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sonicsmooth 03-03-2011 12:42 AM

Insulating under porch
I have a storage/crawl space under my front porch which I'm trying to insulate.

Inspector says it is considered an "attic" because the top is exposed to cold weather, therefore he wants it ventilated before I can insulate the walls, or provide a non-vented solution that is code compliant.

Apparently it's okay to provide non-vented attic if I use spray foam to seal everything off.

However the top of the porch deck has waterproof material. So if I used spray foam on the inside, I would be sandwiching the wood between two vapor-impermeable materials -- the top deck waterproofing and the ceiling spray foam.

Is this bad? I would basically be trapping whatever moisture is there, but not adding or removing moisture. Temperature of the wood would track outdoor temperature, but the moisture would be stuck at whatever it is the day the foam is sprayed. doesn't say anything about this condition.

Do I have a problem? There is not enough height in this space to create a ventilated mini "attic" space and still allow for the required R38 insulation.


Tony99 12-09-2011 12:33 PM

Have You Got any Help
sonics has anyone helped you out on this? I have the same questions and having a hard time getting an answer.

sonicsmooth 12-09-2011 06:37 PM

Hi Tony99,

Actually I finally got the approval from the inspector a few months ago and sprayed it with 7" of high density closed cell foam. There is a provision in the Seattle code which allows me to not put the 1" space if I'm using spray foam. Evidently the 1" space requirement was from a few years ago. The other issue I was having is that since I have an STFI permit (subject to field inspection), the inspector wasn't sure what to do with that, since all the spray foam applications he has seen were submitted through the normal new construction permitting process which undergoes plan review. In my case there was no plan review so I had to email him the foam datasheet and a bunch of stuff from the installer to verify his proper qualifications to spray the foam properly.

Now I have ants, but I don't think that's an issue with the spray foam :)


Tony99 12-09-2011 07:21 PM

Thanks for getting back to me. Did you end up spraying over the wood? And what about the walls? Did the inspector make you finish the over the foam spray. Some one once told me that the foam spray would have to be sealed with drywall since it's not fire rated. What are you doing about heat and air circulation.

sonicsmooth 12-13-2011 05:16 PM

Yes, we sprayed over the wood and the walls. Since this is a storage/utility area, we did not get this part officially inspected yet, so I'm not sure whether the walls need to be covered.

The datasheet reads as follows:
FL 2000 is a Class I formulation, as Tested per ASTM E84, and at a
thickness of 4.0 inches possesses the flammability characteristics shown
ASTM Method E84 Class I
Flame Spread ≤25
Smoke Development ≤450

4.3 Thermal Barrier:
The Foam-Lok FL2000 spray foam insulation must be
separated from the interior of the building by an approved
thermal barrier of minimum 1/2-inch-thick (12.7 mm)
gypsum wallboard or an equivalent 15-minute thermal
barrier complying with, and installed in accordance with,
IBC Section 2603.4 or IRC Sect ion R316.4, as applicable,
except when installation is in attics and crawl spaces as
described in Section 4.4. Thicknesses of up to 12 inches
(305 mm) for ceiling cavities and 12 inches (305 mm) for
wall cavities are recognized, based on room corner fire
testing in accordance with NFPA 286.

sonicsmooth 12-13-2011 05:19 PM

Oh and also about heat and air circulation.

For heat, we don't have an actual heat register in the space since it is a utility space, but it is part of the same thermal envelope as the main house. Also, since this room contains the HVAC system and the air ducts run through the room, and also washer/dryer, it is generally pretty warm even though we're not specifically heating it.

Also, since the room is a laundry area, we have an additional fan, probably 20 cfm (cheap home depot fan) which the hvac guy installed. So we can ventilate if necessary. The inspector had mentioned a fan required for laundry so we installed it. As I mentioned in the other post, this area has not been inspected yet as it is not habitable space.. so I'm not sure what we're going to do with it.

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