Physiological adaptation to heat¶
People adapt to the weather they have recently experienced. ARC prefers the running mean outdoor temperature over a monthly average, because adaptation drops off sharply after about seven days.
People adapt to their local environment in the short term, by adjusting their behaviour and clothing to the outdoor environment they have experienced recently.
Monthly average, or running mean?¶
Some adaptive comfort models reflect this by taking the average mean temperatures in the past month as an indicator of predicted comfort temperatures - the ASHRAE model does this.
However, studies have shown that after only 7 days, human adaptation to changes in outdoor temperatures is significantly reduced.
The running mean is a more accurate indicator. The running mean temperature is an average of the temperatures in the last week, but the model puts more emphasis on more recent days than on earlier days. This is because you are more likely to be affected by the temperatures from yesterday than from six days ago.
This is in line with the European standard method set out in EN 15251.
Which to use
Where localised survey information is available which uses both methods, the running mean figures should be used in preference. The ARC Cool Buildings toolkits build in this preference.
What data you need¶
The tools require the user to input only the hourly outdoor temperatures and the recorded internal temperatures.
To demonstrate building performance using the comfort model it is therefore necessary to have access to measurements of both internal and outdoor humidity and temperature, inside and outside the building.
Ideally:
- internal and external temperature measurements recorded hourly, via data loggers
- loggers placed in permanently shaded spots
- the external logger well shaded and also protected from rain.
If you have no on-site data¶
Where measured data is not available, data from other sources - as local as possible - could be used. For example, publicly available airport weather data, or data from other publicly managed weather stations.
Airport data has limits
An airport is likely to have a different temperature profile from the building and its surroundings, because airports are typically located in open landscapes and may or may not be affected by the urban heat island effect.
Figure not yet included
The source document refers to a figure showing the fall-off in human adaptation after seven days. The chart, and its citation, have not yet been prepared for the wiki.
Source: ARC Technical Criteria - Comfort model - Physiological adaptation to heat
Reference · confidence high · Imported 2026-08-29, not yet reviewed · next review 2026-11-29
Tags: comfort, adaptive-comfort, monitoring, running-mean
Citation key: physiological-adaptation