Most of the heat loss from a home occurs vertically from the heated living space, and through the ceiling, attic and roof. Insulation helps to prevent some of this heat loss, but the attic remains its primary source.
Most home attics have loose fill insulation. It is less expensive and easier to install than batts. With proper installation, it spreads and fills gaps that are more difficult to insulate with batts. Installers should build platforms in attics to raise mechanical equipment, in order to provide space for adequate insulation.
When homes have air ducts for the heating system in the unheated attic, the ducts leak heat into the space where it also escapes through the roof. In these homes, adding insulation to the area between the rafters encases the heating system to reduce the heat loss from the attic.
Snow accumulations on the roof of a home make the heat loss through the attic visible. The warmer temperatures often cause the snow on the roof to melt before it melts in other places. When the outside air temperatures remain below freezing, the drips from the melted snow form icicles and ice dams, especially on homes that need additional insulation. Increasing the insulation prevents some of the heat loss and the damage due to ice formation from melting snow.