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necessary vapor barrier
Thursday, March 5 2009
I probably should have done this in the colder part of the season, but today I finally got around to stapling a sheet of plastic under the flat part of the greenhouse ceiling. Glass wool having an R-value of 19 lies between the ceiling joists here, but it had been the only material isolating the greenhouse from its attic, which is completely open to the flow of outdoor air. The close proximity of cold outdoor to the warm humid air of the greenhouse had created conditions suitable for the formation of condensation in those places where either air mass could penetrate. In the really cold weather the condensation had been substantial, soaking the paper "vapor barrier" beneath the insulation and even causing spots of mold to spread across the frame lumber. Obviously this situation had been untenable. I needed a proper vapor barrier. Thus the sheet of plastic stapled to the ceiling today. It's actually a good thing that I've waited as long as I have to begin finishing that ceiling. Initially I'd planned to use plywood as the ceiling material, but in a condition of what has proved to be continuous maximal humidity, it's clear that wood products are inappropriate. So now I'm thinking of using Wonderboard, that concrete-board-cum-fiberglass-mesh product. Wonderboard could be surfaced with Portland cement to resemble the treatment I've already given to the concrete block walls, and the whole space would look as if it had been cast in a single concrete pour. But even after I've finished the ceiling with a suitably-waterproof material, I'll still have a certain amount of wood framing touching that humid greenhouse air, mostly around the door and windows. I'll probably have to slather on multiple coats of some sort of polyurethane product, perhaps one that comes in battleship grey.
Tonight Gretchen and I watched another episode of the ongoing American Idol season, and I was mostly in it for the melodrama sure to come from Tatiana, this season's least-stable contestant. She did not disappoint. Living up to her last name "Del Toro," in other words, "of bull," tonight she affected a latina accent she'd never used before. It seemed she'd seen Jorge Nunez, another Puerto Rican contestant, survive the first vote-based round despite (or perhaps because of) his accent, and thought an accent might also work for her. She even said almost exactly what Nunez had said, that her accent only comes out when she gets emotional. But she'd been emotional for the whole season and this was the first we'd heard of it. I call bullshit, or, in Tatiana's native tongue, caca del toro.
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