Volume 5, Issue 10 (November 2008)
Condensation Damage Behind Self-Adhering Membrane Flashing and Interior Furnishings on Exterior Residential Walls
This paper will present case studies of condensation damage behind self-adhering membranes installed around windows and other penetrations in exterior walls, as well as case studies of condensation damage behind large interior furnishings installed on the interior surfaces of exterior walls, and in unventilated spaces in Minnesota. The self-adhering membranes that are often used to integrate water-resistive barriers with residential doors and windows can, under certain conditions, lead to condensation and subsequent damage. While wider membranes help prevent inward movement of liquid water to the sheathing and stud framing, they also inhibit outward movement of interior water vapor. By increasing the distance that outward moving vapor must travel, wide membrane flashings trap moisture that can condense in cold climates and cause deterioration of degradable materials. In cold climate regions, condensation damage can also occur in exterior walls behind furnishings such as large mirrors and large cabinets. These interior decorations act as thermal reflectors and prevent interior heat from migrating into the exterior walls. When moisture behind these thermal reflectors is cooled below the dew point, condensation and related deterioration of the wall framing can occur. This paper discusses suggestions for the width of applied self-adhered membranes in cold climate regions and recommends locations for thermally reflecting interior furnishings.