Measure Fabric Performance

Removing the assumptions from energy performance assessments



When setting strategies for improving the energy efficiency of housing, landlords face significant problems in identifying the homes that will benefit the most.

Although there is a lot of data available from EPCs and other forms of assessment, confidence in the data is low and there is no objective test that can demonstrate improvement once the works are done.

The Purrmetrix solution tackles this problem. Using energy and environmental data we directly measure the rate of heat loss through a home’s fabric, producing the heat transfer coefficient (the HTC). It’s a non-intrusive, affordable and quick assessment that can be easily incorporated into normal processes such as an EPC or stock condition survey and will produce a result within a few weeks.

These HTC values are a robust measurement of the true thermal performance of a home’s fabric, and are unaffected by occupancy, climate or housing type, so comparisons can be made across large estates. The assessment can also be used before and after works to give a fair measurement of the improvements that have been made.

Data on internal conditions is also useful to confirm that a warm, dry home has been provided for tenants, and to highlight risk factors such as condensation, ventilation or potential overheat, that might need to be managed.

Working with Purrmetrix provides a true benchmark of building performance, at a time when large scale retrofits are putting increasing strain on budgets for upgrading housing stock.

To calculate an HTC figure requires an address, data on energy consumption and internal temperature. Our toolkit is optimised to provide this data for properties with smart meters already installed, or it can be extended to cover most properties with gas or electric heating where smart meters are not yet installed.

For a home with a smart meter the process is straightforward:

STEP 1. Install environmental sensors. Can be done as part of regular survey visit.

STEP 2. Collect data for three weeks.

STEP 3. Web service provides analytics results, as an automated report or, using an API, directly to your management systems.

For a reliable calculation there needs to be a clear difference between internal and external temperature, so HTC calculations are best performed between October and the end of March.

While each calculation requires three weeks of data to provide a robust result, for early deployments we would recommend four weeks, after which the kit can be retrieved from the house and installed in the next home.

For homes without smart meters we can provide kits that include data capture for most standard gas and electricity meters. Please get in touch to discuss this option in more detail.

Find out more on our technology page, or contact us for a demo.


Purrmetrix Pro provides everything a busy professional team needs for precision management of environments:

  • easily deployed, affordable environmental sensors
  • a flexible and scaleable web service to store the data
  • a full suite of specialised analytical tools to turn the data into information
  • reporting and alerts tools
  • export and API facilities

Got a question? Get in touch!