Building Diagnostics and Infrared Cameras

Infrared photography for thermal analysis has changed dramatically in the last thirty years.  The cost of the cameras has dropped to the point where just about anyone can buy one.  But that doesn’t mean that anyone can understand the information they are providing.  I know someone who uses his infrared camera to find his dog when he lets him out at night!

Most of the infrared cameras come with an adjustable palette.  When I am using the camera for diagnostics, I use the Door leaksblack and white palette because it allows me to quickly identify areas that are colder or hotter than they should be, places where air is leaking in.  These spots are amplified if I am running a blower door at the same time; the air is steaming in, streaking the wall with cold fingers.  That quickly tells me where the weather stripping or the air sealing should be improved.  Note that the difference in color is only a difference in temperature.  It may only be a small difference.  When an infrared camera is used for electronic or mechanical equipment diagnostic, the actual temperature is important.  In diagnosing a house, the difference in temperature not the actual temperature     is tAttic Hatchhe important element.

This image is an uninsulated attic hatch.  It is clear that the insulation level of hatch is different than the insulation level surrounding it.  But unless we look at the temperature scale and know the temperature of the attic, we don’t know if the hatch insulation is R1 or R30.  Looking at the temperature scale, the hottest point in this image (right around the edge of the hatch) is 75 degrees F and the coldest point on the ceiling is 68 degrees F.  The colors make it look much more extreme.  When you are using an infrared with a customer, the color palette is a great sales tool.  And people use them to sell all sorts of things that may or may not be there.

Attic StairsOr look at these attic stairs.  These stairs had cellulose insulation blown in around them and the temperatures are pretty even.  The temperature in the hottest spots (those little white areas at the corners of the steps) is 54.9 degrees F and temperature in the black areas is 46.3 degrees F.

I have tested ducts in houses where the sheetrockers sheetrocked right over the top of one of the supply registers.  The infrared camera made it easy to find when I cranked up the heat and that part of the wall glowed in an attractive, rectangular pattern!  Or if you are thinking of cutting into a wall, you may be able to see where the pipes are before you cut the wall (and the pipes) open.

Infrared cameras do not xray the wall.  They only show you surface temperature and the surface temperature can be changed by external elements particularly the sun.  One house I worked on had a window beside a slider.  The amount of solar gain passing through a window is rated as SHGC (Solar Heat Gain Coefficient).  The window had an SHGC of 0.32 and the door had an SHGC of 0.27.  The sun was pouring through the glass and warming the hardwood floor.  It was easy to see the difference in temperature  with the infrared.  I wouldn’t have known what the SHGC number was without the sticker on the glass, but I could certainly tell that they were different with the camera.

Infrared cameras are wondrous tools, but until you clearly understand them and know how to use them, the information they provide is interesting but not definitive.


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