Should we install a rainscreen in a 10″ wall assembly?
We are building a new home in SE Washington state with 10″ thick walls and wondered if we need to worry about having a rainscreen behind the James Hardi lap siding. We get 17-20″ of rain here annually and have heard conflicting thoughts about whether it is needed in this climate. We just don’t want to end up with any moisture in the wall cavity, but are not sure where it would come from. Here are the details of the wall assembly:
Benjamin Obdyke’s Hydrogap housewrap or Sto Gaurd’s liquid applied WRB over 1/2″ plywood.
Dense pack cellulose in the 10″ cavity of the double stud wall.
Drywall with vapor barrier primer (code requirement)
We typically get blower door numbers at or under 1 ACH, so shouldn’t have very much air leakage.
We are using an HRV for ventilation which tends to make the home even dryer in the cold months.
Is there potential moisture drive from the outside that we need to worry about? Does the liquid applied membrane allow moisture vapor to enter?
Thanks for sharing your knowledge and experience, it is such a help having professionals to draw from!
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