When we talk about insulating buildings, the focus is often on the U-value. This is essentially the sum of the thermal resistance of all the layers that make up a construction, providing an estimate for how it will prevent heat loss. Whilst U-value calculations take into account a number of factors, one aspect of heat loss they don’t consider is so-called linear and geometric thermal bridges. These occur around openings such as windows and doors, or at junctions between the different building elements – providing a path of least resistance for heat to escape. In practice, thermal bridges can account for a significant amount of heat loss from a property, particularly where the construction elements are insulated to a high level, so it is important to carefully address them.
Learn more about thermal bridging.
To determine how well a designed junction can prevent heat loss, we have to carry out additional calculations to generate what are known as Psi-values and Y-values.
