Hi,
I am seeking advice regarding insulation. I am building my retirement home in Ponce Inlet, FL — the east side of Florida just south of Daytona Beach – about 2000 ft from the Atlantic Ocean in a hot, humid climate.
The house is a two-story. The lower level is concret-block. The upper level is 2 x 6 wood frame. The exterior of both levels is 3-coat stucco.
I have seen all sorts of conflicting advice regarding the use of Kraft-sided fiberglass batts. Some say install Kraft sided batts as one would in the north with the Kraft paper toward the inside of the wall.
Some have advised that in hot, humid climates, one should install the insulation with the Kraft-paper toward the outside of the wall.
Others have advised that one should not use Kraft-facing at all so that moisture can dry out unimpeded.
Anyone know what I should really do?? And, why??
Thanks.
gary comfort
Ponce Inlet, FL
Replies
As warm moist air is drawn from the warm side of a wall to the cooler side, it will lose it's moisture in the form of condensation in the wall. In the north, the warm mosit air is usually on the inside and would condense on the exterior sheathing, so we put a vapour barrier on the inside of the wall to stop the moisture from entering the wall system.
Presuming that you will use airconditioning, the cool side of your walls will be the interior, so you want the VB tpo be placed on the outside of the wall.
The problem is that reverse installing a kraft face in a wall that has already been sheathed on the exterior will not provide you with a very good VB since you can't staple the flaps over the studs. There are far better ways to deal with this. I am not in the deep south so there may be other local predominatnat methods, but the first that comes to my mind would be to place a foil faced foam such as Thermax on the exterior and tape the joints. Another way of dealing with this issue would be to use a whole house positive ventilation air exchange system. With the house positively pressurized, all air leaks will be to the exterior instead of sucking the damp in.
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You may also want to check out what your building inspector wants to see. I'm in humid NC, and we have to have a plastic vapor barrier on the inside of the wall.
As a side note, I did a house that had a block walk-out basement. One of the walls that wasn't buried faced south. The interior was framed. After the insulation was in (along with the poly vapor barrier), on a sunny day, condensation would form on the inside of the that wall's poly. Later, as the inspector was doing his rough-in walk through, he said if he was me, he'd slit that poly as soon as I left. He left, I slit.
Expanding foam? Don't worry, we can fix that later!