Glossary
Designing a certified passive building

U-value

This is the thermal transmittance coefficient (also known as the thermal insulation coefficient). It is expressed in W/(m²K) and determines the heat loss (expressed in Watt) through a surface (expressed in m²) as a function of the temperature difference (expressed in Kelvin) on either side of it.

Thermal phase shift

This is the phenomenon that occurs in summer, when the building accumulates heat and then releases it diffusely inside the building, with a more or less significant time lag depending on its thermal inertia. The phase shift represents the time lag between the peak outdoor temperature and the peak temperature inside the building. It is therefore considered an asset for summer comfort, as it delays heat transfer through the building's walls during the day.

Grey energy

Grey energy is the amount of energy consumed during the...