#032 - U-VALUE

The U-value is a measure of heat loss in a building element such as a wall, floor or roof. The higher the U-value the worse the thermal performance of the building envelope is. According to Passive House Design standards all elements of the external envelope of the building should combine to provide a U-value of not more than 0.15 W/(m2K).

In order to calculate the U-value we should know the build-up materials of the building element, their conductivity properties and thickness.

For instance, a 200mm brick wall have high conductivity and facilitate the passage of heat/cold, on the contrary a 100mm insulation panel, usually installed within the cavity of the external walls, has low conductivity and slowly release the heat/cold .

This is why a contemporary insulated house is more energy efficient of a Victorian house. Mr D. Tail is definitely feeling more comfortable in a well-insulated house with a low U-value building envelop.