Sound doesn't have to be complicated...



Sound reduction test

A three panel horizontal sliding secondary glazing unit (1960mm x 1190mm High) was sent to the Building Research Establishment in Watford for testing

How was the test carried out?


A cavity wall was built into the aperture between two rooms of the BRE transmission suite to the following specification

Block thickness             100mm

Block density    1800 kg/m2

Cavity spacing  75 – 80mm

Finished with plasterboard on dabs.


An aperture was left in the wall to house the window. A typical Georgian window from a Builders Merchant with three openers was fitted.



The secondary was installed behind the window on timber liners to provide a minimum pane spacing of 100mm. The condition of the primary window will have an effect on the overall system performance.




How does sound travel?

Sound travels through the air like ripples on a pond surface when a stone is dropped into it. The sound radiates outwards in all directions from the source, gradually reducing in intensity or until an object stops its progress.

Sound (dB Decibels)

Sound is described in different ways but primarily in terms of intensity and frequency. The sound intensity is described in dB. A low dB indicates a soft sound, a high dB value indicates a loud sound.

Frequency describes how high or low pitched the sound is (Hz).

Sound Reduction

A stereo’s volume set at 60dB decreased by…

-3dB is just perceptible

-5dB clearly noticeable

-10dB Half the original volume


Recommended Indoor Ambient Noise Levels



Bedrooms 30-35dB

Living rooms 30-40dB



Private 35-40dB

Open plan 45-50dB


Typical noise levels

50 metres overhead aircraft 140dB

Car alarm 120dB

Passing train 90dB

20 metres from busy carriageway 78dB

20 metres from busy main road 68dB


Keeping sound in - 70% of people admit to feeling harassed by noise

Loud music remains the main source of noise complaints in England, Scotland & Wales.  Secondary glazing is an excellent solution for Hotels, Pubs & Clubs or factory’s close to housing to keep noise in. 


New Glass Technology

Acoustic laminated glass (Silence) is the latest product to come onto the market. Two sheets of glass are bonded together with a 0.76mm thick layer of special acoustic polyvinyl butyral (PVB). Solaglas estimate a 20% improvement over standard glass. Taking this increase into account when installed into our secondary glazing a reduction of 44-45dBs should be easily achievable.

Silence Glass is a safety glass so can be used in safety critical areas and meets the requirements of BS6206.



Test Number

Primary Window Secondary Window





Sound reduction

over test window in %


4mm Glass

None Standard Pile 26  
2 4mm Glass 4mm Glass Standard Pile 39 65%
3 4mm Glass 6mm Glass Standard Pile 39 65%
4 4mm Glass Laminated Standard Pile 40 70%

Get the low-down on U values…



What do we mean by U value?

U value is a means of comparing the heat lost through various parts of a building. A part of a building with a U value of 4.0 W/m²K will lose twice as much heat as one with a U value of 2.0 W/m²K.

The lower the U value the less heat you lose through your windows




Single Glazed window

 U value 5.6 W/m²K


Single Glazed window with Low E glass fitted in the secondary

U Value 1.8-1.9 W/m²K


Living with your windows


Draughty windows affect your comfort

Draughts through your windows can create cold spots around the room, particularly around the legs and feet, as a result heating is normally turned up higher to compensate, even the dog will want to jump up on the settee next to you. The tight tolerances designed into our secondary glazing system keep cold air and dust out whilst retaining the warm air in the building.


Air permeability Test

BS 5368:Part 1

BS 6375:Part 1


This defines the ability of the window to resist air penetration when it is subjected to differential pressure and is a measure of the air which seeps through the test window at given test pressures.

The average amount of air which leaks through a metre of the opening weather seal (as seen from the inside of the window) is measured and the measurements are calibrated in cubic metres (m3), per hour, per metre of opening seal. A two panel slider 1215 W x 1193 H was fitted to a test rig at BSI in Hemel Hempstead.


Test Result


The sample met the stringent test result of Pressure Class 300Pa.




Extensive use is made of air-conditioning in today’s busy offices, shops, and at home. Installing secondary will help to reduce the energy used in cooling the building and also stops cool air escaping out through your windows





Live right up to your windows

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