Exterior Soundproofing That Works - Continued
Sliding patio doors. In the
case of a sliding glass door, conditions occasionally dictate
installing the sliding storm panel on the interior side of the
prime door to provide adequate sill support (Figure 3). Since
sliding-door handles project out from the face of the door and
may interfere with one another, the space between the doors may
have to be greater than 2 inches.
3. Sliding storm panels provide extra sound
insulation at sliding door locations. In every instance
of a secondary door or window, there should be a
minimum 2-inch gap between primary and storm
Gasketing. It is
acoustically important that both prime and storm doors are
well-gasketed with continuous weatherstripping to minimize air
leakage. The weatherstripping should create a flexible,
shape-conforming, airtight seal between door and frame. We use
polyprene or polypropylene bulb weatherstripping because they
maintain flexibility longer than other types of
weatherstripping without stiffening or cracking.
With the correct airtight seal, you can feel a vacuum-type
resistance when you open the primary door with the storm door
closed, and a compressive pressure when you close it again.
Weatherstripping at the threshold, preferably with a flip-down
sweep, is equally important (Figure 4).
4. An automatic door sweep ensures a good seal
against air and noise infiltration at the
In the process of replacing all of the windows and doors and
sealing other points of airflow, a home's exterior envelope
becomes considerably tighter than it was before. As a
consequence, indoor air quality may suffer and combustion
devices may become oxygen-starved. Older homes without vapor
barriers and modern insulation usually continue to breathe
sufficiently; with newer homes, however, we specify additional
ventilation to provide make-up air for the health of the
occupants and normal operation of the home's mechanical
Whatever type of windows or doors are used, proper
installation is critical to acoustical performance. The
principle of tightness is the controlling guideline to ensure
that the acoustical performance is not degraded by flanking
path leaks around the perimeter of the installation. We insert
fiberglass insulation in the shim space between the window
frame and rough opening at head and jambs. Sash-weight cavities
are always abandoned in the window replacement process; we
insulate these as well, being careful not to overfill or
compact the insulation. Again, since noise can leak through any
air gap, caulking and sealing are important. We set and seal
windows and doors in the rough opening with a non-skinning,
non-hardening polyurethane or silicone sealant.
Other openings in the
building envelope also need attention, such as through-the-wall
air-conditioning units, ceiling-mounted attic hatches, and
vents. We've developed some simple gasketed covers, made of
cabinet-grade plywood, that encapsulate and seal the AC unit
and the attic hatch when they're not in use (Figure
5. Custom-made insulated plywood covers seal
attic hatches (left) and through-wall AC units.
Cam-type latches and compressible gaskets ensure a
We review vent openings on a case-by-case basis to determine
if they constitute a significant noise path that must be
treated. We use some simple rules of thumb: First of all, ridge
vents, gable vents, and roof louvers must be baffled if their
aggregate clear opening area exceeds 1% of the attic floor
area. Secondly, bathroom and kitchen vents and range hoods must
be baffled or re-ducted if there is an existing line-of-sight
path between inside and outside.
Baffles usually need to be custom designed for each particular
situation, but the design principles are the same — the
baffle should allow free air movement along a circuitous path
across absorbent material (Figure 6).
6. Roof vents provide a potential path for noise
entry. A custom insulation-lined baffle disrupts and
muffles sound entering the structure.