FLIR thermal camera observations

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Rocky
Posts: 3557
Joined: Fri Sep 06, 2019 12:57 pm

FLIR thermal camera observations

Post by Rocky »

This thing is fun! I made my first surprising discovery. I had put some supposed heat blocking film on one door of my office patio doors (intended to finish the other door later) because the office became quite hot even with blackout curtains in the summer. I wondered what the heat reduction by the film is. So I spot checked each door and the door with the film was 4 degrees F hotter. So I did some reasearch and found that things are not simple. The film is absorbing the IR and heating up. Now the question is how much of that heat is simply re-radiated into the room and how much is radiated back outside. We can't tell but assuming that at least some is going back outside, then the film would be helpful even if the spot thermometry shows it hotter.

So now I am thinking to use reflective film which will not heat up the glass. But then how to tell how much interior heat reduction we are getting? Spot thermometry will simply show the ambient exterior temperature. So here's my plan. Put a conventional thermometer in the space between the blackout blind and the pane. Check the temperature with and without the film. That space is like a little greenhouse, so we expect it to be cooler with the film. I will report my finding after getting full direct sunlight later today. That will be with the absorptive film. I'll also get some reflective film and see how that works.
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Rocky
Posts: 3557
Joined: Fri Sep 06, 2019 12:57 pm

Re: FLIR thermal camera observations

Post by Rocky »

I did the second test above and the result was essentially the same, i.e., the film 'greenhouse' was 5 degrees hotter than the non-film one. My theory is this: The film is installed on the outside of the window. I can't remember why I did that. Reviewing on-line instructions they say to always install on the inside. Maybe when on the outside heat that would normally be reflected by the glass is now absorbed and heats the glass more. I'm going to remove it and then get some reflective film and put it on the inside. It also suggests that it is important to keep the window exterior very clean so as to maximize its reflectance.

So my new toy has already helped me a lot. I would have never thought to do the greenhouse experiment but by just casually pointing the camera around, the problem came to light.
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