Bath tubs and plumbing & Air Leakage and moisture

Plumbing is a common pathway to air leakage, particularly the plumbing connected to bathrooms.

Air leakage due to bath tubs sitting against un-sheathed studs, or holes in the top and bottom plates of plumbing walls in the floor underneath these tubs, are particularly common and should be solved.

But Tubs Air LeakageMoisture problems

These air pathways can be particularly serious since they also may create moisture problems.

The image at top (from DOE) illustrates these types of problems.

Insulation, sealing and materials

Before installing (or reinstalling) any tub you should insulate carefully the exterior walls and seal the wall surface behind the tub: you may use polyethylene foams and sheet materials.

After the drain is installed, the tub drain penetration should be sealed with sheet goods (drywall, plywood...) and spray foam (or caulk, if the penetrations are sufficiently small). Penetrations in the floor and ceiling (namely those connected with the soil stack – the main drain pipe - should be properly sealed with foams.  

Pay also attention to possible electric penetrations, connected to bath tubs.

See: Air Sealing Electrical and Ventilation Openings

See also: