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Rebecca Cague Posted: Apr 07, 2011 08:28 AM	Application do's and don'ts - crawl space and knee walls I have a two part question based on conflicting contractor advice. 1. We want to spray foam our crawl space ceiling to replace the sagging batting and seal up the rim where we loose the bulk of heat from our house into the crawl space. One contractor said the job was impossible because they needed a minimum application distance of14" away from the ceiling (plus the applicators' body) and we don't have that clearance everywhere. Reason being: if you apply the foam too closely, you create concave and convex areas that are a danger for hosting mold. Is this a reasonable concern?? I haven't been able to find any info to refute or support the claim. The second contractor said the job was tight, but they can do it. 2. In the two knee wall spaces in our mostly finished attic, contractor one says they can foam up the rafters and end walls. Contractor two recommended spraying the floor and interior walls instead because half the roofline is enclosed and by spraying the rafters you would be sealing up existing batting, causing a mold problem. It looks like I don't have either soffits or a ridge vent, which contractor one cited as the reason sealing up the roof with foam wouldn't be a problem (even though the top half has batting). Any help on ground truthing these application claims would be very helpful. I certainly don't want to create a mold problem in the process of solving energy efficiency issues. Thanks!
quentin Posted: Apr 07, 2011 08:16 PM	Answers 1) a good sprayer can use a few tricks in spraying to get around that. It may not be as pretty but pretty and effective are not the same thing. We have done places like that plenty of times and never a problem. 2) If it is done right so you don't have and moisture buildup, either way will work fine. Done it both ways based on customer preferences and they both work fine. If it isn't vented right now and you are not having problems with mold, then the idea you will later is very unlikely. Actually it would be LESS likely as the dew point should be within the foam so you will have a drier and better controlled space.

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Rebecca Cague

Posted: Apr 07, 2011 08:28 AM

Application do's and don'ts - crawl space and knee walls

I have a two part question based on conflicting contractor advice. 1. We want to spray foam our crawl space ceiling to replace the sagging batting and seal up the rim where we loose the bulk of heat from our house into the crawl space. One contractor said the job was impossible because they needed a minimum application distance of14" away from the ceiling (plus the applicators' body) and we don't have that clearance everywhere. Reason being: if you apply the foam too closely, you create concave and convex areas that are a danger for hosting mold. Is this a reasonable concern?? I haven't been able to find any info to refute or support the claim. The second contractor said the job was tight, but they can do it.
2. In the two knee wall spaces in our mostly finished attic, contractor one says they can foam up the rafters and end walls. Contractor two recommended spraying the floor and interior walls instead because half the roofline is enclosed and by spraying the rafters you would be sealing up existing batting, causing a mold problem. It looks like I don't have either soffits or a ridge vent, which contractor one cited as the reason sealing up the roof with foam wouldn't be a problem (even though the top half has batting).

Any help on ground truthing these application claims would be very helpful. I certainly don't want to create a mold problem in the process of solving energy efficiency issues. Thanks!

quentin

Posted: Apr 07, 2011 08:16 PM

Answers

1) a good sprayer can use a few tricks in spraying to get around that. It may not be as pretty but pretty and effective are not the same thing. We have done places like that plenty of times and never a problem.

2) If it is done right so you don't have and moisture buildup, either way will work fine. Done it both ways based on customer preferences and they both work fine. If it isn't vented right now and you are not having problems with mold, then the idea you will later is very unlikely. Actually it would be LESS likely as the dew point should be within the foam so you will have a drier and better controlled space.

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