Buildability vs. durability
I’m going to be building a 28×40 (aprox 1500sf living) chalet style house in upstate NY CZ6 (design temp 6f) it will sit on a walk out basement (one narrow end walk out the rest under ground) I am going to put pex in the slab even though I don’t currently plan to ever need it warmer than 55 or so down there.
Been reading on the subject quite a lot, and think that the pretty good house concept you guys have come up with is a great idea, and should get me in a balance point between up front cost, and monthly utility bills.
So I am looking at 4″ of eps under the slab (R 15 ish), 6″ of eps outside the below grade foundation walls (R 23 ish). R40 for the walls, and R60 for the cathedral ceiling, and the best windows I can afford (hoping to go with triple pane upvc from intus, zola, or ???).
First question, I think I should increase the insulation for the above grade part of the foundation to R40, but should this go all the way down to the footer, switch to R20 4′ below grade or some other answer?
I’m looking for opinions on the best way to build an R40 wall (with a rain screen gap), and R60 cathedral ceiling with vented sheathing (I’ve read the cathedral ceiling article several times)
Initially I thought that PERSIST would be the way to go (all of the important sealing happens on the outside of the sheathing where its easy to inspect, and keep continuous), 10″ of foam on the walls would be a pita, but doable (is it as hard as i think it would be to hit a stud though 10″ of foam and a 1×4), 16″ on the roof just seems daunting.
From what I’ve been reading its safe to move 1/3 of the R value into the walls/roof inside of the sheathing, (would use cellulose) is this true? would it require an intelligent vapor barrier, or would sheetrock alone be ok? This would save some $ on foam.
The other wall choices all seem to be variations of a double stud wall or larsen truss, is any one easier to reliably build than another?
The other choices I’ve narrowed down for the roof would either be deep I-joists dense packed and vented (the roof design makes it easy to get a clear path from eve to peak in every single bay) or parallel chord truss’s dense packed and vented.
Is either one better or easier than the other? Is there a better solution I’ve overlooked?
How do you keep all that weight from making the sheetrock sag/bow?
I will be doing most of the work myself with friends/family supplying help. and contractors doing the foundation, setting the heavy stuff with a crane, and weathering in the roof.
If this is too much for a single thread let me know and I will break it up.
thanks in advance
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