I had a Icynene contractor stop at the house I’m building for myself tonight to give me a price. I have 2×6 walls, he’ll put 4 inches. My second floor has a five foot high outside wall to a seven pitch with the ceiling joists at 8 feet. I was going to have him insulate up the run from the five foot wall and then go across the ceiling up against the plywood that makes up the attic floor. He suggested instead of running along the ceiling joists we go all the way up the rafters to the ridge. My attic is five feet high at the ridge. My heat system is Geo-thermal with the second floor trunk line running along the attic floor feeding the rooms from above. He was saying it would be better to insulate the rafters that way the attic is not hot in summer and cold in winter making my heat system more efficient. The attic trunk run is 50 feet end to end. He said if we did the ceiling joists instead of the rafters we would have to spray the trunk line and off shoots in the attic because they would be up against the seasonal temperatures. Also the trunk lines only have a R-factor of 4.3.
My main question, finally, is he also said if we decide to insulate all the way up the rafters we DON’T have to vent the roof. I fine this hard to believe. He claims the Icynene will raise the temperatures for the roof shingles but not as much as a summer in FL. does and moisture will not be a problem.
I’m considering doing the rafters ( with the styrofoam baffles to vent) instead of the ceiling joists. I’m calling the heating contractor tomorrow to get his opinion but would like all of yours also.
Thanks
Roy
Replies
call your roofing material supplier and ask him about warranty on the roofing material is when you do what insulator contractor wants you to do it.
Must be a standard part of their pitch. I heard the same thing from a local (Boise) contractor for a shop I'm sketching out..... --Ken
I worked construction for two summers in Barrow, AK- on the Arctic Ocean. It was common to spray all wall cavities and ceiling/ roof joist bays with icynene insulation. We'd then go back afterwards with a saw to cut the insulation flat with the studs/ rafters. In finished rooms, sheetrock would go right over the insulation. No vapor barrier was used- since the foam created its own. The houses would have whole-house air-to-air transfer systems for fresh air (such as a Van-E unit.... I think they were out of Canada). The living space would be isolated from the dead "attic" space, so the moist air wouldn't get up to the ridge. The outside air was so dry- like a frozen desert- there was no issue with outside air adding moisture into the space. The blow-door test on one of the house I worked on had the equivalent air leakage of the size of a quarter, thus the need for an air-to-air exchanger- a testament to the effectiveness of this type of insulation.
If there is a possibility of moist air getting to the ridge of the roof, in my opinion, it should be vented. The icynene insulation is designed to be a moisture barrier.
I am planning on building my next house using this type of insulation scheme. I intend to use 2x6 metal studs for the exterior walls, built and sheathed inside a workshop. I would like to fill the cavities with this type of material (spray-on foam). I have no experience with it and would appreciate more comments on your alaska experience. I imagine this material is like the expandable foam in a can, is this accurate? Would you have to fill the cavities short to not extend beyond the sheetrock-plane of the wall? More details on striking it off? Also, it seems like the vendors use licensed installers, how is that process to become one?
remodeler
For information on Icynene insulation, directly from the horses mouth, so to speak, go to their website: icynene.com
When I was working in Barrow, AK, the actual spraying of the insulation was done by a subcontractor that specialized in it. I don't believe it to be a DIY if you are doing large areas. The sub. was in tyvek suiting and a positive pressure hood. It's a two part chemical reaction that gets joined at the end of the spray gun. It does take some practice to know how much to fill the cavities to minimize the expansion beyond the edges of the studs, thus the "sawing off" of the excess. And, yes, that's exactly how we did it, wih a hand saw, spanning the studs. This was 6 years ago, so I'm sure there are more advanced ways than that.
I have seen larger spray can versions than what are in home improvement stores- more along the lines of 5 gallon size. Don't know were to get them. Hopefully the icynene website can help. I'll probably sub it out for the second floor addition on my house when I get to it next year. Has lots of positive things going for it.
Thanks for your replies..........
I'm going with my instinct and using the Icynene on my second floor ceiling joists and staying with a cold vented attic.
Roy
I think your insulation guy is right. I'll bet you will lose more money on heat loss/ac loading through the trunk line than you would on shortened shingle life. Moisture is a non-issue with sprayed foam. (other than the need to mechanically ventilate for indoor air quality because the house will be really tight).
What color is your roof?
Steve
Steve.......the roof is slate grey asphalt shingles. After I decided to insulate just the second floor ceing joists I remembered I'm also using Studa-vents in the attic for the drain lines . So that is another reason to have a cold vented attic. If I lose heat or A.C. from the heat trunk line I'll insulate them more than they are.
He called with a price yesterday..........$5900, the house 2900 square feet (4 in. in walls, 5 1/2 in ceiling)
Roy
Go for it! sounds like a good deal with all the benifits it brings. and the vented roof thing has yet to be decideded.
The only do it yourself product I have come across is FOMO insulation. It does come in all sizes of containers (also large refillable containers) with disposable spray nozzles, etc. Do a search on this site to find some discussion of its merits. There was something a month or two ago.
http://www.fomo.com/about.html
-Rich F.
We have a 1923 house in Indianapolis and are insulating the roof with Icynene. No venting, but our roof is tile, and we only had one 12 inch vent anyway. When we were thinking about the venting issue, the only problem I saw was getting rid of moist air that will now be trapped inside. I think we will deal with that when we upgrade our HVAC and have an air exchanger installed on the third floor. We could probably do some kind of vent fan tied to a humidistat, too. My parents had a similar issue with their home's roof, which is insulated with rigid foam panel sandwiched between plywood, and therefore wasn't vented. I think that voided their shingle warranty, but they haven't had any problems in the twenty years since their home was built. I don't know if Florida temps would make venting more of an issue or not, though.