REMOTE wall — single vs. double EPS layer
I am in the planning phase of a REMOTE wall house with construction beginning in June 2016. I have been talking with a foam supplier who is pushing me toward a single ~5″ layer of foam instead of the two layers of 2 inch I had been planning. There are a number of advantages to the single thick layer approach – reduced labor and a significant financial savings are two of the most appealing benefits. However, I am concerned that having seams in the foam that run straight through to the housewrap will cost me efficiency vs having a double layer of thinner foam with staggered seams. Is this concern valid, and if yes, can I negate this concern with a quality installation job with the thicker foam – careful filling of gaps with mildly expanding foam and a good tape job?
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Replies
Jim,
You're right that two layers with staggered seams is a better approach. Whether the difference in performance is worth the added cost is hard to say. It's a judgment call, and it's up to you to make the judgment.
I doubt if the difference between the two approaches would be significant enough to save much money on your heating and cooling bill.
This is just a brainstorming idea, but if you put a 1”x5" strip of flexible closed cell foam in the joints between sheets, could the elasticity of that strip maintain a gap-free joint over time? I am thinking of something like nomaflex insulation, the softer more flexible material used for pipe insulation, which is also available in sheets. Of course, by the time you buy that, cut strips, and install them, it's not clear that the cost is still lower than the two-layer approach, and you would be piloting an unproven approach.
In principle, something like tongue and groove eps would be another great solution, but presumably in your case that special order would cost more than it would save vs. the two layer approach.
Guys thanks for the input. Martin - I also doubt the difference would save much money or energy heating the house, but it's good to hear someone who actually knows what they're talking about say it.
Charlie - interesting suggestions. I have also been thinking of solutions like those you suggest - ripping a lapped edge on the sheets, etc. Everything I come up with eliminates either my financial or labor savings, so I think it is going to come down to a judgement call...or a winning lotto ticket.
Thanks again for the time.