An infrared heat detector can give you a thorough understanding of where your home is losing heat in winter, or gaining it in summer. The more you know about where heat is entering or leaving your home, the more effective you’ll be at controlling energy waste.
With an infrared gun, you just wander around the inside and outside of your house on a hot summer day or a cold winter evening, and point and shoot at windows, outside doors, walls, or wherever else heat may leak through. The detector quickly gives you a complete picture of problems with insulation, sealing, or windows in need of replacement.
Professional home energy auditors often use infrared imaging to show you where you’re gaining or losing heat, but thermal imaging devices are expensive and the audit itself can cost you over $200. An infrared point-and-shoot thermometer doesn’t provide the same pretty graphic printout, but they sell for about $50, so they put this detailed information within reach of the average homeowner.
Most infrared guns come with a beam angle of 1:12, which means that if you point the gun at a wall 12 feet away, then take a reading, you’ll get a reading for a one square foot section of the wall. They also have a laser beam so you can see exactly what spot the reading was done from.
I suggest starting your thermal leak audit from outside. Standing 12 feet back, take repeated measurements with your infrared gun to get an idea of what the reference temperature is. You are looking for the coldest reading in winter, or the warmest in summer when the AC is running.
Don’t take readings on a sunlit wall, because it can skew your results. Rather, wait for overcast weather, for evening, or for the sun to move.
Note each measurement on a sketch of the wall or in note form. Pay particular attention to window temperatures, because windows are big areas of thermal leakage in both hot and cold weather. You may want an inside helper to close shades and curtains after your first reading so you can then note the impact of these window coverings on stopping thermal leaks.
Where readings are much worse than your baseline (hotter in winter, colder in hot weather), take more readings nearby, to locate the extent of the thermal leak. You may have missing or settled insulation, cracks or even holes in the wall, or a gap in a window or door.
Next do an indoor thermal audit of the exterior walls, floor, and ceiling of each room. Choose an interior wall as your reference temperature; exterior wall readings should be cooler than the reference in cold weather, or warmer in hot weather. Again, you are looking for thermal leaks on window panes, around windows and doors, through ceiling light fixtures, in cracks in drywall or plaster, or anywhere that is touching an exterior wall. Take close-up readings of any wall outlets or light switches that are close to the exterior, even if they are on an inside wall.
Take readings of top floor ceilings, as insulation, especially blown in insulation, can get disturbed or matted down in leaky attics. For hot weather readings, do your ceiling readings twice: once in the early morning before the sun has warmed the attic space, and once in the afternoon when the attic is hot, so you can determine how much of that heat leaks into your living space.
You will probably find that windows without their window coverings are your biggest heat leaks, as even the most efficient windows have a much lower thermal barrier capability than walls or ceilings. You can either replace old windows with more efficient ones, add thermal curtains or shades, or apply thermal barrier window film to the window pane itself.
You will also probably find drafts in walls, particularly at light fixtures or where wires or pipes enter the house. You want to seal these as best you can, as drafts can be major contributors to home energy costs. Caulk around the edges of window frames; use wall outlet insulating foam to prevent air from flowing through the outlets. Your bricks may need tuck pointing, or you may have a more severe problem: settled blown-in insulation between wall studs, in which case the only remedy is to gut the room from within and put in new insulation and drywall. If you have no insulation whatsoever you at least have the option to inject foam insulation, which is a cheaper option.
It makes a lot of sense to do your own mini-audit with your infrared heat detector first, and ask for contractor estimates later. If you know where your thermal leaks are, you’ll be able to ask each contractor what approach they recommend for your situation. Calling a contractor over and just telling them the house gets too cold in winter, or too hot in hot weather, means inviting major repairs that might not do any good.
You can use an infrared heat detector for countless other measurements around the house, such as checking hot water pipe temperature before and after adding pipe wrap; measuring the temperature coming out of forced air registers and going into the air return register, if you have central AC, to gauge air conditioner efficiency; measuring frying temperatures on your stove; or finding the ideal location in your basement for a wine cellar.
Whatever model infrared point-and-shoot thermometer you choose, you are sure to get many hours of use out of it, locating the hotspots and cold spots in your walls, floors and ceilings, your garage, your fridge, freezer, your car engine – anywhere you want to know the surface temperature. You can even use it to measure the temperature of your compost heap – without getting your hands dirty!
