Improvements when re-siding
I have recently started soliciting quotes for a complete removal and replacement of my original 1920’s Stucco siding. My home is located just outside of Boston, MA. The stucco is installed just like the interior plaster & lathe was so there is no sheathing and zero insulation. Plywood sheathing and wrap will be installed prior to vinyl siding.
Massachusetts offers incentives to install blown in insulation so I figure I will schedule a company to come after the new sheathing is up and blow in from the outside. A few windows will be replaced as well. Are there any other insulation or energy considerations? This seems like a pretty critical moment where I can fit in other work. I don’t have a massive budget as the siding/window project itself is over $40k.
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There is also damp spray cellulose which is installed before the sheathing. Be sure to carefully tape the sheathing as an air barrier and have it tested. Consider insulation over the sheathing.
I would seriously consider adding exterior insulation if at all possible. There is a big energy savings associated with doing that, and it’s a lifetime improvement. It’s also pretty impractical to do any other time than during a reside.
That exterior insulation would be in addition to installing some kind of “regular” insulation inside the walls. I personally am gradually replacing fibeglass with mineral wool (a bit more R value but mostly because of critter damage), blown in can be very good too, especially if you have some incentives available to help with the installation costs.
Bill
In most homes with stucco siding you'd have enough room to install 1" of exterior polyiso over the 1/2" CDX, or use R6 ZIP-R instead of CDX, which has an polyiso on the interior side of the assembly.
Contractors unfamiliar with exterior insulation might find it easier to deal with ZIP-R, but I believe most vinyl siding can be simply long-nailed through 1" foam, no exterior furring required when it's only that thick. See::
https://s3.amazonaws.com/greenbuildingadvisor.s3.tauntoncloud.com/app/uploads/2018/08/08062439/Vinyl%20siding%20over%20foam%20sheathing.jpg
With ZIP-R the vinyl siding can be attached in the same manner as any CDX or OSB siding, but the ZIP-R itself is 1.5" thick instead of 1/2" thick, and thus needs longer fasteners.
Either of those approaches along with a cavity fill of R13 or greater would bring the wall up to current code-minimum R values in MA. It may be cheaper and easier to use open cell foam both cavity fill and sealant prior to putting up the sheathing & exterior insulation than to dense-pack fiber after putting up the sheathing.