Thermal Comfort – A different sort of problem

Yesterday I travelled up to Glasgow where I’d been invited to give presentation on “Thermal Comfort” to a meeting of the Scottish Region of the British Occupational Hygiene Society (BOHS). Despite a few technical problems which delayed us starting (computers are great when they work!) the meeting went well and it was good to meet up with an enthusiastic group of people which included some new members of the Society.

Most occupational hygienists at some time or other will be faced with a situation where workers are complaining that the environment they’re working in is uncomfortable. Thermal conditions often contribute to this.

Thermal comfort is usually defined as “that condition of the mind that expresses satisfaction with the thermal environment” As this is about individual perception and preference, these problems are amongst the most difficult we have to address.

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It’s most likely to be an issue in workplaces such as offices, but complaints or concerns can sometimes occur in manufacturing environments and other types of workplace. During the discussion, one of the audience told us about problems experienced by bus drivers – not surprising really when you consider that buses are effectively mobile workplaces with their own internal environment. Their large windows potentially presenting problems from radiant heat from the sun (or radiant heat loss on cold, sunless days) and there’s plenty of potential for draughts.

The key thing with “thermal comfort” is that it’s subjective – one person may complain about feeling warm while another may consider the same environment to be too cool – you can’t keep everyone happy all of the time. Studies have suggested that the very best you can do is achieve 95% satisfaction . So there will always be 1 person in 20 who is dissatisfied. Change things for him/or her, someone else will start to feel unhappy! In practice you’re doing well if more than 80% are happy!

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There are two basic approaches we can take to evaluating thermal comfort

  • a Qualitative approach which involves talking to and interviewing people in the workplace and looking around for obvious clues, using experience to make a subjective judgement
  • a Quantitative approach where we carry out measurements. (However, interpreting the results from the measurements presents some difficulties)

I think that the best way to find out what someone thinks is to ask them! There are a number of questionnaires and checklists available from various sources, including the Health and Safety Executive and BOHS that can help with this qualitative approach. However, measurements can also be useful. They can help you to determine what factors are likely to be causing the problem. So, in practice, a combined approach is normally best.

Even if problems can be identified, it’s not always easy to find solutions. Particularly as improving things for one person is likely to upset someone else! Ideally, individuals should be given control over their own personal environment. But it’s not easy to achieve this in practice as changes that one person makes is likely to affect at least some of their colleagues.

The slides I used during the talk are available on Slideshare, including a version with my speaker’s notes.

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2 thoughts on “Thermal Comfort – A different sort of problem

  1. Mike,
    Very good presentation.
    I know that it’s widely stated that the highest thermal comfort satisfaction that you can achieve is 95% (or the 80% that you say is more likely), but I consider that this is only true where people don’t have the freedom to add or remove layers of clothing, although I have known of people complain that they might have to put on a pullover to keep warm!
    The exception is the situation of high radiant heat (or “radiant cold”), or strong draughts that you cover in your presentation.
    But otherwise, if people aren’t constrained by having to wear a uniform, it should be possible for thermal comfort not to be an issue.

  2. Danny

    Thanks for your comments. Fundamentally I’d agree with you. Unfortunately people don’t always always behave logically and in many cases I’ve dealt with don’t seem to appreciate that they can control their comfort by adjusting their clothing or may even be reluctant to do so!

    Another problem I’ve found is that office workers often seem to want to wear light clothing and then turn the heating right up. Only last week I was investigating an indoor environment problem where the daytime temperature was 24 C and the majority of the workers didn’t want to turn it down. They could easily have put on a jumper if that made them feel cool but didn’t seem to think that there employer should make them do that (similar to the situation you refer to). And there’s only so much clothing someone who thinks it’s too warm can remove while maintaining an appropriate level of decency.

    Still, “there’s nowt so queer as folk” as we say up here in the North of England

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