As with ceiling and wall
treatments, the basis of good sound insulation is increasing
mass, structural isolation and effective sealing. The
can be consulted for details of suitable glazing systems.
replacing but upgrading existing glazing -
- Make good any gaps or
cracks in the existing glazing, including edge sealing.
- Secondary glazing can
be installed behind the existing glazing; effectiveness is a
trade off between the size of the gap and the thickness of
the secondary glass and of the original glass; probably the new glass
panes should be 8mm or thicker, and ideally of a different
thickness to the existing glass
- The new inner pane
should be set into a separate heavy well sealed frame;
- The air gap between
the two frames should ideally be at least 100 mm, but above
say 150 mm you are in the region of diminishing returns where
a large increase in air gap is required to make a significant
change in the insulation.
- The side and top
reveals should be fitted with acoustic tiles to reduce
reverberation inside the units; don't be tempted to put
acoustic tiles on the window sill because any condensation
on the windows will run down and be held within the bottom
tiles and rot! This may lead to bad smells.
glazing is being installed
- Be wary of
sash windows, if acoustic performance is important; the sash mechanism
makes it difficult to achieve a good seal, in addition
it is difficult to use heavy glass because of the weight on
- If the noise source
lies off to one side of the window, arrange for side hung
casements, with the hinges closest to the noise source; that
way, the open side of the window will screen the room from
the noise; if the opening light was on the other side it
would tend to catch and deflect noise into the room; the
difference between "screening" and
"catching" can be 10 dBA. The window should be set
well into the windows opening, so that when open, the gap
between the open light and the frame would be set into the
- The glazing can be a
repetition of the secondary glazing systems above, or a
compromise entailing lower cost, space and performance,
- 10mm glass, a 12mm air
gap in the same frame and a 6mm inner glass
- or 6.4mm laminated
glass, 12mm air gap and 10mm glass; consult the
for details of laminated glass suppliers.
for new or upgraded glazing
Clearly, the performance
of windows is better when they are kept shut!. Silenced mechanical
ventilation may be installed such that there is no requirement
to open the windows for ventilation; thereby reducing sound
directory can be
consulted for suppliers. Alternatively there are silenced
passive ventilations which can be fitted over the frame.
Another alternative to
mechanical ventilation would be arranging for opposite sections
of the inner and outer glazing to be openable; thereby
permitting ventilation through the staggered opening whilst
preventing a direct sound path. As a comparison,
secondary glazing can reduce traffic noise by around 35 dBA,
- open glazing (single or secondary) can reduce traffic noise by
around 15 dBA,
- secondary glazing with "staggered"
openings can reduce traffic noise by around 25 dBA.
A 10 dBA
difference is generally regarded as a halving or doubling of
noise level; therefore closed secondary glazing is twice as good
as "staggered opening", which itself is twice as good
as open glazing of any form.
Back to Walls
to Fences >>>