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AIR
SEALING
Seal
air leaks and save energy!
WHAT
IS AIR SEALING?
Ventilation is fresh air that enters a house in a controlled manner
to exhaust excess moisture and reduce odors and stuffiness. Air
leakage, or infiltration, is outside air that enters a house uncontrollably
through cracks and openings. It is unwise to rely on air leakage
for ventilation.
During cold or windy weather, too much air may enter the house
and, during warm or calm weather, too little. Also, a leaky house
that allows moldy, dusty crawlspace or attic air to enter is not
healthy.
The recommended strategy in both new and old homes is to reduce
air leakage as much as possible and to provide controlled ventilation
as needed. For simple house designs, effective spot ventilation,
such as kitchen and bath fans that exhaust to the outside, may
be adequate. For more complex houses or ones in colder climates,
whole house ventilation systems may be appropriate. Such systems
may incorporate heat recovery, moisture control, or air filtering.
WHAT ARE THE BENEFIT SO FAIR SEALING?
Air infiltration can account for 30 percent or more of a home’s
heating and cooling costs and contribute to problems with moisture,
noise, dust, and the entry of pollutants, insects, and rodents.
Reducing infiltration can significantly cut annual heating and
cooling costs, improve building durability, and create a healthier
indoor environment. The size of heating and cooling equipment
can also be decreased, which saves additional dollars. Reducing
air leakage in new homes, as required by the 1995 Model Energy
Code (see page 4), typically costs less than $200 for the average
home and does not require specialized labor.
WHAT IS AN AIRBARRIER?
The ceilings, walls, and floor/foundation that separate the inside
conditioned space from the outside or unconditioned space form
the air barrier and the insulation barrier for a house. These
two barriers differ by the materials used.
For most homes, the sheet goods that form the ceilings, walls,
and floor (such as drywall, sheathing, and decking) are effective
at stopping air leakage. It is critical to seal all holes and
seams between these sheet goods with durable caulks, gaskets,
and foam sealants to create a continuous air barrier. The insulation
barrier is usually made up of standard insulating materials, such
as batt or loose fill products, that do not seal against air leakage.
WHAT ARE THE PRIORITIES FOR AIRSEALING?
Although windows, doors, and outside walls contribute to air leakage,
the biggest holes are usually hidden from view and connect the
house to the attic, crawlspace, or basement. The key is to identify
these areas during the design process, assign responsibility for
sealing holes, and check to ensure that the air sealing was done
effectively. Usually, seal all the big holes first, then the large
cracks and penetrations, and finally the smaller cracks and seams.
WHERE ARE THESE LEAKAGE SITES?
Dropped ceilings and kitchen soffits, ductwork and plumbing chases,
attic accesses and pull-down stairs, recessed light fixtures,
holes in mechanical room closets, and wiring penetrations through
the top plates of walls represent major connections between the
attic and conditioned space. Many times unseen holes or pathways,
called bypasses, occur at key junctures in the framing (such as
at attic-to-kneewall transitions) and permit large quantities
of air to leak in and out of the home. Major leakage sites in
the floor can be found around the tub drain and the numerous plumbing,
HVAC, and wiring penetrations through the floor decking and bottom
plates of walls. In walls, the band joist (for two-story homes),
window and door rough openings, and penetrations through the drywall
and exterior sheathing are primary leakage sites.
Next:
AIR SEALING MATERIALS LIST
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