Sash Windows & Noise

[DuncanC]

I'm hoping that, with all the wealth of experience on this forum, someone might be able to help me.

I live in a Victorian house (built c. 1890) approximately 25m from a busy 30mph road and would like to lessen the traffic noise coming into the house (predominantly through the windows). The house has 4 bay windows at the front, each with 3 sets of sashes (1 over 1). The middle window in each bay is operable (the bottom sash moves freely) however all the other sashes are painted shut. The sashes contain single pane 3mm glass (very few panes are still the original glass) and the windows seem to be in a reasonable condition (apart from a few rotten window sills).

I have read every article I can find on the subject of noise transmission through windows and I get the impression that:

i) The three most influential factors that contribute towards a window's acoustic performance are: Ensuring a good seal between window and frame; acoustic performance of the glass; separation distance of glass panes if double glazing/secondary glazing is used (preferably >50 mm).

ii) Somewhat counter-intuitively, single-glazed laminate is as effective if not better at noise reduction than double glazing (see Pilkington Optiphon Ctr data in http://assetmanager-ws.pilkington.com/fileserver.aspx?cmd=get_file&ref=8222&cd=cd)

Although I recognise that the best acoustic option is to secondary glaze (with a decent sized gap between the secondary glazing and the window), that comes at a cost to aesthetics, or at least I haven’t been able to find any unobtrusive construction that doesn’t detract from the windows. That leaves me considering whether I can get sufficient improvements from the windows by either:

i) Refurbishing, increasing the rebate of the existing sashes to accommodate 10mm acoustic laminate glass, and draft proofing the sash that is operable in each window. However, I’m concerned that there will still be a lot of noise coming through the gaps even with well-designed draft proofing (I wouldn’t want to spend a small fortune on glass that on paper reduces noise by 10dB only to find it is not the dominant source of noise).

ii) Replacing all the sashes with new ones that accommodate DGUs made up of something like 6 mm / (6 - 16 mm) / 10 mm laminated. This is expensive and, although has been recommended to me by companies such as Ventrolla, I question whether this is the right option due to the loss of the original sashes. I have been quoted £20k+ for this option. It also seems to offer no additional acoustic benefits to the refurbish option (although there are thermal benefits).

Does anyone have real world experience of trying to improve the acoustic performance of sash windows that could offer some advice? It’s difficult to know who to engage to help.

I’d also be interested in finding a reputable local joiner in the Surrey area (nr London) who could assist me as I’m not an able DIYer

 

[mims&pip]

Hi and welcome Duncan

I'm sure there will be plenty of extremely useful advice forthcoming from those with experience in secondary glazing, but I just wanted to say that I wish we had gone down that route at our last house. Instead - because my DH (Pip) was adamant he would hate the appearance of secondary glazing - we chose to replace the (pretty rotten, but possibly salvageable) Victorian sashes on the lower two floors at the front elevation of our non-listed, Georgian house with replacement hardwood double glazed sashes containing acoustic glass.

I should add that the front elevation had nine windows fronting directly onto a rural A road with a 30mph limit.......and the traffic noise drove me loopy.

Unfortunately, the seven windows we replaced (from a reputable local joinery co at a cost of £10k) made very little difference imho and had we intended to stay there rather than sell, I think Pip would have had to accept that secondary glazing in addition to the new windows was necessary in order for me to retain my sanity!

Fortunately our new house doesn't have that issue as the Victorian sashes here are on the garden front......although the Crittall windows added when the place was extended in the 1920s come with their own set of problems :roll:

Anyway, hope you have more success on the window front than we did!

Oh, and btw we love pictures here :wink:

Mims x

 

[livias]

You have put forward the best argument that I have ever heard for painting windows shut. Not only that, but leaving them painted shut is the lazy option too. Win Win ! So you only need to consider the central sashes which is much cheaper Not thst I have an answer for you cos my favourute secondary glazing option of magnetic strip / acrylic panels is good thermally but useless at keeping noise out

 

[malcolm]

A fair bit of noise gets through the glass as well as around the edges. Given 2 panes of glass they are best configured using secondary glazing with a good air gap between panes. The air gap reduces noise transmission between the panes, and also acts as a silencer between the primary and secondary window shut gaps. The secondary glazing needs to be well sealed to prevent condensation but the sash doesn't need to be especially well sealed. Secondary glazing is much more effective than double glazing for noise and is as far as I plan to go in this house with it's front on the pavement.

The plastic in laminated glass acts as a damper and takes out a lot of the high frequency noise. Any laminated glass will have the effect. Thicker stuff works better because of the increased mass. Laminated glass does distort the light a bit - look at a car window at an angle. No harm sticking thin laminate in the secondary glazing for a bit extra soundproofing. By itself it won't be as effective as double or secondary glazing in real life.

 

[MatthewC]

I’d also be interested in finding a reputable local joiner in the Surrey area (nr London) who could assist me as I’m not an able DIYer

For a moment I thought you might be my brother Duncan who lives in SW London/Surrey, but he IS an able DIYer!

Replacing all the sashes with new ones ... This is expensive and, although has been recommended to me by companies such as Ventrolla, I question whether this is the right option due to the loss of the original sashes. I have been quoted £20k+ for this option.

Ventrolla would say that; I had a quote for sash refurbishment and found them expensive. Also, if you were to engage them, could I have any sashes with old panes of glass? On refurbishing my neighbour's house they broke the old panes and then fitted entirely new glass; if I had known, I could have had a stock of some Victorian wavy glass for when I get round to doing my sashes - 4 years on and done just one out of seven .

On your original question, I have secondary glazing (acrylic sheet with plastic strip and clips) and am very happy with it. The gap is only 40mm but it does cut out the noise of the town drunks as they go past at 3am. The only issue I had, in doing it myself, was cutting the acrylic neatly.

 

[livias]

Another time buy the acrylic ready cut to size. I found a good cheap suppier online. Will dig out the name on request

 

[88v8]

If you change the glazing in the sashes you will have to change the weights.

As has been said, the main solution is secondary glazing.
The gap should not exceed 4" otherwise there will be excessive heat loss due to convection currents within the glazing.

The secondary glazing must be well sealed to prevent condensation.
This is excellent
http://affixit.co.uk/index.php?main_page=advanced_search_result&search_in_description=1&zenid=f29baa6ad7102bf8004caa49930f45da&keyword=expanding&x=27&y=12
For the same reason, there needs to be some air leakage in the primary glazing, the normal gap at the meet rail will take care of that.

You can create an aesthetically acceptable solution with suitable mouldings.
As to one's level of DIY competence, this develops with practice.
I am sure the same would be true of my foreign-language skills, the only thing lacking is the slightest effort on my part :?

A significant improvement in nocturnal noise performance is also achieved with thick and well-fitting curtains, or internal shutters.

Ivor

 

[DuncanC]

Thanks for all the replies - very helpful.

Mims - I've attached some pictures of the front of the house and in particular the windows. We're fortunate that we are set back a bit from the road and it is really only local traffic (very few lorries). Most of the sound issue for us is the 'swooshing' of cars rather than low frequency rumbles. One thing I notice about our windows in their current state is that the weakest point of noise intrusion is without doubt the gap between the meeting rails on the operable sashes. I presume you had your windows draught proofed when you put the new sashes in. Afterwards, did you find the noise most noticeably coming through or around the sashes?

Similar to Pip, neither of us really want secondary glazing (we like the windows as an original feature of the rooms) but we're trying to balance that against the benefits of some noise reduction. If secondary glazing is the only practical solution, then we will give due consideration to it. It sounds like in your case replacing the sashes did little to help.

 

[malcolm]

I didn't notice the photos of the windows. They look nice and you are right to preserve them as best as possible. Until you have 5 posts the posts are delayed and can be missed so it is difficult to interact with new members. Hope you haven't become disheartened and gone away.

Air leakage could be a big part of the swoosh noise. You can do a test to find out how big the effect of air leakage is by taping all the gaps with masking tape (ideally weak stuff such as frog tape which doesn't pull the paint off).

I've been trying to design some DIY secondary glazing using nice wooden mouldings. Good seals on the secondary glazing will be the trick as secondary glazing is prone to condensation. I don't feel the established companies make anything very nice, and they don't half charge for it. A local carpenter is likely to be able to do a nicer job for less money. They need to be glass for noise - stiffness and mass are important.

 

[88v8]

Lovely windows, but a lot of area and a long perimeter to seal against air ingress.

If that window is typical, you already have Romans and what look like heavy curtains, so I guess that damps down the noise considerably.
In that case you might limit your double-glazing efforts to the rooms where noise is intrusive during the day, as one can draw the curtains at night.
I would divide each sash set horizontally rather than using a single sheet of glass, which would be heavy and prone to breakage when removed for cleaning, an annual task at least.

If one wishes to open the windows during the summer, the d-g will have to slide vertically or be hinged, an additional challenge for sealing.

In wood, the whole job is a daunting and fiddly task. The sliding or hinged secondary frames will have to be very stiff, perhaps wood is not ideal.
In our previous house I had hinged solid brass frames made from U section, they were made by a metalworker. The top of each hinged frame was secured by internal angle brackets so it was removable, and I inserted sealed units into them. Thus, we had triple glazing with about a 4" air gap, it worked well. Alas, whatever pics I took were on film.

The whole job was fiddly, even by my standards, and the panes were smaller.
However I do not see why it would not work on a larger scale. I would be tempted in your situation to do something similar with brass channel, but if you want a quicker fix then perhaps something like the Everest system
http://www.everest.co.uk/double-glazing-windows/secondary/?gclid=CLPu0o2X9MkCFQQcwwodG60Eag&gclsrc=aw.ds
bearing in mind that you are not stuck with their colourways, you can paint the frames, subject of course to not clogging it up with paint.

Bear in mind that the secondary glazing will affect the exterior appearance of the house, if that is important to you. The double reflection. So applying this solution to one upstairs room and not the other, for instance, might look odd.
Hmmm, I'm beginning to sound like a d-g salesman. I'll shut up now.

Sorry to have no simple 'period' solutions.

Ivor

 

[lordmulberry]

We have Everest secondary glazing. Ours is to casement windows and has a 4inch gap. They are fitted to every window to the front of the house and are very effective noise reducers as well as adding thermal insulation. Everest are not cheap but their products seem good.

 

[malcolm]

I've been looking at Duration windows as custom DIY is looking tricky. They seem to be the only ones who will provide a price online, though the price doesn't include installation so you can still do a bit of DIY.

I previously had quotes from Storm windows (nice looking but £8000 for the house) and Selectaglaze (bulky and £5000). The prices seem insane. Duration is looking like about £3000 so I might pop down to have a look at the offerings.

 

[Andys]

I'd be happy to use Duration windows again, we've fitted three secondary glazing units here now, to finish off the windows the PO's hadn't got round to doing, it made the rooms much warmer and made a big difference to our (fairly minor) traffic noise. Bunging a couple of bags of silica gel in the gap helps control the occasional outbreaks of condensation.

The cost saving clearly comes with the risk of mucking up the choice of style, the measurements, forgetting to leave clearances or making a mess of the installation and I was a bit anxious about the first one we ordered but it came out alright.
Pic here:
https://www.dropbox.com/s/8t5w9xq7y4fxato/IMG_20151224_152812317 (640x360).jpg?dl=0

 

[DuncanC]

Not disheartened quite yet, and my thanks for all the advice offered over the festive period.

It seems that the generally recommended approach is to fit secondary glazing (both on this forum and elsewhere). It's clearly the best method of noise attenuation, however I do still have my reservations about the internal aesthetics. Before I look into this in further detail I just wanted to cover off the alternative options for reducing noise.

As a very rough guide I've been advised by several companies that:

i) Single glazed (acoustic laminate): 25% noise reduction
ii) Double glazed (one pane of which is acoustic laminate): 50% noise reduction
iii) Secondary glazing: 75% noise reduction

They also almost universally recommend option (ii) unless the noise issue is considerable. This being the most expensive option, there are clearly commercial benefits for companies to recommend this approach.

These noise reduction statements all seemed a bit too broad for my liking, so I quickly plotted out Pilkingtons' acoustical technical data for comparison of (i) and (ii) - see attached. Interestingly double glazing doesn't seem to perform well at lower frequencies (relative to single glazing) but is markedly better at 500Hz+. Also interesting to note (after some research) that Road/Tyre noise lies predominantly in the 500Hz-2kHz range with a focal point somewhere around 1kHz. If that's correct then I can understand the claims that 10dB (50%) noise reduction is possible with double glazing where the noise issue is from the road surface. Of course the challenge will be that the existing sash frames cannot house such deep DGUs and so this would require replacement of the sashes (and loss of high quality frames).



pip&mims suggested double glazed sashes didn't help much. I'd be interested in any other experiences before making a decision either way.

 

[88v8]

If you have old, precious, wavy glass, characterful, a link with the past, reglazing would cause it to be lost. That would be decisive for me.

Moving on.
I imagine that the manufacturers' quoted attenuation figures for d-g are for casements, where perimeter sealing is easier. Not sashes.

If you wanted to try the laminate, perhaps not too difficult; if the rebate could be machined a little deeper to take the thicker laminate - a DIY job with a router - in addition the glass is heavier and will require heavier counterweights. You know that glass used to be specified in weight rather than thickness.... for a reason.

We had d-g sashes at the rear of our previous house. The sashes were custom made for d-g and so of course were the boxes. The sealed unit air gap was large, 1". Noise was not an issue for us, however if there had been any noise it would inevitably have come in around the perimeter of the sashes and the gap at the meet rail. For this reason alone, I suspect that d-g as a form of noise attenuation would provide little bang for buck.
I am aware that one can apply brush seal to the sashes, I have no experience of its efficacy or appearance.

It has often been discussed on this forum that d-g units have a limited life. Short, and not even gay.

Secondary glazing is undoubtably the optimal solution.
I agree that the aesthetics can be sub-optimal.

Sidetracking, in case it is helpful to someone, in our library, our previous house, we fronted onto what became a rather noisy road, and when I had the library built, I designed it for double casements. The outer casement was single-glaze lead lights. The inner was d-g units. The inner casement had a perimeter seal. Air gap was about 4". No noise.

Double casements... I don't mean a standard casement with two openers..... have you been to Germany for instance? High-quality Period buildings oft were made that way. Two complete, separate, casement frames, the outer opens outwards, the inner opens inwards.

See, this is how the builders left it. See at the bottom left, the inner and outer casements.



Here's the finished article, the outer glazing with the red border, the inner d-g with bead glazing. The inner casements were fastened by unobtrusive 'budget locks'.



It looked pretty good, and the noise attenuation deriving from the 4" air gap and the perimeter seal on the inner casement, was almost total.

So, one could have inner casements made. Opening inwards of course, for cleaning.
In your case, it doesn't work.
The width of your central sash is a killer.

So, back to the problem: Cheaply, you could try this magnetic stick-on in one room.
http://www.extraglaze.co.uk/extraglaze-explained/10-video-guides/23-extraglaze-for-sash-windows.html
It would seal the perimeter gaps. If it works, great.

I would take an incremental approach. One room at a time. That way, if something works, you can propagate it, if not you can kill it off without having expended too much money and done too much damage.

Or perhaps the house lends itself to a switch in internal functions. Move something which is not noise-sensitive such as the kitchen to the front, and the sitting room to the rear. The bedrooms are not an issue because you can close the curtains, blinds, and fit internal shutters.

Sorry, once again no easy answers.

Roll on the electric car.

Ivor

 

[malcolm]

I like your double casements Ivor. Another way to reduce the aesthetic impact of secondary glazing might be to disguise it by fitting a wooden moulding to the inside face. Mine will be black against black frames and I think I might get away with them (see the sketch below). The central sash shouldn't be an issue if you use vertical sliding glazing.

From a noise point of view it is true that 500Hz to 2kHz tends to be the region you would most focus on in development of noise partitions for tyre noise. The noise is centred there and the ear is especially sensitive at those frequencies - we have even evolved to speak mostly in that frequency range. In real life sealing will be as important as the glass. In a car (the thin metal body aims for a good 40dB attenuation with the help of a little sound proofing here and there) you will normally have 2 or 3 rubber seals in the door opening. A 3dB reduction in noise is considered subjectively difficult to notice. 6dB reduction (halving the noise level) would be noticeable, but might not be enough to solve the problem. The dB scale is logarithmic but our ears hear things better when it is quiet so a 50% reduction might be less than you think.

There are no seals in my double glazed window at home and is is just as bad as the single glazed windows for traffic noise transmission. If you go a glass change only route make sure your seals are good as they will be roughly half of the problem. I'm planning to stick secondary glazing on my double glazed window as the seals would be a nightmare to add.