Sound is transmitted through a window by direct vibration of the glass. The larger air space created by secondary glazing decouples the movement of the inner and outer glass, which means they act as separate barriers, thereby reducing resonance and performing better than standard sealed unit double glazing. Airborne sound is also a major problem with ill-fitting windows – a 1% gap in the total window area can reduce sound insulation by as much as 10dB. A purpose-made secondary window seals the whole of the external window with frames bedded on an acrylic sealant and opening panels fitted with high performance seals.
Key Benefits
Noise is unwanted sound and a form of pollution that has negative impacts on health and wellbeing. Measures to control high levels will
Reduce sleep disturbance
lower stress levels
Improve concentration and productivity
Help in meeting noise planning constraints
Regulations and standards
BS8233:2014. Guidance on controlling noise affecting buildings. Applies to designs for new buildings and those being refurbished for a change of use.
Building Bulletin 93: 2015. Acoustic design of schools- performance standards
Sound: Sound is measured as a pressure and expressed in dB (decibels). 0dB marks the threshold of hearing whilst 120dB is the point at which pain is experienced. Our ear responds to loudness which is dependent on both the Sound Pressure Level and the frequency of the sound. The ear is more responsive to higher frequencies, which therefore appear louder. The scale is logarithmic and an increase of 10dB approximates to a doubling of loudness whereas a change of 3dB is just about noticeable.
Acceptable sound levels: The World Health Organisation (WHO) sets out guidelines for acceptable sound levels in a range of environments in ‘Guidelines for Community Noise’ some of which are set out in the table below along with secondary glazing performance comparisons.
Effect of cavity: The cavity is the space between the existing primary window and the secondary and performance improves as it increases.
Effect of glass: Ideally the secondary glazing should have a different thickness of glass than the primary window to avoid sympathetic resonance which will increase noise transmission. Thicker glass with greater mass provides higher levels of insulation and acoustic laminate glass will improve performance at higher frequencies typically from aircraft noise.
Acoustic performance of Selectaglaze secondary glazing
The product range has been tested against single glazed primary windows in accordance with Standard BS EN ISO 140-3:1995 ‘Laboratory measurement of airborne sound insulation of building elements’. Testing was carried out by Taylor Woodrow Technology on openings 1250mm(w) x 1500mm(h) with results reviewed and interpolated by acousticians Hann Tucker Associates.
All figures are based on a primary window with 6mm glass and all figures are shown in mm. T = toughened glass, A = acoustic glassRw dB values for a 50mm cavity between the secondary and primary glazing
Glazing
4T
6T
6.4
6.4A
6.8
6.8A
7.5
8T
8.8
8.8A
9.5
10
10.8A
10.8
11.5T
12T
S10 HS
39
39
39
40
40
40
-
-
-
-
-
-
-
-
-
-
S80 HS
-
40
40
41
41
41
41
41
41
41
41
41
43
43
43
43
S85 HS
-
-
-
-
-
-
-
-
-
-
41
-
-
-
42
-
S20 VS
39
39
39
40
40
40
-
-
-
-
-
-
-
-
-
-
S60 TVS
40
40
40
41
41
41
-
-
-
-
-
-
-
-
-
-
S90 VS
-
40
40
41
41
41
40
42
42
42
42
42
42
42
43
43
S95 VS
-
-
-
-
-
-
40
-
-
-
41
-
-
-
42
-
S41 SHC
-
41
41
42
42
42
42
43
43
43
43
43
44
44
44
44
S41 DHC
-
39
39
40
40
40
40
41
41
41
41
41
42
42
42
42
S45 SHC
41
41
41
42
42
42
-
-
-
-
-
-
-
-
-
-
S45 DHC
39
39
39
40
40
40
-
-
-
-
-
-
-
-
-
-
S50 SHC
-
40
-
-
-
-
41
-
-
42
42
-
43
43
43
-
S41 LO
-
41
41
42
42
42
42
43
43
43
43
43
44
44
44
44
S45 LO
41
41
41
42
42
42
-
-
-
-
-
-
-
-
-
-
S40 FL
41
41
41
42
42
42
42
43
43
43
43
43
44
44
44
44
S46 FL
-
41
-
-
-
-
-
-
-
-
43
-
-
-
44
-
S55 DFL
-
-
-
-
-
-
40
-
-
-
41
-
-
-
42
-
Rw dB values for a 100mm cavity between the secondary and primary glazing
Glazing
4T
6T
6.4
6.4A
6.8
6.8A
7.5
8T
8.8
8.8A
9.5
10
10.8A
10.8
11.5T
12T
S10 HS
43
43
43
44
44
44
-
-
-
-
-
-
-
-
-
-
S80 HS
-
44
44
45
45
45
45
46
46
46
46
46
47
47
47
46
S85 HS
-
-
-
-
-
-
-
-
-
-
45
-
-
-
46
-
S20 VS
43
43
43
44
44
44
-
-
-
-
-
-
-
-
-
-
S60 TVS
44
44
44
45
45
45
-
-
-
-
-
-
-
-
-
-
S90 VS
-
44
44
45
45
45
44
46
46
46
46
46
46
42
47
46
S95 VS
-
-
-
-
-
-
44
-
-
-
45
-
-
-
46
-
S41 SHC
-
45
45
46
46
46
46
47
47
47
47
47
48
48
48
48
S41 DHC
-
43
43
44
44
44
44
45
45
45
45
45
46
46
46
46
S45 SHC
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S45 DHC
43
43
43
44
44
44
-
-
-
-
-
-
-
-
-
-
S50 SHC
-
44
-
-
-
-
45
-
-
46
46
-
47
47
47
-
S41 LO
-
45
45
46
46
46
46
47
47
47
47
47
48
48
48
48
S45 LO
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S40 FL
45
45
45
46
46
46
46
47
47
47
47
47
44
48
48
48
S46 FL
-
45
-
-
-
-
-
-
-
-
47
-
-
-
48
-
S55 DFL
-
-
-
-
-
-
40
-
-
-
41
-
-
-
42
-
Rw dB values for a 150mm cavity between the secondary and primary glazing
Glazing
4T
6T
6.4
6.4A
6.8
6.8A
7.5
8T
8.8
8.8A
9.5
10
10.8A
10.8
11.5T
12T
S10 HS
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S80 HS
-
46
46
47
47
47
47
48
48
48
48
48
49
49
49
49
S85 HS
-
-
-
-
-
-
-
-
-
-
47
-
-
-
48
-
S20 VS
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S60 TVS
46
46
46
47
47
47
-
-
-
-
-
-
-
-
-
-
S90 VS
-
46
46
47
47
47
46
48
48
48
48
48
48
48
49
48
S95 VS
-
-
-
-
-
-
46
-
-
-
47
-
-
-
48
-
S41 SHC
-
41
47
47
48
48
48
48
49
49
49
49
50
50
50
50
S41 DHC
-
45
45
46
46
46
46
47
47
47
47
47
48
48
48
48
S45 SHC
47
47
47
48
48
48
-
-
-
-
-
-
-
-
-
-
S45 DHC
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S50 SHC
-
46
-
-
-
-
47
-
-
48
48
-
49
49
49
-
S41 LO
-
47
47
48
48
48
48
49
49
49
49
49
50
50
50
50
S45 LO
47
47
47
48
48
48
-
-
-
-
-
-
-
-
-
-
S40 FL
47
47
47
48
48
48
48
49
494
49
49
49
50
50
50
50
S46 FL
-
47
-
-
-
-
-
-
-
-
49
-
-
-
50
-
S55 DFL
-
-
-
-
-
-
46
-
-
-
47
-
-
-
48
-
Rw dB values for a 200mm cavity between the secondary and primary glazing
Glazing
4T
6T
6.4
6.4A
6.8
6.8A
7.5
8T
8.8
8.8A
9.5
10
10.8A
10.8
11.5T
12T
S10 HS
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S80 HS
-
46
46
47
47
47
47
48
48
48
48
48
49
49
49
49
S85 HS
-
-
-
-
-
-
-
-
-
-
47
-
-
-
48
-
S20 VS
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S60 TVS
46
46
46
47
47
47
-
-
-
-
-
-
-
-
-
-
S90 VS
-
46
46
47
47
47
46
48
48
48
48
48
48
48
49
49
S95 VS
-
-
-
-
-
-
46
-
-
-
47
-
-
-
48
-
S41 SHC
47
41
47
47
48
48
48
49
49
49
49
49
50
50
50
50
S41 DHC
45
45
45
46
46
46
46
47
47
47
47
47
48
48
48
48
S45 SHC
47
47
47
48
48
48
-
-
-
-
-
-
-
-
-
-
S45 DHC
45
45
45
46
46
46
-
-
-
-
-
-
-
-
-
-
S41 LO
47
47
47
48
48
48
48
49
49
49
49
49
50
50
50
50
S45 LO
47
47
47
48
48
48
-
-
-
-
-
-
-
-
-
-
S50 LO
-
46
-
-
-
-
47
-
-
48
48
-
49
49
49
-
S40 FL
47
47
47
48
48
48
48
49
49
49
49
49
50
50
50
50
S46 FL
-
47
-
-
-
-
-
-
-
-
49
-
-
-
50
-
S55 DFL
-
-
-
-
-
-
46
-
-
-
47
-
-
-
48
-
Never miss one bit!
Subscribe to our monthly Newsletter to receive updates on our news and CPD initiatives.
