Heat can find its way out of the home through a wide variety of gaps, cracks, and holes in all parts of the house, but especially in the attic. For many air sealing tasks, Dr. Energy Saver Of Connecticut recommends two-part foam. The mixture leaves the nozzle in liquid form but expands rapidly to fill and adhere inside cracks and gaps. As it cures, the foam will create a barrier that is both airtight and effective as insulation.