Cellulose Retro Fit Plaster Walls -Good or Bad Idea?
Hi There,
I live in Toronto, Ontario, Canada and I own an older home built in 1912. As many of you likely know, back a century ago the majority of these homes were built without insulation and the walls simply consisted of brick and plaster. My home isn’t much different. It is a brick home, with a 2 x 4 structure, that has open/empty stud bay cavities that are 16″ apart (give or take), with zero insulation. In-between the brick and the 2 x 4 framing is the sheathing and I believe a small drainage cavity gap in-between the sheathing and the brick about an inch or so. The sheathing as far as I can tell is horizontal planks of wood, which I believe has tarpaper on the side facing the brick acting as an air/water barrier. Recently, I signed up for a retrofitting winterizing program with our Natural gas utility company, helping resident to decrease utility costs due to inefficient insulation and to help lessen our carbon foot print. I have qualified for the program but I have some reservations.
They are offering to retrofit cellulose between the stud bay cavity’s. Seems like a great idea given I have no insulation but doing research I have heard this can be not such a great idea. What I’m learning is without a ploy vapour barrier on the inside, this can cause negative impact by building up condensation causing mold and or even rotting the wood structure of the framing. I’m not knowledgable enough on this topic to know if this is indeed a highly likely case with retrofitting cellulose. I’ve also heard certain paints and primers can act as vapour barriers on the inside, but wondering how effective that method of vapour barrier can really be?
We can get some harsh winters here and my home is definirtely most cold come January through March. Gas costs are certainly higher than they would be if it was properly insulated, so I do love the idea of moving forward but not if it poses serious risks to my health and slowly (if not quickly!) deteriorates the structure of my house. If that is the potential risk I’m presented with here, I’d much rather decline the offer and at a later point in time, tear out the plaster entirely, insulate with batts, add a proper vapour barrier and re-dry wall. It’s not ideal, the other method would be easier and cheaper but that’s why I’m here asking the question and hoping for knowledgable feedback on this.
Thank you,
Peter
Replies
https://greensaver.org/energuide-energy-evaluation/
You may want to start with a custom energy evaluation of your home. (walls are only one area to be evaluated)
Dense-pack blown-in cellulose can be an effective method to insulate wall cavities. You should be able to ask for and get referrals for local customers who have lived with results for ten or more years in homes similar to yours.
My son and his young family moved into a house similar to yours over ten years ago. We had to upgrade the original knob and tube wiring in outside walls before having cellulose insulation blown into the wall cavities and above the ceilings.
Hi UncleMike,
Thanks for the reply. I actually did have an energy evaluation done on my place. There are def other areas the house require improvements such as windows and likely new attic insulation. I will work towards those in due time.
I will look to see if i can get referrals from previous customers who've had the same type of work done. For your son's place, how long ago was it done and was it retrofitted through drilled holes or did you tear down the walls? Sounds like it was the drill hole method. I'm assuming all has been well for him so far...
He had wood siding on the outside, the installers removed two courses of siding, drilled holes in the sheathing boards, plugged the holes, and replaced the siding.
Insulation was placed in the attic at the same time.
It was installed 12 years ago and no issues observed.
You likely will need holes on the inside walls.
I would be VERY concerned about the freeze thaw cycle for moisture in the brick.
Masonry is porous. the heat inside the building helps dry the brick.
I have a similar home in Chicagoland. I'm insulating everything else, but not the walls.
This was a Myiad's response very similar question that was posted:
Myriad | Jun 24, 2022 06:16pm | #2
I agree with Bon's remarks regarding the moisture issue but I am pretty sure you can safely insulate the interior of old brick buildings and after checking out Building Science Corporation, I think my method detailed above is acceptable. The most highly recommended way, according to BSC, is to use 1" of closed-cell spray foam directly on the brick and then stud wall with wood and then use sprayed in cellulose to fill stud wall. Polystyrene panels, while being better R-wise, are more trouble to install as you have to have to seal all the panels with either tape or spray foam because there must be NO air space between brick and warm side.
Check out this excellent paper BSC created: https://www.buildingscience.com/file/5801
Your house is different due to the brick having an air gap, but I'd be very cautious.
Best of luck.