Spray Foam Insulation

[Jim Benante]

Has anyone purchased a spray foam insulation kit? I have seen a few online. I have a small area to insulate (60 sq ft room addition) including a vaulted ceiling and want to use closed cell spray foam. I am considering doing it with one of the kits, but wanted to hear feedback on how to work with the foam and what problems I might encounter.

[John Daugherty]

I had the band around my house sprayed with foam. I had looked at spraying it myself. I priced several of the kits. For the heck of it I contacted a contractor and got a bid. It was actually cheaper for me to have him spray the band than I could have done it myself. He also put in more than we had agreed.

[Charles McKinley]

Hi Jim,

Make sure you have an air space between the faom and the roof or you will cook the shingles off in the SUmmer. If you put on a metal roof ignore this. I have looked at the kits several times and it has always seemed expensive for what you get.

edited because I can't remember when it gets hot outside.

[John Hart]

I used the stuff to seal my new addition. The Amish recommended it to me and swear by it....and they are a very insulation-minded people.

[Jim Becker]

Make sure you have an air space between the faom and the roof or you will cook the shingles off in the winter.

This is counter to industry practice in this area for closed cell spray foam.

[Brett Baldwin]

It would be a good idea to check with a contractor for two reasons. It might be cheaper and there are fire code issues with making a total envelope of foam. It is usually a matter of a flame barrier between the enclosed space and the foam but I'd check. My company makes the foam for contractors and they often have disputes with inspectors over these things.

[Ken Garlock]

Hi Jim,
Make sure you have an air space between the faom and the roof or you will cook the shingles off in the winter.

Charles, please elucidate on the roof cooking in the winter.

When we built here in Texas, we were given the option to have a sealed attic where the foam insulation was sprayed to the underside of the roof sheathing. I was told that it is becoming a popular method of insulating in Florida. It seemed a little too new to me, and we went with 4" of Icynene in the ceiling joists plus another 12" of blown fiberglass.

Articles I have read say that only one side of foam or 'bubble wrap' insulation needs to have 3 inches of breathing room, and that is on the attic side.

Maybe the industry has changed its mind in the 5 years since I have investigated the subject.

[Andy Hoyt]

The air space thing is critical - at least a far as I'm concerned, and my experience comes from many years in the timberframing industry.

In a conventionally framed house the insulation is typically installed on top of or in between ceiling joists creating a thermal barrier between living space and the attic or truss area. A vapor barrier is also typically placed between the insulation and the living space. This arrangement allows any moisture that may enter the attic area (via whatever means) to exit through ridge or gable vents. Most of the moisture will be entering through the eave vents.

So if that's the case, why install the eave vents in the first place? The answer to this is that adequate air flow underneath the roof itself is needed to carry any moisture (that might have arrived via aging materials, leaks, poor installation, ice damming, and such) away from the roof. If the roof is not vented it will fail sooner or later - sometimes catastrophically and suddenly.

So when you place the insulation under the roof (as in a timberframe or any other structure with vaulted space) an alternate method of mositure removal must still be undertaken, but choices become less numerous.

If it's a conventionally framed roof with fiberglass batts the simplest way is to install eave vents and those styrofroam channel thingies between the sheathing and the insulation along the entire run of insulation until you're up into the attic space or all the way to a vented ridge.

If it's a timberframed structure (which won't used sprayed foam, but will use either SIPs or 4x8 sheets of rigid foam in a site built arrangement) the insulation goes outside the framing, decking, and the vapor barrier. And on top of the insulation you install strapping (one or two layers, and maybe also plywood sheathing; but this is dependant on the roof finish). We specified and built all of our roofs this way - nationwide. The only failure I'm aware of was one in which a second owner (in his hot arid climate) installed a decorative fasica element at the eaves and blocked up the vents.

With sprayed foam (which I used a few years ago on my barn/shop remodel) you need to know whether the foam is of the open or closed cell variety. Mine was closed cell (better) and when it came time to do the roof I opted to install those plastic channel thingies and spray right on top of them. The spraying was done professionally and that fellow disagreed with me at first about this procedure. We had a ten minute skull session over some quick scribbles on a piece of scrap plywood, and he became a believer. He now insists on venting all his roof installations - regardless of the finish roof material.

Why? Because the roof (as a system and regardless of finish material) will eventually degrade. Weather, low quality materials, the passage of time, and/or poor installation techniques will eventually make their presence known and introduce moisture into the structure. And if you're not properly vented, it will wreak havoc and you won't know it until symptoms appear. Fixing the symptoms might be inexpensive. Curing the disease won't.

Sure hope I said this right. Passing the soap box off to .....

[Jim Becker]

When we built here in Texas, we were given the option to have a sealed attic where the foam insulation was sprayed to the underside of the roof sheathing. I was told that it is becoming a popular method of insulating in Florida.

This is how it is specified in our addition project...a full envelope direct to the roof deck. (R38 with R19 in 2x4 walls) Doing the envelope also simplifies installation of our HVAC system as it's going in the "attic" space...the contractor doesn't need to build an insulated room for it now.

Andy, your comments are intersting. I'll have to have that discussion with the GC and the insulation contractor. We are using closed cell.

[Steve Schoene]

Lots of info on this. One of the sources that supports the closed attic method is www.buildingscience.com. I believe that they have done tests that show only a degree or two hotter roof without the ventilation with foam directly on the roof, compared to the ventilated roof.

[Jim Benante]

I like the input. Looks like i may have hit one of those controversial topics.

I have found a bunch of web sites claiming that venting is unnecessary for closed cell foam applications in vaulted ceilings. It appears this is a relatively new way of thinking and there are still many who do not buy into this argument. I am leaning toward no air space at this point in time, but am open to listening to other opinions and logic.

I have recieved one quote at $1100 for open cell when I asked for closed cell quote, I guess the contractor must not be used to closed cell as he was trying to tell me it would be better to use open cell, but I disagree. I need to get another quote or two, but at about $700 for a kit that will be more than enough I might attempt at completing this myself.

[Andy Hoyt]

Jim - One thing I learned when researching the spray stuff for my barn remodel was that all the contractor's I spoke with were aligned with a particular manufacturer of foam. I found no manufacturer that offered both open and closed cell foams. As such, my assessment was that each contractor was pointing out the features and regurgitating the sales-speak from their respective vendors. That is expected in this franchised society, but it doesn't mean I had to swallow the company line - just taste it for myself.

I posit that if the finish roofing material or its installation fails (to whatever degree) in an unvented application that the water will do damage to whatever is underneath that finish roofing.

But I'm open to learning and even re-learning. So let me ask this:

What is the downside to installing a vented roof system?

[Jim Becker]

What is the downside to installing a vented roof system?

Not much if it can be accomplished merely with baffles...but if it requires something more labor intensive...major cost.

[Ben Grunow]

Ditto on Hoyt's statements above with one addition. If you spray foam dirctly on the underside of your roof sheathing, you will be removing your insulation with the sheathing should the need ever arise (roof leak requires new section of sheathing). We spray foam and always leave an air space.

Jim- we have made this space using small rips (2") of plywood nailed to the rafters and strips of lauan over them for a more expensive but not too bad (used old lauan that was used for floor protection during framing).

I also think the air space does a better job of eliminating ice dams as the roof is "colder" with air flowing under it than just relying on insulation to keep the house's warmth away from the snow on the roof. And in the summer time I think the vents lower the temperature of the materials adjacent to the insulation and therefore imporve the efficiency of the insulation. The idea is that air drawn in at the eaves is cooler than the bottom of the plywood roof sheathing in the summer, by a lot I would guess. PLus the constant flow of air will keep things cooler rather than just keep cooking up until sunset leaving a big hot mass of roofing to cool. I also think (I dont know, I think) the vented systems would lead to longer roofing life due to cooler temps.

Just MHO.

Ben

[Charles McKinley]

Thank you Andy and Ben,

You stated with more information what I was trying to say.

Ben do you use open or closed cell foam? Does the industry vary franchises to franchise or are some companies better at traninig their franchisees than others and doing quality control?

Thanks