Overheating

Welsh Government

Temperatures inside of free running dwellings are heavily influenced by the outside air temperature. Therefore, rising outside temperatures associated with climate change may lead to a risk of internal temperatures that exceed acceptable levels. Overheating in dwellings can lead to issues for occupants ranging from thermal discomfort, to heat stress, to more severe heat related illnesses. While the temperature threshold associated with overheating may vary by person and dwelling, it is defined here as 26°C and reported the percent of hours during the 41-day summertime study period that exceed this temperature. For reference, the Static Criteria within the Chartered Institution of Building Services Engineers (CIBSE) Technical Memoranda 59 (TM59) states that occupied rooms shall not exceed 26°C for more than 3% of annual occupied hours.

Results are presented for the average building along with 11 building classes: three age-based classes (Pre 1919, 1919-1990, Post 1990), three wall-material-based classes (Timber frame, Solid – Stone, Solid – Brick & Cavity), three construction-style-based classes (End Terrace & Mid Terrace & Semi Detached, Detached, Flat), a class for Internal Wall Insulation (IWI) and a class for Double glazing in pre-1919 properties.

Additional information is available here: Wales Housing Climate Analysis Additional Information

Accompanying maps in this series can be found here:

Climate Projections consisting of Daily Maximum Temperature, Annual Precipitation, Daily Relative Humidity and Daily Specific Humidity

Indoor Conditions results consisting of Indoor Air Quality and Overheating

Building Fabric degradation results consisting of Solar Insolation, Precipitation and Relative Humidity 

Case Studies for four representative towns and cities illustrate results at a resolution of 2.2 km, giving insight into the variation that is projected geographically across each area:

Aberystwyth consisting of Climate, Indoor and Fabric

Cardiff consisting of Climate, Indoor and Fabric

Swansea consisting of Climate, Indoor and Fabric

Wrexham consisting of Climate, Indoor and Fabric

For a better understanding of the impact of summertime overheating on houses that have been highly insulated and suggestions on approaches to tackling them go to: Considering summertime overheating in highly insulated homes: factsheet | GOV.WALES

For a better understanding of the impact of summertime overheating on post 1985 properties (including older buildings converted into flats) and suggestions on approaches to tackling them go to: Considering summertime overheating in post 1985 properties (including older buildings converted into flats): factsheet | GOV.WALES

For a better understanding of the impact of summertime relative humidity in older properties and suggestions on approaches to tackling them go to: Considering summertime relative humidity in older properties: factsheet | GOV.WALES

For a better understanding of the maintenance, repair and adaptation priorities of older, traditional properties under a changing climate, go to: Considering repair, maintenance and adaptation priorities for older properties: factsheet | GOV.WALES

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