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Comfort, CIBSE

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CIBSE KNOWLEDGE SERIES

Comfort

Direct and accessible guidance from key subject overviews to implementing practical solutions

The rights of publication or translation are reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means without the prior permission of the Institution. January 2006 The Chartered Institution of Building Services Engineers London Registered charity number 278104 ISBN-10: 1-903287-67-7 ISBN-13: 978-1-903287-67-5 This document is based on the best knowledge available at the time of publication. However no responsibility of any kind for any injury, death, loss, damage or delay however caused resulting from the use of these recommendations can be accepted by the Chartered Institution of Building Services Engineers, the authors or others involved in its publication. In adopting these recommendations for use each adopter by doing so agrees to accept full responsibility for any personal injury, death, loss, damage or delay arising out of or in connection with their use by or on behalf of such adopter irrespective of the cause or reason therefore and agrees to defend, indemnify and hold harmless the Chartered Institution of Building Services Engineers, the authors and others involved in their publication from any and all liability arising out of or in connection with such use as aforesaid and irrespective of any negligence on the part of those indemnified. Typeset by CIBSE Publications Printed in Great Britain by Latimer Trend & Co. Ltd., Plymouth PL6 7PY

ComfortCIBSE Knowledge Series: KS6

Principal author Gay Lawrence Race Editors Justin Roebuck Ken Butcher

CIBSE Knowledge Series Comfort

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Contents1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.1 Use of this guidance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 Thermal comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2.1 What is thermal comfort? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 2.2 What determines thermal comfort? . . . . . . . . . . . . . . . . . . . . . . .4 2.3 Key environmental factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 2.4 Ventilation and air quality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13 2.5 The adaptive approach to thermal comfort . . . . . . . . . . . . . . . .14 2.6 How hot is hot? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16 2.7 Design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 2.8 Practical issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 Visual comfort . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 3.1 Key environmental factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24 3.2 Design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 Acoustic comfort (aural comfort) . . . . . . . . . . . . . . . . . . . . . . . . .29 4.1 Key environmental factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 4.2 Design criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32 Key questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

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Appendix A: Measuring operative temperature . . . . . . . . . . . . . . . . .37 Appendix B: Thermal comfort studies . . . . . . . . . . . . . . . . . . . . . . . . .38 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 Further reading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

Note from the publisherThis publication is intended to provide information and guidance on the subject of comfort for those responsible for the operation of buildings and for the design, installation, commissioning, operation and maintenance of building services, but is not primarily intended for use in design. It is not intended to be exhaustive or definitive and it will be necessary for users of the guidance given to exercise their own professional judgment when deciding whether to abide by or depart from it. Detailed design guidance is provided in other CIBSE publications such as CIBSE Guide A: Environmental design (2006).CIBSE Knowledge Series Comfort

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Introduction

Buildings are designed to meet our basic need for: shelter: protection from the elements security: safety comfort: warmth and light.

Many of these basic needs were originally met by a cave with a fire at the entrance to provide both security and warmth and light. Nowadays, although we might expect more sophistication in delivery, and more facilities, the fundamental needs remain the same. Once the needs for shelter and security are met, the remaining main requirement is for a comfortable internal environment. Whilst this may seem a simple task to achieve, in practice there are many factors to be considered in the aim to provide comfortable conditions for the building occupants. Thus one of the primary functions of buildings and building services systems is to create and maintain a comfortable environment. Achieving the right environment is the main goal of good building services design whether a comfortable work or leisure environment for people or the correct operating conditions for machinery or equipment. Electronic and process equipment often requires far more stringent conditions than people. The main factors that influence comfort for people relate broadly to our senses i.e. touch, vision, smell, hearing. Thus the design of the building services systems must provide a good thermal, aural and visual environment i.e. fresh air and warmth or cooling, no unwanted noise or odours and good lighting. Design criteria exist for all these factors but the choice depends on many variables including use of the space, activity level, clothing level and age of occupants, etc. Decisions on design conditions are made harder by the fact that comfort is a very subjective response with different people having different comfort levels; so the main aim is literally to keep most of the people happy most of the time. In surveys of user satisfaction within buildings* comfort issues, particularly temperature and air freshness, are among those rated as the most important aspects. The same studies also show that dissatisfaction with the internal environment, particularly the thermal environment, is widespread with complaints of overheating in winter and coldness in air conditioned buildings in summer commonplace.* For example the series of PROBE studies in Building Services journal

Definition

Comfortable: at ease; free from want, trouble, hardship or pain; quietly happy. Cassel Concise English Dictionary

Aim The primary aim of building services systems is to create, and maintain a comfortable environment.

CIBSE Knowledge Series Comfort

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All those involved in the design, specification and delivery of the internal environment therefore need a good appreciation of comfort requirements. It is particularly important for building owners and users to be able to explain their internal environmental comfort requirements and to be aware of the constraints on what can be achieved or delivered with building services systems. 1.1 Use of this guidance

This guidance is intended to enable and assist the non-expert client, facilities manager and building user to: understand comfort requirements communicate their needs and requirements to their engineers/advisors.

It can also be used by building services engineers involved in design, installation and commissioning to facilitate discussion with their clients, and provides students with an accessible introduction to the subject of comfort. Detailed guidance on the environmental criteria for design can be found in CIBSE Guide A, chapter 1(1). This publication provides an introduction to the subject of comfort: Sections 24 explain the basic principles governing thermal, visual and acoustic comfort, covering key factors and the main design criteria. Section 5 provides guidance on the information that may be needed when deciding on comfort requirements.

The publication answers the following questions, which can be used to help you find the most relevant sections to you: What is thermal comfort? (section 2.1) What determines thermal comfort? (section 2.2) How does the environment affect thermal comfort? (section 2.3) How do ventilation and air quality affect thermal comfort? (section 2.4) What is the adaptive approach? (section 2.5) How hot is too hot? (section 2.6)

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CIBSE Knowledge Series Comfort

What are the design criteria for thermal comfort? (section 2.7) What can systems deliver? (section 2.8) What determines visual comfort? (section 3) What are the design criteria for thermal comfort? (section 3.2) What determines acoustic comfort? (section 4) What are the design criteria for acoustic comfort? (section 4.2) What questions do I need to ask? (section 5) What information do I need to provide? (section 5)

Finally, a selected bibliography is provided for those who want further reading on the subject.

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22.1

Thermal comfortWhat is thermal comfort?

Thermal environments can be divided loosely into three broad categories:Legislation

The Workplace (Health, Safety and Welfare) Regulations 1992 state that During working hours, the temperature in all workplaces inside buildings shall be reasonable. The Approved Code of Practice (ACOP) to these regulations defines

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