Climate Zone 7, Spray Contractor Says 3 Inches of Closed Cell is all You Need and Nothing Else.
I’m building in Colorado at 11,000 feet, Climate zone 7, approximately 10,500 heating degree days per year, design temperature of -14 and 81. While we do have building codes with supposed requirements for insulation r-value, we do NOT have an insulation inspection by the county and technically anything will go since it won’t be reviewed. I spoke with a spray foam company yesterday about having the interior of the roof deck spray foamed to do a flash and batt just to see what pricing would look like. Pricing is still coming. The owner said that he only does 3 inches of foam on the roof and recommends 3 inches on the walls. No batt insulation at all, just three inches and that is it. This results in just an R21 r-value max. The owner of the company says that is typically what he recommends and most people do that up there who he works with. He said the properties of closed cell spray foam are dramatically different from batt insulation for which the codes are based off of. With the r-value and air sealing of the closed cell foam, that much closed insulation will significantly outperform walls and roofs with dramatically higher insulation values per him. He cited the chart below that 93.8% of the potential benefit is realized with just those three inches not factoring in thermal bridging. Even adding a fourth inch only gets you to 95.82% resistance benefit.
What are your thoughts on this? I just thought I’d share a real life example of this. I’m not going to do what he suggests by the way.
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Replies
jwolfe,
Martin describes what your contractor is trying to do in this article:
https://www.greenbuildingadvisor.com/article/misleading-energy-reports-used-to-sell-spray-foam
On the related question about code enforcement I'll just add that in almost every jurisdiction I know of the lack of inspections does not exempt you from the requirement that you meet all applicable codes and bylaws.
From the IRC:
"R105.2 Work exempt from permit.
Exemption from permit requirements of this code shall not be deemed to grant authorization for any work to be done in any manner in violation of the provisions of this code or any other laws or ordinances of this jurisdiction. "
And further from our code:
"Responsibility of Owner
1) Unless otherwise specified in this Code, the owner of a building shall be the person responsible for carrying
out the provisions of this Code in relation to that building.
2) The owner of a building is in no way relieved of full responsibility for complying with this Code by the
authority having jurisdiction
a) granting a building permit,
b) approving drawings or specifications, or
c) carrying out inspection"
That is total insanity, and frustrating because the spray foam industry is rife with shady salespeople who say the same thing.
The best closed-cell foams are around R-7/in when new. Over time, air displaces the blowing agent inside the foam cells and the foam drops to around R-5.6/in. How long that takes varies a lot but it will happen to all foam eventually.
At 3", that would leave you with less than R-17. That is horribly low for climate zone 7. Even the warmest parts of the gulf coast, except for the Miami area, are required to have R-49 roofs and R-13 walls in the 2021 IRC.
Foam salespeople claim that because foam is reasonably good at blocking air flow, that it performs better than other insulations, as you note. Since you should have a continuous air control layer anyway, that point is moot, and otherwise R-value is R-value. There is nothing magical about spray foam compared to other insulation--they all rely on trapped air to do the insulating, and the testing covers conductive, convective and radiative heat flow. (Another common lie/misunderstanding is that R-value testing does not cover all three modes of heat flow.)
In the 2021 IRC, in climate zone 7 you should have either R-20 cavity plus R-5 continuous insulation, R-13 cavity plus R-20 continuous, or another way to reach a whole-wall U-factor of 0.045, or R-22.2, including framing.
It also says that in roofs or ceilings, you need R-60 cavity insulation.
Some people think the 2021 IRC goes overboard on these values; I think they are just about right, especially in colder climate zones. Even if you step back to the 2015 IRC, you would need R-49 in the roof.
The salesperson was correct, in a way, about the first few inches of insulation slowing heat flow more than additional inches. That's not specific to foam, that's for ANY insulation. Every time you double the R-value, you cut heat flow in half, which means there are diminishing returns.
When using spray foam, I don't use any more than absolutely necessary, because its global warming impact is significant. (Another spray foam lie is regarding low-GWP formulations: the blowing agents in those formulations do have relatively low emissions, but they last nearly forever in the atmosphere and some research says they combine with other molecules to have a much higher impact. In any case, the resin itself has its own, large global warming impact.
Otherwise, I almost always go well above code-minimum insulation levels, as I always find a reasonably good ROI when doing so. If you go with the ridiculously low amounts of insulation your contractor is recommending, you will be less comfortable, you will need a larger heating system, you will be wasting on the order of several to many hundreds of dollars a year in energy costs, and you will be dumping more CO2 into the atmosphere every year for the life of the building than you would if using more appropriate levels of insulation, especially lower-impact types of insulation.
jwolfe1,
Aside from the gibberish graph provided you, the only performance advantage of foam over batts would be the reduced chance of condensation by blocking direct air contact on the interior facing side of roof and wall sheathing. Higher R-value batts would reduce heat loss proportional to the depth and per inch rating and merely require more depth for same placed R value. Combining both batt and foam would be a reasonable approach for achieving the R values you should be looking at for your high altitude. I am at 8,000 and have whole wall values around R-34 and whole roof of R-52+. My design temp range was -16F to 80F. I designed with exterior insulation levels that control for condensation risk.
I do hope you aren't really seeing 81F at that altitude already. I also suspect that you are going to see much lower than -14F more than you might like. Window quality will be a far greater driver of your thermal budgeting so I would strongly recommend you look at the Alpen line of windows. I have found them to be very effective and very wind tight.
One thing that you may not have fully considered is the impact of your elevation on heating and cooking choices. Your nominal pressure is 9.7 pounds per sq in or a bit less than two thirds of sea level. This reduction affects your combustion outputs as well as your air handling equipment ratings quite dramatically. At my level the pressure is 10.9 psi and that fan factor is around 25% reduced capacity for fans. I would need to check more carefully on combustion ratings. For a multitude of reasons I opted to be 100% electric and at that 100% resistance heat and water heating as well. Our dryer simply takes longer than when we lived near to sea level. At minimum be very careful with your choices of heat, hot water and cooking. I have found that far too many "professionals" have no clue about obtaining appliances or furnaces with proper orifice selection. And your water will boil at about 193, so plan your pasta accordingly.
And last, the lack of code inspection is a real thing out here in the wild west. However, your county may not use the most current code and thus the foam agent may be within bounds for proposing such a very minimal level. As Malcolm has pointed out, you are liable to follow whatever year code they have in place at minimum, but I would plan on insulating well beyond in order to save on heating and reduce the size of needed equipment.
onslow,
"This reduction affects your combustion outputs as well as your air handling equipment ratings quite dramatically. At my level the pressure is 10.9 psi and that fan factor is around 25% reduced capacity for fans."
Interesting and something I've never thought about.
Find someone else. It's not going to get better.
My opinion is large amounts of spray foam in construction plans are a huge red flag for lazy design and contempt for your budget.
Did you really have a set of construction plans that did not include insulation?
Would I be wrong in guessing the house is under roof at this point and now you need to find a way to pack R60 insulation into the 10 inches deep rafter bays of the cathedral ceiling in between the dozens of recessed light fixtures and you are over budget?
Spray foam is the most expensive, least green and riskiest way to buy an R of insulation and can almost always be eliminated with modicum planning.
Consider one of the options in this article.
https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work
Walta
Thanks Walta, I do already have a plan to go above code for the walls Bonfiglioli and will only go to r49 (at least) for the ceiling by gusseting 2x4s to the rafters with a thermal break. That will take extra work, but I am doing extensive DIY and up for it. I just wanted to see what pricing would be and what they would suggest.
Just curious, do you have any specifications that would effectively deal with the thermal break across structural members in the walls or roof?
For instance, using a zipR type of sheathing on the walls?
I will have a thermal break with cut foam board in the rafters that will be gusseted with 2x4s, and will do the Bonfiglioli approach for the walls. I'll be using batt insulation.
I'm probably one of the more spray foam positive people on here, and what this guy is telling you just isn't accurate. R value is R value, spray foam is no different than a fiberglass batt here. R49 or R60 is likely your code requirement, and you need to hit that number regardless of the material you use to do it. I'd count spray foam as AT MOST R6 per inch too, so 3" is something around R18 at best. R7 is maybe good for the first year or so, it will drop over time to somewhere around R5.5-R6 per inch.
He's somewhat right about the air sealing. You do get a benefit from that, but it doesn't change the R value. Air sealing can be done other ways too, and spray foam doesn't guarantee a good air seal if it's not installed competently.
I'd probably look for a different contractor if this guy won't do what you want. What he's telling you is spray foam industry marketing mumbo jumbo that is basically a half truth. If he won't budge from that, I'd use someone else.
Bill
I am just going to do it myself like I had always planned.
I use myself as a human lab rat. That being said, I installed 3" of closed cell polyurethane foam in an "extra room" in my home just because I had leftover material upon completion of another project. Never had to hit a code limit or otherwise, but it was an S&G kinda thing. I will attest that it works a hell of a lot better than if I had wasted my time and money putting R-21 fiberglass in the space instead. In fact, the room was getting a little "sweaty" until we upgraded to ductless minis last year, and now I no longer have to crack a window to keep the peace, so to speak. I'm not a scientist in the strictest sense, but I know it worked in a beneficial way. BTW, my home was 1200 square feet when we bought it and used over 800 gallons of oil per year for heat alone. 16 years later, it's over 3200 square feet, and we use less that 330 gallons. I think I earned my stripes on insulation and conservation of energy! (disclaimer: windows, doors, rigid foam cladding, spray foam everywhere and added ductless.....) However, I will say that I've met some really uninformed salespeople in the insulation business, so I understand any hesitancy when taking their word for it. Just remember that no single energy upgrade is going to make the entirety of the difference you may be looking for. It takes a village, so to speak.
The reason the spray foam dodge works is that a person sitting in a room can't tell how well-insulated it is. A lack of air sealing is obvious, but a well-sealed room at R13 feels no different from a well-sealed room at R30. The surface temperature of the walls is going to be the same, which is what you sense.
In the example, 3 inches of closed cell foam is going to be R18, which isn't a big difference from R21 fiberglass. If you can feel a difference it's because the fiberglass isn't well air-sealed.
ICFConstruction,
"I will attest that it works a hell of a lot better than if I had wasted my time and money putting R-21 fiberglass in the space instead"
In what way? You seem to be saying it worked better as an air and vapour barrier, but walls with batt insulation should include those control layers too. Are you saying, as the salesman did, that it has some other intangible quality?
Thanks everyone. Your responses are exactly what I was expecting.
Air seal, air seal, air seal. If you can install exterior foam board, do that. With new construction sealing is relatively simple, with renovations not so much.
I like the flash and batt method when all is said and done, if you have wall/roof depth.