Best windows for sound insulation

roadweary

Hi, we live on a main road.  End terrace but there is a stairway down the (non-glazed) side of our house so some road noise potentially could work its way around the back of the house.

Our double glazed windows are 20+ years old, frames decaying and need replacing.  I mentioned to two companies that have quoted (3 story town house) that I wanted triple glazing due to the noise, and they quoted accordingly.  

I've recently been googling about dB attenuation of different windows and it seems that triple glazing is only marginally better than double glazing for sound proof / noise-reduction windows.  Something about different pane thicknesses to absorb different frequencies.  Perhaps a double glazed unit with one pane being laminated....another article talked about increasing the air gap.

Then a relative spoke to me about needing trickle vents and that some kind of acoustic device would be needed to stop the noise just coming through there....in my mind's eye I imagine cracking the window open one mm in a car on the motorway...

Anyhow, what my experience has highlighted is that I'm not overly impressed by the information I've received so far from the companies that quoted. Neither of them have said I should consider anything other than triple glazing.

Does anyone have experience of good companies that might be able to advise on this?

Any idea on the difference between the cost of double glazed and soundproofed / noise reduction windows?

So far we've been quoted triple glazed front and back, but in reality, it's mainly the front of the house that requires the extra sound insulation.

Thanks

grumpy_codger

For better sound insulation all three glass panels of a triple glazed unit must have different thickness. Air gaps between the panels have to be different two.

roadweary

grumpy_codger said:

For better sound insulation all three glass panels of a triple glazed unit must have different thickness. Air gaps between the panels have to be different two.

Any advice who to use for supply and fitting?

grumpy_codger

I don't know, sorry. It's just general knowledge based on my friends experience in another country (where such units are easily available).

ETA: I found some correspondence - in fact two out of three panels had the same thickness - 6-10Ar-4-16Ar-4 (mm).

Ar = argon

Woodstok2000

Secondary glazing will be more effective,and much cheaper. Something like this: https://thesoundproofwindows.co.uk/noise-reduction-products/high-performance-secondary-windows/

roadweary

Woodstok2000 said:

Secondary glazing will be more effective,and much cheaper. Something like this: https://thesoundproofwindows.co.uk/noise-reduction-products/high-performance-secondary-windows/

My wife isn't keen on that....plus we still need new double glazing, so quite the price to do both at the same time..

twopenny

How long will it take to replace it?
There is a kit using a pane with self adhesive magnetic strips that you can apply to the inside frame.

I used them years ago over a louvre pantry window to stop bugs and the like and it worked well. Very easy to do.

WIAWSNB

I don't have the answer for you, RW. 
But some possibly relevant points;
1) I'm guessing that the seemingly marginal improvement of triple over double will be largely down to the double having already made the bulk of improvement, so further layers will have less additional effect. It's like wall insulation - the first 3" will be utterly transformative, but subsequent layers make little additional improvement.
2) That is not to say that triple isn't worth it - if noise is a significant issue, which it clearly is, then it will almost certainly be.
3) On that note, I haven't yet looked at how the noise reduction values are specified, but if it's in dBs, it won't be a linear scale, so even a one dB reduction should be noticeable (I think). 
4) I suspect that, in general, aluminium-framed windows will be more reliably-effective than PVC due to better, less flexing, 'opener' fit and seal. But I could be wrong. It could also be that 'soft' PVC frames absorb more vibes than hard Ali. All I'm saying is, do compare frame naterials!
5) Accuracy and quality of installation is paramount - frames fitted completely 'square', no twisting, and all frame sides fully foamed-sealed the whole frame depth. The bottom cill will likely be sealanted, and the window board will add a further seal. But emphasise your requirement, and ask what each potential installer can/will do to mitigate against sound travel. 
6) Check and compare frame thicknesses and number of rubber seals.
7) Yes, trickle vents are a pita, and will almost certainly allow some high frequency sound travel through even if closed. This is because they are usually just plastic shutters, probably only around 3mm thick, sit on one side, most likely don't have seals, which all compares poorly against a 75mm-thick double-skinned PVC or other frame. But, I understand they are required. I guess there's always the possibility of lightly foam-filling them if there is any sense they are allow sound through (but check). 
As you say, any gap at all will be like cracking open a car, or house, window a fraction - high frequency sounds make themselves noticeable first; birdsong, the hiss of tyres on wet roads, etc. 

twopenny

I did some searching on this and found that triple glazing had little effect even with a soundproofing film but a little might help.
There is also acoustic silicone which is supposed to make a difference.

There are some good threads and YouTube videos about someone who has experimented with all sorts. Worth looking them up but remember to delete cookies after before the next search or you'll just get more of the same info.
If I find the link I'll post it but don't have time now.

ic

I live below the flight path to Manchester Airport.  I moved into my current house during a lock down.  As the flights resumed I found the night time flights would disturb me.

I had new windows but they were badly installed.  I first made sure the sashes pulled tight closed replacing some pull blocks with better ones, as well as exposing the gaps around the frame, raking out the minimal dribbles of expanding foam the installer had used (I bet he can use a single can for multiple houses the way he applied it), and then fully filled the gaps with low expansion foam.

I then replaced the glass units with double glazed acoustic units - the outside pane is now 6.8mm laminated glass made up of three layers.  The inner pane is just standard 4mm glass, though I took the opportunity to specify low-e soft coat on it for improved thermal efficiency.  If buying new, there are frames that can offer improved acoustic deadening too - I wasn't interested in replacing the entire window though.

The upgrade to acoustic units was quick and easy, with replacement of eight panes in a bay window plus a side window taking only an hour.  The sound isn't gone, but the volume level has decreased such that I'm no longer woken by the big jets like I was.  The cost from a local supplier delivered, for me to install, was £661 for the nine units.  I disposed of the old units at the local tip.

I also installed two layers of 100mm of acoustic insulation in the loft above the bay window and bedroom over the existing insulation where it wasn't already boarded - I can't attest that made much difference - but again it was a fairly trivial if dusty job.  Wickes sell rolls of acoustic insulation for around £60.

I was impressed enough with the acoustic units that I've replaced a further 14 units around the house in other living/working spaces - and intend to do the remaining eight when budgets and enthusiasm allow.

roadweary

@ic - I definitely need new frames, but very interested in those glass units you've described.  Do you have a link to the manufacturer / supplier for those units please?