How To Seal An Attic Vapor Barrier

Even though we apply vapor barriers to exterior insulated walls in cold climates it s no longer recommended for ceilings floor of the attic.

How to seal an attic vapor barrier.

The paper facing contains a layer of impermeable asphalt that prevents water vapor from passing through it. Attic vapor barrier detail for cold climates. Seal the attic access. Plug open stud cavities.

This barrier is meant to keep moisture from getting to the insulation in the walls and ceilings and it is required by building codes when insulating most houses. Apply self adhesive foam weatherstrip tape to the top edge of the stop. Using other kinds of tape will compromise the waterproof seal and render the barrier useless. Though some batts come with a paper or foil facing that can act as a vapor barrier tom silva prefers to use 6 mil polyethylene sheeting cut to fit between the joists and with seams sealed by foil tape to prevent moisture from seeping into insulation.

Vapor barriers are sheets of plastic or other material placed on one side of insulation sheets. Most forms of attic insulation benefit from the addition of a vapor barrier to protect them from the harmful effects of moisture which can reduce their effectiveness over time the following are a few simple steps to help you undertake the task properly so your vapor barrier retains heat without damaging the insulation. Finish the wall within a month of installing the barrier to prevent damage to the surface and protect the vapor barrier. Think of a glass of ice water.

During the energy crisis of the 1970s a prevailing belief took root where it was thought that tightly sealing walls and ceilings with a vapor barrier was essential to blocking heat transference and reducing energy costs it was soon determined however that unless the seal was absolute moisture that did get into sealed walls could create serious structural problems and health issues such as. How to use plastic as a vapor barrier in the walls. Because it s nearly impossible to seal penetrations in the ceiling the reality is water vapor will get into the attic. Do not add a vapor barrier on top of the insulation in your attic since the paper facing on the existing insulation is the vapor barrier.

Weatherstrip the attic access hatch or door. If you re insulating from scratch put the right vapor barrier in the right place. Cut 1 3 boards to fit the perimeter of the opening and nail them on with 6d finish nails. In any case the vapor barrier must point to the warm side.