air sealing

[philupthegastank]

ive already posted some pictures of the tear down im doing on a farm house i bought. Once the house is completely gutted i will be resealing the house and insulating. should I use caulk or foam spray? on small spaces I think caulk would be fine, but for the bigger areas, i was thinking spray foam from those cans would work well. Only thing is ive heard that if you use spray foam, since it expands that it can warp wood and cause other openings to happen because of the expansion of the foam. do you think thats over exaggerated or an actual concern?

 

[Dune]

Wow, that would be an expensive way to go.
First the question; No, you needn't worry about expansion seeing that your walls only have one side.

Suggestion; Contact local installers about spray foam.
Professionally installed spray foam will
1. seal the air leaks very well.
2. Insulate better than any other system
3. Actually add structural integrity to the building.

Payback on such an old structure will be quicker than usual, assuming you tighten up your doors and windows.

 

[philupthegastank]

i have 2x6 exterior walls, and from what i could find online, it would be around $4k. I can seal the stud cavaities and doors/windows and trouble areas with caulk/spray foam with roxul comfortbatts for a lot less than that.. i just dont have that money for spray foam insulation.

 

[Wisneaky]

i have 2x6 exterior walls, and from what i could find online, it would be around $4k. I can seal the stud cavaities and doors/windows and trouble areas with caulk/spray foam with roxul comfortbatts for a lot less than that.. i just dont have that money for spray foam insulation.

They make window and door can spray foam that doesn't expand as much. You should call some contractors though because you might be able to find a good deal on getting the place spray foamed.

 

[bag of hammers]

FWIW - I went with polyurethane (eg Great Stuff) in the joints and cracks, then Roxul. Spray foam by pro was my preference but 3x the cost and I just didn't have the room in the budget.

 

[semipro]

Consider "flash and batt". You get the air sealing of foam with the economy of batts. (broken link removed to http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/flash-and-batt-insulation)
Also, if you DIY some of the foam work consider investing in a pro foam gun. You won't regret it. http://www.homedepot.com/p/GREAT-STUFF-PRO-14-Foam-Dispensing-Gun-230409/202892513
https://www.hearth.com/talk/threads/spray-foam-gun-recommendation.73362/

 

[Hogwildz]

Flash and batt is a good system, but any irregularities in the foam surface (hump etc) could translate into uninsulated empty air pockets between the two.
Not sure how much an issue it would present. But sounds like anything my be better being it is an old farmhouse, and prolly has little to no R value to start with.

 

[EatenByLimestone]

You could also do a foam board then seal around it. I'd use a foam gun for that over the great stuff cans.

Since you have the walls open it would be worthwhile to have the bays sprayed with borate to keep wood boring insects out.

 

[sportbikerider78]

If you can't afford a 100% spray foam job, consider doing some of it yourself with a big kit (not the canned stuff at home depot) and do the trouble areas... Corners, around windows, foundation sill...ect. And then insulating with traditional methods other areas.

(broken link removed to http://www.ebay.com/itm/Touch-N-Seal-U2-110-Spray-Closed-Cell-Foam-Insulation-Kit-110-BF-4004520110-/390766898277)

I'm going use a kit like this when I insulate parts of my basement with rigid closed cell foam. Any awkward areas that would require lots of cutting, will get sprayed.

 

[Wisneaky]

If you can't afford a 100% spray foam job, consider doing some of it yourself with a big kit (not the canned stuff at home depot) and do the trouble areas... Corners, around windows, foundation sill...ect. And then insulating with traditional methods other areas.

(broken link removed to http://www.ebay.com/itm/Touch-N-Seal-U2-110-Spray-Closed-Cell-Foam-Insulation-Kit-110-BF-4004520110-/390766898277)

I'm going use a kit like this when I insulate parts of my basement with rigid closed cell foam. Any awkward areas that would require lots of cutting, will get sprayed.

I just used a kit like that. It was a 200 sq ft one that I got at Menards for $288 worked very good.

 

[semipro]

You could also do a foam board then seal around it. I'd use a foam gun for that over the great stuff cans..

If you have more time than money this may be the way to go. The DIY foaming kits turn out to be very expensive per volume of foam applied especially when compared to foam board.

 

[dznam]

Consider "flash and batt". You get the air sealing of foam with the economy of batts. (broken link removed to http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/flash-and-batt-insulation)
Also, if you DIY some of the foam work consider investing in a pro foam gun. You won't regret it. http://www.homedepot.com/p/GREAT-STUFF-PRO-14-Foam-Dispensing-Gun-230409/202892513
https://www.hearth.com/talk/threads/spray-foam-gun-recommendation.73362/

Two things you need to be very careful with in a "flash and batt" system are:

1. Use closed cell foam (vapor impermeable) for the foam layer as open cell is moisture vapor permeable and its use can result in the buildup of moisture under your sheathing.

2. Make certain that for your location (weather/temperature ranges) the dew point is always located inside of the foam where there can be no vapor. Otherwise you can get a buildup of moisture in that section of your wall using the fiberglass, cellulose, roxul, etc. This means having an adequate thickness of closed cell foam sprayed. In a colder climate, this may be 3 inches or more! Early flash and batt systems that used just a thin "sealing" layer of foam resulted in some big (mold) and expensive failures. and have been largely discredited.

 

[bag of hammers]

I was keeping an eye out for the foam kits here - finally started selling them out of a local building supply - I almost fell over when I saw the price - they wanted almost $500 for a kit that would do @ 200 sq ft @ 1" thick. I thought about it for my crawl rim but I took the cheapskate route - couple cans great stuff put a nice bead in the bays, roxul over that. I know there's been a lot of folks advising against soft insulation in rim joist areas but I've pulled sections out to inspect a few times and after a few years it's all dry and clean.

Those kits are great but at the end of the day, you gotta do what you can with what you got....

 

[sportbikerider78]

I was keeping an eye out for the foam kits here - finally started selling them out of a local building supply - I almost fell over when I saw the price - they wanted almost $500 for a kit that would do @ 200 sq ft @ 1" thick. I thought about it for my crawl rim but I took the cheapskate route - couple cans great stuff put a nice bead in the bays, roxul over that. I know there's been a lot of folks advising against soft insulation in rim joist areas but I've pulled sections out to inspect a few times and after a few years it's all dry and clean.

Those kits are great but at the end of the day, you gotta do what you can with what you got....

The kit I posted was 110sqft and 1" thick for about $185

 

[semipro]

The kit I posted was 110sqft and 1" thick for about $185

That's 9.2 cubic ft. for $185 so cost is $20/cubic ft.
A 2" XPS 4x8 foam board is 5.3 cubic ft. for $36 so cost is $6.70/cubic ft.
Of course using the board requires more labor and the extra cost of canned foam to seal the edges.

 

[semipro]

2. Make certain that for your location (whether/temperature ranges) the dew point is always located inside of the foam where there can be no vapor. Otherwise you can get a buildup of moisture in that section of your wall using the fiberglass, cellulose, roxul, etc. This means having an adequate thickness of closed cell foam sprayed. In a colder climate, this may be 3 inches or more! Early flash and batt systems that used just a thin "sealing" layer of foam resulted in some big (mold) and expensive failures. and have been largely discredited.

Could you provide a reference? I'd like to read more.
I understand the dew point within the foam concept. I hadn't heard about the moisture issues with thin flash and batt systems. I could see where closed cell foam flash could create water issues. However, it would seem that open cell foam flash would allow moisture to pass through rather than condense.

 

[dznam]

Could you provide a reference? I'd like to read more.
I understand the dew point within the foam concept. I hadn't heard about the moisture issues with thin flash and batt systems. I could see where closed cell foam flash could create water issues. However, it would seem that open cell foam flash would allow moisture to pass through rather than condense.

Between the Building Science Corp website and the Green Building Advisor website you'll find a wealth of information on flash and batt. You don't want open cell as it'll trap the condensate against your sheathing.

 

[semipro]

semipro said: ↑
Could you provide a reference? I'd like to read more.
I understand the dew point within the foam concept. I hadn't heard about the moisture issues with thin flash and batt systems. I could see where closed cell foam flash could create water issues. However, it would seem that open cell foam flash would allow moisture to pass through rather than condense.

dznam said: Between the Building Science Corp website and the Green Building Advisor website you'll find a wealth of information on flash and batt. You don't want open cell as it'll trap the condensate against your sheathing.

I know those sites well. In fact my reference above is from one of them. I haven't come across valid reports of flash and batt causing rotting sheathing though many posting comments alluded to it.
I'm guess the theory is that warmer moist air can make its way outward though the open cell foam and then condense on the cold sheathing. Once liquid, the water is trapped between foam and sheathing.
Or, that closed cell foam of inadequate thickness would result in condensation forming on the foam surface, potentially wetting the insulation.
For the former, I can see where that could cause problems and the anecdotal reports may be founded in fact.
For the latter, it would seem possible that some small amount of condensation might form but its impact on the batt insulation would be minimal. Maybe if enough formed it could damage studs or sill plates.

In any case, thanks for the info.

 

[dznam]

I know those sites well. In fact my reference above is from one of them. I haven't come across valid reports of flash and batt causing rotting sheathing though many posting comments alluded to it.
I'm guess the theory is that warmer moist air can make its way outward though the open cell foam and then condense on the cold sheathing. Once liquid, the water is trapped between foam and sheathing.
Or, that closed cell foam of inadequate thickness would result in condensation forming on the foam surface, potentially wetting the insulation.
For the former, I can see where that could cause problems and the anecdotal reports may be founded in fact.
For the latter, it would seem possible that some small amount of condensation might form but its impact on the batt insulation would be minimal. Maybe if enough formed it could damage studs or sill plates.

In any case, thanks for the info.

If I run across the specific cite I'm recalling, I'll post it, but old bookmarked sites"didn't survive my switch to a new laptop. In any case, your understanding is consistent with mine (or is that vice-versa?!) with respect to open and closed flash and batt.


There are also a number of contractors and other members of GBA up here who, in my research on this subject, relayed first hand stories of early flash and batt woes. IIRC, most of the issues related to the forming of black mold as a result of moisture accumulation in the insulated cavities, not structural damage. The system hasn't been around all that long in popular use, so it's possible that structural issues just haven't made their way to the surface yet. The thinking on flash and batt has evolved quite a bit over the last few years, as you probably know, and no doubt will continue to evolve. No doubt that climate will play a role in "optimal solutions" - e.g. Virginia may tolerate different solutions than Maine.

In any case, we focused our build budget on "good bones" and went with closed cell everywhere in our small cottage, in part because of the severity/changeability of our local climate and because it seemed to generally constitute "best practice" and we wanted to have as bulletproof a build as possible.

Just finished wrestling with a SIPS house and sips seam sealing, wrapping, strapping and roof membranes is another brain-damaging topic!

Good luck with your research - let us know if you turn up anything else interesting!