Air
Sealing
Air sealing is important,
not only because drafts are uncomfortable, but also
because air leaks carry both moisture and energy,
usually in the direction you don't want. For example,
air leaks can carry hot humid outdoor air into your
house in the summer, or can carry warm moist air
from a bathroom into the attic in the winter.
Most homeowners are
aware that air leaks into and out of their houses
through small openings around doors
and window
frames and through fireplaces and chimneys. Air
also enters the living space from other unheated
parts of the house, such as attics, basements, or
crawlspaces. The air travels through:
-
any openings or cracks where
two walls
meet, where the wall meets the ceiling, or near
interior door frames;
-
gaps around electrical outlets,
switch boxes, and recessed fixtures;
-
gaps behind recessed cabinets,
and furred or false ceilings
such as kitchen or bathroom soffits;
-
gaps around attic access
hatches and pull-down stairs;
-
behind bath tubs and shower
stall units;
-
through floor cavities of
finished attics adjacent to unconditioned attic
spaces;
-
utility chaseways for ducts,
etc., and
-
plumbing and electrical wiring
penetrations.
These leaks between
the living space and other parts of the house are
often much greater than the obvious leaks around
windows and doors. Since many of these leakage paths
are driven by the tendency for warm air to rise
and cool air to fall, the attic is often the best
place to stop them. It's important to stop these
leaks before installing attic insulation because
the insulation may hide them and make them less
accessible. Usually, the attic insulation itself
will not stop these leaks and you won't save as
much as you expect because of the air flowing through
or around the insulation.
When natural ventilation
has been sharply reduced, as in a more energy-efficient
house, it may be necessary to provide fresh air
ventilation to avoid build-up of stale air and indoor
air pollutants. Special air-to-air heat exchangers,
or heat-recovery ventilators, are available for
this purpose. It is also possible to incorporate
a supply of fresh outside air into your heating
and cooling system. This arrangement can be used
to create a slightly higher pressure inside your
home, which will prevent uncontrolled outside air
infiltration into your home.
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