REMOTE retrofit
I recently learned about the REMOTE/PERSIST building methods and think it’ll work well on my house. I’ll be removing old fiber cement siding and adding vapor barrier faced, shiplap, 4 inch polyiso (good deal on seconds from a local manufacturer). It’s a small house, with only about 750 sq ft of wall space to retrofit (a newly built addition on one side). I’ve landed on exterior foam because I plan to replace the siding to match the addition anyway and don’t want to settle for 3.5″ of dense packed cellulose. The main floor is heated by a single ductless heat pump.
1-How necessary is it to use peel and stick (Grace ice and water shield) membrane for the entire wall surface? If I tape and seal the polyiso well, is this necessary? Would 6 mil poly, Tyvek, or even tar paper work as well?
2-Tightening up this 112 year old house will require an ERV/HRV. By my calculations, I’ll only need 40-50 cfm. Would the Panasonic spot ERV provide enough fresh air to the bedrooms where it’s needed most while sleeping? It will be cheaper and much easier to install than the Inteli-balance model because of the need to run insulated ducts through the attic to each room. However, the inteli-balance model is ~75%+ efficient and the spot model is 66%.
This site has taught me so much about building science and I very much appreciate it! Makes me want to go into building full time!
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Pat,
Can you tell us your climate zone or geographic location?
The main purpose of the peel-and-stick layer in the original PERSIST approach is to provide a bulletproof air barrier. The Alaskan builders who perfected the REMOTE approach experimented with other methods of providing this air barrier, and these other methods can work. Ideally, after installing your air barrier, you would verify the rate of air leakage through the wall with a blower door. You want your air barrier to be as tight as possible.
Among the possible ways to create an air barrier are (a) You can tape the seams on the existing sheathing. (The probably won't work on a 112-year-old house, though, since your house probably has board sheathing, not plywood sheathing.) (b) You can install a durable housewrap -- ideally, one of the stronger membranes from Europe -- and tape the seams. (c) You can tape the seams of the polyiso (and detail any penetrations for airtightness).
One of the biggest challenges to a project like yours is to figure out how to flash the windows. If you are installing new windows, that challenge is easier to tackle.
Thanks Martin. I'm in Seattle, climate zone 4c. I'm replacing all windows and planning on "outies" to match the outside look of the new addition. I plan to add 2x bucks and flash around the windows with peel and stick membrane.
You're correct that the sheathing is board rather than sheet. One thought was leaving the existing tar paper, if it's in good condition after removing old siding, and concentrating on sealing the polyiso very well. I'm wavering, however, because I don't want to kick myself later for saving $500 by not using peel and stick. If it was a bigger house I'd be concerned more about material cost.
I too debated this issue when doing my REMOTE addition/renovation. I decided to use ice and water method, using a lesser grade peel and stick membrane on the walls. The cost was comparable to house wrap and it allowed me to get weather tight before I got to the insulation. The only downside was that the lesser grade peel and stick is not nearly as sticky as the good stuff especially in colder temperatures, so I found it required roofing nails to stay in place. It does, however, have a similar performance rating.
Thanks Joel. I just found Grace Select, which I'd assume to have the same adhesive as their other peel and stick. It certainly is more affordable (~@$.37/sq ft) than the thicker Ice and Water Shield ($.62/sq ft). I think this might be my solution, given it'll be behind foam and therefore more protected than under shingles, and still fulfills it main purpose of air and water barrier.
Grace Select is the product i used on the walls. It is not as sticky as the other peel and sticks I have used, no matter what the specs say. It is also thinner. One advantage is that it is more manageable for a one-person install. It can be repositioned (at least in colder weather) more easily. I bought a bucket of 1 1/4" roofing nails and installed like felt, overlapping 3", nailing about a foot on center at the exposed edge.