What is a thermal bridge when its at home?
Heat makes its way from inside to outside following the path of least resistance. These paths, where heat flows faster than through surrounding material, are known as thermal bridges.
THERM is a computer program developed at Lawrence Berkeley National Laboratory (LBNL) used for modelling two-dimensional heat-transfer effects in building components, particularly at junctions or anywhere where a thermal bridge occurs. A thermal bridge is an area within a building which has a significantly higher heat transfer than the surrounding materials resulting in an overall increase in heat loss (and therefore an increase in energy consumption) and lower surface temperatures (which can result in problems such as condensation).
In Passive House design, the maximum allowable difference in heat loss between a thermal bridge and the surrounding insulation is 0.01 W/mK. This value is called a psi value. Thermal bridges, if not anticipated and ‘designed-out’, can significantly increase the energy consumption in low energy buildings.
THERM gives us insights into surface temperature and heat flow and allows us to optimise construction details. It also helps us to predict problems such as condensation, mould growth, moisture damage, and structural degradation.