- Posted by: Ana
- Category: Roofing
The roof, attic ventilation, and attic insulation all act together as a system
The roof color will affect the temperature of the attic. Dark colors will absorb more heat than light ones. However the most important factors of attic temperature attic ventilation and insulation.
Shake roof were very good at not absorbing heat, and not transferring it to the home.
Tile is surprisingly good, even though the concrete absorbs a lot of heat, it does not transfer the heat into the house because it is not in direct contact with the roof deck.
Asphalt roofs absorb the most heat and transfer the heat into the home, and also back out of the attic in winter.
There are special types of asphalt roofs that do not absorb as much heat, as normal ones. These roofs are energy star rated and qualify for federal tax credits.
Attic ventilation is the most important factor in keeping the attic cool.
We want the air to enter the attic from the soffit area and exit as high as possible towards the peak of the roof.
We would like this air flow to be balanced, 50% entering the lower area, 50% exiting the top.
The importance of proper ventilation has become more recognized in the last several decades.
An under ventilated roof will “cook” the shingles. This will void manufactures’ warranties.
Heat blisters are caused by under ventilated attics. Many roofers try to call heat blisters “hail damage”
Many different types of attic vents are available; Static vents, ridge vents, gable vents, “Whirly Bird, wind turbines”
It is extremely important to not short circuit the attic ventilation.
Solar powered attic vents combine the best of both worlds, they allow condensation to escape in winter, and will move huge amounts of air in the summer.
A very common problem is vaulted ceiling houses built in the 70’s. Often times there is no attic, and the ceiling cavity is packed full of insulation, making it very difficult to ventilate.
Condensation can be a big problem in under ventilated attics. The condensation will slowly freeze, then melt all at once, staining ceilings, and act just like a roof leak. Tell-tale signs; elderly people who keep the house very hot in the winter, and run a humidifier at a high level. Frost on inside of windows is an indicator of high humidity levels.
The attic must breathe in the winter to exhaust condensation.
Attic insulation is the best money saving home improvement that can be done.
The payback is quicker than any other type of home improvement.
A typical home loses 40% of its conditioned air through the ceiling. Heat & Cool air.
Most homes built in the 70’s and before have about 3.5 inches of attic insulation.
Energy was cheaper than insulation
Today’s Standard for our area is R-49, or about 20 inches of insulation.
Puffed up fiberglass is better than cellulose because over time the cellulose will “slough down”, loose height and compress itself. This is bad because the small air pockets are what give insulation it insulating property’s.
It is very important to not block soffit vents.
Ice dams are created by a perfect storm of bad conditions. Poorly insulated attic allows too much heat to rise from house into attic, poor ventilation at eave allowing this heat to melt the snow on the roof deck. Asphalt shingles transfer heat, which melts the snow rapidly, then rapidly re-freezes at night and starts cycle of ice formation at eave.