As promised, here is the low-down on the various types of insulation that we’re using in the new house. I’ll start from the inside out:
That’s the insulation that we’re using for acoustic purposes in the interior walls and floors throughout the house. We’re not putting it everywhere, but we’re using it for places where we want to minimize noise transfer from room to room, such as the bedrooms, bathrooms, and laundry room. This isn’t your standard out-gassing, scratchy fiberglass; it’s made of recycled blue jeans, treated with (non-toxic) borates for fire-, mold-, and pest- protection. It’s much denser than fiberglass, so it makes a good acoustic barrier, and it doesn’t produce any harmful vapors (fiberglass has formaldehyde). It’s also as soft as you’d expect old blue jeans to be, so you don’t even need gloves to install it, and since it’s made almost entirely of recycled material, it’s eco-friendly.
Next is the spray foam that we’re using to insulate the ceiling and interior wall of the garage, as well as the band-boards, which are the structural components that the joists and trusses are anchored into. This is what we planned to use for these spots from the beginning, although I did a bunch of research into other materials. The downside to spray foam is that it’s quite a bit more expensive than alternatives. However, Jeff the Builder felt that it was important to seal the garage from the rest of the house, and since the foam expands to fill all the nooks and crannies around the ductwork and joists, it was the best option. It also provides very good thermal and acoustic performance.
As noted before, the entire wall structure of the basement is made of Superior Walls, which are insulated, precast concrete sections. We got the Xi model, which has an R-value of 12.5. [Note: R-value is the standard measure of insulation performance, and it's linear; for example, R-20 is twice as well-insulated as R10. Standard 2x4 frame walls are usually insulated to R-13, and 2x6 frame walls usually go to R-19.] Since most of the basement is underground, thus well-insulated by the earth, R-12.5 should be plenty, but we’re having JtB add more foam board insulation to the above-ground portions of the walls of the mancave, bringing those walls to R-20.
We also insulated the floor of the mancave before pouring the slab, which is a step that is often overlooked but highly recommended by building experts. Even though the ground is a good insulator, it’s always around 55 degrees (that’s Fahrenheit, in case our British readers were freaking out), so it’s hard for the basement to get fully warm if there’s nothing but concrete on the floor. By insulating the slab, we should have a nice, warm basement in the winter.
The SIPs that form the roof and exterior walls of the house have polyurethane foam in the center, so we don’t need to use any additional insulation there. The ones we have are rated at R-24 for the walls and R-40 for the roof, which is far beyond standard insulation.
I should also mention the concept of thermal breaks (don’t go to sleep on me here!): In standard walls that are framed with wood studs, the insulation (usually fiberglass batts) only fills the cavities between the studs, which means that the portion of the walls where the studs are is essentially uninsulated. Consequently, an R-13 rating for this kind of wall is over-optimistic; the effective R-value is probably around 10, assuming no air leakage, which stud-framed walls are prone to. The SIPs and Superior Walls have no uninsulated studs in the middle and are completely sealed from air leakage, so their real-world R-values are pretty much the same as their rated R-values. [Technical note: the Superior Walls do have concrete studs, but they are wrapped all the way around with insulation]
The only weak links in our insulation are the windows and doors, but even there we got the highest-performing ones that we could get (within reason). We’re using all double-pane, low-e, argon filled windows, and the doors are fully-insulated with foam.
I think it’s time for me to end this lesson.



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Posted by Jennifer 

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