The effect of improving the U-value of a building element can be illustrated by using a thermographic camera to produce a thermogram before and after the improvements.

A thermogram is an image that shows the heat emission from a building. Red indicates areas with warm outside surface temperatures, i.e. much heat is lost. Blue areas are cold areas where less heat is lost.

The top thermogram on the right hand side shows the building before additional insulation was applied to the wall and thus improving the U-value of the wall.

On the lower thermogram it can be observed that a greater part of the building is blue meaning that less heat now is lost. However, there is still room for improvement, e.g. insulating around the cellar of the building.

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Why u-values matter
Understanding u-values