spray foam (open/closed) and cellulose
Sorry to pose questions that have probably already been discussed. I am getting set to insulate a renovation and addition that has 2×6 framing. I’m planning to do the roof decks (most of the roof will get a baffles so that the deck is ventilated) and then all my walls. Here are my questions:
1. Installers lean towards open cell. I think it is just easier for them to work with. Given that cellulose (dense pack or wet spray?) has only slightly worse air infiltration but similar R-value, should I just go with the cellulose in the walls?
2. Someone told me closed cell will cause problems because there is no opportunity for moisture transport. I have 1/2 inch continue rigid (taped) on the outside. I’m not sure where water will condense. I was not planning on putting a vapor barrier under the drywall. Am I better off staying away from closed cell despite the much higher R-value? Price might keep me away from closed cell, but I would like to know if I should not even be asking for closed cell quotes.
3. Are there significant difference amongst the different brands of spray foam. I know that there are nasty compounds (banned in Europe) in some or all of these. I am wondering if there is one brand that stands out from all the rest in terms of quality and toxicity.
4. A friend told me about a spray foam application from quite a few years ago where he later observed 1/2 inch (or more) shrinkage in all directions. Did he have a bad installer or do these problems still occur?
5. Are the standard baffles used to keep batts out of soffit bays going to keep roof decks ventilated when the rafter bays are spray foamed? Seems like they might get squished to nothing thus blocking all ventilation.
6. I have some attic areas that will be accessible (one will actually have a furnace). Does anyone have experience applying fire proof paint/spray to these foams?
Thanks in advance for any suggestions/answers. regards, mark
Replies
The latest issue of FHB has an article on spray foams. It covers closed/open cell, R-values, proper installation, long term R-values, cost, and a few more things. You might go to the FHB home page and check for a link to the article there, or just pick up the magazine at a local store.
BTW, please fill out your profile. Knowing what area of the country you live in will influence the advice you get on the vp or no vp issue.
There have been many extensive discussions about this.
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a bad spray foam job, is a bad spray foam job, most issues are caused by ignorance, spraying to thick (leads to cracks and fissures), spraying wet/froozen lumber (shrinkage), bad mixing (gooey mess that never sets), poor planning (spraying off areas that shouldn't be), and more poor planning. All this spraying isn't worth much if other details are missed, caulking between trimmers, headers, stools around door/windows, gaskets bwtn sills and plates etc. Attic baffles are a pet peeve, almost everyone installs them, but many are rendered useless by bad insulation jobs, try making your own with 1/4 ply between the rafters, blocking off space btwn them and the top plate, whats the use in ventilating if half the product winds up in the eaves ..
spray foam is often regarded as the cure all for bad planning, it ain't ..
take your time, check out a couple of their jobs before they'te closed in, get the right contractor
mwalter
as has been pointed out, buy FINE HOME BUILDING and read the article.. Let me answer your questions though from a non technical side.. First spray foam will make the whole house siffer and quieter. It adds a amazing amount of rigidity. (so much so that a SIP is 200% stronger than a stick built house)
Definitions;
a SIP is a structural insulated panel made with foam and 2 sheets of OSB.(and nothing else)
a stick built house is one which is built with traditional 2x4's
Weaknesses of cellulose are similar to the horror stories you've heard about foam. Improper installation can and does result in settling which leaves a portion of the bay uninsulated, using too much moisture to spray it which can be retained in the walls indefinitely.
As for foam's impenetrability to allowing moisture to go through it, that is true which is a good thing.. cellulose if it gets wet rapidly losses it's R value right down to nothing. Foam on the other hand doesn't which means that if your house gets that damp inside you still have full insulation value.. You don't want any airflow in your stud bays.. any airflow scrubs heat out. If it can't get through the foam and the studs pretty much protect themselves (at least as well as any stud will using any insulation) you have the optimum protection..
Sheetrock over any foam It affords you the best protection.
Conclusion, there are a lot of myths about foam out there, most spread by installers with a vested interest in some other insulation..
Conclusion, there are a lot of myths about foam out there, most spread by installers with a vested interest in some other insulation
Frenchy has a vested interest in SIPs, he has a couple of myths about cells he likes to spread.
Weaknesses of cellulose are similar to the horror stories you've heard about foam. Improper installation can and does result in settling which leaves a portion of the bay uninsulated, using too much moisture to spray it which can be retained in the walls indefinitely.
Wet spray cells don't settle, they dry to whatever shape/size they are when sprayed.
cellulose if it gets wet rapidly losses it's R value right down to nothing. Foam on the other hand doesn't which means that if your house gets that damp inside you still have full insulation value..
Frenchy has a thing about wet cells, but if your house is that wet you probably oughta be worried something other than R value.
Joe H
Joe
May I assume that you are willing to warrantee all celluliose installations?
I thought not. I have seen just such examples where sprayed celluliose settles and leaves voids. Usually after someone does a infrared picture to find the heat loss spots and they tear down the sheetrock to repair those spots..
Frankly celuliose has some great features about it.. it's done normally with recycled newspaper which I few is nice eviornmentally.
However the fact remains that moisture affects the R value of celluliose and closed cell foam not at all.
If you can promise everyone that no moisture can ever leak into a wall and it will never be incorrectly installed then by all means use celluliose if you wish.. since I have never seen a house torn down that didn't have some decay indicating moisture leaked in someplace I feel very confident prefering foam to celluliose.
One final point.. Yes I feel SIP's are superior top sprayed foam. they are structurally stronger and do not have the transmission losses of wood that studs have.. another words it acts like a thermos bottle with regard heat retention. Whereas studs transmit heat from the interior to the outside..
So are you willing to warantee all SIP installations."At the present time, approximately twenty multifamily buildings in Juneau, Alaska, built prior to 1996, have been reported as damaged due to moisture at the top OSB skin of SIP roof panels. It is hard to get a reliable figure giving the exact number of roofs involved because some of the buildings are multifamily units within a single building. "http://www.sips.org/content/technical/index.cfm?PageId=161Any product will produce poor results when it is misused and misapplied..
William the Geezer, the sequel to Billy the Kid - Shoe
I had my new construction sprayed with closed cell (Gaco 193) last weekend. I put 3 1/2 inches under the roof deck (unvented) to get the required R-20 and 1 inch in the walls for sealing and strength. This also has a perm rating of 0.3 perm/inch vs the Gaco 183 (not as smelly) with a perm rating of 1.4. There is almost no smell after 2 days. According to the applicators (my next door neighbor) all closed cell foams use the same "A" compound,polymeric methylene diphenyl diisocyanate, made by Nippon polyurethane inc. The "B" side is proprietary. Cost is around $ 1.00 a board foot.
You need to tell us where you are located. Climates differ. Check out http://www.buildingscience.com
I'll take a few of these Qs while noting that frenchy managed to spread one myth while attempting to debunk others. He did that by failing to note there is a definite diff between open and closed cell foams. Closed cell foam give approx twice the R-value as open or cellulose and closed cell foam is a VB while open celled will hold moisture.
Since you have a VB in the i/2 rigid on exterior, you do not want a sheet VB inside the studs creating a space to capture moisture either.
If you choice comes down to cellulose or open foam, go with the densepak cellulose and a vapour retarder.
if you can afford closed cell, you'll never be unhappy with it.
Shrinking back from all sides sounds like the older foams used where that was common. polyurethene foam is a tenacious glue that will crack in the middle before it separates at the edges, but that kind of shrinkage displayes itself immediately because it cures in a few seconds. Causes can be spraying on cold surfaces or a bad mix or filling too deep at one pas, all of which is correctable immediately. once the job is done and inspected, it is done. Open celled is cheaper, but the salesmen for the open celled foams borrow heavily from claims only proven for closed cell foams to push their cheaper product and without mentioning the problem of it retaining water.
I'm sure there is a place for it, but I haven't figured out what it is yet.
for the green crowd, there are soy based closed cell foams, I hear, but there is no problem with toxic off gassing in the polyurethene unless you stay in your house while it is burning down.
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Piffin.
I'm sorry that you assumed I was talking about open cell foam. I have never seen it used locally so I have no experiance with it.. The sole exception is the stuff I poured in my cement block walls in a limited attempt to provide some insulation where I wasn't allowed to replace the wall with ICF's.
I did not have to assume YOU were talking about any certain kind of foam. The discussion to that point concerned open celled and you did not differentiate, but lumped all together as simply foam the same mistake the salesmen for open celled make, tho they probably do it intentionally to favor their product.
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the aged R-value of closed cell foams doesn't appear to be significantly greater than open cell foams. They appear to settle out around an R5 in the 15-year age test. that's good, but it's not so very much better that it alone would make a decision on foam usage if other factors were more important. Such as installed cost.A l've seen people do combinations of closed and open cell layers for greatest economy. I think that is a very viable solution to the question. Open cell is still often cheaper per R than closed, and you don't lose R over time.-------------------------------------
-=Northeast Radiant Technology=-
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Well you are in the business so maybe you have source to show only R-5, but that is still way better than the R3.5 for open.All the recent I see on closed shows settling on to about r6.5 to 6.8. Some open cell competition wanting top claim closed drops to 6.2.Never heard as low as R5 before for closed cell tho I suppose possible if mix was for a very high density application, but that would be more expensive to do, would it not?
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most sources I've seen seem to indicate a drop of about R-2, and most polyurethane starts at about a 7.5 is better than 3.5, sure, but not so much better that it's dumb to do anything else. teh primary benefit of foam is not R-value, but airtightness, and you get that with either foam.the difference of R19 to r27 for a full 5.5" thickness is real, but it's not incredible. and very, very few people do full 5.5" thicknesses in any spray foam, but much fewer do it in closed cell.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Please add moisture to those numbers.. on fiberglas, celluliose, and foam. we all agree that the R value numbers come from labratory conditions which has zero moisture in it.. the real world doesn't
Moisture affects celluliose and fiberglas dramatically and closed cell foam not at all!
all the more reason to use closed cell as the outer layer.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
absolutely! however I don't see open cell used around here. Which is why I always get caught off guard on the subject..
Oh by the way I do use some open cell foam in my house! it's used between the floors as a media to reduce sound transmission with absolutely no way of absorbing any moisture other than what is present in the house. (and totally imaterial for the use it's used for)
I just noticed you are only a stone's throw from me. I have some friends in Gardiner too.
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Good stuff Piffin :D drop me an email some time. I don't get out to islands very often, but once in awhile it's known to happen. it would be good to shake your hand.-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
I printed your contact info from your website.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"we all agree that the R value numbers come from labratory conditions which has zero moisture in it."And you have a copy of the ASTM standards showing the EXACT test conditions that they are run over. Most testing standards have detailed requiremenets of the exact conditions under which they run the tests..
William the Geezer, the sequel to Billy the Kid - Shoe
"Moisture affects celluliose and fiberglas dramatically and closed cell foam not at all!"It also affects open cell foam. Slower than some others, but the results are worse.Open cell will hold water, LOTS AND LOTS OF IT..
William the Geezer, the sequel to Billy the Kid - Shoe
And as I've reported I see no use of open cell foam around here. I wonder why someone would use open cell foam where it has the potential to absorb water. Frankly wouldn't that be a misapplication that be considered a misapplication? Something like using celluliose where it would be exposed to rain?
Your SIP's are open cell..
William the Geezer, the sequel to Billy the Kid - Shoe
Sorry, no their not! they won't aborb any water! It's been tried!
Something like using celluliose where it would be exposed to rain?
Frenchy, where do you get this krapp?
Don't you have a roof on your house?
Wet cells aren't a problem, water leaking into your house is the problem.
Who cares what R value wet insulation has?
If there's water leaking into your house it needs fixing no matter what the insulation.
Why do you continue to post this nonsense? You have no experience installing cells, you're giving advice on a subject you have no knowledge of.
Joe H
Good luck with that.He's been keeping that ball in the air, ju7ggling and doing tricks with it, spinning the ball on his nose that way for a lot of years
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I'll answer a few things:
They've taken out all the nasty chemicals that they used to use in the 70's. The new foams are generally blown with water (open cell) or non ozone depleting gases (closed cell). They no longer shrink and the formulation and equipment is much better in terms of getting the proper ratios and consistency of foam. If you haven't had these two types in your hands, get a contractor to show you, as you might be surprised at the differences in rigidity and density.
You need to be very careful with vapor barriers!!! Never use double vapor barriers/retarders, as you can end up trapping moisture in the wall cavities and giving it no chance to escape. Say hello to mold then.
If you have exterior XPS or polyisocyanurate with the seams taped, I'd recommend open cell foam for the walls, as it will not create a second vapor barrier on the interior side of the sheathing. As for the attics, I suggest an unvented attic assembly (no baffles, no venting) and closed cell is best , although it is significantly more expensive. Open cell is fine for most applications, but you're asking for trouble if you insist on venting where it is not needed. Take some time to read up on unvented attic assemblies. I suggest Buildingscience.com for a detailed technical explanation of this.
As for the ignition barrier requirement, this is an unfortunate circumstance (i take it it's being inspected), because if you've ever held a flame to the foam, it doesn't burn. (although there are some legit reasons for the code) You can spray a coat of intumescent paint or drywall that section and separate it.
I swear by spray foam, but I do like cellulose, it's cheap and if you have an installer in your area, it's not a bad choice for the walls. However, you can't do an unvented attic assembly with cellulose, and this is probably the single most significant energy upgrade you can make. Email me if you need more info.
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Thanks for all the responses. I have updated my profile to reflect a Columbus, Ohio location. We get a little of everything here, but are mostly considered a heating climate. I keep hoping for the definitive answer on best practices, but there are too many variables.