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80 sq. m. green passive house

Hi,
I am planning to build 1 floor 80 sq. m. house with SIP on planar foundation with simple flat - mono pitch roof. My "sandwich" will look like this:
SIP 124mm = 12mm OSB3 + 100mm eps + 12mm OSB3 + 200mm NEPS from outside + inside (vapor barrier + gypsum + gypsum).
And this is what I get with such sandwich: http://www.u-wert.net/berechnung/u-wert-rechner/?&d0=1&mid0=195&d1=1&mid...
Foundation will be insulated with 150mm EPS.
Floor will be insulated with 300mm EPS.
Roof (SIP 124mm + 45mm rockwool from inside)
The inner walls of the house will be from silicate bricks.
Ofcource there will be HRV.
House heating will be electric (202 eur/270USD per year).

I chose SIP, since my house will be small, it will be easy to build on my own and price is very acceptable.
My climate is Humid continental.
Any suggestons?

Asked by Tomas Batonas
Posted Tue, 08/26/2014 - 05:01

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2 Answers

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1.
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Tomas,
It's going to take some work to translate your question -- from metric units to English units, and from a few mysterious abbreviations to terms we can understand.

It sounds like your SIPs will consist of 1/2-inch OSB, 4 inches of EPS, and 1/2-inch OSB. By U.S. standards, that is a very thin SIP. It has an R-value of about R-16.

I'm not sure what material you are referring to when you describe an interior vapor barrier. SIP walls do not need an interior vapor barrier -- the EPS is a vapor retarder -- but they do need an interior air barrier.

I have no idea what you mean by "200 mm NEPS" -- but I am guessing that it is a type of expanded polystyrene. Installing rigid foam on the exterior side of SIPs is somewhat controversial, because you end up with a foam sandwich -- the outer OSB face of the SIP is sandwiched between two layers of rigid foam. On balance, I don't think this is particularly risky, but some experts recommend against it.

Will you have a low-slope roof or a steep-slope roof? The installation of exterior rock wool insulation on roofs is usually limited to low-slope roofs.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 08/26/2014 - 07:21
Edited Tue, 08/26/2014 - 07:24.

2.
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In Europe we have houses from SIP, which has such wall: 7.9 NEPS + 4.9 inches SIP sandwich + aluminum foil, wich is glued to OSB from house interior + 2 inches of wool + gypsum + gypsum.
NEPS - graphite-enhanced polystyrene (neopor).
So on neps we put decor + neps reduces the opportunity to appear for cold bridges from outside.
Aluminum foil acts as an extra vapor protection and as protection from toxic substances such as glue wich connects OSB and polystyrene.
Wool acts as a sound protection + you can hide wires there.
Roof will be flat with 4-6% of the slope. So there are headache how to properly install SIP roof + protect it from rot.
Such wall commended couple guys, who builds houses from SIP. There are SIP with 12 inches and more. But for me is cheaper to buy 4.9 inch SIP and stick 7.9 inches of NEPS to that SIP, since i can not put decor on OSB (since it will be wooden boards).
A lot of people say, that it is very difficult to maintain a long-lasting airtight in SIP house and there are a lot of chances for condensation.
You are suggesting to go with thicker SIP and forget about additional polystyrene from outside?
I am just looking best way for walls for my passive airtight house.

Answered by Tomas Batonas
Posted Tue, 08/26/2014 - 09:40

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