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I live in Bombay (Mumbai), India. I'm planning to install sliding sound-proof windows in a room. There are two common types of window frames manufactured here; one is aluminium, and the other is PVC, which is some kind of plastic. I've had conflicting information about which is better. I was told one the one hand that plastic deteriorates under local conditions, which is mostly very hot and humid (the location is a stones throw from the Arabian Sea), except during the monsoons, when we get torrential rain.

On the other hand, I talked to someone who works for a company called Beautex, and the person insisted there was no problem, and that PVC is actually better from a sound-proofing perspective, though they did not offer any reasons why. They do sell PVC windows in India, as can be seen here.

Personally, I'd incline towards aluminium without further information, since I've never heard of aluminium deteriorating, and it is quite strong and durable.

So, the question is, which is preferable and why?

Addendum: Reading the question How can I prevent aluminum window frames from heating up when they're in full sun? made me wonder if sunlight heating up the aluminium will be an issue. The window frames will certainly be exposed to direct sunlight for part of the day, though I'm not sure how long. The windows do have small roofs above them, to help keep of the rain, which may help.

NOTE: This is the same room as shown in The best kind of tiles for using on floor and walls, though it now no longer looks as it did in this photo. Since that time the wooden windows have been removed, and the small roofs over the windows have also been replaced, though the new ones are of a similar size.

UPDATE: I eventually went with uPVC windows, not aluminium. After research, I discovered that there are uPVC windows which are manufactured that are suitable for Indian climate conditions, and they seemed to offer better soundproofing than the aluminum ones did. Possibly better insulation too.

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Soundproofing as it relates to windows is all about mass -- the denser the materials, the more sound reduction you'll get. PVC is, indeed, typically more dense than the far more lightweight aluminium and so will will resist noise transfer more. However, the amount of surface area made up by the frame is absolutely dwarfed by the glass itself. Any differences in the frame will be massively overshadowed by the properties of the glass, make it a moot point.

PVC/Vinyl windows do a far better job of restricting conductive heat as they are a much better insulator than aluminium. Aluminium is really one of the worst materials to use from an insulation standpoint.

However, PVC/Vinyl will eventually "melt" in a hot environment. Recycled PVC will do so far faster than virgin PVC, but even the latter will eventually sag enough that opening and closing the window will be tricky. Assume maybe 15-20 years.

Aluminium will last indefinitely. That and the price are typically the two big selling points of that material.

In short, neither has a true advantage from a soundproofing perspective (the glass does quite a bit, though) but PVC is a better choice from an insulation standpoint if you are willing to replace the window every 15 years or so. If you don't care about the insulation value and don't want to replace the window, then aluminium is the way to go.

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  • How big an issue is the greater conductivity of aluminium vs the lesser conductivity of PVC in practice? Does it make a big difference if the window frame is exposed to direct sunlight?
    – Faheem Mitha
    Commented Jun 13, 2014 at 15:33
  • The actual difference depends largely on the size of the frames as well as the internal construction of the frames. In general, though, yes, there will be a notable difference in heat transfer. Aluminium has a heat transfer coefficient of 205 W/mK at 25C whereas PVC is only 0.19 W/mK at the same temperature. Calculate the surface area of all of the aluminium frames and create a conceptual "square" of that size. Assume that there is a hole in your wall that is that size, with little/no insulation. That's the effective result.
    – Kurt Granroth
    Commented Jun 13, 2014 at 17:07
  • Is it possible to have a hybrid type setup, by say coating the aluminium with something? Alternatively, the WP article on anodized aluminium says "Anodized coatings have a much lower thermal conductivity and coefficient of linear expansion than aluminium."
    – Faheem Mitha
    Commented Jun 13, 2014 at 18:14
  • Anodized aluminium is intended for more durable aesthetic coatings. Its lower thermal conductivity and such actually work against it, due to its differences from the aluminium (it can crack, if the temp changes too much). Aluminium can be made more thermally responsible by inserting a thermal break in the middle of the frame. With the right design, it can get close to the thermal properties of vinyl. Cost becomes a factor, then.
    – Kurt Granroth
    Commented Jun 14, 2014 at 0:41
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I think the only reason you may choose PVC over aluminum is the price deference.
In Greece (sun and cold in northern parts) the best choice is aluminum - heavy type ( this has to do with the profile width) - with a good engineered thermal break ( pieces of rubber within the profile).
This solution lasts for years without shape deterioration from sunlight. The cost difference though may be significant .

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  • Thanks for your comment. Is the cost difference between PVC and aluminium significant where you are? I don't think that would be an issue here, but is PVC cheaper where you are, and if so by how much? Also, is having a thermal break in the aluminium standard practice, and how much does it add to the cost? Kurt also mentioned the possibility of a thermal break.
    – Faheem Mitha
    Commented Jun 14, 2014 at 21:26
  • As l can recall there maybe a more that 50% price difference to buy a good quality heavy type profile with thermal break. The thermal break is not a standard practice and you have to ask for the specific aluminum profiles. Thermal break addition is making the profile more expensive but you have to ask for offers. I remember that a contractor told me that if you cannot afford the thermal break and thermal insulation is a primary concern better buy PVC. One last notice. The outcome of the installation is severely depended on the quality of the crew that will perform the task.
    – Konstantinos Chertouras
    Commented Jun 15, 2014 at 7:18
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We live in the Canary Islands, just off the coast of Africa in line with the Sahara. We have bought a house with ugly aluminium windows and have been deciding on whether to have aluminium replacements or UPVC. The cost of UPVC is slightly higher here. We have decided to opt for UPVC for a number of reasons. Aluminium is harder to maintain here. A mixture of sun and regular sand in the wind makes aluminium look dirty and dull. It requires regular cleaning and polishing. UPVC needs less maintenance. UPVC has a better thermal value, therefore keeping the house cooler inside. It also has better security features. I hope we were correct! AET

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  • It does rather depend on the quality of the aluminium and UPVC windows, as well as the installation. But I think UPVC is a perfectly reasonable choice, all things being equal.
    – Faheem Mitha
    Commented Jul 12, 2018 at 23:57

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