We’re converting our loft and living on a fairly busy road we want to reduce the traffic noise as much as possible. Does anyone know how to soundproof while also achieving the required uvalue?
I would have thought soundbloc plaster board would be the best bet.
Rockwool is pretty good accoustically as well being a good thermal insulator. Recycled polyester is good and classic glassfibre is OK. I used two layers running at 90° and that gave pretty good results. Just about anything that gets you to R7 will stop most of the sound, even celotex type boards, they won't be as good as rockwool though. Try to break mechanical sound paths using plastic or even metal suspenders. I used them on one side and that's better than the other where I used crossed wooden support frames.
I suspect most noise will end up coming through the window assuming you fit one. I'd consider triple glazing if noise is an issue, or double glazing and secondary glazing. I'm no expert but understand that secondary glazing is better at reducing noise as it will have a large air gp, but its not as neat perhaps as triple glazing
The devil is in the detail, e.g. if you have a bucket of water and one small hole it leaks, same with sound, if any gaps in place sound gets in, so look at junctions, especially windows AND how the window connects to the wall/roof detail, also check where services penetrate through, another area that gets missed. If you get all that right sound and thermal insulation will improve.
In terms of sound proofing mass helps as mentioned above soundbloc, just check your thermal insulation too and how to deal with roof slopes and ventilation. Worth asking your building control person as they will deal with sound insulation for new builds and adaptations. Good luck, post pictures of the project;)
I recently insulated my attic flat - lath and plaster walls with a gap to sarking boards and slates. My aim was thermal insulation - . It has 4-6 inches of celotex now and all gaps filled with bodgers foam.
What was surprising is how much difference it made to sound. Not only transmitted sound from the outside but also the acoustics of the flat. It sounds very different
So from my experience well fitted celotex will make a significant differnce even tho its not intended as sound insulation and may be enough for you
Worth asking your building control person as they will deal with sound insulation for new builds and adaptation
They won't have a clue. There's no testing for sound break-in from the outdoors that's needed for BC sign off. This is all dealt with at a design/planning level, e.g. specifying the required glass thickness. No one actually tests that the noise from outdoors is attenuated enough (or even that the specified glass is installed, for example). The only time it gets looked at (on new builds at least) is if there is a complaint after the dwelling is occupied.
There are regs and testing required for dwelling to dwelling sound transmission though. If you are in a terraced/semi-detached house and your neighbour's attic is already converted you may have to have the sound transmission between the two tested (and construct the conversion with this in mind)
Overall, you need the services of an architect (or a specialist "acoustic consultant*") who can look at what the existing building is and then make recommendations. You won't get it right just by sticking in extra mineral wool and an extra layer of plasterboard. I think the solution is likely to be a room within a room type construction. Essentially that means the internal walls and floor of the new room are isolated from the roof structure.
*Avoid anyone selling a specific noise reducing product for true independent advice
Some great advice there. Thanks to you all.
Don't know if you're having a Velux window fitted in your plans but if you do the noise when it rains will drown out any traffic noise 🙂
You want to add mass to the structure in order to mitigate against the low frequency sounds such as traffic noise (especially busses and hgv’s)
Rockwool is your friend in this regard, try to isolate the internal skin from the external roof and walls as much as possible to reduce the chance of flanking transmissions.
Don’t use Triple glazing for noise reduction, it makes a very small difference in the overall sound Reduction. utilise a specialised acoustic glazing such as pilkington optiphon.
Make sure you use noise attenuating ventilation, lots of people pay a fortune for noise reduction, then cut a great big hole In the window frame for trickle vents or walls for passive ventilation.
Don’t use Triple glazing for noise reduction, it makes a very small difference in the overall sound Reduction. utilise a specialised acoustic glazing such as pilkington optiphon.
I had a choice between triple glazing with 3 x 4mm glass or "phonic" with 1 x 4mm and 1 x 10mm.
I can't remember the air spaces but do remember that the sound reduction in db was almost identical. I asked the saleman why they bothered with the "phonic" which had very average thermal performance and he didn't really have an answer. I fitted the triple glazing which also has 75mm frames and the sound reduction is impressive.
Anyhow ask for the db figures and make your own mind up.
If you use identical thicknesses of glazing then you have the coincidence dip at the same frequency in each pane thereby allowing for increased transmission through the window. As odd as it may sound 6/16/4 double glazing blocks more sound than 6/16/6.
For road traffic noise you need to look at the Rw Ctr reduction.
4/16/4 double glazing = 25dB
6/16/4 double glazing = 28dB
4/8/4/8/4 triple glazing = 27dB
6/16/6.8 acoustic laminate = 34dB
Where do those come from, rt60. Those figures are nothing like I've seen from manufacturers and I did a fair bit of reasearch before ordering. Here's an example:
Trybaphony: 37 to 43db reduction.
Triple vitrage Summun: 38db reduction.
And the link:
IIRC, the ultimate sound deadening is rockwool (you can get stuff specifically for sound attenuation but I'm not convinced it's significantly better than the regular stuff and it's pricey) then sound reducing plasterboard, then resilient channel, then more sound reducing drywall. However as others have said, a window or vent or almost anything that bridges your walls will undo your good work.
Edukator, Those figures are from a mix of British Standards and acoustic reference books (I am an acoustic consultant) I would guess the difference in the figures is based on the way different countries assess the sound reduction of façade elements.
In the UK we look at the frequencies most likely to cause disturbance from traffic noise, (the lower frequencies) and then assess the reduction across the whole frequency range rather than the total reduction, as this will be far greater towards the higher frequencies so will mask the fact that the frequencies that cause a problem wont be stopped anywhere near as well.
So from different sources which isn't a fair comparison, some of which are British stanadards which are highly unlikely to include the gasses, treatments and mebranes the manufacturers add to improve thermal and acoustic performance, and the differences in frame performance as triple glazing generally uses much deeper frames wtih labyrinths.
I'd rather compare numbers for windows from the same manufacturer tested under the same conditons in their specific frames with the gasses treatments and membranes they normally use.
I agree different solutions will produce differing result at different frequences but 27db from your table compared with 38db from Tryba is enormous.
Anyhow I walked home one day and heard my house making a strange noise, as I got closer I had a WTF moment when I realised it was the pegged open shutters rattling. It was only when I got really close I heard that junior was playing his base loud enough to make the house shake, but the noise through the windows was quieter than the rattle.
Ok well apart from the fact that there is no such thing as a standard dB and when someone states dB it could literally mean anything, it doesn't even have to refer to sound with no other information it could be referring to the number of pigs in a field. This means there is no way of comparing a simple statement of this will reduce by 38dB with anything else unless there is more details (weighting, metric etcs).
One glazing specification will give you 3 different levels Rw, Rw C and Rw Ctr. They are all dB reductions and can legitimately be given for the sound reduction of the window, and that is why we get paid to specify façade mitigation rather than the developers or architects simply reading a dB number on a web page.
The data is all from the same testing methodology, but the BS doesn't cover all possible glazing specifications, frame specs etc make no noticeable difference to the sound reduction of the glazing system.
The data is all from the same testing methodology, but the BS doesn’t cover all possible glazing specifications, frame specs etc make no noticeable difference to the sound reduction of the glazing system.
That is so counterintuative even if you are an acoustic engineer. So counter intuative I tried Googling and every Google result says you're wrong. Here's one:
https://www.dynamicwindows.com/sound-transmission-class/
Experts should never assume non-specialists are ignorant idiots. People from other fields with a scientific background are very fast learners who understand basic priciples and can rapidly apply them to new fields. Why not just admit that the figures you initially presented were selectively contituated, poorly presented and chosen to suit your anti-triple glazing personal agenda. 🙂
You're not the only one, and yet objectively it beats double in every respect except light transmission and solar gain (which when people add solar control membranes to double glazing to achieve the same is hardly a problem). And is very close to phonic glazing unless you find strange reasons to ignore manufacturers measured db figures.
Well if you want to go read BS 12354, calculate some composite SRi values and come back to me... (specialist situations it will make a difference, generally domestic premises however no).
https://www.regencyglass.co.uk/sealed-unit-types/noise-control/
one quick google search, take the top link and we have manufacturers data. The figure you want is the Rw Ctr (tr for traffic)
So to sum up according to regency glass:
Well-designed triple glazing will always out-perform well-designed double glazing and by quite a margin.
Badly designed triple glazing will perform margianlly worse than well-designed double-glazing.
So if you want good sound and thermal insulation spec well-designed triple glazing.
And as per my original post, acoustic laminated glazing will our perform both by a significant margin.
And what you omit to say is that well-designed acoustic laminated triple glazing will outperform the equivalent acoustic laminated double glazing and by quite a margin - as proved by your own link. Spec for spec triple always wins. Thank you for helping me to prove that.
Don’t use Triple glazing for noise reduction
is bad advice, as in false, misleading and just plain wrong
And what is the spec of your amazing sound reducing triple glazing?
because if its what 99% of it is, then it will be 4/4/4 and therefore will be far inferior to even a basic acoustic glazing. You can spec glazing to do almost anything, you can have glazed units that out perform even a brick/block wall, but that is a very specialist solution.
If you go to a window firm and ask for triple glazing you will get 4/4/4 that will not be as good as acoustic glazing.
And a high end double glazed optiphon unit will outperform the best triple glazed unit in the regency glazing specs.
But it won't be far off according to people like Tryba and will outperform thermically.
There's another point we haven't mentioned is cost. Unless people are stupid rich they'll go for a compromise taking into account cost, thermal performance, acoustic performance and availability. In my case having done the rounds I settled on triple with a uw rating of .9 that falls into the middle of the chart in your regency glass link. The uW rating for the best double glazed windows from the same company was 1.2, that was typical. In acoustic terms (manufacturers claims) the triple was much better than the double and very close to the phonic double (just a 10mm outer glass, not laminated, the laminated version was beyond what I was prepared to pay). The phonic double was no better than normal double in thermal performance. The triple had the advantage of deeper frames which in my renovation allowed a much better junction with the interior wall insulation thus reducing the thermal bridge. I speced no vents on the noisy side of the house placing ventilation where noise wouldn't be an issue.
We can do this all day but anyone who has read this far has enough information in the links to make up their own minds.
I've made my mind up
Pay particular attention to eaves/soffits on the road side , and if you can,concentrate ventilation on the other.
