DABA78
Registered Users
Posts:19
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| 10/04/2008 1:31 AM |
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Hello!
I was just wondering what type of insulation material is most suitable for the attic of an ICF home.
Or, is there not necessarily a "best" choice for every situation?
Thanks!
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Chris Johnson
Registered Users
Posts:340
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| 10/04/2008 12:41 PM |
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One manufacturer makes a product called ceiling technology, great product although not going to fit everyones budget. Alternative is to spray Demilac or the likes to the underside of the roof deck and the attic becomes conditioned space.
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Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
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DABA78
Registered Users
Posts:19
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| 10/04/2008 9:18 PM |
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Thanks for the reply, Chris!
I hadn't heard of those products...will do some reading up on them.
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Aaron McKinney
Registered Users
Posts:44
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| 10/05/2008 4:28 PM |
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I believe Chris mentioned a method called having a "non ventilated attic". I've been told that with an ICF shell, decent windows and a non ventilated attic- just those three things- you will reduce your average energy consumption by 50%.
Does that sound right Chris? |
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dmaceld
Registered Users
Posts:494
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| 10/05/2008 4:55 PM |
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I had a local company spray Icynene (10" nominal, R38) on the underside of my roof in both house and garage. Probably 2 to 4 times the cost of cellulose but much, much, better insulation. Good insulation with air tight envelope. A secondary benefit is it makes it a whole lot easier and practical to use the attic for storage as you don't have to have running boards or other provision to keep from tromping down insulation.
When I did the heat load calculation for my house the heat loss came out the same with either roof underside or ceiling insulation using same R value for both.
Contrary to usual practice I'm circulating the conditioned air totally through the attic and crawl space. The crawl space is the supply plenum and the attic is the return plenum.
As far as best choice there a lot of considerations, cost being a big one. But, the poorest insulation you can use is fiberglass on the ceiling with a vented attic. In the winter cold air drops through the fiberglass to the ceiling sheet rock, gets warmed, and rises carrying a lot of house heat with it right out the vents. In summer the radiant heat from the roof sheathing passes right through the fiberglass to the ceiling transforming the ceiling into a huge radiator injecting heat into the house when you're trying to keep it out.
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Building house - what a way to spend retirement! |
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DABA78
Registered Users
Posts:19
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| 10/05/2008 9:42 PM |
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Thanks for teh additional info!
I should mention that the attic I'm considering is already vented. It has three vents, at the tops of gables, as well as a ridge vent along the peak.
I guess that rules out the spray on the underside of the roof. However, sounds like fiberglass might not be a good option either!
Seems like I recall reading about "rigid foam" insulation....does that come in panels which can be placed between attic joists? Perhaps that would be a possibility...
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Alton
Registered Users
Posts:314
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| 10/05/2008 10:18 PM |
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| Having a vented attic does not rule out spraying under the roof deck. The vents can be blocked. Spraying closed cell polyurethane between the rafters/trusses will insulate the roof and also make the roof assembly stronger. |
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Alton C. Keown
Residential Designer and Construction Technology Consultant
Auburn, Alabama
334 329-0957 AT&T Cellular |
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dmaceld
Registered Users
Posts:494
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| 10/05/2008 10:54 PM |
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DABA78,
Alton mentions closed cell polyurethane. There is also open cell polyurethane. Do a search on this website, and elsewhere, and you will find a fair amount of discussion about open cell vs. closed cell. Both have their benefits and trade offs. There isn't a conclusive answer for every case one way or the other. If you go the spray foam route you will need to decide which way to go. My insulator said open cell is about half the cost of closed cell on an R value basis.
Blocking the vents is worth considering. Losing the cost of them shouldn't be a big deal.
Another option to consider is closed cell spray about 1 to 2" thick on the roof, or ceiling, with cellulose, or maybe even fairly tightly packed fiberglass, over it. You will have to use wire mesh or something of the sort to hold the non-foam insulation up against the roof. This gives you the benefit of the air tightness of foam at a lower total cost, or so I'm told. If you are really into the green thing take a look at shredded denim insulation. It's made from recycled blue jeans. I don't know about the cost, but I don't think cheap is a proper description!
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Building house - what a way to spend retirement! |
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Manfred
Registered Users
Posts:58
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| 10/06/2008 3:32 PM |
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| If you go with closed cell spray foam you have to consider covering it with a thermal bridge. Some of the properties in closed cell foam are based on oil or its derivative. The best way to overcome this is to spray the bulk with the closed cell foam and 1"-2" with open cell foam. Open cell foam is water based and is considered a flame retarder. Just something else to think about. |
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John Clem
Registered Users
Posts:4
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| 10/06/2008 6:55 PM |
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I am not an expert on insulation, but, as I understand it, the 2 lb. closed cell foams and 1/2 lb. open cell foams are really just the same product applied differently. In the 2 lb. configuration, it is water impermeable while the 1/2 lb. installation will allow water vapor migration. You can buy either petroleum or soy based foams.
I do not know what type of roofing material is being used, but, spraying foam against the bottom of the roof deck will void some shingle manufacturers warranties.
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Home Design
ICF Distributor
www.clemdesign.com |
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Manfred
Registered Users
Posts:58
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| 10/06/2008 11:07 PM |
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Clem,
closed cell and open cell foams are applied the same way, through a spray gun - applied in the same fashion! Please don't lead people down the wrong path with making false statements. Closed cell foams are based on petroleum or oil or whatever you want to call it while open cell foams are based on water. That the closed cell product is flammable is a known fact and needs to be covered with a thermal membrane. A open cell foam covering can be such a membrane since it is non-flammable due to it being water based. This has nothing to do with a product being impermeable, permeable or semi permeable.
Most shingle manufacturers have acknowledged hot-roofing. They will give you a warranty. Hot-roofing is practiced all around the country and nothing new to the asphalt shingle industry. |
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foamitgood
Registered Users
Posts:4
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| 10/06/2008 11:18 PM |
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DABA78
Either system, conventional,sprayed directly to attic floor or an unvented attic system with all vents sealed off and foam sprayed to the roof deck will perform excellent. The major factor is usually cost spraying the roof deck can sometimes double the square footage to be sprayed it all depends on the roofline.If you have heating cooling ducts, storage, or cathedrial ceilings spray the roof deck. If you have a steep roof line,no heating cooling ducts, and want to save some money spray to the sheetrock. Open cell sprayed to a 5.5 inch average will perform flawless. Closed cell also is an excellent choice but due to the square footage in an attic it can get rather pricey. Consult a reputable foam contractor that has been in business several years and has references. Either system closed or conventional will be no problem for someone with expierence at spraying foam. |
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John Clem
Registered Users
Posts:4
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| 10/07/2008 8:47 PM |
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Manfred,
Seems you need to do some fact checking before you respond. As I said, I am not an insulation expert and was simply stating what I believed to be the case. Maybe you are an insulation expert or maybe not.
Not all closed cell foams are petroleum based. Do a search on soy-based foams. A quick google search will show that soy based foams are available as either open or closed cell forms.
These foams are not water based! Water is used as the blowing agent (it makes them expand). I found manufacturers that use water as the blowing agent for both .5 lb and 2 lb foam.
I only did a quick check, but I could not find any manufacturers stating that their closed cell foams required being covered with another product. Not sure if this is such a known fact or not.
As far as hot roofing, this was not permitted by the manufacturer I used 18 months ago. As I stated, it might be something to verify before you take the word of somebody on a web forum.
I would always recommend consulting with a local supplier in order to make sure. |
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Home Design
ICF Distributor
www.clemdesign.com |
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dmaceld
Registered Users
Posts:494
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| 10/07/2008 11:50 PM |
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The insulator who did my house said when they're spraying 2 lb foam closed cell foam you don't dare stay in the area for more than a few minutes without a respirator with an air supply because the fumes will make you very loopy. With Icynene, and open cell foam, only the sprayer needed a respirator with air, and that was mostly to prevent inhaling foam particles. Expanding foam particles in the lung ain't good news!!! Helpers and observers were in no danger from fumes.
As far as covering one foam and not the other, the IRC requires all foam to be covered with a thermal barrier, or ignition barrier, depending on how the area that is foamed is used, unless the foam has been tested IAW various NFPA or UL test procedures. Icynene requires a spray on ignition barrier over the entire foam application if the attic air is circulated through the living space. Dimilec requires the ignition barrier on the gable walls but not on the roof for the same situation.
I say there is no one simple answer, for either thermal barriers or formulation, that cleanly applies to all closed cell or open cell foams.
As far as hot roofing, Owens-Corning doesn't say one way or the other. Just be sure to follow their installation instructions, which are silent about hot roofing.
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Building house - what a way to spend retirement! |
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Manfred
Registered Users
Posts:58
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| 10/08/2008 9:10 PM |
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Hi Clem,
you might be right and I might be wrong. I did look up soy foam, bio foam etc. I will not dispute what you have said since I found no evidence to contradict. But...to my defence, my rant was based on polyurethane based foam. The blowing agent for the closed cell being petroleum based and the blowing agent for the open cell being water based.
In NC, it is required to supply, install a thermal membrane over top of the closed cell foam with a petroleum based blowing agent. Only makes sense since the blowing agent even after expansion is part of the cured product, hence flammable. THe solution for this has been indicated to either a) a 1/2" covering of drywall or b) a simple covering of a water based paint. According to the code you want to buy 15 minutes against fire engulfement.
The open cell foam with the water based blowing agent does not require such covering because it adds no fuel to any fire. I am sorry for the confusion. Technology advances every day and truly I have not heard of a closed cell insulating foam application not being based on a petroleum product. Can you enlighten me to what product this is? I could not find it on my internet search.
Thanks,
Manfred
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GRickard
Registered Users
Posts:38
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| 10/08/2008 10:07 PM |
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Just to get back to the original post. While sprayed in icenene is a really good partner to an ICF wall, it is considerably more expensive. You may want to price some different options to determine will a perfect match ever pay for itself? I found that 14 inches of cellulose will do a great job at alot less cost. Keep in mind that it doesn't cost anything to get different quotes. Good luck,
Greg |
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Chris Johnson
Registered Users
Posts:340
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| 10/09/2008 7:58 PM |
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Posted By Aaron McKinney on 10/05/2008 4:28 PM
I believe Chris mentioned a method called having a "non ventilated attic". I've been told that with an ICF shell, decent windows and a non ventilated attic- just those three things- you will reduce your average energy consumption by 50%.
Does that sound right Chris?
Yes, your energy consumption can be reduced...a lot, I won't quote 50%, too many variables to consider, like how many times the front door is opened and closed, location, foundation prep, type of heating system, etc., etc.
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Chris Johnson - Pro ICF
Napa, CA
Come for the wine, Stay for the ICF work |
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Vermonter
Registered Users
Posts:49
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| 10/12/2008 3:02 PM |
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Check out this method of roof insulation
http://www.buildingscience.com/documents/primers/bsp-035-designs-that-work-very-cold-climate-juneau-ak/section-2-the-basic-very-cold-climate-house/ |
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