Ventilation Tips :
Ample Attic Ventilation:
Frost Damage on Attic Roof Sheathing
The best vented attic will have a continuous ridge
vent along the peak. Along the lowest edge of the roof overhang,
it will have a continuous soffit vent. Having either one vent or
the other alone won't do. Air must come in at the bottom of the
roof in order to circulate out at the top. Almost 85% of every
attic is improperly vented. *Soffit
vents are designed to take in air, roof vents are designed to exit
Attic insulation placed correctly:
The insulation between your rafters should stop at the outer edge
of the house's outside wall. That way it won't block fresh air
from the soffit vents at the low edge of the roof. With blown-in
insulation like cellulose, "channel vents", or "baffles", made
of plastic foam or cardboard need to be inserted between rafters
to keep the loose insulation from falling onto soffit vents.
Be sure the insulation hasn't flattened the vents or baffles.
Stand in the attic with all lights off. You should be able to
see daylight from the soffit vents at the roofs edge. Giving
immediate attention to these areas will ensure that your attic
is being properly vented, and you can expect to get the full
life expectancy out of your building materials.
Another common, but unsatisfactory
practice, allowing heat to enter the attic, involves installing
bathroom exhaust vent duct into the soffit vents, rather than
correctly installing the duct to an outlet vent. Bathroom exhaust
vents should be vented out through the roof with a travel span
of no more than 6 feet. Soffit vents are inlet vents, not outlet
vents! Everything that exits the house at a soffit vent immediately
re-enters the house in the attic space, because that is what
soffit vents do, they bring in outside air flow. Not only will
this add heat, but it will also add humidity and moisture to
the attic, defeating the very reason for installing the bathroom
fan in the first place. This is a REAL PROBLEM! Even
a home with functional attic ventilation can now develop mold
on the roof sheathing cavities above these unsatisfactory ducts.
Now you have no air flow, added heat and humidity in a dark,
moist environment - THE PERFECT CONDITIONS THAT MOLD
NEEDS TO GROW.