Quote:
Originally Posted by Belmont Resident
.... There was a problem with the house holding water during the plaster curing time and dehumidifiers were brought in to solve this.....
....I would think that having the most insulation possible on the roof is the best option.
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In both concrete and plaster curing, part of the water is tied up by chemical reaction and becomes part of the solid result. The excess water must be removed by evaporation. Ultimately, that water should be removed from the air by mechanical dehumidification or by ventilation. One should not expect or want all that moisture to go out through the walls.
Nearly all cases of ice damming at the edges of roofs are due to warmth getting to the roof surface. Much of the time this is due to heat carried by air leakage from conditioned space into the attic (vented attic) or the roof cavity in the case of a cathedral ceiling. Can lights in the upper floor ceiling are notable heat leaks, even those rated "air tight" (AT), and from a building science point of view are generally a bad idea in those locations. But any air leak that carries heat from conditioned space to the roof deck contributes to conditions that lead to ice damming.
More and more attention is being given to building science issues, and some builders have learned how to get it right, but sadly some still just build the way they've always done it. Insistent homeowners who prefer form over function also are part of the problem.