Anyone built with SIPs?

as with any form of construction there can be problems .
I worked on many in their early days one of the first problems to arise was caused by vapor in the home its self . it would collect in poorly caulked joints causing the outer layer of OSB to swell and rot around the joint.
condensation was the biggest draw back and still is . wood be it framing or OSB will absorb and expand when in contact with warm moist air .

That was my biggest concern in reading about it. I have not used it though and I don't know anyone who has. I love the log cabin plan!

I looked into cordwood... actually cut a cord or so of cypress, just for that purpose (still stacked out by the barn... the sapwood has rotted down...). If I were doing a cordwood home, with that much snow, or monsoon rains like we have here, I'd have extra long rooflines, to keep the moisture away.

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I guess this is a bit of a rabbit trail but do you have to seal the outside of cordwood homes? Does moisture soften the outside of them?

You can get SIPS made with different 'skins'. Some come with cement board, and when made with poly foam, since it is poured into the cavity and then expands, there are no glue voids.

Again, if you are in a humid climate, you will want a dehumidifier as well in the house, and a good quality heat exchanger.

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As I said, if I was going to use SIP's, I'd go with STEEL. They're not much more than OSB.

As for cordwood- I can't imagine using that in areas like ours where the termites are rated extreme. That's one reason I like ICF or steel SIP's- not many critters can eat 'em. They can tunnel in the foam, though.

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Yes, you should seal.
And, like MushCreek just mentioned, it can be a real challenge for those in termite areas. However, like any other wood material in termite areas, I wonder if borate treatments would mitigate that? Not to mention a stemwall of some sort that would lift it up higher than grade would at least provide some protection against subterranean termites....

Truth be told, there aren't a whole lot of building materials that termites don't like unless you go with pure concrete!

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I'll let you know in a couple of years. We had thw cabin foamed this summer.

A vapor barrier si only recomended with open cell foam. If you use one with a closed cell foam then you have a problem with having 2 vapor barriers that moisture can get trapped in between (think of condesation when you add plastic to the outside of a window).

The roof sides we went with 3" foam the 3.5 inches fiberglass to fill the space. The end walls have @3" in a 2x4 wall. I'll fill in the remainder with foam as we sheet rock them.

This is what the kitchen are looked like before adding the fiberglass



And after with the rock moved in

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Great discussion by the way-lots of ideas and lots of points of view. Thanks for the links Gary. The double stud wall is about as simple as it gets and while obviously more material intensive, I think a double stud wall with spray foam filling the void could probably provide some pretty impressive r-values.

As I understand it, the most important part of house to insulate is the roof. At some point, I don't think it makes sense to spend more on double stud walls, or more insulation, in the walls. I think it would make more sense to spend it superinsulating the roof. I'm no expert, just repeating what I've heard.

Well sure, heat rises and leaves through the roof in many cases, but it will eventually leave the structure somehow. I would guess that if you had two identical homes, both with R-30 roofs, but one with R-15 walls and one with R-30 walls you'd see a big difference in energy usage between them. Don't forget also that during the summer the sun is beating on the walls and the roof.

Hi,
A square foot of wall is just as important heat loss wise as a square foot of ceiling. The heat loss equation is the same for both:

Heat Loss = (Area)(Tinside - Toutside) / Rvalue

You will get just as much benefit increasing insulation on walls as you do ceilings.

The only small exception is that the air in a room tends to be a little warmer up at the ceiling, so the (Tinside - Toutside ) is a little greater for ceilings. But, usually air in rooms is pretty well mixed, and this is a small effect.

One reason people tend to insulate ceilings more is that its often cheaper than insulating walls. Its pretty easy to insulate up to R50 or R60 in a typical attic -- just dump in more cellulose. But, insulating walls to R50 is very hard and expensive. Things like the double stud wall or the wall with inside horizontal strapping for more insulation depth don't add a lot of cost, and give high wall R values with little thermal bridging.

By the way -- heat does not rise! Heat goes to cold -- it does not mater whether the cold is up down or sideways. The thing that confuses people about this is that hot air rises -- but that's only because heating it makes it less dense. Heat is equally happy to up or down or sideways -- it just needs a temperature difference and a conduction path.

Forgot to mention that there is a home heat loss calculator that lets you see how much heat you are losing through walls, ceilings, windows, ... separately: http://www.builditsolar.com/Referenc...s/HeatLoss.htm






Gary

I recently helped a friend build a timberframe with SIPs wrapped. Frame and panels went up in 5 days and the rest we did.

As far as the DIY aspect, the panels are HEAVY. A crane or lift is required. Seams were splined and then foamed making a continuous envelope. Drywall is already installed. These things are very tight.

Cutting window openings is different, but you can rent a saw specifically for this and a burner to melt out foam for the framing of the rough opening. Wasn't very difficult.

There were wiring chases built into the panels, so wiring wasn't really an issue.

My friend and I were also concerned about the longevity of the panels. Considering the frame will most likely last well over 100 years and OSB is not exactly known for it's lifespan. There was a company in NH that will build panels with Laminated T&G outside, but they were cost prohibitive.

I have nothing bad to say about them, but don't know how they will stand the test of time.

Double stud walls are looking better and better all the time. There are plenty of good illustrations on the net so it's easy to visualize how they go together if you know a little about framing to begin with. Spray foam seems to be the only way to go if you want to completely eliminate moisture issues and air infiltration though. I've heard of DIY kits, but I'd want to get some hands on practice with a pro or experienced DIYer before investing in a kit and working on my own house. I guess the alternative is getting everything framed and sheathed then just subbing the foam job out-I have no idea what the cost would be though. Lots to think about, but again, thanks to solar gary for the heads up on the double stud wall.

Maybe ET1 SS will chime in on his DIY foam job on the steel building used as a house. Its very doable, but depending on what R value you're going for, it can be very expensive.

The DIY spray kits are typically $1/bdft (board foot: 1square foot, 1" thick) The last quote I had was $2/bdft for the first inch, then $1/bdft for the rest. It made the 2" expanded foam board look cheap at $0.39/bdft, including the Great Stuff needed to seal it in place. Ebay has several people that will spray your building for what you normally pay for the foam. ($3,400 for 4,500bdft for one current add)

Michael

Edit: Take a look at the Fastkick gun. Basically its an air powered batch sprayer. If you're doing a lot of foam, this might be a good option.