Helpneeded:challenged related to exterior insulation + siding over asbestos shingles with plank sheating
I’ve read several articles and postings here and on other sites related to encapsulating asbestos siding, but I have not found much about this combination:
My 1955 home in maryland has asbestos shingles over plank sheathing with what appears to be tar paper as a vapor barrier under the shingles. The walls are 2×4 studs with the original thin Gold Bond Rock Wool craft-backed insulation, and 1/2″ drywall on the interior walls
I’d like to encapsulate the asbestos rather than remove it, and use a Vertical siding (board and batten style). I am leaning toward vinyl siding that looks like board and batten. I’d like to add a layer of exterior insulation since the R value of the old Rock Wool is pretty lousy. (Vinyl siding that has stryofoam backing is also availale).
In order to minimize shattering the asbestos shingles, I’d like to put furring strips over it and then attach the new siding to those. I have successfully experimented with screwing the furring strips with coated, self-tapping screws (like deck screws) and they go right through the shingles with no damage.
My thought was that I could use 2×4’s as furring strips to have a solid material to nail the siding to, and then I could put thicker (R4?) rigid foam board insulation strips between the furring strips (maybe with caulking or spray foam where the edges touch the furring strip)… OR possibly use a layer of rigid foam board first, the furring strips over that. Then I could use my siding of choice over that.
I do not know how these layers will affect dew point in the walls. Some things I have read lead you to believe that the asbestos shingles and old underlayment serves as a vapor barrier and everything else can be treated as exterior and not to worry. Other things indicate that the layer of foam board introduces a second mold risk (under the foam).
I presume normally you would use some sort of house wrap under the siding, depending on the type of siding I choose (vinyl, hardie board, real wood). But the challenge is the fact that the furring strips would be HORIZONTAL, which prevents any moisture or water incursion from draining if you put a solid covering over the face. Maybe that is mitigated by using either a rain screen (under a solid/flat silding) or by using vinyl siding which by it’s nature creates vertical air channel.
I would welcome any advice on the best choices for insulation, siding, and method of installation using green materials/methods and minimizing risks of problems like dew point/mold.
Thanks,
Lou
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Replies
Bite the bullet and remove the old siding. You are putting good money over a liability. If you know it is asbestos, you have to disclose it when you sell.
Look into the regulations in your area. Asbestos shingles do not usually have friable asbestos, and even when they are damaged, torn, removed, many times there is no resulting friable material, so in many places you would not need to even encapsulate the work area - nothing is getting airborne by removing them.
Removing them may be alot less expensive than you think. In some parts of the country, a homeowner can do their own removal, because it is not considered dangerous or a risk. I have heard of a person who lived in an area that allowed a homeowner to remove x sf per calendar year themselves. They took time off at the end of the year/beginning of the year, and removed 2 sides. Then they spent the spring patching up, fixing and residing. Did the same thing 2 years later.
I have considered that but was also thinking there might be some benefit to leaving the shingles in place (an extra layer of barrier against outside elements). In addition, if I do remove the shingles, I still need to understand what would be the ideal way to add exterior insulation over exposed planking, while providing a nailer for the siding, and it that would be handled any differently than if the shingles remain in place.
Remove the asbestos containing material.
Then do some research for the best way to airseal from the exterior for your climate, and how much exterior insulation you need and post your conclusion here for review & advice.
As far as a nailer for the siding, there are many articles here on using long fasteners to go through nailers and exterior insulation and secure into the framing.
If you install exterior insulation, you can seal it as part of your air sealing project. If you install nailers every 16" through exterior insulation, the nailers can become part of the rainscreen system behind the siding.