Do I Need New Flashing for Retrofit Windows?

Adhesive Membrane and Flashing

• Many older houses have window frames constructed from wood. The wood is usually durable but inspect it for damage because it might need to be replaced. Damage can include insect infestations, warping and age-related deterioration. If the wood needs to be replaced, then aluminum flashing strips must be installed around the window frame. Before installing the strips, however, wrap the entire window frame area, including the sill, jambs and the horn, with an adhesive, waterproof membrane. The sticky membrane is available in rolls from hardware stores and home improvement centers. Once in place, slice the adhesive to fit and conform to the coverage area. Because retro-fit windows and the wells in older homes might not be built in standard configurations, the adaptable nature of adhesive membranes makes them well-suited for this task.

Flashing and Insulation

• Install flashing from the outside. This allows access to the entire window area. The flashing membrane should cover the entire frame area, including crevices. At the junction where ledges meets sills, the membranes should overlap. This helps protect against leaks. Avoid sealing the bottom edge of windows as this opening will allow trapped water to exit. Once the membrane has been placed, the insulation can be installed. Older windows might be double-hung. Retro-fit windows often eliminate this excess bulk. The result is a void between window and wall that should be filled with insulating material. If the void, or other empty space, is not filled, heat will escape and water can get trapped.

Benefits

• The benefits of installing insulation and flashing around retro-fit windows are the ability to keep heat inside the home and prevent water from seeping into the home. Water can also seep into walls where it collects, condenses and becomes a suitable growing environment for mold and mildew. During cold weather, trapped water freezes and thaws. The expansion and contraction of water causes cracks and other damage to the wall and window well. These cracks further increase the possibility of more leaks and more damage.

Considerations

• Although retrofit windows have improvements over older, classic windows, they are still not as energy-efficient as new, low-emissivity windows. Because not all retrofit windows feature protective coatings and gaseous protective layers, flashing becomes more important to strengthen and protect the windows and home.