Thermal performance of windows by means of thermography and heat-flux meters

The replacement of windows is the most common renovation measure in Finland. There are also problems in new buildings especially with new thin light metal-framed windows, even though the U-value of the pane would be acceptable. The minor defects in the installation may cause LAQ-problems - because of seam leaks and thermal bridges. There is no general procedure for condition survey of windows based on measurements. In this paper a procedure for testing windows in in-situ conditions is presented based on case studies. Thermal performance of windows can be measured using thermography and supporting methods, like heat-flux measurements and air leak tests. Even though the absolute results may include interfering factors, we can compare the windows with each other (depending on the conditions) and make decisions on the quality of the installation work and the thermal performance of windows.