Delta T

Hi Folks, I am having a real difficulty with the lack of delta T when trying to use my camera during an inspection this time of year. When there is no AC, not cool enough to run the heat with the temp outside and inside at 80 degrees. I had some success with getting in early, but hard to get RE agents on site and owners out of house at 6 AM! In the evening it just doesn’t cool quick enough. I am offering a scan with each home inspection but end up looking goofy and unprofessional trying to explain why I can’t scan at this time, come up with clear pics of water intrusion and spending a ton of time testing with moisture meter. Any tricks or tips?


You must establish a delta T of at least 10-15 degrees when performing an IR inspection.

I get summer month IR requests all the time, but I always ask if they have air conditioning, before I schedule the inspection. Without A/C in the summer months, you might as well put your camera way.

I’m still using my IR camera today. I had a request last week for locating hot water pipes encased in concrete and one yesterday for locating a freon leak in an A/C line.

I showed up at an IR inspection the other morning after having the delta-t discussion with the client and he had it…the house was 82 degrees. :shock:

Get a small space heater and work each wall as needed and every floor as needed. even if it 100Degrees out you can work a wall. with a space heater.



Thanks for the feedback folks. Dave, I still use my camera for showing heat loss in the heating system ducting/piping and missing ceiling/attic insulation. It just bugs the hell out of me when there is not sufficient Delta T to do a scan. Larry, LOL! Did you thank him? Ron, that would be helpful with an energy audit type application but would turn a standard inspection into an all day event. I guess I will have to deal with the limitations of the technology and the agents unwillingness to think outside the box. :twisted:

In my opinion, home inspection is not usually a practical use for thermal imaging. A few months ago, I purchased a Flir B-60 and took the level one training. I have used the camera on many inspections and although it has a great “Wow” factor, it still cannot beat my experience and a simple moisture meter. I have found many areas of moisture penetration which the thermal imaging had showed no sign.
The problem is of course, the lack of Delta T. In my area, where the year round temperature is close to 68-70 degrees, and there is no air conditioning, it is impractical to heat a home to 90+ degrees prior to inspecting. Even during our rare heat waves, I have found the use of thermal imaging very limited.
I have not put any effort into advertising the use of thermal imaging during inspections to avoid the embarrassment of using this “great new technology” only to show my client a blank screen. I will only bring out the camera, unannounced and when the conditions warrant it’s use, which is rare.
I am scheduled to attend energy auditing training which may have a practical use for the thermal imager, but until then, I really have what amounts to a very expensive toy.
Fortunately, I am extremely busy, but if I purchased the IR camera in hopes of increasing business, I would have been very sorely disappointed. I would encourage those of you thinking about purchasing a thermal imager, to consider the limitations of the tool prior to plunking down the cash. I have no regrets for purchasing the tool. When practical, it is a great tool, unlike any other. But it is just that, a tool, when you need it it is great to have, but it certainly is not the center piece of any inspection.
I realize that two months of use is not much, and level one training is minimal. I am still experimenting with the use of the thermal imager and hope to find more uses as time goes on.

Quit giving away the IR. Only schedule it when the conditions are conducive. The national weather service (NOAA) has all kinds of charts and grafts to plan your inspection. Your IR trainer should have taught you that you can not do IR 24/7/365… If you explain the concept of IR to your client there should be no egg on your face.

Delta T is the 900 pound gorilla that thermographers must respect.

I like that one :smiley:


Me too…John know what he is talking about on that one. All I can say is thank goodness for HVAC.

David -

Weather charts are nice, BUT as you well know in many parts of the country there are several months where the I/S and OS are too close to get a decent Delta T / AND a Real Estate Transaction DOES NOT stand still. They had 5 / 7 / 10 days to get ALL inspections done - AND now that some RE Markets are moving again - MANY Agents and Sellers are giving no grace period. So what the man said was a real valid point.

When stuck in a poor delta T condition, I choose the black & white pallet
and adjust the scan to a narrow window… in order to draw out more
anomalies. If there is just a delta T of 2 degrees between inside and
outside… you can still find defects.

Double up on the moisture meter as well.

This is great advice. I prefer to use the black and white to find anomalies, then take the picture in high contrast (Fluke’s high contrast). For the report I find that clients can visualize more with a vivid color palette. Black and white is by far the easiest to focus in and find problems with, IMO.

Jason Kaylor – JJ
VP of Specialty Products
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Things to do to get some delta T.

  1. Around here the nights are generally cold enough to get plenty. Arrange to scan early even if you do the visual later on.

  2. Arrange for a closed house on a hot day. (shades down, doors closed, windows closed etc) The exterior temp should rise faster then inside. I’m still experimenting with this as it depends on how hot/ how sunny outside. But it should give you a window of several hours.

  3. Use a portable space heater and push heat into a wall. I use a 2 burner gas powered unit. The radiant heads will heat up a surface pretty quick.

  4. Turn on the heat. As long as it’s working properly there’s no reason to not turn up the heat.

  5. Experiment with span and range. Even under less then ideal conditions the span and range can help resolve an image. (I learned this doing horse scans.

  6. As others observed use black and white.

I don’t understand the embarrassment using a moisture meter. Even if I find a glaring anomaly I’m going to confirm with the meter in any case. As long as you don’t overblow the IR as some magic wand then using a meter is not an issue.

Ditto plus…

Its rare that I don’t have an AC to play with but when I don’t, I scan anyway. DT is a limitation that should be spelled out in your agreement and it is what it is on the day of the inspection. So should the fact that the use of IR doesn’t imply that all defects can be discovered.

We can’t find roof leaks with a standard inspection when it hasn’t rained for 2 months but we don’t reschedule the inspection because of it.

Depends on where you live and work. NOT using IR here in the tropics is what we’d call in the business…un-smart. One thing I can agree with you on is that IR is NOT always the right tool for the job no matter where you are.

Wishful thinking. Just in the month of May I was low-balled by $125 and $250 respectively.

Same here! I have basically packed up the IR and raised my basic home inspection fees back up and am basically taking a “working vacation” by doing just basic home inspection like everybody else.

I had a $2600 inspection where I was talked down to $1900. I said sure! The guy wanted an engineer to do the inspection but couldn’t find one. So I threw in a “no holds barred full-blown inspection”(building, HVAC (x14), IR Interior, IR Flat roof) quote. He commenced to try to talk me down. So I said sure I just won’t make the second trip out to do a nighttime thermal imaging evaluation. So he turned around and settled for a basic home inspection on a commercial building by somebody else who isn’t even qualified to inspect residential properties.

Oh well, that’s the market these days. At least I’ve got work coming out of my ears! I just need to learn to control myself and not carry anything more than a flashlight into the inspection…

Here’s one from today. This is a wall chase in a garage that conceals a 3 inch plumbing vent. The vent stack flashing for this vent is split and leaking. The staining was visible and I didn’t need IR but just wanted to highlight what can be found with virtually no DT other than what nature provides. The home has no AC and has been sitting for a year. The stain created an evaporative cooling effect. Having a camera with good thermal sensitivity helps as well. This image was not manipulated at all and the camera was in the auto mode.