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The debate between proponents of unventilated "hot" roofs and ventilated "cold" roofs has been raging for years. Hot roof advocates argue for sealing all wall penetrations against convection (at outlets and vents stacks, for instance) and applying a perfect vapor barrier. They claim that these measures keep moisture from entering rafter bays, thus eliminating the need for a ventilating air space between the roof insulation and the sheathing. Cold roof advocates like me admit that it is theoretically possible to build an unventilated roof, but caution that it is almost impossible in practice to build it to perfection. The most conscientious builder will still have trouble installing insulation, caulking, and vapor barriers to the