A Cheap Infrared Laser Thermometer Makes a Great Thermal Leak Detector...

Infrared laser thermometers are great, affordable gadgets for finding draughts and thermal leaks in buildings.

They come in several forms:

Laser thermometers for cooking (checking temperatures of hot plates and food)
Non-contact thermometers for medical use (checking temperatures of various body parts)
Infrared thermometers for automotive use (checking temperatures of engine, coolant, A/C, exhaust etc.)
Multipurpose IR laser thermometers (see our recommendations)

Infrared Laser Thermometer from Black & Decker (the TLD100)

But we are mainly interested in using IR thermometers to find draughts and thermal leaks, as fixing these sources of heat loss is one of the easiest ways to reduce a building's heating energy consumption.

A non-contact infrared thermometer with a laser pointer is an affordable alternative to a thermal imaging camera (the ultimate tool for visualizing heat escaping from a building). Whilst thermal imaging cameras cost well over a thousand dollars, expensive even for a professional energy auditor, you can pick up a handheld IR thermometer for much less money...

For example, the excellent Black & Decker TLD100 costs under $50 at Amazon...

These laser thermometers don't give you a live colour-coded video of the building's heat loss, but they do make it much easier to find out where heat is escaping.

Recommended for Buildings: The Black & Decker TLD100 Thermal Leak Detector

There are lots of affordable multipurpose infrared laser thermometers (see our recommendations), but the TLD100 has a multi-coloured laser sighting that gives it a big advantage for the specific task of finding thermal leaks:

Point it at something cold and the laser shines blue...
Point it at something hot and the laser shines red...
Point it at something room temperature (the approximate temperature you want your walls to be at) and the laser shines green.

You can find out where heat is escaping by pointing the Black & Decker at the wall and looking at the colour of the laser beam. You don't have to keep checking the digital display. The multi-coloured laser is a simple enhancement, but it makes a big difference when you're hunting for draughts and other thermal leaks.

Take a look at the advert below to see how the TLD100 works (and the smile it puts on the face of the guy using it...):

Where to buy a TLD100 Thermal Leak Detector

Amazon's prices on the TLD100 are the most competitive that we've seen, and they don't have any hidden shipping charges. Check the current price of the TLD100 on Amazon, and take a look at the highly-favourable user reviews at the same time.

Multipurpose infrared laser thermometers

For detecting thermal leaks in a building we like the TLD100 for its multi-coloured laser pointer, but there are plenty of other affordable infrared laser thermometers on the market.

Technical specs to consider when buying an IR thermometer

Temperature range – how high and low can it measure?
Distance-to-spot ratio – how focused is the field of measurement? A 1:1 ratio is bad – you have to hold the thermometer really close to the point you want to measure the temperature of. But a 10:1 ratio is much better: if you hold the thermometer 10 inches away from the wall, you will be measuring the temperature of a 1-inch-diameter circle around the laser dot.
Accuracy – how accurate are the temperature readings? Bear in mind that the accuracy depends on the temperature of whatever you're measuring – typically the accuracy gets worse at high or low temperatures. Quoted accuracy figures often refer to the accuracy within a specific temperature range (not across the entire temperature range covered), so take care when comparing the specs of different models. Also remember that, just because the screen displays the temperature to the nearest 0.1 degrees, that doesn't mean that the reading is accurate to within 0.1 degrees (hint: it probably isn't).

Recommended budget multipurpose models

We think that the following three models are all great budget choices. They all have laser targeting, good temperature ranges, a choice of Celsius and Fahrenheit, comparable levels of accuracy, and lots of great user reviews on Amazon.

Kintrex IRT0421 Non-Contact Infrared Thermometer with Laser Targeting – a temperature range of −60C to 500C, or −76F to 932F, and a 12:1 distance-to-spot ratio.
Mastercool MSC52224A Infrared Thermometer – a temperature range of −50C to 500C, or −58F to 932F, and a 12:1 distance-to-spot ratio (last time we looked Amazon erroneously listed the distance-to-spot ratio as being 2:1, but that's a typo). Interestingly a gentleman in the Amazon reviews mentions that this particular model is a "a valuable tool for paranormal investigating", though we've no reason to believe that it's any better or worse for this task than other similar models... Admittedly we don't know a lot about paranormal investigating...
Raytek MT6 MiniTemp Infrared Thermometer – a temperature range of −30C to 500C, or −20F to 932F, and a 10:1 distance-to-spot ratio. Note that there's also an MT4 model, but its specs aren't as good and Amazon usually has it priced similarly, so we think that the MT6 is the better choice of the two.

All the budget models above are very competitively priced, but you can go even cheaper with a model like the Actron CP7875 PocketTherm Infrared Thermometer. However, the Actron doesn't have a laser pointer, and its distance-to-spot ratio is a lousy 1:1, which means you have to hold it really close to the thing you're measuring the temperature of. To look for thermal leaks in ceilings you'd need a step ladder... So we wouldn't really recommend it for energy-auditing purposes.

Another popular model is the Fluke 62 Mini Infrared Thermometer – it has good reviews and its specs are comparable with those of the recommended models above. However, at the time of writing, it costs considerably more than the Kintrex, the Mastercool, and the Raytek (which, incidentally, is owned by Fluke), so we wouldn't recommend the Fluke 62 unless you can get it for a comparable price.

Is it wise to get a multipurpose IR thermometer?

The TLD100 has a big advantage over the more multipurpose IR thermometers as it has a multi-coloured laser pointer that makes it ideal for finding thermal leaks...

But, although the TLD100 has a temperature display screen, it doesn't have as wide a temperature-detection range as the multipurpose models listed above (it only covers −30C to 150C, or −22F to 302F ), so it's not so well suited for making cooking or automotive measurements. And its distance-to-spot ratio is 6:1 – great for scanning walls for thermal leaks, but not as good as the multipurpose models for focused long-distance measurements.

It's also worth noting that none of the multi-purpose laser thermometers are great for medical use – you don't want to go shining lasers in people's eyes, and the medical infrared thermometers tend to offer better accuracy at temperatures around body temperature (this is balanced by their much lower overall temperature-measurement range).

All in all, if you're a professional energy auditor looking for a cheap alternative to a thermal imager, or if you want an IR thermometer just for inspecting your own building(s), the TLD100 is probably your best choice. If it's important that you can use your laser thermometer for other (non-medical) tasks as well, one of the multipurpose models above might suit you better overall.

After you've found and plugged the leaks...

You might want to find out how much energy you've saved. This is where degree days come in! If you are new to degree days, we suggest you start with our introduction to degree days. Then take a look at our detailed article explaining how to use degree days to calculate energy savings.