Windows, acoustic level and recommendation help

[sw879]

Hi everyone

 

We are having six new windows installed in our maisonette.  As it is in a conservation area they all must be sliding sash windows.

 

4 windows are width x height: 883mm x 1435mm 

1 window is width x height: 1139mm x 1852mm

1 window is width x height: 2330mm x 1600mm

 

The widow supplier has told us that the acoustic level for these windows is 40db.  My concern is that this is not high enough for the area we live in because the front and rear of the property abut a road.  We would have preferred 50 - 60db windows.  The supplier has said that the maximum profile for the glazing is 25mm.  If they were to fit 51db windows they would need them to have a thickness of 42mm, and therefore need to use a different profile of the windows (tilt & turn windows).  They say that the sash windows are impossible to make with such a thick glazing.

 

Is this true, and if so is there anything else we could do to reduce the amount of noise?  

 

The windows come in pine/hardwood.  We can opt for meranti but this is 10% more expensive than the finger jointed pine. They also have accoya but this is 50% more expensive. Is it worth going for the more expensive frames instead of pine?  Will this help with the noise at all?

 

The quote we have for all 6 windows in pine is £8,500 net which includes the transport and fitting cost.  Being completely new to this, does it sound reasonable?   I have only had one other quote from thesoundproofwindows and they were around £5,000 more so to me it does seem like a good deal.

 

Thank you for all your help.

 

S

 

[Dreadnaught]

Have you considered adding secondary glazing separately and in addition? It can be very effective at reducing noise.

[sw879]

13 minutes ago, Dreadnaught said:

Have you considered adding secondary glazing separately and in addition? It can be very effective at reducing noise.

 

We haven't actually.  I will check with them to see if this is possible, thank you! 

 

I forgot to mention in my initial post but our other main concern is potential break ins. Because of new fire and safety rules we have to remove the bars in front of our existing windows.  Although I do prefer this as it makes the property look a lot nicer, I am concerned about our security.  Even without the secondary glazing, would these windows be good enough to withstand a break in? 

[nod]

I’ve installed 30 sash windows in our build 

We went for the best acoustic that we could find 

Which isn’t that good compared to a much cheaper standard rubber sealed window frame 

The design doesn’t lend itself to good airtightness 

If you can talk the planners out of sash it would be a better option 

We couldn’t 

 

[Moonshine]

51 minutes ago, sw879 said:

We would have preferred 50 - 60db windows. 

 

umm, that is an incredibly high spec of window (assuming they are Rw), and i would be interested what they are saying window build up meets the Rw 51 dB, and you would probably be looking at a thickness over a standard frame

 

here is some sash windows with very good acoustic performance (test data up Rw 42 dB) which can accommodate up to 35mm thick glass.

 

https://www.bereco.co.uk/timber-windows/sliding-sash-windows/

 

I would suggest that you fit an acoustic sash window as a first stage, and if noise is really still an issue, fit secondary glazing as mentioned by @Dreadnaught in the rooms where it is still an issue.

 

Acoustic-Data-Report.pdf

 

Also are all rooms an issue with noise, do all six face onto the road? 

 

What is the noise that disturbs you, general average road traffic or intermittent loud noise's from the road. 

 

Edit: btw what sash windows are in there at the moment? if they are old, single pane of glass, with poor seals around the edges that is going to be about Rw 25-29 depending on the seal quality. Also how are you now going to ventilate the space, as the new sash's will have good seals and won't provide air ingress which you may be relying on to background ventilation.

Edited January 28, 2020 by Moonshine

[sw879]

Hi Moonshine

 

Thank you for your very helpful reply.

 

I think I was mistaken when I said 40db.  It is in fact 33db that the supplier said he can offer us.

 

I will contact Bereco and see what they can offer but the idea of having a sash window followed by secondary glazing is a good idea.  

 

All 6 windows face the road but we only want 3 of them to be soundproof because they are bedroom windows.   The property is in a busy part of town, so there is a lot of road traffic at the front, along with building works, road works...etc.

 

The existing windows are very old, so old that one of them doesn't open anymore!  I hadn't thought about ventilation when it came to the windows but we are installing air conditioning in all the rooms so that should be fine I imagine.

 

Thanks again.

[Moonshine]

1 hour ago, sw879 said:

I think I was mistaken when I said 40db.  It is in fact 33db that the supplier said he can offer us.

 

I will contact Bereco and see what they can offer but the idea of having a sash window followed by secondary glazing is a good idea.  

 

All 6 windows face the road but we only want 3 of them to be soundproof because they are bedroom windows.   The property is in a busy part of town, so there is a lot of road traffic at the front, along with building works, road works...etc.

 

The existing windows are very old, so old that one of them doesn't open anymore!  I hadn't thought about ventilation when it came to the windows but we are installing air conditioning in all the rooms so that should be fine I imagine.

 

Thanks again.

 

yeah 33 dB isn't great, i think plan in now how and which products you may use for secondary glazing, but stage 1 is just the sash window by itself and see how that performs.

 

You need to consider background ventilation and how you achieve this, as you don't want to have your A/C on all the time for this, you may need to think about acoustic trickle vents on the sash windows (ask Bereco if their frames can accommodate these), though you have to bear in mind that the acoustic rating of these vents need to be matched to the window spec (i,e at or slightly higher than the window), see below for a high rating acoustic trickle vent

 

https://www.greenwood.co.uk/product/95/2500ea-5000ea

 

Also if you end up having trickle vents for background ventilation, and then fit secondary glazing you then have another barrier to get the fresh air through.

 

I don't know if you have an architect, but i would suggest you ask him about how background ventilation will be achieved (i am sure you don't want your A/C running 24/7 for it)

Edited January 28, 2020 by Moonshine

[sw879]

Thank you so much Moonshine. You’ve been a great help.

 

I put your questions to the window supplier and they have said the following:-

“The accoustic glazing that I have suggested is 33.1 accoustic laminated / 12 / 33.1 accoustic laminated 25 mm. It has protection 40 db. 

 

I will also add the tricle vents, just to the background right? We have only one kind of trickle vent hidden in frame. If you have any requested type of the trickle vents, please send me the drawing and dimension of them so I will confirm you if we fit them. 

 

Our trickle vent are not acoustic they are normal, but if it is from the rear of the house, it should be ok. Please, find attached the drawing of our trickle vent system.”

 

Are normal trickle vents fine or do they have to be acoustic? I’m wondering if maybe we can buy acoustic vents from another supplier or does it have to be from the same company?

 

Thank you so much again.

 

Best wishes

 

S

[Moonshine]

15 minutes ago, sw879 said:

“The accoustic glazing that I have suggested is 33.1 accoustic laminated / 12 / 33.1 accoustic laminated 25 mm. It has protection 40 db. 

 

I will also add the tricle vents, just to the background right? We have only one kind of trickle vent hidden in frame. If you have any requested type of the trickle vents, please send me the drawing and dimension of them so I will confirm you if we fit them. 

 

Our trickle vent are not acoustic they are normal, but if it is from the rear of the house, it should be ok. Please, find attached the drawing of our trickle vent system.”

 

Are normal trickle vents fine or do they have to be acoustic? I’m wondering if maybe we can buy acoustic vents from another supplier or does it have to be from the same company?

 

That sentence in bold makes no sense to me, what is the 33.1 figure? if its mm its a hell of a thick piece of glass and will be very heavy.

 

This is where i bow out, as i don't know your plans nor where you are getting back ground ventilation from (rear of the house?), but typically it is from the room that you are in, be that from trickle vents or a mvhr.

 

if you have trickle vents in these rooms then they should be acoustic, otherwise you are circumventing the expensive windows you have just specified/fitted.

 

The drawing they have provided is an over the frame vent, and not typical. 'usually' trickle vents in upvc/alu are 'in frame' as shown below (its the horizontal bar on the top of the frame)

 

 

If it was an in frame vent, you could buy and fit your own, all the frames need are slots / hole put in them  (see below) that the trickle vents go over.

 

[Temp]

+1 to @Dreadnaught.When the M3 motorway was built near my parents house my father fitted sealed unit double glazing. Soon after he had finished we were told that we would be offered free double glazing to reduce noise. The expert they sent told us that double glazing designed to minimise noise should have a much bigger air gap - something like 5-6 inches. We ended up with tripple glazing - the inner pane being secondary double glazing fitted to the inner edge of window sills with a big air gap. These could be opened to put photos etc on the window sills. 

 

I don't know for sure if that's the best design but if you can wait a few years my son hopes to study Acoustical Engineering!

 

 

 

Edited January 28, 2020 by Temp

[Temp]

https://www.gsecg.com/benefits/secondary-glazing-sound-insulation/

 

"To achieve optimum performance we often advise that secondary glazing is installed with a gap of 150mm – 200mm from the primary window."

[sw879]

Thank you so much for your replies!

 

@Moonshine I'm slightly concerned about acoustic trickle vents and whether they actually work.  I hadn't considered ventilation at all so I will have to look into this and see what else we can do. Perhaps maybe having something in the wall in the hallway.

 

@Temp Yes, i'm not too keen on the design either.  Good luck with your son's studies  I'm afraid I can't wait that long!

[Moonshine]

3 hours ago, Temp said:

 @Dreadnaught

I don't know for sure if that's the best design but if you can wait a few years my son hopes to study Acoustical Engineering!

 

It's a good topic / profession ?

[Temp]

Only taught at two universities - Southampton and Salford - and he has offers from both. Just needs to pass his A levels now!

[Simplysimon]

do you have the depth to have a heavier section window installed as sash and case come in two basic sizes? if you are intending on staying for a long time in the property, then fitting accoya would be worth it due to the reductio in maintenance and longevity of the material.

[sw879]

38 minutes ago, Simplysimon said:

do you have the depth to have a heavier section window installed as sash and case come in two basic sizes? if you are intending on staying for a long time in the property, then fitting accoya would be worth it due to the reductio in maintenance and longevity of the material.

I think we do have enough depth but I will leave it to the experts to tell me if there is space when they visit the property. I’m not really good with these sorts of things.

 

I’ve heard accoya is very good as you say but the window company has said this will cost 50% more! 

[Moonshine]

1 hour ago, Temp said:

Only taught at two universities - Southampton and Salford - and he has offers from both. Just needs to pass his A levels now!

 

Yep, though other uni's do MSc's in acoustics, I got my two degrees from one of those.

[AliG]

We have triple glazed windows with 39dB noise reduction. 33dB is pretty standard double glazing. 

 

As your maximum profile is 25mm, I suspect the supplier meant 6.8/12/6.8 glazing. or 6.4/12/6.4. It tends to be that glass with a whole number thickness is plain glass and with a x.x thickness is laminated. Laminated tends to help noise reduction, also mixing thicknesses, so it might be 6/12/6.8. I am not convinced that the reduction from that glass would be 40dB, but whatever it is, it will be as good as you get with double glazing.

 

What I find is that in fact most of the noise that we hear comes not through the glass but around the edges of the windows, through seals etc. We don't have trickle vents, but they are awful for sound transmission, so certainly have them sound reducing, or eliminate them if you can. Because sash windows are hard to seal, secondary glazing will help the most and make a bigger difference than better glass.

 

Anyway, sealing all the gaps as well as possible will probably be the biggest improvement you can get. Try walking slowly past a window when it is noisy outside, you will hear various points that are much noisier. On our house, applying a bead of mastic around the outside edge of all the window frames made a big difference as noise was getting around the frame. Also making sure all windows are adjusted to shut as tight as possible etc. Even where there is no draught I can sometimes hear noise coming through gaps.