Black Knight Secondary Glazing
Black Knight Secondary Glazing

Secondary Double Glazing for Noise Reduction

Generally noise will enter your building through the windows and doors. This is evidenced by the difference in noise that you experience when the windows are open and when they are shut. 

Our Black Knight range of secondary double glazing windows gives good noise reduction and our upgraded Black Knight Heritage range using specialist acoustic glass will give you the highest level of noise insulation possible.


Effective noise insulation depends on a number of elements and different solutions are required depending on the circumstances. 

For each particular application it is important to pay attention to the material that the primary window is made from together with the type and thickness of the existing glazing, the cavity distance that can be achieved between the existing primary windows and the new secondary windows and the type of glass that needs to be used in the secondary glazing.   


Of all of these the most important is the gap between the two windows. The level of noise reduces the further it has to travel and ideally a gap of between 150mm and 200mm, if achievable, is preferable to get the optimum reduction - this is why just changing the primary window to a double glazed system, while making a significant improvement to heat loss,  will not make any appreciable difference  to the noise levels; the gap is nowhere near big enough.


                                       Get a no-obligation quotation



The visual impact of secondary glazing

It is wrongly believed by many people that secondary windows are ugly and obtrusive.

This could not be further from the truth - our secondary windows are designed to be

discreet and effective and should not be mistaken for the kit-form systems that do little

to keep the character of your property. 

They are designed to be easy to fit, very effective and when the optimum cavity can be achieved they will make a considerable difference to the noise levels you experience.


In some cases you will not be able to, or want to, achieve the optimum gap between

the primary and secondary windows and we are happy to supply the information you

need to make your decision as to which way to proceed to gain maximum advantage in

your particular situation. 

















Some Information about Noise


  • Noise is measured in decibels (dB).
  • Human hearing is not sensitive to all frequencies of noise to the same degree and for that reason measurements are averaged using an electronic measurement to mimic the response of human hearing (dBA).
  • Across the range of frequencies & volumes of noise the perception is heard in diffferent ways and this is averaged out and expressed as the weighted reduction (dB Rw).
  • Because traffic noise is a major source of noise irritation a further measurement reflecting urban road traffic noise is also used - this is known as reduction of road traffic noise and is expressed as dB Rt.
  • When noise is measured it is not a "straight line" graph every increase (or decrease) in noise of 3dB is really a halving or doubling of the perceived noise level:

   As an example: 


   4 young babies crying simultaneously will typically give a noise measurement of about 116dB
   2 young babies crying simultaneously will typically give a noise measurement of about 113dB 
   1 young baby crying will typically give a noise measurement of about 110dB


   So is this example the noise has halved and then halved again giving a reduction in measurement of 6dB in



Dependant on the existing glazing and the type of glass used in the secondary windows and the cavity achievable we would expect performance figures as follows: 


Minimum Reduction


35 dB Rw        General Weighted Reduction

29 dB Rt          Reduction of Road Traffic Noise


Maximum Reduction


48 dB Rw        General Weighted Reduction
42 dB Rt          Reduction of Road Traffic Noise



Application suitability


  • road traffic noise insulation.
  • train & railway station noise insulation.
  • aircraft & airport noise insulation.
  • street noise insulation.


Secondary Glazing - benefits


  • improved energy rating
  • reduced carbon footprint
  • smaller heating bills
  • retain the character of traditional windows
  • excellent thermal insulation
  • elimate draughts
  • increased security
  • maintenance free - an occasional wipe with a damp cloth & a drop of oil to the moving parts

Get a no-obligation quotation