Filippína et al. [54] using stepwise selection and multivariate
analysis evaluate historical consumption of natural gas for heating in multifamily buildings. Data
from 72 apartments belonging to different buildings, with different orientations and levels were
used to generate 14 energy classes (clusters). The stepwise method applied by the authors allowed
them to select the useful area, volume, envelope area, envelope area/useful area, envelope area/
volume, passive zone area, volumetric heat loss coefficient, and weighted mean internal
surface temperature as the variables
categorizing the annual energy consumption.