Old house with no sheathing/vapor barrier
brettelrod
| Posted in Energy Efficiency and Durability on
I have an old house with no sheathing or vapor barrier, just clad siding on top of studs. I have the interior gutted and I am set to add batt insulation and new drywall back as it was originally. Should I add felt on top of the insulation and under sheetrock as a vapor barrier…still allowing the wall assembly to dry to the outside? or will it condesate on felt in summer and rot studs/etc.
ps I am in SC…really hot/humid.
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Replies
Are you running air conditioning and keeping the windows closed till during your long warm season?
As to tar paper, do not put that by the drywall.
Charles,
Your first challenge is to install something that resembles an exterior air barrier and water-resistant barrier (WRB).
There are two common ways to do this when working from the interior on a house with no sheathing:
1. Install strips of asphalt felt in each stud bay, up against the back of the siding, before insulating. This is usually done by cutting wide strips with flaps on each side -- the flaps are used to staple the asphalt felt to the sides of the studs. (For more information on this technique, see Sticking With Spray Foam for My Renovation.) The main disadvantage of this approach is that the felt is not really an air barrier.
2. Install 1"x1" vertical sticks in the corners of each stud bay, up against the back side of the siding, followed by rigid foam that is installed in an airtight manner (with caulk or high quality tape) against the "sticks." This method leaves a 1-inch air space between the back of the siding and the rigid foam. It is a more airtight method than using asphalt felt.
Once you have done either of these steps, you can go ahead and insulate your stud bays. I would use cellulose if I were you, not fiberglass batts.
On the interior side, don't install any asphalt felt of polyethylene. However, you should pay attention to airtightness when you install your drywall, especially at electrical boxes.
Charles see this link... http://foursevenfive.com/product-category/air-sealing-system/interior-membranes-air-vapor-control/