
A homeowner, “tjones1014” is in the planning stages of a complete gut rehab of his house in northern Georgia, on the line between Climate Zones 3A and 4A. Built in 2001, the house has vinyl siding applied to bare OSB – no WRB or exterior insulation. T Jones has a plan for a new wall assembly, but has questions about moisture risks and drying potential. As always, taken from the GBA forums, here, this is the topic of today’s Q&A Spotlight.
Vapor control and drying potential
The scope of work T Jones is considering starts with removing the vinyl siding and existing windows and repairing any damaged OSB sheathing. He then plans to install Tyvek Commercial wrap and tape the seams. This a mechanically-fastened WRB that he likes for its known durability and 28 perm rating–it’s vapor open. He’ll then install new fiberglass Pella windows with the flashing properly integrated with the housewrap. Then, for a drainage gap and ventilation space, he plans to install Obdyke’s Slicker Max, a woven mesh rainscreen, and James Hardi fiber cement siding. The wall cavities will be filled with Rockwool mineral wool insulation and the interior finish will be latex painted drywall.
T Jones writes that he is worried about the potential for condensation and moisture accumulation in the wall. He’s not sure if he needs more vapor control on the interior or if his plan will allow the assemble to dry adequately in either direction. With the start-date approaching fast, he doesn’t have much wiggle room on the exterior, but is wondering if the OSB seams should be taped before the housewrap is installed? Inside, he is wondering if he should use a Class II or smart vapor retarder. And generally, wants to know if there are any other…
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