Draft. These pages were imported from the ARC Technical Criteria document (16 April 2026) and have not yet been reviewed in this format. Several thresholds are still being settled and are flagged on the pages concerned.

Designing a heat refuge

The passive measures that keep a heat refuge below its limit when the power is off: orientation, shading, reflective surfaces, heat-shedding roofs and window openings.

The Heat Refuge is a cooler, sheltered space which building occupants are able to use for extended periods during heatwaves, and which stays below certain temperature limits even when electrical mains power cuts out. The Heat Refuge may be a single space or may be a zone including several rooms in a building.

• Designers and builders must ensure that during extreme heat events the Heat Refuge remains below 32-35oC through passive (non-mechanical) design measures
• Orientation – to minimise the amount of time direct sun heats the walls, roofs and floors and external surroundings. Typically, this involves aligning the longest /largest external faces of the building to face north and south (in hot climates the sun is higher in the sky to the north and/or south during the day) and aligning the narrow/smallest faces of the building to face east and west (the sun is lower in the sky to the east and west, and more sunlight falls on east and west facing walls and windows. Good solar orientation of a building is an extremely effective way to reduce the amount of heat from the sun from getting into a building.
• Shading to walls and windows include
  • extending the roof edges to extensively shade walls and windows and even shade external ground areas around the building is highly effective at keeping buildings cool.
  • Adding lean-to or canopy roofs against walls
  • Tops and side of windows can be shaded using various features fixed to the walls
  • ventilated window shutters (on the outside of the window)
  • ventilated shading louvres within the window opening
  • externally positioned perforated security screens (Mashrabiya)
• Reflective surfaces – brilliant white (the most reflective) or paler colours help reflect the suns heat away from the building’s roof and walls. This is particularly important where there is no ceiling in the room, and occupants are exposed to the radiant heat coming off metal roof sheets. It also works well to reduce heat being radiated onto (and through) any e.g. plasterboard or concrete ceilings below. Keeping ceilings cooler is important.
• Heat shedding roofs – heat builds up quickly in enclosed roof spaces, - if the hot air cannot escape from the roof space it transfers its heat to the ceiling materials, making the ceilings hotter. Heat is then radiated from the ceilings onto the occupants below. Provide ventilation to the roof space at the eaves, allowing cooler air in, and have dedicated areas that let the hot air out of the roof towards the top of the roof, also designed to keep the rain out.
• Use the window openings to provide air movement for cooling breezes. Make sure window openings are large enough to allow a high level of air movement. Ventilated shutters, louvres or venetian blinds can be used to increase or decrease how much air passes through a window – i.e. air movement can be controlled by the occupants. The important thing is to avoid sizing the openings to be too small in the first place, and to make sure they are placed on opposing walls of the space, or at least on adjacent walls – rooms with a single window should be avoided. This also requires windows to be placed carefully, to provide cross-ventilation - ideally openings of equal size on opposing sides of spaces to allow the free flow of air across the space. If the space is to be sub-divided with an internal wall, consider making the partition ‘perforated’ to avoid blocking air movement from the window thereby improving cooling cross ventilation. Lowering the window cills of windows provides better cooling by allowing air to pass across more of the body area of occupants, standing, sitting or lying inside on windows also works well. Creating openings in ceilings ‘to let hot air rise out of the room’ is not generally considered to be very effective in domestic buildings and may allow more heat into the space than it lets out – treat this potential passive measure as ‘experimental’ at this time.
• Draughtproof glazed windows for when air conditioning is turned on - inward-opening casement windows or glazed bifold patio-doors will be needed for the operation of the Heat Refuge in two modes – natural ventilation mode and air conditioning mode. In natural ventilation mode, the casements are open, to allow for full opening of the window area for effective cross ventilation. Fitting an insect mesh screen across the window opening is necessary for areas with mosquitoes. This typically reduces airspeed (the critical factor for cooling the body is the speed of the air movement) through the window by about 50%. The glass areas of sliding type glazed windows typically occupy 50% of the opening area of the window and the insect mesh areas of these windows slow air movement by 50% - so the reduced distribution of cooling breeze across occupants’ bodies when using sliding type glazed windows needs to be considered carefully by designers and builder.
• powered fan(s)
• lighting
• power socket(s)
• If an adequate mains power supply is available, this space should also be fitted with mechanical cooling, but passive measures must be favoured to anticipate maintaining cool temperatures during power cuts.

The reason for installing air conditioning in the Heat Refuge is that in places where power cuts are anticipated or even scheduled, occupants can pre-cool a room with the air conditioner and rely on the good design of the space to preserve that coolth for as long as possible during the power cut.

For a room (or rooms) in a hot dry climate with adequately cool nights, this means that well shaded, high thermal mass, cooled at night by natural ventilation via large openings is important.

In a hot humid climate, the room (or rooms) should be provided with the following features

• Additional wall, floor and/or ceiling insulation - to preserve the coolth.

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Source: ARC Technical Criteria - 227
Pattern · confidence medium · Imported 2026-09-12, not yet reviewed · next review 2026-12-12
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Citation key: heat-refuge-design