open cell versus closed cell spray foam?
This may have been discussed already, but what are the opinions on open cell versus closed cell spray foam insulation? I know about Icyenene, are there other products anyone has found to be better or comparable in your opinion?
I was thinking of insulating with Icyenene, omitting the vapor barrier on the inside, wrapping with felt paper, and siding with wood. For extra insurance I was thinking of building a rain wall or rain screen behind the siding, as well as backpriming all the siding.
I live in an area that is very cold in the winter and hot and humid in the summer, I’d rather not wrap the house with a vapor barrier (meaning, plastic on the interior walls and ceilings, as is common around here). I understand about indoor and outdoor moisture problems, and the ineffectiveness of damp insulation, and the trouble with poor indoor air quality, etc. Maybe I’m just old-fashioned but my insticts tell me a house should be able to breathe.
Any thoughts?
Replies
where are you building?
I am building in central Pennsylvania where temps can go down to mid-teens in the winter and we experience hot, humid summers. I did use Icyenene on my roof two years ago (part of the house is finished). Once I began heating the 2nd floor( cathedral ceiling under the roof) with electric baseboard, my electric bill only jumped $20 a month. I did not use a vapor barrier, I filled the rafters to 71/2 inches.
I had baffles in place for venting the roof through the ridge but the heat and expansion from the installation of the Icyenene may or may not have collapsed them. (The installer did a test first with my baffles to see if they could take it, and they worked alright in the test. However, upon installation many baffles began to pop off the plywood.) I'd use the cardboard type baffles if I could do it over.
I like Icyenene for it's green value, it's been used in alot of homes where chemical sensitivity is an issue. My concerns between open and closed cell have more to do with breathability of the house and wether or not it's good or bad for the house to breathe. So maybe the title of this question should have been "to breathe or not to breathe?".
>"to breathe or not to breathe?"I come from a different perspective than most here, in that my houses (I design a specific type) are arguably the tightest construction that is possible. They have 3" continuous polyurethane foam, 3" continuous concrete, plus a membrane that blocks water and air. If we're gonna have leaks, it'll be at poorly built or installed doors and windows, or chimneys, or vent openings, etc. and not through the walls.Empirically speaking, my daughter's friend visited the other day and when she walked in said, "Your house always smells so good. I wish my mom's house smelled that good." It's not from cookies, air freshener, etc.We have precluded the possibility of random and unwanted air infiltration, and instead, make the air do what we want it to. The house is positively pressurized so that it doesn't tend to draw air inside. The air that does come in is through an intake vent that goes through filters and the dehumidifier before it's circulated. That means we control the quality of the air rather than let any ol' air come in and then try to condition it from all the places it leaks in.No comment on if breathing is good for the materials in a frame house, or if attics should be vented or not (we don't have attics!). Just offering that I don't see that "breathing" (or leaking, imo) through the walls/roof is a positive thing, and I prefer better control of the air quality.
AFAIK, all of the spray-type foams are closed cell. If they weren't, the bubbles in the foam would collapse and you'd be left with a puddle of goo.
You are dead wrong. The blowing agent is what determines whether its open cell or closed cell. Icynene IS an open cell foam (and it dosent collapse). The Corbond brand is a closed cell foam. The big difference is that closed cell foams are roughy twice the R value per inch, and are an moisture barrier.http://www.icynene.com
http://www.corbond.com
AFAIK, Icynene and Corbond are both derived from Polyurethane.As you correctly point out, Icynene is a lightweight foam that uses water as a blowing agent. It's density is quite low, it's very friable (like hardened shaving cream), and it gets about R3.7/inch. If it's thick enough, you may even consider it a vapor barrier, at least that's what our contractor advised us when we filled our 5.5" deep stud cavities with the stuff 100%.In the old part of the home, we used Corbond to fill the 4" stud bays to 3.5". The R-value of Corbond is about 6.5/inch when old and it is much denser, harder, etc. The insulation guys didn't like it as much because it made them work harder than the Icynene. However, Corbond will strengthen your walls and even in small thicknesses it is considered a vapor barrier due to it's impermeability.Both types of insulation should be covered by fire-retardents (sheet rock, etc.) because once they go, you'll have a heck of a time putting the fire out. I prefer Corbond simply because of it's higher R-value and impermeability, but it is pricy. Corbond used to be blown with R22 or somesuch, nowadays they use a ozone-safe blowing agent.
Do a search on this and you will find more discussion on it than you care to read. A good thread was "Spray foam vs. Fiberglass". I am also considering the Icyene insulation and have pretty much decided to do it.
Keep in mind that I am by no definition "a professional" and this is only my opinion but here are a few things I have picked up...
Yes the Closed Cell foam has a higher R value but it does go down over time as the cells lose the gas trapped inside and gas is replaced by air. It should still be higher than the open cell but not nearly as dramatic as it is initially.
I think the decision of which foam to use really depends on the moisture issues you have to deal with. If you deal with lots of moisture and have great need for a moisture barrier, then the closed cell is probably your best choice. I would choose that if I were doing a basement. If you are in a climate where you have limited moisture and only need for things to breath a little to help with condensation, the open cell seems to be better at this. Open cell (Icynene) does not act like a sponge but it is supposed to allow some vapor to escape. Moisture will likely occur regardless of which you choose in any area where temperatures on one side are very different from temps on the other much like your glass of cold water gets wet on the outside. I dont think either foam solutions can be counted on to fix moisture problems within the home and will require some Ventilation solution. The main advantage of the foam as mentioned above is the air seal. Both will accomplish this.
Do an adavanced search .
Or click on message count just under the Energy... folder. And check the all of the threads.
And at the bottom of the screen there is a place for "50 more" to view older ones.
There have been several very specific threads on this in the last month.
Here is a very interesting thread in another discussion regarding foam insulation. In particular check out the posts by "Energy Rater La". Independent Insulation efficiency seems to be his profession and her certainly seems knowledgable. I do have a problem reconciling some of his concerns with the fact that I have not seen a single person that installed the foam insulation that did not think it was a good decision after the installation.
http://ths.gardenweb.com/forums/load/build/msg0221454815819.html?49
I think Energy Rater is raising these concerns:* Before you air-seal your house, make sure you've dealt with sources of moisture (VB in basement floor, fans in kitchen and bathrooms) ow you've turned your house into a mold factory.* Make sure you have some kind of house ventilation system that ensures 0.25-0.35 air exchanges per hour.* If you have CAC, will it be oversized after you insulate? Then your AC system will contribute to the mold factory.All basic stuff well known to anybody who does their research, and probably news to a lot of people who do insulation for a living....
What really interested me was that he said one could achieve as good of air sealing results with traditional batt insulation by such methods as extensive caulking and dry wall taping. He also discussed that the foam houses that he has tested were far short of being truely air sealed due to poor application and had dissappointing thermal leaks. Energy Rater was not an advocate of the foam systems yet every single instance that I have come across after extensive net research shows the home owner very pleased with the results. You are very correct stating that his primary concern was that the moisture problems were not being dealt with properly but overall, he certainly did not champion the potential of the foam insulation system.
I still think it has a lot of merit. I just wonder if the benefit is really worth the 3x expense.