Cellulose, Housewrap, Foam Board, and Rainscreens?
I previously asked, what is the proper wall assembly for dense packed insulation? After doing some research online I have discovered that dense packed cellulose can absorb and release moisture vapor or condensation without degradation to itself or adjacent building materials. However, any moisture absorbed by the insulation needs to be able to escape. The companies that manufacture cellulose do not recommend using vapor retarders in general. Interestingly, they use the term vapor retarder and vapor barriers interchangeably. The current International Building Code (and its companion codes) defines a vapor retarder as being 1.0 perm or less when tested with the desiccant method using Procedure A of ASTM E 96. Based on the response I received on my last post and this information, it appears the use of house wrap would be appropriate as long as it has a 1.0 perm rating or greater. This information leaves me with a few follow up questions.
Can anyone recommend a good house wrap for my situation?
I am thinking about adding some eps, xps, or polyiso in addition to the house wrap. 1) I have read that eps, xps, and polysio all have different permeability ratings; will the addition of such a product inhibit the perm rating of the house wrap and the ability of the moisture to escape the cellulose insulation? 2) Any suggestions on which type of foam board I should use in conjunction with the house wrap? 3) Should the foam be installed on top of or under the house wrap? 4) Can anyone recommend a specific product?
In regards to creating a rain screen, can the house wrap or foam board be used as a drainage plane? Any preferences on using furring strips in conjunction with Cor-A-Vent or drainage mats like Driwall rainscreen.
In addition, I plan on siding the house with fiber cement. Can anyone recommend a superior way of fastening the siding to the wall assembly? What length nail or screw should I use to penetrate through the foam board if I do not use wood furring strips? Can I apply the siding directly over the drainage plane?
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