Co-Heat Testing

Coheating testing is a means to determine a ‘real life’ whole-house heat loss rate: this rate is linked to thermal losses through the fabric, plus losses from air-leakage, again through the fabric. It is a means to compare the thermal performance of:

• A newly-built dwelling’s fabric in comparison to calculated predictions (in SAP for example).
• An existing building’s fabric before and after improvement works are undertaken.

This enables meaningful conclusions to be drawn regarding the effectiveness of fabric improvements.

Coheating testing is also a vital component of many Post-Occupancy Evaluations: these best practice checks are increasingly being undertaken to understand whether a building, in its constructed rather than theoretical state, is fit for purpose.

Why Stroma?

Stroma was one of the first commercial testing organisations to undertake coheating tests in the UK, the first of which was completed in February 2009. Subsequently we have been involved in tests on private residences, Technology Strategy Board-funded retrofit projects, and social housing retrofits for commercial clients to evaluate the effect of the improvements undertaken.

The Procedure

This is a measurement of heat loss through the fabric of the building; Therefore, all intended points of ventilation are temporarily sealed prior to commencement of the testing.

The equipment deployed within the tested building includes electric heaters connected via power meters to a thermostat, axial fans to agitate the air, and thermocouples, which are all spaced evenly throughout the property; all of which are connected to a modem enabled data logger. Where required, heat flux sensors for party walls are also installed. To monitor the weather conditions, an external thermocouple, anemometer, and pyranometer are installed externally.

With equipment installed and operating, the thermostats are all set to a temperature (nominally 25°C). The equipment continually records all the readings for temperature (internal/external), energy use, solar irradiance, and wind speeds. The recommended minimum period of monitoring is 7 days, which requires an initial 3 days of set up.

The data collected is used to calculate the thermal coefficient of the building, which encompasses all envelope elements including roof construction, wall construction (incorporating doors and windows), floor construction, etc. The results can be used to prove actual fabric performance and used as a basis to compare dwellings.

Stroma can undertake coheating testing of dwellings and small buildings throughout the UK, providing they have sufficient mains power supplied and will remain unoccupied for the duration of the testing.

For further information about coheating testing and its benefits, please contact Technical Manager, Marc Cowlin at This e-mail address is being protected from spambots. You need JavaScript enabled to view it , or call 0845 621 1111