Replies

1. 
   mgensler|Nov 16, 2021 07:01am|#1

   I would ask for an independent lab test from them. My guess is these are numbers before it is fully cured. I specified the amount of spray foam in inches to try to avoid this and my contractor pulled out a report right before they started showing their foam was 7.2 or something. I told him it didn't matter, I still wanted the x inches I specified. His report was written by the manufacturer and I couldn't tell where they came up with the R value.

   Not sure about the wiring question. I have some wires encapsulated in foam and it has been an issue.

2. Expert Member
   Michael Maines|2021年11月16日上午09:19|#2

   R-value testing is pretty specific, including aging for six months before testing. But sample size and environmental conditions while aging are flexible, so you could test the same exact foam two different ways and get two different results. Closed cell foam will lose R-value over time and will eventually reach R-5.6/in, the same as still air, once air displaces the blowing agents inside the tiny bubbles in the foam. Open cell foam maintains its R-value.

   For health and environmental reasons I only use foam when nothing else will work. But if you're set on using foam, if open cell meets your total R-value requirements and will not pose a moisture accumulation problem, it's a better bang for the buck--both "cost per R" and embodied carbon emissions per R.

   Both open cell and closed cell foam are created by exothermic reactions, with closed cell being more strongly exothermic and thus having a higher temperature that in theory could melt electrical cable. But spraying over cable is commonly done and I have never heard of an example of it causing problems. (I have heard many examples and seen a few myself where foam did not cure properly, resulting in expensive remediation, however.) If you want closed cell foam, the newer HFO-blown formulation has about 25% the global warming impact of older HFC formulations and does not get as hot while curing.

3. 
   oldbungalow|Nov 16, 2021 09:45am|#3

   我们在电线上完成了喷雾泡沫，这不是问题。
   You have to be careful if you have CPVC pipes though, including the orange sprinkler kind. They should not foam those as it could lead to failure. PVC drains/vents are OK, they're quite thick and not under pressure.