How to insulate and sheathe my walls?
Hello,
I am renovating a 1920s home in Vermont. Its a four square New-Englander with a hip roof.
Right now we have the old plaster stripped off, and lath exposed. What I would like to do is;
1- Blow in cellulose insulation behind lath.
2- Plaster over the lath.
I am wondering if the lath will contain the cellulose or if the 1/4″ or so gap between the lath will exhaust a mess of cellulose. I would also like to know if the plaster can key once the cellulose is in, or is the cellulose going to block my plaster from locking into the lath? I am new to plaster and cellulose, so I am hoping to get some advise before I wast time and money…
I appreciate your thoughts,
Justin
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Replies
Justin,
As far as I know, the gaps between the lath are going to be a problem. Cellulose will leak out of those gaps, and you'll have difficulty dense-packing the cavities.
Dense-packing cellulose is tricky work, so you are probably going to be working with an insulation contractor. Trust your contractor to provide good advice.
If I were you, I would (a) mark the stud locations on the subfloor, and (b) install rock lath (a product that looks like drywall) over the wooden lath. Then your insulation contractor can drill holes through the rock lath to insulate your stud bays. Once that work is done, you can repair the holes and install plaster over the rock lath.
-- Martin Holladay
Thanks USER-756436,
I will be renting the DIY machine and tackling the insulation myself...
So, I guess my answer is; Plaster the walls, leaving access holes. Blow in the insulation. Lath and plaster the holes after insulating...
Does this sound accurate?
Thanks,
Justin
You'll definitely need at least some blowing mesh to deal with the gaps. The rock lath idea would be even better. Depending on the condition of the ancient nails the blow out risk of the wood lath would be pretty high with a 2-stage blower capable of 4lbs density, but with freshly nailed/screwed rock lath it should hold up fine.
Getting to 3.5lbs minimum density everywhere (recommended for places as cool as zone 6, which is all of VT) is next to impossible as a DIY with a single-stage rental blower of unknown condition. You can probably beat 3lbs though, which might settle a bit over then next couple of decades, or maybe not, depending on just how much seasonal humidity cycling it experiences. Google up some dense-packing instructional videos before diving in. You may have to fab up your own dense-packing tubes & reducers, etc. if the rental place doesn't supply dense packing setups.
Justin,
I agree with Dana. You are unlikely to get a successful dense-packed installation yourself with a rented blower. Hire an experienced insulation contractor with a powerful blower.
-- Martin Holladay
Depending on where you are in VT, some of us could recommend some specific insulation contractors that have excellent dense-packing skills. There are some others in VT who do not.