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meth 01-26-2009 01:19 PM

Insulation - Cellulose vs. Icynene
OKay guys I know this has been discussed on here before and I have gone back and read numerous previous posts - However I am still confused! I am looking at adding insulation to my attic. My home is about 18 years old, approx 3,000 s/f. The attic is unusable due to the trusses and my a/c unit and duct work is up there. I have some fiberglass insulation there now, although I know its not nearly enough. I have been contemplating either blowing in cellulose insulation or spray foam (Icynene). I have had a couple of contractors come out - one for the cellulose and one for the icynene and of course I received conflicting advice. Currently the attic is vented by soffit vents, ridge vent, and even a couple of gable vents ( I believe thats what they are called as they are installed in the end peaks). The Icynene guys tells me that he will seal all the vents with the spray foam and then spray the exterior walls in the attic as well as the underside of the roof decking - thus completely sealing the attic into "conditioned space". Now this is contrary to the little knowledge that I have and have been taught by some old school contractors who believe that venting is mandatory. In fact when I presented them with the idea of Icynene they thought I was out of my mind for even entertaining this concept. Anyway, the contractor measured out the space and will work up a quote that I am expecting tomorrow. His suggestion was to not only do the attic but also the sill plate in the basement. He also told me to not consider cellulose in the attic since my a/c unit is there and that I would not have 14 inches of space between the bottem of the unit and the floor joists to get the proper level of cellulose and that if I ever needed to service the unit (or anything else in the attic) it would be a nightmare with the cellulose since there is no walking space.

Now the cellulose guy comes and say's no problem this is a perfect application and I can blow in 12 inches of cellulose, ensure that there is proper baffling at the soffit vents and even construct a retaining type wall to protect the a/c unit. Additionally since my master bedroom is above the garage he says he can drill a small hole in the garage ceiling and blow in cellulose to help keep the bedroom warmer as well. He was also very skeptical on the idea of sealing the attic vents and what that would do to moisture in the house and its effect on the shingles.

I am so CONFUSED! To top this off I am planning on installing a new roof in the summer, going over the existing shingles since there is only one course there.

I am expecting the Icynene to be significantly higher in cost and will have to weigh out the return on investment - I am just so confused on the theories of which is better and is having an unvented attic in Northeastern New York really smart?

joel v. 01-26-2009 03:23 PM

An attic needs ventilation. If this is a single story you will need to have moore vents(raft-r-mates) from the soffit to the top of the insulation and if it's a 1 1/2 story then moore vents in the sloped part of the celing . For a full 2 story you do the same as a single story. The spray foam doesn't normally show a return on investment for a 1 or 2 story but with a 1 1/2 it will eliminate alot of ice when filled right up. You HAVE TO have ventilation though. The shingles will get hot in the summer and there has to be a way to cool them. If you really want to warm it up get it to at least R-42. Make it R-60 if you want to have an even lower heating and cooling bill. The guy spraying the icynene must own either a roofing business, and/or a fuel company. You will have venting problems and it will cost you more to heat your house. Basically I'm saying you'll be wasting your money with the spray foam and that guy is lieing to you.

meth 01-26-2009 03:30 PM

Thats what I was afraid of - its a 2 story home and I figured the attic needed to be vented, although he says it doesn't and even in some of the posts I read here the claim is that the attci becomes a sealed conditioned space.

jaros bros. 01-26-2009 04:30 PM

Actually, the icynene contractor is correct in his remarks. It sounds like he is going to turn it into a hot roof. Shingles are now rated for this and warrantied and it is possible to do what he's doing. It wouldn't be my recommendation though. The cost is far higher and cellulose blown in is good bang for your buck...make sure they install wind washing. Also, in the case of the rim joist you should the icynene because in that application it is the only thing to use in a cold climate.
Another option would be to have the icynene contractor just spray inbetween the ceiling joists. This would be a lot tighter than the cellulose, plus there will be a lot less material used and therefore cheaper.

Josh Jaros

meth 01-26-2009 06:51 PM

Thanks for the reply, the Icynene contractor said he wouldn't spray the joists in the attic, that it had to go to the roof decking? I will compare the two quotes when I get them. What is wind washing?

I will look into the hot roof also, not sure if this equates to me if I will be shingling over the existing roof.

I also asked the Icynene contractor about just doing the sill plate in the basement but he said that the job would be too small and maybe not worth it cost wise, I asked for a quote anyway so we'll see what he comes back with

meth 01-27-2009 08:42 AM

Just to be clear on my previous post - the Icynene guy said he wouldn't spray the floor joist in the attic, only the underside of the roof decking

jaros bros. 01-27-2009 09:20 AM

Did he give you a reason for why he wouldn't do this?

Josh Jaros

meth 01-27-2009 09:38 AM

just that it was not the "proper" installation of the product

jogr 01-27-2009 10:56 AM


Originally Posted by meth (Post 220023)
just that it was not the "proper" installation of the product

More than likely he just didn't want to deal with removing the old fiberglass since you can't spray the foam on top of the old fiberglass. He just wants to come in and start spraying. Which is also why he's just going to spray the vents closed rather than remove them. When you go to reroof and find the ridge vent glued in place by the foam you are going to have a heck of a time removing it without damaging/cracking the foam insulation. If you crack the foam you've just lost the airtight seal which is one of the key advantages of the foam.

Both the foam and the cellulose are great products and either will work fine if applied correctly which means that the most important thing is selecting the right contractor.

meth 01-27-2009 11:40 AM

I thought we would have a problem with the ridge vent - I'm leaning more and more to just going with cellulose

Winchester 01-27-2009 07:18 PM

One of my previous posts....

Originally Posted by Winchester (Post 212735)
Unless you incorporate a Hot Roof System. My brother-in-law did this to his new home a few years ago and he's completely satisfied with his choice and how energy efficient his home is.

IMO, if you want the bang for your buck, then go for the cellulose. If you're in it for the long term savings and can afford it, then go the spray foam.

Also take into consideration this years Tax Credits 10% of cost, up to $500.

The foam is perfect for the basement rim joists. I think the contractor maybe indicating a back out for that "small job" basement project trying to get the whole quote. With the economy the way it is, I'd think he'd be trying to get what he could. You might be able to use this to your advantage to get a better deal?

Best of luck. :thumbsup:

meth 01-27-2009 08:30 PM

Thanks, I was expecting the quote on Monday, it still hasn't come so I'll give him another day. I asked him to split the quote between the attic and the rim joists in the basement. I'm thinking of doing it there since it seems like a good place to save, however I have no idea how much it is going to cost - it could blow me out of the water!

meth 01-30-2009 12:53 PM

Okay just received my Icynene estimate - Was given 2 quotes - one for an R-20 for $5,900.00, the other for a R-30 for $7,400.00. The R-20 price seems reasonable, however I am not sure if it makes sense to increase the R value to R-30? The gable walls and vents will only be insulated to an R-14 and the sill plate in the basement will be an R-14.

I thought the attic was supposed to be at least an R-40? What do you guys think?

Wildie 01-30-2009 04:51 PM

Your ductwork should be insulated as much as possible. I would go with the crib around the a/c unit!
R40 is the standard today! In my house, although I had cellulose blown in the walls, I opted for fibre glass bats run across the ceiling joists! They can be lifted for maintenance and then returned to there place!
There are some that argue that attic space doesn't need venting, I've never seen a case where it caused any harm!

Chemist1961 01-30-2009 05:10 PM

Before you take the plunge and to learn more about ventilation for the attic suggest you review this site

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