Replies

1. Expert Member
   Armando Cobo|Jun 13, 2022 09:51pm|#1

   If you tape and stagger the seams, you can get greater envelope tightness. If you use an approved tape by the foam manufacturer, you cam make the outsulation a moisture barrier.
   You can research lots of free information about wall assemblies, rigid foam and WRBs in this website.

2. 
   IdahoBuild|Jun 13, 2022 10:07pm|#2

   Thanks Armando,
   My original plan was to use 1 layer or 2", until a watch a Joe Lstiburek talk about place that he had built and 'kicked himself' (my words, not Joe's) for not thinking that he'd have been better off with the staggered seams on the exterior insulation from 2 layers. If I use 2 layers, stagger seams and seal with approved tape; would that make the Delta Vent layer obsolete/redundant?

3. Expert Member
   Armando Cobo|Jun 13, 2022 10:42pm|#3

   Joe's barn its a thing of beauty, remodeled into their office at first, and then it became a party hut nowadays and the epicenter of Summer Camp, and yes, by experience, he has taught many of us in the BS world that even he is mortal, and he's used his own lesson to teach us that its better to install two layers than one (or four or five as his barn got in the fix). Make sure you install bug screens too.
   You could delete the Delta WRB, but if you can afford it, leave it there as "belt and suspenders", I usually spec a less expensive WRB (taped).

4. Expert Member
   Zephyr7|Jun 14, 2022 12:35am|#4

   Two layers is better for the reasons already mentioned, but note that they don't have to be the same thickness. Sometimes it is advantageous to use a sheet of 1/2" and another, thicker sheet to make up the rest. Use the thinner sheet on the inside side, so that the thicker, stiffer sheet will help to keep the finished surface flat. This type of stackup still blocks airflow through the insulating layer, but is sometimes easier or cheaper to build.

   Bill

5. Expert Member
   Malcolm Taylor|Jun 14, 2022 11:07am|#5

   IdahoBuild,

   这是一次权衡。毫无疑问，两层更好，但是这种优势是否超过了它们的两倍以安装的劳动力，可能非常依赖于人工成本多少。