Is there a downside to foam insulation
I’m considering foam insulation in an upcoming renovation. The walls in the renovated areas will be stripped of drwall, so I can pretty much insulate with anything I want. I like the idea of foam’s sound deadening properties. Is there a downside? Can it create a favorable environment for rot if moisture gets in? If not, it seems the only downsides are cost and the inability to fish wires later.
Replies
I have found ants nesting in the foam on houses before. I also don't think you can get the R-factor you need, but I may be wrong. I'm sure that would depend on your locale.
Foam provides the best R-value you can get.
most now have borates included to resist ants and the old urea- formaldehyde off-gasssing is nearly negligible unless your guy is using older formulas.
Cor-bond is good on all counts, IMO..
Excellence is its own reward!
I guess I'm a little behind on my foams these days! :^}
Your not supposed to use the spermacide kind!!!!Mr T
Do not try this at home!
I am an Experienced Professional!
No wonder ants like it!
I have SIPs so I'm a little differant, but wow does it make the walls stronger, and quieter! My brother in law just is finishing up his renovation and loves his foam walls, In fact he's gonna foam the additions too!
he claims no problem doing wiring, you just do it before you foam.. In the couple of area's he thought might call for added wires in the future, he ran some plastic pipe.
As for moisture, you still have wood so that if you have leaks it will rot, however the foam itself is water proof thus vapor is not a problem..
Wow, it's the SIP's that make you a little different. And here I though it just came naturally.<G>
Seriously, the only downside I can think of to foam insullation would be with the old styles that carpenter ants and bees ect. loved to eat and burrow in. I believe this isn't much of a problem anymore. Or if you for some reason needed some permiability of the walls. Proper ventilation systems would solve those problems. Overall, it seems like a superior way to go.
Billy,
I was a wacko since youth... I'd claim earlier but my memeory isn't that sharp..
Gees, now you tell me. And I'm gonna bring my wife to meet you.<G>
I too admit to being a wacko from birth. Actually, I was less of a wacko then. . . . I think. <G>
One possible down side, although it might be minor in your situation, is that some of the foams are flammable and none are fire resistant. I believe that icynene is not flammable but will melt at a fairly low temperature. For fire protection, you need to cover foam with a fire resistant material such as sheet rock.
(you can read the blurbs on icynene at:
http://www.icynene.com/index.asp
Based on what I read on the website, I can only get about R12 in a 3.5" wall. That's sort of a bummer, huh?
anyone familiar with the soybean based foam insulation?
http://www.michigansoybean.org/new_page_4.htm
that doesn't sound correct.. which foam are you using? Foam is rated higher than fiberglas or any other insulation..
aside from that I assume that you realize that when you are talking stick built you only achieve 80% of actual rating.. That is, there is a two by four every 16 inches with an R value of close to nothing.. add in the top/bottom plate where there isn't any insulation, window headers and cripple studs, and anyplace where the 2x4's are doubled up in actual testing stick frame is a very poor way to hold heat in.
That's the reason I went with SIP's but of course you can't do that in remodeling...
I just came from a three hour class on walls presented by Corbond. There is no need at all for ventilation with good foam installation. he made a good case against ventilation..
Excellence is its own reward!
Just what was his case against ventilation?
I've read a few articles about sick building syndrome. Many are convinced people in super-insulated homes with little ventilation have problems due to indoor air pollution.
Now, not sure I buy their whole bill of goods, but there seems to be some merit in it.
Just curious what the guy had to say about it.
If I built a house, I'd have them spray foam. Well worth the extra money in my view. Or maybe use SIP's.
Short version is that well installed sprayed in foam eliminates the dew point so no condesation happens and so you don't need to vent escaping moisture out..
Excellence is its own reward!
Sick building syndrome -- Sure it's a real thing.
The deal is that tight houses are a very good thing.
So is ventilation.
You can't build a tight house and not provide adequate ventilation.
(well, you can, but then everyone will get sick)
Some people say that a house needs to breathe, and that you need to provide ways for fresh air to flush through the house. That leaky houses of the past were better because they provided this.
But work your way backwards through this logic.
If you're afraid to build a tight house, how leaky should you build it?
Should you punch holes in the walls or the ceilings?
Or both?
How big should the holes be?
Is sucking radon from the basement the best way to provide air changes?
You should build tightly, and provide mechanical ventilation.
At least, that's what I think.
Dan
One of the biggest causes of sick building syndrome in super tight houses is that the HVAC unit is not sized down accordingly. When the HVAC system is oversized it only runs long enough to cool the air but it does not have time to cycle, filter, dehumidify and fully "condition" the air before the thermostat kicks it off again.
The result is a moisture laden, moldy house full of unfiltered air. That does not make for a healthy human environment. If the HVAC system is correctly sized mold should never be an issue. Especially on a non-vented house where the infiltration of outdoor contaminates is minimized.
As for foam, pour yourself a cup of steaming hot coffee in a styrofoam cup and hold it for a while. That is the insulating power of 1/16" of foam. Nuff said...Kevin Halliburton
"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity." - I.M. Pei -
Good point, and well stated.
I think in most cases a normal HVAC guy would simply put the same system in every house using a formula factored on the sq. footage. Most probably wouldn't understand the great savings in the lower air infiltration and higher insulation values. But, this is mostly because SIP's is still something most HVAC people haven't come in contact with.
As I think I stated earlier, if building my own house, I'd probably use SIP's. At the least I'd have it insulated with spray insulation.
I earlier posted a couple downsides I'd read about to foam insulation, that some bugs like to burrow in it, and I forget what else now. Just to address the question of the initial poster. All are minor problems, most of which have been or can be easily fixed.
Later
Have a good week.
Gonna go see that wacko guy that hangs around here.
Hiya Piffin,
You were at that seminar in Rockland? He came down to Taunton Press today and condensed his seminar to an hour and a half. But then we ate lunch with him and talked about it more.
Yes, Closed cell polyurethane will provide the best R-Value (He measured about R-7 per inch at Architectural testing service in Knox PA).
Fishing wires: Since you can get a great R-value with only a few inches, This Corbond guy only sprays a few inches in a wall. Fishing wires is a breeze. Ever try to fish wires through a fiberglass wall or dense packed cellulose?
Venting: No need for it. We had an interesting discussion about roof venting. We talked about a conventional roof venting scheme and the conclusion was that in order for it to work properly, the ceiling needs to be leaky and there needs to be poor insulation details. Since roof venting is dependent on warm air in the attic rising and therefore sucking in new outside air to drive a convective current, the insulation detail needs to be weak. He said that he's repaired a bunch of rotted ridgecaps from moisture condensing on the roof sheathing, but the venting system working poorly (good ceiling sealing, good insulation details) and not moving the moisture out.
I'm in the process of developing an article about why and how not to vent a roof with a guy who does the same thing -- hawks polyurethane foam.
When are we going to develop an article Piffin?
Dan
If you do write an article, I'd love to hear a bit about the soy based foam.
I won't write it, I'll edit it.
But the subject of the Soy foams came up and here's what he said:
It's a new technology. They haven't worked out the bugs yet blah, blah, blah.
But the more important point was that the earth isn't going to hell because of polyurethane foam insulation. It's going to hell because houses are rotting and being torn down after ten years or less. The problem is stripping hillsides to build houses poorly, then tearing them down to replace them. The houses don't even last long enough to grow another 2x4. And fossil fuels going through the roof because of poor insulation details.
Sure, maybe they're better in the small picture (maybe), but they're not really focusing on the problem.
Their track record is small, so he's not ready to gamble on them.
That's all I know about it.
Dan
Dan:
Well, that about sums it up. I agree that the foam itself can reduce environmental waste with the higher insulating value and reduction of wasted (tear out) materials.
That said, I'm just intrigued with what they can do with soy these days. It'll be interested to see where the product goes in the next decade.
Question RE: your discussion of roof venting
I am under the impression that adequate attic venting is also important in summer to allow heat to escape from the attic.
Seems that you were referring to venting as it regards to the heating season, but wouldn't you still want it in the summer?Any jackass can kick down a barn, but it takes a carpenter to build one.
Well, Yes and No.
If you're insulating the underside of the rafters, as we're talking about, them you don't need to vent the roof because the insulation will keep the attic conditioned. Roofs that are insulated are like walls that are very out of plumb.
We don't feel compelled to vent walls.
Now if the attic floor is where the insulation is, the sun beats on the roof and heats it. The roof radiates heat into the attic. Warm air rises as cool air takes its place. The hot air in the attic rises out of the ridge vent and is replaced by relatively cooler air sucked through the soffit vents. The heat of the roof drives the convection current, and the system works.
If you use the correct soffit and ridge vent ratio and combination.
The system works, but what work is it doing? Yes it's a nice convection current. But is it cooling the roof? I doubt it since the roof in in direct sun. A shade tree would do a better job of that. Is it lowering the cooling bill of the homeowner? Maybe by a couple of bucks, but better insulation details would be FAR more efficient. Where are most air conditioners and ductwork located in the south? The unconditioned, hot, and now breazy, attic. The convection currents will create a negative pressure such that the warm air shooting out of the ridge vent seeking replacement will suck cool air out of the (always) leaky A/C ducts. Since the A/C air is cooler than the outside air, the gods of physics may prefer it to the warmer outside air (but that's only a guess).
The better system would be to move the building envelope from the ceiling (attic floor) to the underside of the roof deck, and keep the a/c unit and ductwork inside the conditioned building envelope.
So what do you do if you don't want to completely re insulate your attic? Seal all the penetrations in your ceiling, insulate the crap out of the ceiling with Cellulose, and seal any leaks from the crawlspace/basement. If the venting system works, it probably won't do too much harm...
See FHB # 125 Fixes for Damp Moldy Houses, #105 Fixing a Cold Drafty House and #130, Insulating with Cellulose and #153 Sealing a Crawlspace for information about sealing and insulating the ceiling and crawlspace.
I hope that helps, I've really got to get back to work now...
Dan