Housing Specification Blog

Homes are hotting up

July 31, 2013 Alexandra Blakeman Housing Issues

We’ve had a spell of lovely warm weather. Housing experts are now warning homeowners about the dangers of living in a home that’s too hot.

As a nation we’ve got a little cosy. At the first sign of a breeze, we’re guilty of cranking up the thermostat rather than donning another layer.

The government is making headway towards Zero-Carbon 2016, and thanks to effective insulation and airtightness measures, new builds are only getting hotter.

Which properties are most at risk of overheating?

  • Location: Summer temperatures are generally higher in South East England. Built up neighbourhoods will be at higher risk of overheating as a result of the
    urban heat island effect.
  • Type of properties: Many factors affect the risk of overheating, including built form and orientation. Flats, especially on the top floor, are identified as being at highest risk.
  • Fabric characteristics: Internally insulated homes (especially when heavily occupied during daytime), lightweight constructions, homes with darkly coloured facades, homes with roof lights, and homes with large areas of unshaded glazing.
  • Orientation and exposure: Homes with east or west orientation, homes on streets with less tree cover. East facing windows are especially problematic for daytime occupied dwellings. Although south facing rooms can experience overheating, they are easier to shade from the high angle summer sun.

Aside from the environmental factors, a hotter home can cause skin problems, such as eczema, lethargy, poor concentration, disturbed sleep and fatigue.

An increase in temperature of more than 4° ͨ could more than double bacterial growth rates, leading to higher risks of food poisoning and the spread of germs.

The Department for Communities and Local Government carried out an investigation into overheating homes.

The report emphasised that both MVHR and district heating are becoming more common in new housing. Concerns have been identified over whether they are being operated in a way that may worsen the overheating risks.

Many modern apartments are built with mechanical ventilation with heat recovery, which is mainly intended to reduce winter heating bills through recovering heat from exhaust air and using it to heat the incoming fresh air. MVHR is necessary in dwellings which have been constructed in a very air tight manner and cannot rely on natural ventilation for incoming air.

Effective measures to combat overheating:

Low Cost

  • Fit internal blinds or curtain linings with a solar reflective coating.
  • Apply solar reflective paint to external walls and roofs to reflect the sun. This is particularly effective on older properties, with solid brick walls.
  • Consider installing external wall insulation, instead of internal, because it allows the existing thermal mass to remain exposed.

Low to Medium cost

  • External shading should accompany increased insulation and airtightness measures. Shading should be designed to be seasonally sensitive and/or user controlled (e.g. retractable awnings, shutters). External window shutters are often the most effective single measure for reducing overheating because they block solar radiation and heat gain.
  • Fixed external shading above windows will block solar gains from the higher altitude summer sun, whilst allowing gains from the lower altitude sun in the other seasons for natural daylight.
  • Solar reflective coatings for flat roofs are also effective for top floor flats.


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