Why statistics and square meter method is not usable for comparison energy performance among heterogeneous buildings.
In one brochure from a consultant corporation they say that 50% of all building have an over consumption of 50%. This would give a generic over consumption of energy by 25% in Sweden, calculated as an average .
An simple comparison would give 25% more energy than necessary before anybody reacts. A comparison over all building would focus on older building where change is expensive.
By experience we now that older building often consume 2 times more energy than newer building. But they often have few technical system and their consumptions is in line with what they should consume. Newer building on the other hand often consumes much more energy than they should, because of the amount of dysfunctional technical systems, and to make changes is often both simple and cheap.
If we make a statistical selection among building by age then we risk to concentrate error data into our selection result. We will allow a much higher energy consumption among newer buildings.
To make a statistical selection with any quality we need at least as many parameters as we do in calculations, like climate, facade and window area, installations, user profiles etc.
To compare building with m2 method is extremely uncertain. The result is more depending on climate shell relative floor area than actual energy consumptions. Focus tend to be toward older building where changes are expensive.
A better, cheaper and more reliable way is to calculate for some actual years and compare it with the real consumption.
