Rehab house – wall assembly
Ok folks, give me your feedback on this one… Working on a rehab project that is in a historical area. Interior of the home is 100% gutted and open. Exterior, however, I am required to save about 50% of the existing siding. I cannot remove the sidings or trims in these areas per the historical powers. Under the siding is the normal 1x sheathing boards (run on a diagonal) like you see in a home of this age. Definately has gaps between some boards. My concern is about water getting behind the siding/trims and into the wall assembly. So, what is the best insulation materials to use at those locations? I’m currently leaning towards blown in cellulose with no vapor barriers or retarders, no foam (open or closed) and definately no fiberglass batts. Interior drywall will be paperless… that is my current plan.
Couple quick notes. Project is in Indianapolis so it is techically a “cold climate” but we are right on the border. AC is definately used so this wall needs to be able to dry both directions. The home does have nice, wide overhangs so that makes me feel some better about keeping weather off the historical sidings and trims.
Any insights would be appreciated.
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Replies
Micah,
You may be interested in in checking out the July/August 2010 issue of Home Energy magazine. On page 44, there is a short article titled "Retrofit of a Drainage Plane," with recommended details for insulating walls without sheathing. Although your house has sheathing, it has no WRB, so the solution might apply to your case.
Julie Groth installed strips of Homeslicker in each stud bay, from the interior, against the siding, and then a layer of 1/2-inch rigid foam. Once these were in place, the stud bays were filled with spray foam.
Of course there are disadvantages to this technique, but it is an intriguing solution to the problem of maintaining an air space behind the siding -- or, in your case, sheathing.
Are you sure you don't have asphalt impregnated felt paper between your siding and 1x sheathing boards? You would be able to see this through the gaps.
That was a building practice in turn of the century housing in my neck of the woods (my house included). Depending on conditions the felt paper could be in decent condition and still be acting as a WRB.
Micah,
With good roof overhangs, exterior siding and trim in good condition and well-painted, and all exterior joints caulked (the sealed face method) - and your highly breathable interior layering - this house should last another 100 years.