Dense pack Q: Can fiberglass batts be extracted without demo’ing a wall?
OK, a few more insulation questions more question, then I think I’ve hit my quota for the week (year?) 🙂 I want to learn a bit more about dense packing a wall just so I have that as a data point to make my final decisions.
1) I’m wondering if faced fiberglass batting varying between 15 and 50 years old can be pulled / sucked out through a slot in a wall in order to dense pack cellulose. Most of the fiberglass is the super itchy yellow stuff that I just assume leaves the premises. I know you can dense pack on top of it, but something tells me that is not the best solution to optimize wall performance.
2) If it can’t be easily removed, and sheet rock has to be demo’d, how do you dense pack the wall after recovering? Do you just leave the top few inches open and then cover it at the end, or are holes cut how they would be with an existing wall?
3) If one wanted to use the double wall method, would the inside wall have to be a full 2×4 or would slimmer studs suffice?
4) Finally, can dense packing be used in tight attic spaces where the sloped roof meets the joist?
Thanks!
Ryan
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Replies
Ryan,
If your existing stud walls are filled with fiberglass batts, it doesn't make much economic sense to try to remove the fiberglass batts and replace the fiberglass with cellulose. Instead of following your plan, simply concentrate on air sealing.
If you really want to increase the R-value of your walls -- an effort which is unlikely to be cost-effective -- then installing an interior or exterior layer of rigid foam makes more sense than building a double-stud wall.
However, if you are absolutely determined to follow your plan, I imagine that you could remove a 12-inch high strip of drywall, the length of the room, from the bottom of each wall, as well as a 12-inch high strip of drywall from the top of each wall, and try to wrestle the fiberglass batts out. It's a silly plan, but anything is possible. (Really, before I attempted this, I would just blow some cellulose into each stud bay, and compress the batts.)
If you want to blow cellulose into the stud bays after your fiberglass wrestling match, you could patch the drywall at the botttoms of the walls and fill them with a hose from the top. If you really wanted to.
It's sometimes possible to get old batts out by removing a strip of siding & sheathing, but usually not. If you have 27 nail points grabbing the batt it's pretty much impossible (unless you're a real glutton for punishment, and have more time than sense.)
It's fine to leave the fiberglass in there and dense-pack over it. It's sometimes possible to get a dense-packing tube between the fuzzy side of an R11 and the sheathing by running air-only on the blower while inserting the tube, but there's an art to it. With R13s it's practically impossible, but you can drill multiple holes per bay and get fairly high density along with a substantial improvement in air tightness.
The performance improvement boost is primarily due to better air tightness, but with 50 year old mouse-nested R11s the raw R value is bumped up too. With R13s in good shape, reasonably installed, it's probably not worth it.