Thermal Bridge Assessment
Simply put, a thermal bridge is a highway that lets heat out of a building in winter and attracts heat gain in the summer. Thermal bridges are generally caused by junctions between the wall and the floor, junctions between the wall and the roof, holes in the building envelope for pipes and cables, window and door reveals and steel wall ties used in masonry construction.
Thermal bridges can broadly be classified into three:
Repeating Thermal Bridges: these are common and predictable bridges that follow a pattern and are repeated over an entire of a building’s thermal envelope. An example is ceiling joists in cold pitched roofs when insulating at ceiling level.
Non-repeating Thermal Bridges: these bridges are the opposite of repeated thermal bridges. They are usually found where there is a break in continuity of a building’s thermal envelope or where materials with different thermal conductivity meet and they occur periodically. An example is reveals around doors and windows.
Geometrical Thermal Bridges: these bridges are caused by the geometry of the building. The more compact a building is, the less chance there is for a thermal bridge to be created. In other words, more corners in a building’s geometry means more chances of thermal bridges at the wall to floor junctions, wall to roof junctions and junctions between adjacent walls.
The effect of a thermal bridge is mostly felt in a well-insulated and air tight building because when these highways are present, the positive effects of the building’s insulation and air tightness are negated.
How to Avoid Thermal Bridges
The best and easiest way to avoid thermal bridges is to minimize them as best as possible through proper planning, design and construction and by achieving a thermal bridge coefficient of less than 0.01/W(mK).
To achieve a thermal bridge free design, it is crucial to only engage people that understand the importance of a thermal bridge free construction and are properly trained in that area.