Carl Brahe
Clever adaptation of infrared technology allows home and business owners to identify places where air leaks or poor insulation waste energy. Infrared thermometers have been available for a few years at prices that make them affordable for the average home owner. By adding an LED light and threshold meter to the IR thermometer it’s easy for a person with no training to find small changes in temperature around doors, widows, walls, floors and ceilings. This tool, called a Thermal Leak Detector, can pay for itself quickly in increased comfort and energy savings.
I found one made by Black and Decker on Ebay for $39.99 including shipping. Sears has them for slightly more. I also found them online for as much as $99. Energy savings from repair and upgrades made as a result of using this tool can make up the price in a very short time. A small air leak in a door, or window, may not waste a lot of energy, but a small air leak in all your windows, doors, walls, ceilings and floors can add up. They can have a combined leak the size of a large hole in the wall.
When you turn on the leak detector it sets the threshold temperature according to where you point it. You might point it at a door near the edge to set the threshold. Bring it very close to the gap between a door and frame to determine where the temperature changes. The tool measures the surface temperature of an area whose size is determined by how far away you hold it. If you hold it 1 inch away it will measure a .16” area. If you hold it 1’ away it will measure a circle 2” in diameter.
Set the threshold temperature by pointing the tool at a surface that represents the temperature that the area you are examining would be if it were performing well. If you are examining a door frame point at the frame a couple inches from the edge holding the tool a couple inches away and turn it on. The temperature of the frame in this spot will appear in the display. This is the reference temperature (threshold temperature). A scan temperature is also displayed when you point the tools somewhere else. When the temperature increases above the level you set the light that is projected where you point the tool will turn red. If the temperature drops more than the temperature change setting the light turns blue. The temperature change is also called delta T. This can be set to change the light color at 1°, 5° and 10°F.
After setting the reference temperature to the temperature of the door frame and the Delta T to 1°F, bring the tool about an inch away from the gap between the door and frame. Scan the gap and notice what happens. The temperature will naturally be warmer at the top of the door than at the bottom. Hot air rises. You may notice a spot where the temperature fluctuates more than at other spots. This is a likely air leak. If the temperature rises slightly, but consistently, the door is probably well sealed. Places where the temperature changes suddenly indicate failed weather stripping that probably needs replacement.
You can use the same procedure on windows outlets, switches, junctions of walls with walls, ceilings or floors. You may find that trim at floor and wall junctions need to be removed so the gaps behind can be sealed with caulk, foam or other sealants. Outlets and switches may be sealed with foam gaskets and outlet plugs.
Did you ever suspect that the builder left out insulation? This tool can help you identify places where there is no insulation. Set the reference temperature by pointing at any spot on the wall, floor or ceiling you are examining. Scan the surface slowly from about 2’ away. If the light color suddenly changes and then changes back to green as you continue to scan, this may be an area with less insulation that the area around it. The IR image shows where insulation was left out of the ceiling during construction. This same area can be outlined by the color changes using the thermal leak detector. Color changes that last for only inches of the scan may be things like screws or nails, metal hangers or junction boxes or other objects. It may also indicate small gaps in the insulation. Temperature anomalies may indicate air leaks, inadequate insulation, moisture or other defects.
Color changes may be caused by moisture in building materials. Areas where water has penetrated and wet building materials tend to be non-uniform in shape. In the first IR image the area in question is perfectly rectangular. It’s not likely that water would make this kind of shape. Water soaks in shape more like the image below.
Infrared waves pass through glass and change to ultraviolet. For this reason you can’t measure the surface temperature of glass. The thermal leak detector manual claims that when you point their tool at glass it will return the surface temperature. It will actually measure the reflected IR, or the temperature or objected reflected by the glass. If you want to measure the surface temperature of reflective surfaces stick a piece of electrical tape on it. The temperature of the tape will be the actual temperature of the surface.
For most people a thermal leak detector can bring substantial energy savings where a whole house pressure test or IR scan is prohibited by cost or availability. An afternoon armed with this tool, some weatherstripping, caulk and foam insulation will leave your home or business more comfortable and energy efficient. It may also save you hundreds of dollars in heating and cooling costs.