Q&A: A Forum for Green Building Experts and Beginners

If a product has a perm rating of 5 at a 1" thickness. What is the perm rating at 10" thick? Is the math as simple as taking the perm per inch and dividing by thickness or is the relationship non-linear? What happens when you add a coat of primer and two coats of latex paint?

I am building a home. I live in the same mixed-humid climate zone as Louisville, Kentucky.
My HVAC contractor has installed ductwork in the attic. (I did not want this, but he insisted it was necessary for air conditioning).

Steel ductwork runs up a chase from the basement to an attic manifold. Flexible insulated tubes branch of this to each rooms ceilings. Also, return air flexible tubes to another ductwork manifold that runs back down to the basement geothermal unit.

Turning a garage into a habitable room and we are installing a new wood sub floor (needs to be 5" higher than the slab) over an existing concrete slab. We are presuming there is no membrane below the slab. In past jobs we have put down a 6mil membrane and floated PT 2xs with 3/4" ply on top. I am wondering if there is a better method by which we didn't use pressure treated wood. Any ideas are appreciated. Thanks.

We're embarking on a new project, stripping off the siding and adding several inches (4-6") of polyiso to the exterior. We'd like to be able to do a blower door test before we add the rigid to make sure we've done a good job air-sealing. The existing, for the most part, is a post & beam frame with 2x infill framing, plywood sheathing (looks like 1/2" CD or CDX) and then 1" of EPS covered with 1x ship-lap pine. Plan is to use some kind of housewrap, full coverage ice & water on the roof, presumably some gasketing or spray foam will be necessary at the sill.