THE BIG IMPACT OF IMPROVING SMALL THERMAL WEAK SPOTS IN BUILDING ENCLOSURES By Stephen Hunter, P.Tech.(Eng.) Stephen Hunter is a building envelope specialist at Sense Engineering in Calgary. He provides building envelope engineering services for new and existing buildings.
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hermal weak spots in a building enclosure can contribute significantly to heat loss and gain, even if they make up a relatively small area. Improving those weak spots can thus substantially improve thermal performance overall.
Multiplying the U-Values of each assembly by their respective areas in m2 and summing the results gives the total thermal transmission through the enclosure per degree temperature difference in W/K, not including that associated with air infiltration and solar heat gain.
The U-Value of a building enclosure assembly is expressed in watts per square meter-Kelvin (W/m2∙K) and represents the heat flow through a 1m2 area for each degree Kelvin in temperature difference across it. Well insulated assemblies have low U-Values, while poorly insulated assemblies have high U-Values.
Consequently, the amount of thermal transmission contributed to the total by an assembly or component is determined by both its area and U-Value. If the U-Value is sufficiently high it can contribute substantially to total thermal transmission through the enclosure, even if it makes up a relatively small area.
Figure 1: Rendering of the example building.
38 AN ABECN/ABECS PUBLICATION
Figure 1: Rendering of the example building.