Practical advice during a heatwave¶
What occupants can actually do when it is dangerously hot - siestas, moving around the building, tepid showers, fans, when to open and close windows, and a solar-backed shelter.
During a heatwave the following advice is recommended.
Siestas¶
Siestas lower your metabolic rate, and therefore you produce less heat.
Changing location¶
Larger houses with courtyards typically have thermal diversity, which means temperatures are different in different parts of the house. Occupants can use this by moving to a cooler area of the building - for example, north-eastern rooms may be cooler during part of the day.
This is one reason the three-zone strategy matters: it builds that diversity in deliberately.
Taking a shower¶
Taking a shower helps cool the body through evaporative cooling.
However, a study showed that this impact is temporary and goes away within 20 minutes. The water must be tepid or lukewarm - cold water causes the body to respond by constricting blood vessels, which works against cooling.
Evaporative cooling¶
Evaporative cooling works in hot dry climates, as it increases the humidity in the air, which lowers the dry bulb temperature.
This only works where there is a difference between wet and dry bulb temperature, and the maximum performance depends on the wet bulb temperature. See measuring thermal comfort.
It is therefore not a useful measure in hot humid climates.
Fans¶
Fans increase air speeds, which aids sweating. See thermal comfort models for the air speed discussion, and for the caution about when fans stop helping.
A key consideration is ensuring the occupant is facing the middle of the fan, as air speeds are significantly lower when the person is not directly in the airstream.
Closing windows and curtains during the day¶
While people in hot climates are used to closing windows and heavy curtains during midday, this adaptive behaviour is not intuitive in milder climates.
Curtains limit the amount of solar gain entering the space. However, ideally you want to stop the solar gain outside the glass - see the external shading measures in designing a heat refuge.
Opening windows overnight and in the evening¶
As temperatures cool down in the evening, it is important to open the windows to allow the thermal mass in the building to release its stored heat.
If this process does not happen, the building will be hotter the next day.
Creating a shelter with batteries and solar panels¶
In many cases, due to power cuts, it is necessary to rely on solar panels to power one space that acts as a shelter. The panel and battery need to be connected to a socket, a light source and a fan.
This is the practical minimum version of the heat refuge.
Source: ARC Technical Criteria - Appendix 1: Heatwave advice
Reference · confidence medium · Imported 2026-08-29, not yet reviewed · next review 2026-11-29
Tags: heatwaves, occupants, behaviour, ventilation, fans
Citation key: heatwave-advice