Thermal imaging is the best way to detect if the insulation around windows and doors is sufficient. It also detects if any heat loss is happening through the window and door itself.
What a thermal imaging camera is essentially a heat sensor that is capable of detecting tiny differences in temperature.
The infrared radiation from objects is collected by the camera and creates an electronic image based the temperature differences.
This infrared radiation is not normally visible by the naked eye. KC Window & Door uses the camera's to find many defects in gaps/voids in insulation, leaking weatherstrip, or improper seals around windows and doors. The scan can also show heat loss through surrounding walls to even water damage behind walls and/or the origin of water leaking from the outside to the interior of the home.
The images below show the temperatures difference. The lighter the color, the warmer temperature. Purple to Black show improper insulation and significant heat loss.