Geoff333
Member
I'm building a new house (in Sydney) and I'm trying to get the balance right when choosing windows. The house is across the road from a train line so we need to get noise reducing windows, but we'd also like to ensure their energy efficiency. From what i've read, there doesn't seem to be one solution that achieves both objectives.
Any advice would be appriciated.
Geoff, you have probably seen a lot of material in your search.
This page seems to put the acoustic situation quite well:
http://www.stegbar.com.au/products/windows_and_doors/glass_and_glazing/acoustic.php
For railway noise, a window with an air-space of at least 100 mm seems to be required.
Such a window would provide little thermal insulation (Is that what you mean by "energy efficiency"?). Perhaps you should have the best normal double-glazed unit that you can afford, and add another thick glass window over 100 mm from it.
johnmath
Member
Yes there is a difference, but in reality, the loss in thermal efficiency going from, say, 10mm to, say, 100 mm is inconsequential. Other things to consider - use different thickness of glass inside and outside - there is critical frequency that passes through glass depending on thickness. Using different thicknesses spreads this to prevent one frequency getting through. Suggest 6 mm laminated (for security as well) external, 4 mm internal, thicker for more noise reduction if you can afford it, eg 10 or 12 mm external.
Also consider whether you want solar gain - yes for north, not so important for south, definitely no for east or west windows. One pane can be low e glass.
As johnmath mentions, the direction your windows face makes a difference. Which direction is the railway?
An efficient window plan must be a compromise. If you need the house to be sealed against temperature extremes and noise, have very small windows. If you need sunshine or views, make them as large as required. If you need ventilation, they need to be openable, but that will let in a lot of noise as well.
Geoff333
Member
Thank you both for your advice. Much appriciated.
The railway line is to the north of the house (beyond the backyard and a road), which i suppose is the whole problem. The back of the hosue (facing north) is the living area downstairs and bedrooms upstairs. We are keen for the light into those rooms, but are concerned about the noise. I'm not that stressed about noise during the day, but mainly about nighttime noise in the bedrooms.
The cost of double windows is probably making them unlikely, so i'm probably leaning towards thicker glass (6mm or 10mm). Then the question is about thermal efficiency. Since double glazing is not an option (poor noise control), the choice is limited to laminated glass or some type of window film.
Options i've seen so far include ComfortPlus glass, EnerLogic film, and KristaBond glass coating. Do you have any thoughts and /or experience with any of them? Any rough price comparisons would be great too.
cheers
Geoff
Geoff, I don't have the figures at hand (dymonite69 usually does) but I am surprised that you think normal double-glazing has poorer noise control than various single-glazing options. I should have thought that normal double-glazing, with panes of different thickness, would be your best option. What specific advantages do you see in the single-glazed alternatives?
It is a pity that the noise is coming from the north side, where you will want to catch the winter sun.
So far as keeping out noise at night, heavy close-fitting curtains could do wonders, and you need them anyway to keep heat in during winter nights.
If you have scanned the thread "Low Energy Houses" you will know that I have had all my north curtains on a timer to close on winter nights (and summer days) for 14 years now.
johnmath
Member
For the bedroom windows, there wil be a compromise between the size of the windows - ideally largish for solar gain, smallish for noise performance. The biggest issue for noise is poor sealing of the window/frame. For this reason you want to avoid sash or sliding windows, which generally do not seal well. Casement or awning windows usually clamp shut against a seal and have better acoustic performance as a result.
In Europe double glazed "tilt and turn" windows are used very widely and have excellent thermal, noise and ventilation properties. (for an example search google or see: http://cozyhome.com.au/Tilt-and-Turn-Windows-Double-Glazed-U-PVC)
I once lived in a townhouse on a street corner in the CBD of Adelaide near the central mail exchange. Between 2 & 4 am about 100 vehicles would roar down my street as the postal staff finished sorting the previous day's mail and raced home. My bedroom had one aluminium frame double hung sash window on one street frontage and two French doors facing the other street frontage.
I solved the noise and sleep disturbance problem by adding a secondary double hung sash window inside the first. The secondary window was aluminium framed and designed for good sealing. I was able to get 100 mm air gap for good acoustic performance. I slept with my head against this window so it was quite significant. One thing I didn't expect was I eliminated the cold draft of air coming off the window glass in winter, making it much nicer to sleep.
The two sets of French (double) doors were more difficult. I could have added a second set of doors opening inwards, but the size of the room would have meant that was inconvenient. The doors were essentially panel doors with solid frames and glass panels set in the top half and thin ply panels set in the bottom half. I had the original 3mm glass replaced with 12mm laminated glass - the thickest that would fit into the frames. Then I simply nail a thick MDF sheet over the bottom panels on the outsides of the doors. I installed Raven airtight seals all round with double seals (one inside, one outside) where the two door leaves butted and also on the bottoms of the doors.
I measured the sound levels in the room after this was done with a sophisticated and expensive environmental monitor from an acoustic consultancy. I don't remember the actual numbers now, but the loudest noise in the room at night was the noise of the occupants breathing!
I have giving this example in the hope that is helps you understand the principles involved in noise reduction through windows from a practical sense. Generally window companies are interested in selling a "product" not a "solution". Solutions don't always have to be complicated or expensive.
Hi Geoff,
Some glass only STC ratings of a few glass combinations:
4/14/4 (IGU baseline) – STC 31
6.76/12/6 - STC 37
6.5Hush/12/6.38 - STC 38
8.5Hush/8/6 – STC 38
10.5Hush/8/4 – STC 39
10.5Hush/6/6.5Hush – STC 40
12.5Hush / 8 / 4 – STC40
12.5Hush / 6 / 6 - STC 41
*Remembering that:
Changes in STC Rating Changes in Apparent Loudness
+/- 1 STC points Almost imperceptible
+/- 3 STC points Just perceptible
+/- 5 STC points Clearly noticeable
+/- 10 STC points Twice (or half) as loud
Another important aspect is how well the window seals, as air leaks become great points for acoustic penetration. Unfortunately low frequency noises, such as trains, are much more difficult to block out.
For some information on what an STC rating is read this document's below:
http://www.soundproofingcompany.com/soundproofing101/understanding-stc/
http://www.soundproofingcompany.com/soundproofing-articles/low-frequency-bass-problems/
I think you my want to consider secondary glazing for the important rooms (mainly bedrooms). Acoustic double glazing throughout the rest of the house will be (in my opinion) sufficient, and still achieving good thermal performance.
Thanks,
Kurt
Morbo
Member
Miglas Windows said:
+/- 10 STC points Twice (or half) as loud
is that 10dB explained using finger puppets?
http://www.sengpielaudio.com/TableOfSoundPressureLevels.htm
So 40 STC would turn a diesel truck into a family home, no kids?
Carpets and curtains and the like help a lot too to get rid of echoes. Just walk into an empty room and into one that has something in it, big difference.
Avoid any gaps, too. Granny got double glazing next to a busy road 20 years ago. Its really quiet. As soon as you open the window just a little bit, the noise is back.
Morbo said:
is that 10dB explained using finger puppets?
http://www.sengpielaudio.com/TableOfSoundPressureLevels.htm
So 40 STC would turn a diesel truck into a family home, no kids?
I'm not sure what you're getting at?
But an STC of 40, is a transmission loss of 40dB in rough terms - obviously different frequencies behave differently - as i mentioned low frequency noises (like a diesel engine would be) are much more difficult to cut out.
Thanks,
Kurt
Morbo
Member
agree. The table I linked is not about at which frequencies either, just to have an idea. Angle grinder and jet pane are different frequencies as well and the human ear is not linear either. 
Trucks are limited to 86dB or so these days anyway.
And the good news is, there is no public transport / trains between midnight and 5AM...
Insulation in your walls does not like low frequency noise either. Suppose except cost there is no real benefit in rice paper houses.
Again for the 100mm gap in glass, cannot see why its that bad. Its the only form of wall cavity insulation until 2012 in this country anyway, 10mm plasterboard and 10mm avg pine timber does not really do that much. Its just the current standards take air gap as R0, because its too hard to calculate. Better go for nominal R values of bulk insulation as quoted by supplier.
Suppose you would not get one of these with your windows or for your wall details:
