SIPs vs. spray foam on exterior walls to air-seal my building envelope.
echristian1
| Posted in Energy Efficiency and Durability on
I am having a new home built. I was planning on using spray foam insulation and want to air seal my building envelope. Will the use of SIPs in place of standard stud walls and spray foam in those walls air seal my home just as well?
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Replies
Eric,
It's only possible to seal your home's thermal envelope well if someone pays attention to the details. Both SIP homes and homes with spray foam can be very leaky.
The only way to be sure that your home has a low air leakage rate is to methodically attack all seams and transitions. There are many seams and transitions in SIP homes as well as homes insulated with spray foam, and these are the areas that you need to address.
To answer your original question: either approach can work. It's up to you to be sure that the leaks are sealed and the envelope performs well.
Thanks for the feedback. So I guess the SIP's themselves are airtight and if I were to use them I would need to ensure the seams where they meet on all sides are sealed.
Follow up question- All things being equal which method costs less in general to have a air tight envelope in the end? (My framer started yesterday (in the basement), so to move to using SIP's at this point might be a problem but worth the delay and hassle if there is a substantial cost savings.)
Eric,
These costs vary widely from region to region. The only way to know your local costs is to call up contractors and suppliers and get bids.
Eric,
It's most often the transitions: wall to lid, wall to floor, floor to rim..., wiring & plumbing that creates the air leakage. Those issues can/will happen regardless of the construction style. You can get a good air seal with both methods. Just be diligent like you would with any other important matter.
You got lots of foam in your choices. There are other ways that don't rely on SPF or EPS...
Don't change horses in midstream. If the home has been designed for stick framing and you've already started with stick framing, changing structural systems by moving to SIPs at this point is a bad idea. And what with the delays and the inevitable unforeseen consequences the change will almost certainly cost you more.
But as Albert suggests it's not too late to reconsider your insulation options. You have enough lead time to make better choices there.
James of course is right. So many that ask questions here, have already started their project in question.
Martin, it happens so often that GBA might want to address this in some or many ways.
AJ,
Are you suggesting a blog on the topic of, "prepare plans and specs before you begin construction"? Because if so, I must say that this advice is part of even the most elementary introduction to design and construction... and is therefore known by most GBA readers.
Of course, in the real world -- especially in the case of owner/builders -- people have been known to put the cart before the horse.
Martin, yes. Do the stats on questions asked by first time posters. Time after time they are mid project when asking whatever. The other aspect I see as a builder is the homeowner doing the research who is then going to do what, train their builder? Seems to me the builder needs to be selected that already employs said system successfully. Or said builder be bought a subscription to GBA by the interested questioning to be future homeowner.
It's a situation of "a little knowledge is more dangerous than no knowledge." IMO
IE; The Hawaiian roof thread. If I was a contractor there and was given "Aj's" advice from that thread, my best next move really would be to hire an engineer to design the rebuild solution thereby properly transferring the design responsibility to a knowledgeable insured entity.
We all are learning so much from GBA but I think as part of your "signature" Martin, a point should be made to join GBA and partake in hiring one of its pros to further their individual needs and quests.
A win win.
Any openings on your board of directors? Lol