Poly Spray Foam Question

[DirtyLittleSecret]

Alright.  So, Im considering another build (A-frame this time) and have been looking into Polyurethane spray foams. 

My primary question is this: it seems many foam companies recommend 1" of foam and the remainder via fiberglass insulation.  I live in an "R30" geographic area, but dont want to go beyond 2x10 construction.  Since high density R30 fiberglass insulation is ~8.25", does 1" of foam negate the need for ~1" of "unfilled" space?

My second question is what is the best "do it yourself" foam application kit out there?  Im noticing a tremendous spectrum of costs for essentially what looks to be equivalents.

Much appreciated,

Dirty

[DirtyLittleSecret]

Seriously, nobody on here has 2 cents to add to this? 
I thought someone would at least have an opinion! 

[PEG688]

My opinion would be hire the spray foam done , the kits are more for foaming out a rim joist area , or small spots on a remodel.

  With 2x10 rafters you'll need more than 1" of foam to get to your desired R value, let the pro tell you what you need for foam.

Make sure you get all your pipes , vents , penetrations in place before you spray.

G/L PEG   

[Don_P]

I agree, although flash and batt has proponents I'd be more comfortable knowing there wasn't the possibility of a dew point problem at the 1" transition. A friend did the DIY cans to try it out, and then called in the pros after blowing through a grand pretty quickly. We just had the house I'm building foamed, they put in 5.5" in the walls and 8" in the roof of open cell (roughly half the price of closed cell). They did a great job of masking off, spraying in some tough places, trimming and cleaning up. They did a 5000+ sf house with a high greatroom ceiling in 2 days. They had the right equipment, metering pumps, heaters, compressors, large capacity hoses, air saws, scrapers, etc, and the skills to do the job right, you just won't get that out of those little cans.

[Canvasman]

I looked into the kits, it is cheaper to hire someone than buy all the kits. You also have to be carefull about temp of building and canister temps, wereas the pros can foam down to 20degrees F. The foam people here all want to foam the wall only, no flash and batt due to dew point concerns. Also none seem big on open cell, closed cell only. On a different aspect, some also didn't want to put cellulose into my cathedral ceiling, as they felt on a 4-12 pitch the cellulose would slide down the pitch.
Eric

[rwanders]

If you are building a NON-vented cathedral ceiling----cellulose and fiberglass are not recommended.  Spray or properly installed rigid foam is correct.  Vented cathedral ceilings can be done with various products, but actually achieving adequate venting plus insulation is very difficult unless you are in a very mild climate.  I wouldn't use open cell foam---closed cell is impermeable to water vapor and is much superior, but it is more expensive.

RW

[Don_P]

We were contemplating either fiberglass or foam on the job. I had three bids on doing foam and all the companies offered closed or open cell. All three suggested open cell as the best value for what we were doing. The R value per inch is lower however the open cell was superior to fiberglass and seals points of infiltration, which is the biggest problem with fiberglass. We filled the 2x6 walls and discussed roof thickness. In our climate 8" in the roof of open cell was considered to be a good value. One company offered 10" but he said that additional thickness would probably never pay off. The bidders felt that if we had a high moisture condition that closed cell would make sense but that is not the case in a typical residence. Open cell can dry. We have several houses out there with both and I've not had problems. Closed cell does strengthen the structure but that was not a problem with the building. The closed cell was about double the price so the decision seemed to be pretty easy. Every climate and situation is different.

[Squirl]

Much of what I read and heard, closed cell was preferred.  I don't know if that was from the higher R value or higher cost.

I researched the different types.  Almost all reviews stated they were almost identical between on the companies.  They all seem to be about the same price too. About $1 per board foot for R-6.8, which is about $.25 per board foot more than rigid foam of the same R value.  From what I read including a few members here that have done it, it wasn't that hard to keep a relative even amount sprayed.  Many of the foam companies I read promote flash and batt as an alternative, but recommend full foam insulation.  First, as many others have stated, there is a concern about moisture. Second, they sell lots more foam that way.  On large jobs a spray foam contractor can usually do it cheaper, that doesn't mean they always will.  They order the materials in bulk in 55 gallon drums and pay freight shipping.  This brings their materials cost way down and you are paying more for the labor and their expensive equipment.  Normally it doesn't cost anything for a few quotes. 

You could also go with a thin layer of spray foam and rigid foam on the outside.  There are many ways to insulate a roof.  And an A frame is all roof.

[TheWire]

I built my cathedral ceiling out of 12" I Joists.  I Put 10" bats in to leave a 2" air space then put 1.5" foil faced foam on the inside of the ceiling.  I taped the seams with foil tape.  I did it this way when full spray foam came in at too much $$$.  I had to put on furring strips prior to installing the T&G pine.

[Okie Bob]

Not sure I can add much to this question but, I built my lake house using Icenene closed foam and could not be happier. As an example, last summer in Tx was brutal, to say the least. My house is maybe 1500 sf and I had it sprayed top, bottom and side walls. I have  a 12 12 pitch metal roof with a loft in the back half so my options were limited with no attic at all. So, I have a total enclosure encased with a min of 4" Icenene.
My electric bill during the worst month of the summer was a whopping $104 and if you can beat that, I'd sure like to know about it. We kept the thermostat at 72 the entire time. I also have an 18 SEER (?) HVAC unit with variable speed fan and multiple stage compressor which I'm sure helps. I could not be more happy and highly recommend the added cost of the Icenene....I may be blowing the spelling but, if you are looking for spray foam, you'll surely have heard of it.
Okie Bob

[Don_P]

The Icynene I am familiar with is an open cell foam although I see on their website they do have both.

I've also done roofs with exposed beams, T&G, several layers of foam sheets with seams offset and taped, 2x4 sleepers, plywood sheathing, tarpaper and shingles. We call that "wrap and strap".

[DirtyLittleSecret]

The more I look into the spray foams the more I wind up interested in simply installing the pink R-Tech (R-7 per 1") paneling and sealing up the gaps with the "canned" alternative.  This is what I did for my first cabin and its like an ice/sweat box.  Unfortunately it made an insane mess while cutting.

I was planning to do 1-2" of spray foam and then R30 fiberglass, but was more concerned with meeting the minimum ventilation requirements. 

However, Im now more curious as to how one vents an "A-frame"... might lead to spray foam being the best alternative for the application.