The flash-and-fill application in the attic simplifies the air sealing process where there may be many air leakage paths. The continuous spray foam creates a single airtight layer at the ceiling before additional insulation is installed. It is important to review the previous air sealing procedures if there are non-IC-rated pot-lights, service penetrations subject to movement, and chimneys in the attic. Flash-and-fill is especially efficient if the celling is a material with many gaps, such as wood panelling or tongue and groove boards. In addition to air sealing the attic, closed-cell spray foam can provide a continuous vapour barrier at the ceiling plane, further reducing moisture entering the attic from the living space.

This procedure is for the flash-and-fill application in an accessible attic.