An illustration of summer heat flow and the effects of different levels of insulation.
Summer Insulation Benefits
In the summer, heat from the hot outside air flows through the walls, windows, and attic into your cool home. Also, the sun's rays warm up your roof to well above the temperature of the air. This heat flows to your attic, and then into your home.
On a sunny, summer day the air inside a poorly-ventilated attic can be over 30 degrees warmer than the outside air! This means that in the summer, heat is entering your home from the attic much faster than from the walls.
You can reduce the summer heat flow from the attic even further by having Radiant Barrier and Attic Fans installed with your insulation.
An illustration of winter heat flow and the effects of different levels of insulation.
Winter Insulation Benefits
In the winter, heat from inside your warm home flows through the walls, windows, and attic out to the cold outside air.
The heat loss to the attic is significant because of the fact that heat rises. The air near the ceiling can easily be 10 degrees warmer than the air near the floor in the winter time. The heat flows to the attic quickly if there is no insulation to slow it down.
Despite the constant heat flow into the attic, the attic remains cool because the roof is not insulated. The result is a constant drain of heat from the house, which means that you constantly have to pay to put it back in (using your heater).