Infrared Building Inspections

Infrared Building Inspections
This article is provided courtesy of Snell Infrared,
a thermographic training company.

When winter approaches you should consider checking the performance of the buildings you live in or work in. The comfort problems that often plague buildings are usually caused by missing insulation or excessive air leakage. Too often comfort problems are "solved" by adding extra heat -- the long term cost of which can be astronomical.

Buildings are insulated to control conductive losses or gains of thermal energy. When the proper levels are installed correctly, heat transfer by conduction is minimized and you are comfortable. Typically about half the energy used to condition a building is controlled by the insulation.

Missing or damaged insulation is easily located with a thermal imaging system when there is approximately a 20°F (11°C) temperature difference from inside to outside. To minimize the effects of the sun, especially on south and west facing walls, this work is best done at night or on cloudy days. Don't forget the sun can continue to influence a building 6-8 hours after sunset. It is also common to find insulated walls that appear uninsulated. The culprit is air moving through the insulation, degrading its performance.

Air leakage is the other major component of a building's energy use. While some air exchange is essential for a healthy building, too much is costly. We compensate for decreased comfort by turning up the thermostat. Air leakage is a major problem in commercial buildings, often leading to frozen water pipes in cold climates. Air leakage may also result in moisture damage to the insulation which further degrades the performance of the building.

Typically air leakage is not effectively controlled with insulation. Several other important strategies are often used including sealing and pressure balancing of the air systems and air sealing of the thermal envelope of the building.

Viewing air leakage can be tricky, because you are not seeing the air. You are seeing the effects of the air flow. Air moves in buildings due to pressure differences.Warm air escapes out the top of the building. It is replaced by cold air coming in the bottom. This pressure driven movement is called a "stack effect" because the building essentially acts like a chimney. Air leakage can show up in a thermal image with a 5-10°F (3-6°C) temperature difference from inside to outside. To see the effects of cold air infiltration look from inside on lower floors. Go outside and look at the upper portions to see the effects of warm air exfiltration.

You can also simplify and enhance air leakage patterns by using a blower door fan or another means of creating an artificial pressure difference. It is not unusual to find air moving great distances through floor, ceiling, and wall cavities before you can actually feel it enter a room. Two common sites for air leakage are around the sewer vent pipe and in wiring chases. Once you have located problems, whether related to conduction or air leakage, the next task is finding solutions. Those may be complex, or they may be as simple as installing a few dollars worth of caulk or adding another layer of insulation. Regardless, it is vital to recheck the building again after the work is completed to make sure the problem was really solved. When you do hit on the right solution, you should be able to see it working. You will probably also feel it in your pocketbook as well as increased comfort levels.