Energy Performance Certificates: An Alternative Approach


Energy Performance Certificates (EPCs) are deeply flawed and do not present an accurate or useful picture of building energy efficiency to buyers and tenants.

This is the conclusion of the latest Common Weal Policy Paper produced by Dr Keith Baker and Dr Ron Mould of the Common Weal Energy Working Group. The paper can be downloaded in full here.

The paper defends the objectives of the EPC framework as it is extremely important that buildings are built and maintained to as high an energy efficiency standard as possible and prospective buyers and tenants should have an easy to understand baseline of comparison between properties so that they can make the best decision about their buying choices and price offers as possible.

The current framework – introduced by the EU in 2007 – is based on analytical and statistical models about the energy efficiency performance of the various materials that go into the construction of the building in question. This modelling will essentially score various components of the building based on previously tested thermal efficiency characteristics. Under this regime, a set of double-glazed windows would be given a higher score than a set of single-glazed windows and a certain type of wall insulation of a given thickness might be given a different score from a different type of wall insulation of a different thickness.

This procedure comes with significant drawbacks. If the thermal characteristics of a material are not on record, then the score must be approximated using a similar (but unlikely to be identical) material. The thermal efficiency of a material may also be affected by real-world factors such as quality of installation (a window becomes significantly less efficient if it is installed badly and the frame leaks air and heat) and changes with the seasons, temperature and other factors not easily replicable in the testing facilities. Real-world occupational use of the building (how much energy one uses, at what time and in which rooms) can also influence the actual outcome compared to the models. It also goes almost without saying that the age of a building will cause energy efficiency to change with time, usually downwards, and that repairs, maintenance and upgrades can affect scores as well in ways that may not always be captured by the current system.

A much more effective method of calculating the energy efficiency of buildings will be to adopt an alternative framework based on directly measuring the thermal losses of the building in operation at intervals such as one year post-construction, 3-5 years post-construction and then prior to any sale of the building. Scotland could introduce this measure now as a mandatory assessment in public procurement and recommend it as a voluntary measure for the private sector.

Replacing the use of abstract models with real world data will allow buyers to make more informed decisions about the properties they are interested in and gives occupiers the potential of making changes to their behaviour to maximise the energy efficiency potential of their home and minimise their energy bills.