Heat can sometimes leak out of the windows and doors into the outside air. If we take a picture of the house in infrared light we can see just where the heat is leaking out.
The image on this page is called a thermogram. Temperature differences are shown by colors in the picture. Anything that is white, red or yellow is warm. Cool places in the picture are black, pink and dark blue. Light blue and green are in-between warm and cool.
The warmest areas occur where the most heat is leaking out. Did you know that most of the heat that escapes from your house leaks out through large windows and around doors? Click on the picture to see a whole block of houses in infrared light.