Building energy performance: Sphere area as a fair normalization concept

Residential building energy performance indicators are compared with a different approach for the normalization of the characteristic yearly primary energy use. The purpose is to analyse which approach results in a fair assessment of more compact, energy-efficient building geometries, and of smaller building size. A normalization by floor area is shown to result in a poorer energy performance rating for smaller buildings. The notional building approach, as recently introduced in various countries, does not lead to a fair assessment of efficient geometries. Furthermore, the choice of reference characteristics to calculate the energy performance rating has a different impact on buildings with different characteristics. An average building approach is introduced as an improvement of the notional building approach. Form-efficient buildings are found to achieve a lower energy performance rating, but the choice of the reference characteristics is still present to a limited extent. As a second alternative, it is proposed to normalize the energy use by the sphere-area approach: the area of a sphere with the same volume as the rated building. This method leads to a fair assessment of form-efficient buildings and creates an incentive for more efficient building geometries and typologies.