cool air or water.




It is vital for everyone involved in considering a cooling system –clients and designers alike - to ensure that a building’s cooling

loads are reduced as far as is practicable. Whatever equipment isinstalled must be as efficient as possible to reduce waste. Those

two principles are inviolate – they’re not negotiable. Clients needto accept them, and designers need to uphold them. Once cooling

loads have been driven down, and the equipment efficienciesdriven up, sources of on site or off site renewable energy can be

used to offset the remainder. This sequence is important – justbecause renewable energy is clean (and often free), doesn’t mean it

is acceptable to waste it. In fact, wasting renewable energy is

arguably a greater crime than wasting fossil fuel energy, as there isso little of it to go round.

Twenty five years ago, cooling systems tended to rely on simplemechanical refrigeration based on chlorofluorocarbons (CFCs).

Today, cooling involves far greater complexity, and often requiresmore than one system. Commissioning, controlling and

maintaining these systems places a greater burden on both theconstruction team and the client’s premises management team.This publication therefore provides some key commissioning andmaintenance guidance, along with key design checks for each

technology described.

There is much more that can be said, but for more detailedguidance on commissioning and operation, readers are urged to

consult other BSRIA guides that go into these topics in far greaterdetail. A list of these guides is provided in the appendix.

This guide is chiefly but not exclusively concerned with central

systems. It covers all of the most popular types of centralmechanical cooling systems and other important types such as

absorption cooling, even though the purists might argue that thisis not mechanical cooling.

Whatever cooling system is being considered, clients and designers

are urged to keep things simple, install it well, plan forcommissioning well in advance, and fine-tune it during the initial

period of operation. It must be easy to maintain, andstraightforward to control. A provision in the budget for seasonal

commissioning may also show dividends. Occupants of buildingslike stable conditions - they don’t like disruption, and they don’t

like unreliable or unmanageably complex control. And of coursecomfortable people are productive people. When selecting a

cooling system, that’s a good place from which to start.




CONTENTS Page

INTRODUCTION 2

ALPHABETICAL LIST 6

OVERVIEW OF COOLING SYSTEMS 7

CENTRAL SYSTEMS 12

RENEWABLE COOLING 34 TECHNOLOGIES

CENTRALISED AIR SYSTEMS 43

LOCAL SYSTEMS 51

COMMISSIONING 57

MAINTENANCE AND UPKEEP 58

STANDARDS AND REQUIREMENTS 60

REFERENCES AND BIBLIOGRAPHY 62

GLOSSARY OF TERMS 64



OVERVIEW OF COOLING SYSTEMS

A full air conditioning system provides complete control of airtemperature, humidity, air freshness and cleanliness. In practice, the termair conditioning is often mis-applied to describe systems that do notprovide full control of humidity in the occupied space. Systems without

humidity control are more correctly known as comfort cooling systems.This guide uses the term cooling to cover both air conditioning andcomfort cooling systems.

The decision to cool a building requires consideration of many factors,including the following:

Cost. Both initial costs and life cycle costs

Comfort. The level of thermal comfort required. Clients andtheir designers need to determine whether internal conditionscan be relaxed, allowing internal conditions to rise to say 25

oC in

peak summertime conditions instead of maintaining say 21 oC in

order to save energy, reduce the size of the air conditioningplant, or even forgo air conditioning altogether

Control. The level and types of control required

Complexity. Clients and designers need to determine what typeof system will be appropriate and how difficult it will be tooperate and maintain. A full air conditioning system providesclose control of air temperature and humidity, but this comes at aprice

Noise levels. Some air conditioning systems adversely affectnoise levels in occupied areas. The amount of acceptablemechanical noise will need to be determined

Adaptability and flexibility. To meet possible futurerequirements

Energy use. The amount of energy required to operate theplant. A refrigeration and air-handling plant can account for amajor part of a building’s electrical load

Global warming potential. The environmental effects ofchillers can be determined using the Total Equivalent WarmingImpact (TEWI). This is a measure of the global warming impactof equipment based on the total related emissions of greenhousegases during the operation of the equipment and the disposal ofthe operating fluids at the end of its life. This takes into accountboth direct fugitive emissions, and indirect emissions producedthrough the energy consumed in operating the equipment.TEWI is measured in units of mass of carbon dioxide (CO

2)

equivalent

Plant space. Air conditioning systems can require a largeamount of space to accommodate the refrigeration and air-handling plant. Access for operation, maintenance andreplacement must be considered.

The most common types of cooling system can been classified ascentralised or partially centralised air/water systems, or local systems.

illustrated guides set of 5 (sample)

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