I am going to be working on a super quick build coming up in 2 weeks. The house will be built in 106 hours from start to move in - Extreme Makeover Show - and spray foam is going to be used as an insulator. We are performing air sealing around headers, doubled-up studs/sisters, plates, etc...well before insulation (at least 12 hours or so), but my question to the IR gang is this:
Do you think if there was enough Delta T between the inside of the house which may have sporadic heaters, but will have like 200+ people working in it, and the outside to use IR while the foam is being installed? I have heard you are supposed to give it 24 hours, but have not imaged it myself when freshly installed. I am thinking like 10 minutes after it is sprayed, if there are one of those bypasses that are hard to see and normally in spray foam (regardless of what your spraying is telling you), do you think it would show up? Or do you think the heat from the chemical will be radiating for too long to use IR? and destroy the image opportunity? The build is happening so quick that I will not be able to pressurize the house until completion, so any misses/air leaks will become tougher to remedy - and some never will be fixed.
Ten minutes doesn't sound like very long. No conditions are perfect, right? Hope you get some lens time and it ends up in the final cut! Let us know how it goes.
I'm assuming the is spray-allied foam rather than injected and also assuming the outside is cooler than the inside. If so, you should be able to depressurize the building (assuming you can with 200 people going in and out!) to about 20-30P, pulling cooler air into the building. The foam is both exothermic and heated during installation. Though I've not imaged spray-allied immediately after installation, the thermal contrast should be there to do it. Typically even a 5F delta temperature from inside to outside is sufficient to locate air leakage issues, especially on the inside while depressurizing.
My only concerns would be (1) damaging it before it sets up (a very small risk) or (2) causing cool temperatures that would affect the set time (check with installer or manufacturer, again, probably a low risk).
I certainly agree that imaging with depressurization is essential to ensuring the work performs as intended. I've all too often found small, but "deadly," holes in an otherwise seemingly impenetrable layer of foam. The attached shows problems along the top plate and T-walls; the work was done by a highly qualified contractor. Once we located the many small problems, it was simple for them to be corrected—before the sheetrock was hung!
Given your situation, I'd urge you to try a test run BEFORE "D-day!"
I have been working with spray foam contractors in the area doing that exact test - usually only 25p giving me a longer inspection time.
This house will not allow me to depressurize, so I was hoping that the people and constant movement would help create a Delta T that would allow me to find those holes without pressure.
I completely agree with you about spray foam must be tested!!! My pitch to all of those spray foam contractors that are not using me yet is "Give me your best house and if I don't find six problems, then I will do all of your work for free!!" The one that took me up so far is my best client and is now becoming the leader in the area by ensuring his product is installed properly.
I don't think it is fair, on anyone, for code officials to be verifying the insulation if it is spray foam. I don't think it will be too much longer before all of these companies have litigation against them or begin using this testing method to provide the complete air seal!! Spray foam companies need to stop hiring painters and begin hiring building science trained applicators - at least Envelope Pros!!
Thanks for the help!
"This house will not allow me to depressurize" I'm not sure what the issues are, and I respect that sometimes people think there may be issues (mainly related to pollutants) with depressurizing, but if you are going to pressurize, you'll need exterior conditions that are very challenging: little or no wind, no sun or bright overcast, and temperatures around 50-55F or less (assuming 70F inside). Even then, the signatures are often less distinct on the exterior. I might opt for smoke (inside) as the primary and thermal (outside) as the secondary at that point. Or talk them into depressurizing based on dramatically improved results—I'm sure you'll find your six problems and then some!
With very little cure time you are sure to get a lot of deltaT. I would also recommend covering the lens/camera with a thin plastic bag to avoid the isocynate aerosols. Use a smoke pencil to confirm that areas of cold contrast are infiltration.