If you're looking to save energy in construction, you should become familiar with the following concepts. They are included in the building energy certificate and will appear again and again over the course of planning: Annual primary energy demand (QP) This is how much energy a house needs annually, from energy production to heat generation. End-of-year energy demand (QE) You should procure this amount of energy annually - for instance in the form of heating oil, gas or pellets. Annual heating demand (QH) Your house needs this amount of energy while heating, in order to maintain the normal inside temperature. Transmitted heat loss (H't) You can take into consideration the heat loss through exterior surfaces (wall, roof and floors on the ground).