Exterior Rigid
Last Post 02 Dec 2013 07:15 PM by Surfsup. 43 Replies.
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SurfsupUser is Offline
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29 Nov 2013 06:55 PM
Just as a recap the roof is going to be this:

SS metal roof
#30 felt or synthetic
Sheathing
TJI 14" joist cavity 24" o/c
2" rigid polyiso board ripped to 1' 11-3/4" wide wedged between each TJI leaving 1-3/8" vent (R-12)
1" closed cell SPF for air seal (+R-7 for R-19)
HD batt or spider to fill the rest of the cavity which is 9-1/2" left open
gypsum

R38 is required so 38-19 = R19 batt but with the 9.5" I can use a R30 HD batt which is only 8.25" thick for a total of R49. leaving the lower nailing span gap alone. I guess I can use 1" rigid board and 2" ccSPF...

Can you do 1" rigid, 1" ccSPF and 8" ocSPF on top of that? (instead of the batt)
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30 Nov 2013 04:33 PM
You're adding complication and steps that add cost. Skip the c.c. foam, put in ~R20 iso (3-3.5"), sealed at the edges with FrothPak or can foam, and either blown fiber or o.c. foam for the rest of the cavity fill. There is no such thing as a decent fit with batts in TJIs. If you're going with o.c. foam, skip the FrothPak- o.c. foam done right will provide as-good or better air sealing. You'll be at about R50 center cavity with that stackup.
SurfsupUser is Offline
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02 Dec 2013 07:02 PM
OK I will do 3" rigid with the rest ocSPF. Thanks for hanging with me!
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02 Dec 2013 07:15 PM
OK So a summary, ZONE 5:

ROOF:

SS metal roof 3:12 pitch light gray color
#30 felt or synthetic
Sheathing
TJI 14" joist cavity 24" o/c
3" rigid polyiso board ripped to 1' 11-3/4" wide wedged between each TJI leaving 1-3/8" vent (R-18)
6" open cell SPF (Demilec Agribalance)
gypsum

WALL:

siding - Hardi Lap or LP Smartside
3/4" polyiso rigid board
wood sheathing
2x6 walls
2x6 cavity filled with open cell SPF Demilec Agribalance
CertainTeed Membrain or Intelloplus or equiv
gypsum
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