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Roof Ventilation and Insulation
Are Key in Memphis
One of the most critical factors in roof system durability
is proper ventilation. Without it, heat and moisture build up in an attic area
and combine to cause rafters and sheathing to rot, shingles to buckle, and
insulation to lose its effectiveness.
Therefore, it is important never to block off sources of roof ventilation, such
as louvers, ridge vents or soffit vents, even in winter. Proper attic
ventilation will help prevent structural damage caused by moisture, increase
roofing material life, reduce energy consumption and enhance the comfort level
of the rooms below the attic.
In addition to the free flow of air, insulation plays a key role in proper attic
ventilation. An ideal attic has:
- A gap-free layer of insulation on the attic floor to protect the house
below from heat gain or loss.
- A vapor retarder under the insulation and next to the ceiling to stop
moisture from rising into the attic.
- Enough open, vented spaces to allow air to pass in and out freely.
- A minimum of 1 inch between the insulation and roof sheathing.
The requirements for proper attic ventilation may vary greatly, depending on the
part of the United States in which a home or building is located, as well as the
structure’s conditions, such as exposure to the sun, shade and atmospheric
humidity. Nevertheless, the general ventilation formula is based on the length
and width of the attic. NRCA recommends a minimum of 1 square foot of free vent
area for each 150 square feet of attic floor -- with vents placed
proportionately at the eaves (e.g., soffits) and at or near the ridge.
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