I have a 19th-century house that lacks insulation entirely, including any deteriorated material. The walls are wood-framed, with lathe and plaster on the inside and wood weatherboarding on the outside, plus vinyl siding over that. During a recent rewire, I removed the baseboard and noticed I could see the back of the weatherboarding. My question is: can I blow in cellulose insulation into these walls, despite the absence of a vapor barrier?
3 Answers
You didn’t mention your climate zone. If it’s generally dry and water never gets inside those walls, dense packing can work. Just ensure you have a continuous air barrier, likely at the plaster layer. Don’t forget that humidity and moisture can change the game, especially if you’re in a wet area!
Make sure to check if there’s any vapor barrier hiding between the siding and the weatherboarding. If there isn’t, you might want to install new siding before blowing in the cellulose. Otherwise, I’d personally avoid it; trapping moisture could lead to mildew issues down the line.
You can definitely blow in cellulose! Just keep in mind that the vapor barrier should ideally be between the conditioned space and the insulation. Having it outside, as part of the siding, can actually cause moisture issues. If you're worried, consider applying a paint-on vapor barrier on the inside of the walls. There are products specifically designed for older homes, so your local paint shop should have good options.