School me on spray foam for new construction

[wal1809]

I read every little thing I could on open vs closed cell foam before spraying my home. We just moved our home from a slab to a pier and beam. We moved it up the hill plus up on piers so there is no way to flood again. I opted for treated beams and floor joists. When we did the stone underpinning insisted on multiple vents to keep air flow in any wind direction.

I know some of you will balk at this but I opted for open cell underneath the house. He is why. Open will allow water to in and it will allow water out. Closed cell will not do either. The reasoning behind the open cell choice I made is future leaks. We all get them, it happens. I have 1 1/8th subfloor mad by Ameritech. It will not take water for weeks, I know because I tested a left over piece. If I were to develop a leak and had closed cell under the house and the top finish coat of my floor is snap lock vinyl, the water will sit right on the wood and no chance of getting out until you tear everything out. So on a pier and beam high enough and vented enough, I feel confident we will be ok from moisture build up due to condensation. If I have a water problem I can get under the house and target the area and draw the water out. I have tested the open cell for moisture content between the floor and the open cell foam and have had zero moisture at the floor or the joists. If the house is low to the ground and poorly vented, I wouldn't do it.

[Banded Drake Calls]

What are the prospects of spraying existing construction and how severely does it effect cost?? I know there will be a lot of variables that will affect cost but in general would you say it's double?? Just for an example.

Not doubled by any means. For attics you're talking an extra .15 to .35 per sq ft of roof depending on company. For walls they aren't exposed I'm really not sure. It's a different process as they have to drill holes at the top of the wall between each stud.

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[Notaguide]

A few years back it wasn't kosher to foam the attics down here on the coast due to the higher humidity causing mold issues. Is that still the case?

I'm seeing it becoming more common on higher end homes on the middle coast. Humidity is a factor but controlled by AC air exchanges requiring companies to size correctly, use correct equipment (2 stage), and proper installation practices. Other parts of the state including my area have become efficient in design and install with trial and error over the past 10-12yrs. that may not be there yet.

[8mpg]

What are the prospects of spraying existing construction and how severely does it effect cost?? I know there will be a lot of variables that will affect cost but in general would you say it's double?? Just for an example.

Spraying existing construction is almost the same cost. The question will be whether or not you want the fiberglass sucked out before spraying. My house was done as a remodel.

I read every little thing I could on open vs closed cell foam before spraying my home. We just moved our home from a slab to a pier and beam. We moved it up the hill plus up on piers so there is no way to flood again. I opted for treated beams and floor joists. When we did the stone underpinning insisted on multiple vents to keep air flow in any wind direction.

I know some of you will balk at this but I opted for open cell underneath the house. He is why. Open will allow water to in and it will allow water out. Closed cell will not do either. The reasoning behind the open cell choice I made is future leaks. We all get them, it happens. I have 1 1/8th subfloor mad by Ameritech. It will not take water for weeks, I know because I tested a left over piece. If I were to develop a leak and had closed cell under the house and the top finish coat of my floor is snap lock vinyl, the water will sit right on the wood and no chance of getting out until you tear everything out. So on a pier and beam high enough and vented enough, I feel confident we will be ok from moisture build up due to condensation. If I have a water problem I can get under the house and target the area and draw the water out. I have tested the open cell for moisture content between the floor and the open cell foam and have had zero moisture at the floor or the joists. If the house is low to the ground and poorly vented, I wouldn't do it.

You made the right choice. Joe Lstiburk addresses that situation specifically in his white paper study.

https://buildingscience.com/documents/insights/bsi-009-new-light-in-crawlspaces

[MadHatter]

I read every little thing I could on open vs closed cell foam before spraying my home. We just moved our home from a slab to a pier and beam. We moved it up the hill plus up on piers so there is no way to flood again. I opted for treated beams and floor joists. When we did the stone underpinning insisted on multiple vents to keep air flow in any wind direction.

I know some of you will balk at this but I opted for open cell underneath the house. He is why. Open will allow water to in and it will allow water out. Closed cell will not do either. The reasoning behind the open cell choice I made is future leaks. We all get them, it happens. I have 1 1/8th subfloor mad by Ameritech. It will not take water for weeks, I know because I tested a left over piece. If I were to develop a leak and had closed cell under the house and the top finish coat of my floor is snap lock vinyl, the water will sit right on the wood and no chance of getting out until you tear everything out. So on a pier and beam high enough and vented enough, I feel confident we will be ok from moisture build up due to condensation. If I have a water problem I can get under the house and target the area and draw the water out. I have tested the open cell for moisture content between the floor and the open cell foam and have had zero moisture at the floor or the joists. If the house is low to the ground and poorly vented, I wouldn't do it.

Exactly what I was saying. Plan ahead, and if there's the possibility of a leak, go open cell.

[Dirtymike]

following

[Bisch]

My 30x40, with 14'walls shop is getting foamed as I type this. 1.5" closed cell everywhere for $4900.

Bisch