Hi, i have several questions about SIPS and i've found that the manfucaturers are little help. they have no con's to list about the products >.<

I'm living in southern canada and live in one of the few places of the world that experiences both extreme's in weather. From +40 degrees in the summer to an easy -40 degrees in the winter. it's advertized that SIPS don't require any form of barrier, just a sealant at the seams and joints. is this true? i intend on using insulated rigid board in the inside to help insulation, but as far as keeping my building envelope secure, what should i have in addition to the panels? 

nothing...just a house wrap.

what kind of insulated rigid board do you plan to use? rigid foam? if somehow you'll get moisture between SIP and the extra layer of foam will be very difficult for the SIP to dry. I wouldn't add rigid insulation to a SIP wall (interior or exterior) because the installation and detailing becomes critical. If you really want to add consider some sort of spray foam. so water vapor doesnt represent an issue.


good luck
Adi

You may consider going with a thicker sips panel instead of adding foam board.

i live in eastern ontario- keeping mind this is all hypothetical but i was going to be using rigid foam on the interior and typar barrier on the exterior for added resistance. money is not an issue in any way, i just to design a house that is 100% air/vapor proof and tip top energy efficient. which, if anyone has any experience with geothermal heating, i could use to some advice on that as well. thanks for the posts and help everyone.

Dear Étaoche, we manufacture SIP'S in Quebec and, your question is one that i have in my mind since the beginning of our opération, we suggest a god urethane seal between panels, a neoprene memebrane between panels when install in winter, a vapor barrier tape on the joint, and if our customer have a minimum of doubt, he could install a vapor barrier of polythene .006 mm inside.

The first operation should be enough from the laboratory test but, laboratory and job site situation is always different, and a polythene is a few cents per square feet, so if you have any doubt on the installation of your panels...go for it, install the polythene, and do not try to redo the world.

Good work,

Pierre Desjardins
Banerpan
450-546-9047

I live in West Quebec, in a SIP house and I have a geothermal system.

The idea with the SIPS is that the interior layer, like OSB, is an effective vapour barrier. So long as all seams are properly sealed, an additional barrier isn't needed. The fear in putting up anything on either side of the SIPs is that vapour will get trapped and start to degrade the SIPs' sheathing component. This is bad because in the SIP the sheathing works with the interior foam as a single unit for structural strength. There was an infamous situation in Juneau, Alaska where, if I understand it correctly, a number of SIPs homes were built and because of poor seam sealing in the roof panels, they rotted and caused some failures. I would want to be certain that if anything was put directly against the SIPs on the interior that it would be perfectly sealed and not let any vapour sneak in between it and the SIPs. If it is on the exterior it should be vapour permeable/ "breathable" or allow for some ventilation.

As to extra foam on the inside if possible, spec a thicker SIP which probably is just incrementally more expensive and not much more than buying and adding sheets of foam. Adding additional layers of foam inside just add complexity and possible problems - like the issue mentioned above - and are no more efficient and likely less air tight. Just stick with the SIPs and you will only have one set of seams to seal.

Also, look into the principles of the German "Passivhaus" standard. By making your envelope super-thick and airtight - super-thick walls/roof, triple glazed windows, compact and simple design, etc. - you end up needing very little in terms of mechanical heating and cooling.

I committed to a geothermal retrofit system ($30 000, minus $7000 in fed. and prov. rebates) before I really understood the idea of a superinsulated envelope and should have put a big part of that geothermal money into a "Passivhaus" level of envelope efficiency (I think it is more than 80% more efficient than an R2000 home!). Yes, geothermal can save you 50-70% over conventional oil/electric heating (which is fantastic), but unless your house is as insulated and airtight as it can be, you are still burning energy to heat/cool the neighborhood. Also, make sure you first conceive your envelope efficiency before you size your geothermal and air exchange systems, as you don't want them too big from a cost and efficacy point of view.

Dear Maceo, I just read your comment and i have to say that your point of view is good, my suggestion of polythene as a protection as a vapor barrier inside would please the architecte BUT it is true that if hunidity goes between the polythene and the OSB, trere are possibility of faster degradation. I have to admit that i agree in everything you wrote, i could not have said it better.

Pierre Desjardins
Banerpan Panel
450-546-9047