Having 2nd thoughts about spray foam insulation..

5 years ago

Basement is framed and ready for insulation. We had planned on spray foam, but are having second thoughts due to potential toxicity. We cannot add in rigid foam at this point as all framing, fireblocking etc is complete and we don't have enough access directly to concrete walls. What are other options if we don't want to do spray foam? I've read bad things about fiberglass and vapor barriers. Not sure about Roxul and if it needs a vapor barrier? There is alot of conflicting info out there....

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Comments (4)

Bruce in Northern Virginia
5 years ago
last modified: 5 years ago
In general, you need a vapor barrier on the side of the wall that is the source of moisture. In a basement, this means the vapor barrier goes next to the concrete wall. A below-ground concrete wall is always a source of moisture, even if it is sealed on the exterior.

Is your wall framed with pressure-treated lumber everywhere its in contact with concrete? Is there space behind the framed wall to slip in a moisture barrier ( 6 mil plastic sheeting, etc.)? If you can add a moisture/vapor barrier against the concrete, then you should be fine with using Roxul in the wall cavities. I think Fiberglass would also be okay if you can keep out the moisture.

However, I don't think spray foam will be an issue for toxicity unless the place is burning down, since you must install drywall over it as a fire barrier anyway.

Bruce
Nadine
Original Author
5 years ago
Wall is framed away from concrete..anywhere from ~1" to 6" depending on the wall and plumbing etc. I have read some questionable things about spray foam and off gassing. We originally had looked at the rigid styrofoam, but thought spray foam would be better. It's just that I've been reading some iffy info about it recently.
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Thanks bungeeii. I actually made contact with a spray company that had a certified Energystar auditor working with them. They did an energy audit today and took measurements to estimate the job. They estimated the following rebates, and will put these terms in the contract as stipulations before any work is done: 1. audit costs $400 with $125 rebated if the work is done. 2. $1000 govt rebate off the top for a thin barrier spray in the attic floor. I don't have the exact terminology in front of me, but it is basically a skim coat of foam onto which is blown cellulose or other for attic insulation. 3. up to 50% rebate ($5000 max) depending on the results of the energy audit. Because I have high efficiency furnaces and on-demand hot water, she says that I will rate at a 25%+ energy savings, which will put me at the 50% rebate from the govt. The rebate takes about 10 weeks. So, in their example, if the job costs $11,000, I pay $10,000 plus the $400 for the audit ($1000 "instant" rebate for the attic thing), then get $5000 + $125 back in 10 weeks. After my contractor subtracts out what he was charging me for fiberglass, I should net out at a very reasonable number. The people today were my third estimate, and I believe they were the most knowledgeable about the right thing to do. I'm just waiting till next week for their estimate. Thanks again, I think I'm finally getting the right game plan together!
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-20C is roughly four degrees below zero Fahrenheit---not unusual in many parts of the Midwestern or Northeastern U.S. in the winter months, and I'm sure not unusual for much of Canada. Here's what we were told in a much milder climate when we had an energy audit of our house: If the wall is open, use standard insulation. If the wall is not open, use spray. But again, we are in a much milder climate (rarely goes below 30F or above 80F), and there may be some performance benefit to one or the other as you get into colder temperatures. Where we are, the performance of similarly rated insulation of each style is supposedly comparable (and in fact they ended up recommending that we not bother with any at all, since it is very low on the "bang for the buck" list in our climate---attic insulation, weatherproofing, etc. are far more important). I imagine this would be quite different in colder areas where the heat loss through uninsulated walls is more significant.
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The moisture problem on the roof deck may occur when the deck is colder than the air rising into the attic. How is a whole house dehumidifier going to solve this problem in the winter. During the winter houses in SE PA are struggling to raise their humidity level to 40%. Many are running humidifiers in the winter which will further aggravate the problem. I have looked at a lot of new houses in the NJ and PA area. I can't recall any having HVAC equipment in the attic. I have never seen a house with a spray foamed roof deck either. I am skeptical you will find an insulation contractor who has experience doing this in a new residential home. If you do find one, you know the questions to ask. See if his answers make sense.
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Considering insulative sheathing has made it's way into prescriptive minimums, I think it's more of a requirement than allowment. The "+" value in wood framed wall R value below denotes insulative sheathing prescriptions. Typical framing results in walls where 20-30% of a wall's total area, has no cavity insulation, which drags down the entire wall area's performance. For owners or designers after the most "R per inch" insulative sheathing is more effective than cavity insulation as it better encapsulates framing and structural components. This potentially increases airtightness, reduces thermal bridging and keeps structural components warmer, reducing chances of condensation and rot. The last feature may be why codes are beginning to adopt insulative sheathing as best (minimum) practice and calculating the minimum insulative sheathing is important for wood framed walls in cold climates. In the warmer climate zones of 2 and 3, a 2x4 wall with 1/2" of insulative sheathing outperforms a 2x6 wall and is thinner. As for Open Cell foam in roofs, I agree it's a relatively new practice posing risk and the same is true for Closed Cell. That's why many experts recommend insulative sheathing on top of roof structural sheathing and why the traditional unconditioned attic is appealing, as long as it has an airtight ceiling plane (tough part) and a thick layer of loose fill insulation. Roof leaks are typically more common and damaging than condensation and I think closed cell complicates discovery and repair more than open cell, but in cold climates I would prefer closed cell. Martin's article sounding the alarm about modeling studies is useful, but I think the onus mainly falls on field results and the vast majority of open cell roof decks seem to be working fine, other than the unfortunate reality that most spray foam installations are below code minimum performance. A good friend of mine is building in TN and we just went through all this. He was able to get good pricing for a flash coat of closed cell against the bottom of the roof deck, followed by filling the rest of the rafter cavities with open cell.
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CLC
5 years ago
I am extremely cautious about products and off gassing and toxicity. I was terrified of spray foam, especially after reading some horror stories about odors and offfassing with improperly cured foam. We weighed all of our options, and went ahead with spray foam , and I am so glad we did. It works well and aside from the day of application, there has been no odor whatsoever. Once it cures it won’t offgas (unless it is on fire)
worthy
5 years ago
last modified: 5 years ago
Stick with your first thought: spray polyurethane foam (spf) against the foundation wall--best choice is closed cell as you've left very little space between some of the framing and the concrete wall.

It's effective, impervious to moisture and will keep your foundation wall from becoming a source of condensed water dripping down to the floor and into your finished drywall. Just be sure to only use experienced installers, such as members of the professional Spray Polyurethane Foam Alliance.

If it were in my budget every time, I'd use spf; second choice is extruded polyurethane boards (XPS).

[BTW, putting polyethylene sheets against the foundation will only ensure the collection of moisture on the mouldy cold wall, which will run off into your finished wall. This was a recommendation up to the early 1990s in our jurisdiction and one was advised to run the poly under the baseplate into the finished space, so the water would run off that way. Yikes! ]

Having 2nd thoughts about spray foam insulation..

Comments (4)

Bruce in Northern Virginia

Nadine
Original Author

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Having 2nd thoughts about spray foam insulation..

Comments (4)

Bruce in Northern Virginia

NadineOriginal Author

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CLC

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Nadine
Original Author