POE: The Performance Gap

Posted by on Aug 13, 2014 in Post-Occupancy Evaluation | Comments Off on POE: The Performance Gap

This post is part of a series on post occupancy evaluation (POE). Click here for the main article.

The performance gap describes the well-recognised disparity between designed and in-use energy consumption. There is extensive interest in the performance gap right now; see Zero Carbon Hub’s work: http://www.zerocarbonhub.org/current-projects/performance-gap.  There are many examples that show that the performance gap observed when using complex technologies to make a building zero carbon is often greater than when a fabric first approach is used. Conversely, many traditional buildings use less energy in use than they do when simulated (usually because residents live in uncomfortable conditions).

Passivhaus buildings in Europe have demonstrated in-use energy consumption very close to the simulated targets*. This is because the standard assumes a high level of comfort as standard and the assumptions within the calculations better reflect how low energy buildings really behave.

We thought we would put this to the test and identify the performance gap for some of the Passivhaus buildings that we have been involved with.

 

* As pointed out by one of our blog readers, this statement is slightly misleading. The data we were referring to is presented on passipedia for those who can access it. The summary of the data on passipedia states “Different users, even if they live in identically constructed houses, frequently have very different consumptions: deviations of ±50% from the average value are not exceptional.”   A variation of ±50% from the simulated targets could be argued to be quite significant.  However we observed that, although there is variation amongst users in both Passivhaus and non-Passivhaus developments, the data suggests that the variation from the mean is lower in absolute terms in Passivhaus developments. Perhaps our statement above should be amended to ‘Passivhaus buildings in Europe have demonstrated in-use energy consumption close (±6kWh/m2.yr) to the simulated targets’.