Best insulation for a brownstone
Hi! We are gut-renovating a brick rowhouse in Hoboken and, In spite of reading the excellent articles on this site and in Fine Homebuilding, I still don’t know what do do about insulation to maximize energy efficiency and be as “green” as possible. The plaster was removed from the party walls and they are mostly framed with the studs on the flat flat to maximize interior space. The insulation contractors I’ve spoken to are recommending open-cell foam on the party walls but in those rooms we will only get 2″ of depth (There will be a lot of wasted foam, I think.) Is there a better insulation material option for the party walls (and maybe one that would give us the benefit of some additional sound-proofing from the neighbors)?
On the front & back exterior walls, the plaster has also been removed but the framing is traditional (there’s about 6″ of cavity depth on the front wall due to the frame-out for the pocket shutters, and a little more than 4″ in the back) as well as the cockloft, contractors are recommending filling the cavities with closed-cell foam–is that the best choice?
If the community could let me know “best practices” for brownstone insulation, I would really appreciate it–I am very aware that I have one chance to fet this right!
Suzanne
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Replies
Did you read this article? https://www.greenbuildingadvisor.com/blogs/dept/musings/insulating-old-brick-buildings
The party walls have conditioned space on the opposite side, and don't NEED to be insulated. But if you're leaving the 2x furring in place (whether full-dimension rough 2" or milled 1.5" 2x ) the greener option is to trim 1.5" or 2" sound & fireproofing rock wool to fit. eg:
http://www.roxul.com/products/afb/
or
http://www.jm.com/content/dam/jm/global/en/building-insulation/Files/BI%20Data%20Sheets/Resi%20and%20Commercial/BID-0163_MinWool%20SAFB_Data%20Sheet.pdf
Rock wool won't air seal the way open cell foam would, so you might want to fix penetrations and apply a flexible paint-on or spray-on heavy bodied sealer to the brick to improve air tightness (which will itself improve the soundproofing) before installing the rock wool.
At a full 2" the mid-density rock wool delivers ~ R8-R8.5, at 1.5" thickness it's good for R6-R6.5.
If you're having a hard time finding the stuff or you don't want to split thicker batts into thin batts, insulation4us.com carries Roxul AFB in 1.5" and 2" thicknesses (as well as other thicknesses) in a couple of standard widths, and doesn't demand that you buy it 2000 square feet at at time the way some commercial construction distributors would. Their minimum shipping is pretty steep if you only need a 100-200 square feet, but if you need 2000 square feet it's "reasonable".
Susanne,
In most areas the governing factors determining what you can and must do to the party walls will be what the code requires in terms of fire rated and acoustical separations.There may be some leeway as it is a renovation, but the place to start is your local building inspector.
Suzanne,
1. Are the walls of your house made of brownstone (a type of sandstone) or made of bricks? Or are these walls a combination of bricks and brownstone?
2. Is the party wall a framed wall (just wood framing) or does it consist of brownstone (or bricks) with furring on one or both sides?
I had presumed brick + furring in my prior response...