Over the past dozen or so years my opinion on spray foam insulation has evolved from being a strong advocate to being slightly skeptical.

I have come to the conclusion that any well-designed new building can be insulated with any properly installed insulation. When it comes to renovations, however, spray foam often has some distinct advantages.

About eight years ago, I installed spray foam on the roofline and floor of my house, which, I now realize, was not a particularly good decision. Since I had no HVAC ducts in the attic, I probably should have insulated and air sealed the ceiling, and sealing and insulating the crawlspace would have been a better choice as well.

But that is all water under the bridge. I would have preferred to use something else in my current renovation, but since the floor and roofline were already insulated with spray foam, it didn’t make sense to switch products (and relocate the thermal enclosure location in the process).

What should I do with the walls?

Ready for insulation, I hired an experienced Icynene installer to insulate the new walls, roofline, and floor areas, as well as to touch up some thin areas from the earlier install.

I chose not to install any insulation on most of the existing exterior walls as they were not being stripped. The existing wood lap siding is in excellent condition, and with no sheathing or weather barrier, I was concerned that installing insulation would lead to moisture retention in the wall cavity and possible damage to the structure and siding. Since the climate in North Georgia (Zone 3A) is relatively mild, I decided that the added value from wall insulation would not be worth the risk of moisture damage, and removing either the siding or the plaster to allow the walls to be insulated was not in the budget.

At the one small section of wall where the interior was exposed, I installed felt on the inside of the wall to keep the insulation away from the siding, providing a sort of makeshift rainscreen between the siding and the insulation. I can’t say for sure how well this will work, but there is enough of a roof overhang that any moisture that gets in the wall cavity should be able to dry out, keeping the wall safe from damage.

Rolling towards completion

Insulation and drywall are installed, interior finishes are moving along smoothly, and the house should be ready to re-occupy close to the end of the year. The outside work is progressing, although some bad weather and the Thanksgiving holiday slowed progress a bit.

I’m looking forward to seeing how well the Home Slicker rainscreen works with the siding – a combination of reused and new material. And I am particularly interested in seeing the Perennial wood porch flooring and rails installed.