Cellulose Insulation – Remodel Question
Done some cursory reading about cellulose insulation. Situation: partial remodel and addition – all walls will be opened. Damp spray seems to be problematic because of drying time and it often never does actually dry (this will be a remodel in winter in potentially rainy northern California.).
Do we go with dense pack? Also read about insulation installers that put up permeable webbing at the stud bays and blow it in without the dampening agent. Alex Wilson wrote in an article:
“Finally, in an open wall cavity, some cellulose insulation contractors install plastic mesh between the wall studs and blow the insulation into the walls through the mesh. This way, moisture doesn’t have to be added and the walls can be closed in right away without worry about trapping moisture.” Is this common?
Can someone recommend a good manufacturer? Leaning towards dense pack until swayed otherwise.
Thanks in advance!
Daniel
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Replies
Daniel,
Choosing the right manufacturer is much less important than choosing the right installer. You want a cellulose installer who has been doing it for years.
If you are opening up your walls, most builders would choose to install the cellulose behind air-permeable netting or to use the damp-spray method. Either method works fine. Unless you have a very tight schedule, a damp-spray installation shouldn't be a problem. With a little patience, it will dry.
I disagree on the importance of the manufacturer. There is a spectrum of quality in cellulose insulation. The source of paper (clean, post-industrial or dirty, mixed post-consumer), the uniformity and size of the fibers, the type of fire retardant (borates are great, ammonium sulfates are problematic and can corrode metal fasteners), and the other additives (such as mineral oil to limit airborne dust) all make a difference in the quality of installation and performance.
Secondarily, the quality of installation depends on the experience, equipment and integrity of the installer.
But there are three options for cellulose installation:
1) damp spray open cavity
2) insulweb open cavity
3) closed cavity densepack
Each has its advantages and disadvantages. If drying time is an issue, then avoid damp spray, though it packs very uniformly with good density.
If there are lots of interruptions to the framing cavites, then an insulweb installation my be preferable, though getting good density may make it difficult to install drywall over the bulge.
With straightforward framing cavities, the simplest installation technique is a closed-wall blow through either the drywall or the exterior sheathing. A good installer with a good blower can achieve very high densities without bulging the drywall. One method for this is to leave a 6" gap between upper and lower drywall on exterior walls, with a 12" wide strip of insulweb or window screen pinned behind the gap. The cellulose tubes can be inserted through slits in the webbing to fill the lower and upper wall sections, and then the gap is patched with 3/8" drywall for a seamless finish.