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Productivity and the heat

by mel starrs on July 19, 2006

in Building Physics, Productivity

Today is the hottest July day on record in the UK with temperatures reaching 36.3 degrees celcius at Gatwick and 33 degrees at my desk (the thermometer had been in the shade – I moved it into the light to get a better picture)

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This was with outside air temperatures at 29 degrees in Leeds.  Of course, there are still naysayers who think global warming is all a big con:

but I’ll stick to siding with the majority of scientists on this. 

Back to my desk and the question of productivity.  This month’s BSJ has an article authored by an ex-colleague, Doug King, with a graph plotting temperature against human functions.  The article isn’t specifically about overheating, but it helps me make my point:

Above 25 degrees, mental performance reduces by at least 20%.  If we equate this directly to productivity, it is possible to work out a cost benefit analysis of providing cooling to buildings, especially existing buildings which are poorly designed (providing opening windows on a deep plan building with a 120W/m² heat gain does not qualify as a ‘naturally ventilated’ building!).

If you have a staff of 100, a 4 day heat wave could cost you 600 hours of lost productivity.  Using a typical figure for engineering consulting, this could equate to around £12,000.  This will obviously vary depending on how much your employees earn the business.  Weigh this against the cost of installing cooling (using a low/zero carbon solution, of course) which will last 10 years and the numbers start to look very interesting.

I am still an advocate for natural ventilation where possible, but a truly sustainable building is one which is fit for purpose.  If a building cannot be designed to operate at a sensible peak temperature using natural ventilation due to high occupancy densities, then adding cooling does not necessarily negate the ‘sustainability’ of the development. 

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