Mid Century Ranch rainscreen retrofit
So I recently purchased an MCM ranch in climate zone 6A that was built in 1965. The exterior walls are framed with 2x4s, and I plan on completely renovating the house over the next 2-3 years. I have seen some wildly fluctuating R value recommendations for the exterior insulation in a rainscreen application. The IECC recommendation for my application as shown in the attachment shows 1″ XPS with R19 spray foam in the stud bays. I am considering 1 1/2″ XPS (R7.5) with new R13 batts. The 1 1/2″ XPS is a good thickness for me as it gives me a clean 3″ from the face of sheathing to the face of siding with my airspace and chosen siding. Does this seem reasonable, or am I missing the boat on this one? Thank you in advance for any input!
~Jeff
Replies
I don't have the answer to your wall/insulation sandwich question but do have a few thoughts on your project based on your description. I'm a remodeling contractor in MN and have worked on 3 whole house exterior insulation/windows/doors/rain screen/roof remodels in the last 5-6 years and they were all very time consuming and expensive. They did not involve removing the wall cavity insulation/plaster/electric/base trim etc as you have mentioned doing.
I'm assuming you are not a builder because of the time frame? It's fine if you're not but a huge chunk to bite off. Will you be living in it while working on it for 2-3 years? If yes, does your spouse know about this arrangement :)? It will strain your relationship if you are both not "all in".
What is the end goal of this project? If this is not your forever home (doing it for comfort) or in a very desirable area there is no payback for what you are proposing. You might as well build a new house and put ZIP-R on it and skip the dust and headaches.
Thank you for your reply!
1). You are correct in that I am not a builder. My background is actually commercial building envelope design, installation, and project management (unitized curtainwall, skylight, ACM cladding...and rainscreen).
2). Yes we would be living in it during that duration...and at THIS point, my wife IS on board. She is a library director that helped to work through a couple complete library renovations, so she is sympathetic to some building challenges (at least ones that don't serve as a primary residence).
3). Your last statement is precisely what I was looking for. While we DO want this to be our forever home, I was never convinced that what I was proposing would give a decent ROI. Yes, there is a certain level of comfort that I would like to add, but it would be a negligible improvement (IMO).
Thank you again!