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Dow Styrofoam SIS(Structural Insulated Sheating)

Posted by duckwacker (My Page) on
Wed, Aug 27, 08 at 12:01

Looking for anyone who has used this product. I'm told it just came out this year and is a 3in1 product that would replace traditional osb, rigid foam board and housewrap in one application. I've just started building my house in NE Georgia and was planning on using osb and house wrap only. My exterior framing is 2X6 on 16" centers and 10 foot walls. I intend to use damp sprayed cellulose between the studs giving me a R-21.

The price of this product is roughly 4 times the price of OSB. The 1/2 inch sheet gives a R-3 value.

Would this product be cost effective in a hot summer mild to cool winter climate?

Here is a link that might be useful: Dow Styrofoam SIS


Follow-Up Postings:

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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

If you go this route, you might consider pricing osb,wrap, and foam board panels out seperately and compare to the dow system. Other considerations would be that running seperately would be a tad more labor intensive as im assuming the dow system would install in one pass.


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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

New here, usually on Orchard forum. I do a little building. Any time I have investigated anything new (SIPS,ICFs, etc.) they turn out to cost too much for me. I am pretty sure four times as high as OSB is too high for me.
I live in Eastern Washington and, for example, we get framing done for about $7 using recent legal immigrants. It is a depressed area so we need to build as cheap as possible. Also when we deal with someone new we have to take the time to ask exactly what is included in their quote. Sometimes it is surprising.
It always comes back to conventional built for me. I use the KIS method. Keep it simple. Also if you will notice that website states it is in "market test".
IMHO YMMV


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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

Old schoolers generally stick with tried and true. There are so many "new" materials/technology out there these days that will make any head spin. Leading to a bottom line is that it's a pretty safe bet to go with what high end, reputable builders are using on homes in your area that works, builders concerned with energy saving techniques.


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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

Not available here yet. Pricier than I thought.

An alternative would be to use t&g XPS as sheathing, if permitted, or add it to the exterior of the OSB with or without a housewrap.

In a cold climate, following Building Science's recommendations, on this home I used 1" t&g XPS as sheathing with no housewrap, blocking the 2x6s all way around on both floors.

51 Chel. ext. XPS i
Tongue and groove expanded polystyrene boards used as sheathing provide R5 thermal insulation, act as drainage
plane behind the brick paper, and as a vapour barrier and airblock. (The bays were covered in EIFS)


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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

Thanks for all the input so far. The local building supply is pushing this product. I have seen a sample of the 1/2 inch thick product. It has a thin fiber backing and what looks like Isocyanurate insulation in the middle and a waterproof film on the outside. Doesn't appear any sturdier than rigid foam board.

I'm just trying to build the most energy efficient house I can without over doing it. I don't mind being cutting edge but I don't want to take on an experiment.

Keep the comments coming!


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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

Why is the store pushing it? We'll never know, but that sort of thing always bothers me, especially with a new product. I like introductory offers but I don't like being a guinea pig.

Toss me into the old-timer's pool. I want to see and hear about at least ten years of real life use before accepting a 'new' product. EIFs are an example of why.

My feeling is that you can have quite a lot of already-tested insulation for the cost difference of this product.


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RE: Dow Styrofoam SIS(Structural Insulated Sheating)

have you looked at SIP's?

like everyone else the SIS is a new product to me.

I'll look for more info & input.


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modified to add...

SIP's is osb on both sides, where as SIS is osb to interior of house, dow to exterior.
it would eliminate wrapping house as needed with SIP's
which would off set cost of SIS by not paying for housewrap
and labor to install.
windows & doors would be easy to flash, and thermal bridging due to 2x, in stick framing would be eliminated.
Dow makes a good product.
The blue board is a closed cell, the white filling is an
open cell (same as SIP's)

Will you be getting a decent price?
Sometimes distributors will give new products a discount
to be used as 'model'. Check into it.
But be prepared to oversee taping of seams and flashing of
windows & doors. (you would have to do this anyway..or it is best if you do. it is your vested interest to educate yourself..you'll be living there, builder will move on)
Crew would have to be educated in this type of build also.
and in my experience...ITRW..the crew does not read install
directions. A factory rep may be needed..and if he/she wants to sell this product he/she will make the trip.

best of luck.


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