I am an architect in Charlottesville Virginia looking for info on the pros and cons of Icynene insulation.
In additon I have the following questions: I understand the basics of how Icynene works (see below) but need assurance that I can delete soffit, ridge and gable end vents without any ill affect. Waht about the IRC 2003 roof ventilation requirements? If the roof sandwich is now insualted will all attics spaces need to be conditioned and mechanically vented? Is this product and the installation details tested?
HOW ICYNENE WORKS – The foam is a vapor barrier and since most of your vapor comes from outside it seals it out. Also ridge vents and gable vents were traditional used to provide moister and condensation to escape. With traditional insulation there is an air gap between the insulation and roof structure. This allows for hot air to build up and cool creating condensation. With that your wood can rot. With foam there is no gap and thus no hot air to create condensation. Also the foam decreases the attic temperature by 60% so you don’t have the extreme temperature changes that occur with fiberglas.
Replies
Do a search of "icynene" on this site, or "hot roof" or "unvented roof" and you'll get a wealth of discussions on these topics.
One thing you should definitely do is go down to the building department and ask your inspector if s/he will accept an unvented roof insulated with foam. As far as I know, there is no reason you could not install typical insulation baffles and spray against those, leaving the usual 1" vent space under the sheathing, and preserving your soffit-ridge vent path, but you'd have to talk to your installer about that.
The thing that puzzles me about the blurb you quoted is that they say "The foam is a vapor barrier and since most of your vapor comes from outside it seals it out". That's contrary to what a lot of folks say, which is that the moisture originates indoors, and attempts to migrate thru the walls. You'd think that insulation with a high perm rating, like foam, would stop that moisture from passing out thru the wall assembly. All of this talk about housewraps etc. focuses on the ability of vapor to get out if it does get in... so foam would appear to change that entire equation.
Another source of discomfort for me is the fact that a roof leak would go undetected for a long time (especially with a closed cell foam), probably long enough for the roof framing to rot out. With a typical roof leak and FG or cellulose, water gets thru and stains the sheetrock quickly, which prompts you to fix the roof. Not that I expect my roofs to leak, but it could happen.
The major advantages of closed cell foam appear to be (a) that moist air from the interior of the building cannot migrate thru the insulation to the dew point, getting the insulation wet, and (b) you get a very high level of air sealing, so that windy weather outside does not push cold air thru the building envelope.
I've got a project to insulate shortly and am trying to sort thru all of this stuff. It's not easy! I'm leaning towards blown-in FG at the moment, but have not decided.
David,
First, please read my previous post to save re-typing...I understood the part you were mentioning, but they are wrong that icy is a VB.The part about moisture coming in from outside is probably referring to the walls and in context, the fact that our OP Architect is living and working in Virginia. In a cooling climate where one can expect in this day and age, the interior space to be air conditioned to a lower temp than the outside air the majority of the time, the VB should be placed on the outside, because any infiltration will condense in the wall cavities if the VB is one the inside. In the heating climates it is the opposite. To be fair, the icy does slow infiltration way down, but does not totally eliminate it..
I would use icy in some instances, but I reallly do get tired of hearing of their salesmenmaking flase claims for the product as though they were selling Corbond. I believe they read the Corbond studies and literature and ignorantly or dis-honestly fail to notice that they are selling a different chemical product.
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You are correct about moisture from the outside being an issue--I am guilty of being west-coast-minded, and have not been to Virginia in 30 years. Some of you folks live where it gets very cold and very hot... sometimes I forget that.
Also, I have mostly looked into Corbond, not Icynene, and actually don't know much about the latter. It might be a lousy VB. Corbond appears to be a near-perfect VB.
I still find the competing claims and whatnot about foam to be quite confusing. There is not a concensus about whether it's a good thing or bad, as far as I can see, as each type has its adherents.
it's fantastic if you can afford it. Another side benefit that every customer comments on is that it makles the house quieter from outside noises - traffic, windstorms, what have you.
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Icy is definitely NOT a vapour barrier. I would not buy a product from a company making false claims. They indicate that they do not understand their own product. That can lead to other installation errors in judgement.
It does often, when installed properly, with enough completeness and thickness act very similarly to a VB insofar as it eliminates a dew point for condensation to occour. But then again, there have been many reports here at BT of Icy holding water like a sponge.
The polyurethene sprayed in place foam insulations are a closed cell and ARE VB in fact. They also provide approximately twice the R-value as Icy does. I repeated hear the installers and salesmen for Icy make claims that are based on the properties of polyurethene insulation and the reseach of the leading brand name product, Corbond from their site and book, "Walls that work"
Denspac cellulose can also provide similar effectiveness as Ivy in certain situations, in that both reduce greatly the convection curents that undermine the effectiveness of traditional FG batts.
i'm sure if you google for the advice of Joe L ( I can't spell his name) at the Building science website, you will learn more about the subject based on his long experience with scientific testing, inspoections of houses, and investigation into this to base your own conclusions on.
As for the roof, there are some shingle manufacturers who void warrantees on hot roofs, regardless of the manner they are created, based on studies that show the composition shingles may have a shorter life span when exposed to more heat over time. This is true, but to a very small degree. We are talking only a few months out of a twenty to thirty year comp roof.
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Check out Corbond which is a closed cell foam and has twice the R value as Icyene