Keeping Cool in a Heatwave – Controlling your home

Controlled Ventilation:

    • On a hot day: close all doors, windows and vents that let in hot air. These may vary with the time of day and the wind
    • Cool off at night to let you sleep better and cool your whole home before the next hot day, possibly with the help of fans:
      Let hot air out by opening windows or skylights at the top of the house.  An extractor fan may help.   Draw in cool air by opening ground-floor windows or vents where the air is cooler outside. Many windows can be part-opened in secure ways that won’t let a burglar in. For example restrictors like these or these can be fitted to wooden sash windows, letting them only open 100mm when you want.
      If your home is only on one floor, purge the hot air at night by opening windows or vents, to give through-ventilation, if possible.

Avoid unwanted heating from appliances, lighting, etc

    • Choose low-energy appliances & lights: use them only as needed
    • Is your hot water system well insulated?
    • Is your fridge or freezer in a hot place? It will be inefficient and make that place even hotter. Fridges and freezers work best in cool places, although check the user-guides for operating ambient temperatures: a garage may be too cold in the winter.

Thermal Mass from brick, concrete or stone stabilises temperatures. External wall insulation, with the thermal mass of the walls inside, steadies temperature and reduces peaks indoors. Although internal insulation might be better for a west-facing bedroom that you want to cool quickly after the evening sun. You can benefit from the thermal mass of solid floors by covering them with tiles, rather than thick carpets.

Insulate walls and roofs, especially those that get hot in the sun.
In general insulation for winter warmth helps you keep cool in a heatwave too. Reflective, silvery insulation (eg: multifoil) can reduce heat radiating down from a hot roof. Draught-proofing is important too.

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