An infrared heat gun can help you get a thorough understanding of where your home is losing heat in cold weather, or gaining it in hot weather. The more you know about where heat is entering or leaving your house, the more effective you'll be at controlling energy waste.
With an infrared heat detector, you just wander around the inside and outside of your home on a hot summer day or a cold winter evening, and take readings at windows, outside doors, walls, or wherever else heat may leak through. The device helps you get a detailed picture of problems with insulation, sealing, or windows in need of an upgrade.
Professional energy efficiency auditors often use an infrared camera to show you where you're losing or gaining heat, but thermal imaging devices are expensive and the audit itself can cost you more than 0. An infrared point-and-shoot thermometer doesn't provide the same pretty printout, but they sell for about , so they put this level of detail within reach of the average homeowner.
Most infrared point-and-shoot thermometers come with a beam ratio 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. These guns also come with a laser beam so you can see exactly what spot the reading was done from.
I recommend beginning your infrared thermal audit from outside. Standing 12 feet from the wall, take a series of readings with your infrared heat detector to get an idea of what the baseline temperature is. You are looking for the coolest temperature in winter, or the warmest in summer when the AC is running.
Don't take measurements on a wall in sunlight, which can mess up your results. Instead, wait for cloud cover, for evening, or for the sun to move.
Note each measurement on a sketch of the house face or in ordinary notes. Pay particular attention to window temperatures, because windows are major sources of heat leakage in both hot and cold weather. You might benefit from 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 leakage.
Where measurements are considerably worse than your baseline (warmer in winter, colder in summer), take more readings nearby, to locate the extent of the thermal leak. You may have gaps in, or settled insulation, cracks in the wall surface, 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 inside wall as your baseline; exterior wall temperatures should be colder than the baseline in cold weather, or hotter in summer. Again, you are looking for thermal leaks on window panes, around windows and doors, through light fixtures, in cracks in drywall or plaster, or anywhere that is touching an outside wall. Take close-up measurements of any wall outlets or light switches that are close to the exterior, even if they are on an interior wall.
Check the temperatures of upstairs ceilings, as insulation, especially blown in insulation, can get pressed or matted down in leaky attics. For summer measurements, do your ceiling readings twice: once early in the morning before the sun has heated the attic space, and once in the afternoon when the attic is hot, so you can see how much of that heat leaks into your living space.
Chances are that windows without their window coverings are your biggest heat leaks, as even the most efficient windows have a much lower R-value than most walls or ceilings. You can either upgrade old windows with more efficient ones, add thermal curtains or blinds, 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 home. You should seal these as much as possible, as drafts can be big energy leaks. 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 serious problem: settled cellulose 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 the walls have no insulation at all you may just be able to inject foam insulation, which is a cheaper option.
You should consider doing your own mini-audit with your infrared gun first, and ask for contractor estimates later. If you have identified your big thermal leaks, you'll be able to ask each contractor what solutions they recommend to your problem. Inviting a contractor over and just telling them the house gets too cold in winter, or boiling hot in summer, means inviting major repairs that might not help at all.
You can use an infrared heat detector for countless other measurements around the home, such as checking hot water pipe temperature before and after adding pipe wrap; reading 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 cooking temperatures on your stove; or finding the best location in your basement for a wine cellar.
Whatever model infrared gun you choose, you will doubtless get many hours of use out of it, locating the hot spots and cold spots in your walls, floors and ceilings, your garage, your fridge, freezer, your car engine - anywhere you need to know the surface temperature. You can even use it to measure the temperature of your compost pile - without getting your hands dirty!
