3.2 Health impacts of the thermal environment

The previous sections discussed how the thermal environment affects the comfort of building occupants. And the impact on comfort is the main influence the thermal environment has on building occupants. But the thermal environment also has some health issues, which will be discussed in the following

3.2.1 Heat strokes

Heat stroke is the most serious heat-related condition. It occurs when the body becomes unable to control its temperature: the body's temperature rises rapidly above 40°C, the sweating mechanism fails, and the body is unable to cool down. Body temperature may rise even further within 10 to 15 minutes, and many of the important functions of the body will begin to shut down. Heat stroke can cause death or permanent disability if emergency treatment is not provided. Infants, children and the elderly are more vulnerable to heat illness than other age groups. 


3.2.2 Effect of uniform temperature indoors

Time spent indoors with a fairly uniform temperature may have negative health effects. Spending time indoors with slightly cool temperatures (e.g. below 20°C) may stimulate bodily processes that help prevent obesity (van Marken Lichtenbelt et al., 2009; Bluyssen, 2013).

3.2.3 Sleep quality

The temperature in the bedroom has an impact on sleep quality. There are large personal and cultural variations in preference. Some prefer always to have their bedroom window open and the heating switched off, even in mid-winter, while others prefer the bedroom temperature to be the same as in other rooms of the house. Some prefer thin sheets or blankets, while others prefer a thick duvet.

Surprisingly few studies give a scientific response to this discussion. There is no clear guideline as to what temperature and bedding will give the best sleep quality. What is known is that overheating reduces sleep quality. The bedroom should not be too warm, and it is particularly important that the time at which you fall asleep is not too warm. CIBSE Guide A states that sleep may be impaired above an operative temperature of 24°C (Laverge et al., 2011; CIBSE, 2006).


Bluyssen, P. M. (2009) The Indoor Environment Handbook, RIBA Publishing.
CIBSE Guide A. (2006) Environmental design. Chartered Institution of Building Services Engineers, London.
Laverge, J., Janssens, A. (2011) Physiological and Sensory Human Response to IEQ Indicators While Asleep. Proceedings of Indoor Air 2011, Austin, Texas
Van Marken Lichtenbelt, W. D., Vanhommerig, J. W., Smulders, N. M., Drossaerts, J.M. a F. L., Kemerink, G. J., Bouvy, N. D., Teule, G. J. J. (2009) Cold-activated brown adipose tissue in healthy men. The New England Journal of Medicine, 360(15), 1500–8.