Thermal Performance In Buildings
Thermal performance of a building refers primarily to how well a building is insulated from the external weather conditions in order to achieve a comfortable temperature internally. This means keeping the internal temperature higher than the external temperature or lower than the external temperature (not a common occurrence in Ireland). The comfortable range of room temperature is 19-22 degrees C.
There are a number of factors that determine the thermal performance of a building. The best known factor is the insulation value of the materials used in the fabric of the building (i.e. floors, walls, roof). This value is known to most of us as the U-Value of the material. The lower the U-Value the better. If the U-Value of a material reached 0 (hypothetical) it would prevent any energy (heat) from being lost.
Other Factors Influencing Thermal Performance
Other factors that influence the thermal performance of a building are air-tightness, cold-bridging, junction details and how the materials are brought together or fitted on site. If a high performing material is poorly fitted its effectiveness can be dramatically reduced. One result of poorly installed insulation is “thermal looping”. A thermal loop is a movement of air driven by warm air rising at one end of the loop, and cool air descending at the other end, creating a constantly moving loop of air.
U- Values are a true reflection of the thermal performance, only when the insulation is fitted correctly. No matter how thick the insulation is or how good the material is, if it isn’t fitted correctly and an air gap is formed then the performance of the structure is drastically affected. Heat flows from a high temperature point to a cold temperature point, and will find the path of least resistance. In a traditional masonry structure where an air gap occurs between the insulation and the cold masonry/block surface, air can circulate from the warm side of the insulation to the cold side. The heat is pouring out at this point.
A number of studies have been carried out in the area of thermal looping and have shown the phenomenon can cause the U-value to be almost twice its calculated value. To prevent thermal looping from occurring 100% contact with the material on the warm side of the Insulation is required for insulation to work effectively. This is more easily achieved with timber-framed systems and insulations that can be more easily tight-fitted.