This message has been cross posted to the following Discussion Forums: Housing Knowledge Community and Historic Resources Committee .
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We're working on the restoration of a c.1875 vernacular Italianate home. The exterior walls are composed of full 2x4s with 3/4" painted shiplap siding nailed directly to the framing (no sheathing). The cavities were filled with brick nogging. At the interior, the lath and plaster comprised a 1-1/4" overall thickness. Due to the discovery of extensive rot and insect damage, the damaged interior plaster wall finishes have been removed as has the nogging, and the bare wood back face of the siding has been exposed (and yes, most of the siding boards have a slight convex curve at the exterior). We're planning to insulate the cavities, then sheath the interior with 3/4" plywood and cover that with 1/2" GWB, which will get our wall surface back where we need it to be in relation to the casings and mouldings we've preserved. My questions are as follows:
- We're considering priming the exposed back of the siding using an oil-based primer or even a liquid house wrap product such as Ben Moore Super Spec Latex Vapor Barrier Primer Sealer 260 to help stabilize the siding and provide a measure of protection for the insulation that will of necessity be immediately beneath the siding. Both we and the owners are skeptical of the test results for such liquid house wraps with regard to their potential toxicity.
- While rigid or batt insulation will not meet code requirements for R-value, both we and the owners are reluctant to use a higher R-value spray foam insulation such as icynene for the same potential toxicity reason. The owners and local officials are, if necessary, willing to take what they can get in terms of R-value.
Can anyone weigh in on the the use of primer, liquid house wrap, and spray foam insulation at a dwelling of this type, or provide other solutions with which you've had experience? Much appreciated---
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Robert Silarski AIA
Principal
S&Co.'Architecture+Design
Nyack NY
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