Secondary Glazing is the most effective solution for reducing intrusive noise through glazing. Using Reveal Fix frame formats, attaching the unit to the side wall of the reveal rather than to the face of the primary window, enables the secondary unit to be positioned away from the primary window to improve sound insulation. The wider the gap the better the sound insulation (see table). With the right spec,reductions of 50 decibels (dBs) can be achieved, reducing sound by 3dBs - equivalent of halving the noise entering a room.

A reveal fix option is applicable when there isn’t sufficient frame on the primary window to attach the unit. If fitting secondary glazing
to existing double glazing to enhance acoustic insulation, it is important to ensure a different thickness of glass is installed. This ensures
the structure of the 3 panes is not uniform and will improve the sound wave dissipation. If you are unsure of the existing structure, normally
a 6.4mm thickness of glass would be advisable.

The Difference the Cavity Makes
The gap between an existing primary window and the secondary unit makes a big difference to the level of noise insulation. Unlike sealed units,
where the two pieces of glass are rigidly coupled together, the primary and secondary windows act as independent barriers to the transmission
of noise. The greater the cavity between them, the better the dampening effect of the combined window. A minimum of 100mm is recommended.

Mind the Gap
Gaps around window frames representing just 1% of the frame area allow the passage of sound that can reduce noise insulation levels by as
much as10 dB. Clear View secondary windows are tailor-made with very effective seals to shield the whole window opening and minimise
leakage.

Choice of glass
A wide range of glass types ensures optimum performance. The inner and outer glass should have different mass to avoid ‘sympathetic
resonance’ which increases noise transmission at higher frequencies. Thicker glass improves performance, particularly at lower frequencies.
Acoustic laminate glass has a special interlayer that helps improve high frequency performance and is particularly suited to dealing with traffic,
rail and aircraft noise.

 

Sound reduction
The figures on the table opposite are
subject to the condition of the existing
primary window.
NB: A reduction of 3dB will reduce noise
levels into the room by half.
We recommend an air-gap between the
existing glass and the new secondary
glass of 100mm to an optimum of 150mm.
If the air-gap is increased from 100mm
to 150mm, then the sound reduction
performance is increased by approx 25%.
The table, right, shows anticipated sound
reduction guide in dBs, based on the
existing primary window being a 4mm
single glazed unit.

 

Primary

Glass

Air-Gap

(mm)

Secondary

Glass

dB

Reduction
4mm 100 4mm float 40-42
4mm 150 4mm float 42-43
4mm 100 6mm float 42-43
4mm 150 6mm float 45
4mm 100 6.4mm laminated 44-45
4mm 150 6.4mm laminated 45-47
4mm 100 6.4mm Stadip Silence 46-47
4mm 150 6.4mm Stadip Silence 47-48
Click to find out more about how
Secondary Glazing from Clear View
can help you with:


Want Specialist Advice? Call 0114 279 2875 or email here