Aluminium frames - Insulation properties

[Mcblurter]

Hi everyone
Can't seem to find any posts on this but let me know if there are.
Am doing a reno with a west facing wall. Will use double glazing and the builder has ordered aluminium frames. I have checked other web pages and shows that aluminium is a good conductor so will get hot/cold and reduce the overall effectiveness. I will be using blinds and drapes so will assist but just wondering if anyone has had experience with aluminium vs wood vs pvc etc. I'm in Melbourne at it can get bloody hot and very cold so any advice would be welcome.
Am getting some other quotes for frames with thermal breaks etc, but would prefer just to get reno completed so we can get a normal family life back!!!
Cheers
McBlurter

[silentC]

I think that as a percentage of the area of the window opening the frames themselves are very small and would have little impact on the insulation properties of the house. But that's just my gut feeling.

[Barry_White]

Although timber would not transfer heat or cold the same as aluminium as Silent says the surface area would be insignificant in the overall scheme of things.

If you were doing it yourself on existing timber windows it would be cheaper but from memory when they manufacture them they create a vacuum between the glass and that is difficult with timber because it is pourus.

The main issue would be the in the long run the maintenance of the timber could be a real pain and aluminium window manufacturers have perfected the double glazing.

I used to install double glazed windows in high rise buildings and the thermal properties of the aluminium wasn't an issue.

[pharmaboy2]

I'd go for the aluminium too, as Barry says, the seal for the double glazing needs to be perfect..

In europe, the PVC windows are the cheap version, yet here they are way more expensive than aluminium - so go figure!. I'd guess the articles you may have read come from a northern hemisphere perspective, where outside temps maybe 20C below - if you've ever touched metal thats at minus 20 when you have slightly sweaty hands, it might immediately become apparent why you would be weary of aluminium in those sorts of climates!

BTW, for western sun, the double glazing isnt very effective at all - best to shade for summer, but the DG definatelely works wonders for keeping in the warmth for winter.

[johnc]

Double glazed windows come as two pieces of glass with a small gap with inert gas in the space. It is the same window regardless of frame. The seal holding the panel in place shouldn't vary much, rubber seal on one and silicone on the other and timber is better for heat retention, although the difference could only be negligable. Regardless of timber or aluminium the double glaze is everything the frame two tenths of stuff all. Of more importance would be sealant to stop air movement around the outside edge of the frame,sneaking past the architrave.

John

[Mcblurter]

Thanks everyone for the quick response, has certainly eased my mind. Most of the area will be glass so frames shouldn't impact that much. Also good to know about the keep heat in but not out. Have planned for a small verandah and also look at some outside blinds or awnings to provide further shade. I think the PVC are expensive as they are seen as a "green" alternative to wood and aluminium, although as with everything there are issues around the use of chlorides etc
Thanks again
Mcblurter

[TWC]

Hi McBlurter,

I can strongly recommend a Blockout shutter particularly for any west facing window or opening. Although not cheap, (neither is double glazing, especailly if you replace the whole window to get it), you have the added benefit of security and with the larger air space you get better thermal efficiency.

If views or looks are important then I guess there might be a trade off, but in our kitchen, especially during summer, the difference was totally amazing.

It went from an unbearable heat, without the oven on, (worse when cooking, if that is possible) and even when helped along by ducted airconditioning, there was little or no relief in the kitchen area.

After installation of the shutters, we were extremely satisfied with the result. It was an amazing experience to enter the house after a day of 40+ temperatures, to find it cool enough not to require the airconditioner, just because the shutters were down for the day. They also work very well in the winter for keeping the heat in.
The 2 windows are single glazed, 3mm glass, 2100 * 1500 and 1500 * 2400 with aluminium frames, so it was amazing just how much heat came through the 2 openings.

The larger the air space between the panes of glass or the shutter and the glass the more efficient it will be for both thermal and noise insulation.

All windows I have made with double glazing have been made from timber (WRC) and I always go for a mimumum 12mm air gap. This usually means that the window sashes are larger than normal dimensions, for the timber to accommodate the glass. It is a very common setup in Europe, with many people even going as far as triple glazing, but I believe this is overkill in our climate. Thermal break aluminium windows offer a good alternative, but last time I looked, they too were extremely expensive.

By the way, each individual glass panel is sealed (2 panes of glass separated by a metal strip and sealed) and the timber has no effect on the efficiency of the double glazing unit, other than to say timber is more efficient than aluminium in the whole window package. But timber requires more maintenance, so most people prefer the easier maintenance of aluminium, where the usual double glazed air gap is only 6mm. Almost as effective to use laminated glass in that case with a coating on the glass.

We will be installing shutters instead of double glazed windows in the rest of our house, as we were that impressed with the end result. Far better than I first thought possible and no need to replace existing windows.

Hope I haven't made it too difficult to understand and that you achieve a workable solution for your situation.

Cheers
TWC

[Mcblurter]

Thanks TWC
Our house is an old concrete commission house and is great in summer. Only a problem if we have 3-4 days of over 30 degrees, then a bugger to cool down. We are getting some openable skylights as well and will have block out blinds on those and will probably need to do the same in the extension. We are putting in a clerestory window so hopefully get some air flow happening which should help. Also have a solar heater which in summer helps cooling by pulling hot air out from up near the ceiling.
Have you got shutters? I personally don't like them that much, must get really dark inside. We have some awnings that is the vision weave stuff, so can see out and have some light which is good. Have also seen some stuff on the net which looks like very thin, perforated aluminium which looks good, and expensive!!!
Might be a bit of trial and error (and saving before we spend even more money!!!) Thanks for the tips.
Cheers
McBlurter

[myla]

hello,

seriously look at secondary window framing on the inside with either single pane or double-glazed unit, this will kill any double glazed unit on the market and is a very easy technique

it does change the appearance but well worth it, as mentioned the bigger the air gap between panes greatly improves things for heat & noise (up to a certain amount i think 100mm)

most double glaze here is just catering for the green movement, all over europe, even housing commision 20-30yrs old, they use two-window type set up with around 100mm air space, they open into each other for cleaning etc, like shutters

thankyou

myla

[Metung]

Rylock make a double glazed window with aluminium on the outside and timber (Vic ash) on the inside. I have just done the whole house in them and think they are fantastic. The bloke who did the energy rating said they made an enormous difference to the overall energy rating of the house.

[Mcblurter]

Hi Metung
Asked them for a quote, still waiting!!!!!
Cheers
McBlurter

[kiamaian]

Rylock make a double glazed window with aluminium on the outside and timber (Vic ash) on the inside. I have just done the whole house in them and think they are fantastic. The bloke who did the energy rating said they made an enormous difference to the overall energy rating of the house.

I have obtained a quote to install these type of Rylock windows in my new house.
I am concerned though that I have to finish the interior frames of the windows and am frightened that I will not get a professional finish. One option would be to stain the windows so the wood grain is not hidden and do the reveals in the same manner. However, if I do this the nail holes in the reveals made during the installation of the windows will look very unsightly.

I would be interested Metung to know what finish was applied to your windows and whether you are satisfied with the final appearance.

[commoo]

I fabricate aluminium windows and we use double glazing quite alot.
Double glazed units are usually filled with argon gas.
Some of our customers opt for what we call sunenergy glass on one side of the unit.
This reduces the amount of heat that comes through the unit.
There is one other "Expensive" alternative.
You can actually put venetian blinds in between the two panels.
These function the same way as normal blinds where they tilt and are able to be opened fully where the blind is drawn upto the top of the window.

[Sir Stinkalot]

Most energy raters are now calling up 'thermally broken' aluminium frames to get the 5 star rating. This is often the cheaper option to double glazing. As you are going double glazing already I would go this with the thermally broken frames and then you will be on a winner. There are a few manufacturers now offering thermally broken aluminium frames as a standard at the same price as aluminium frames.

[Metung]

Kiamaian,

I have used a marine varnish on the reveals,. At this stage I have only given them a couple of protective coats. I am embarrassed to say that was over 15 months ago but they still look pretty much as good as a the day I did them, even the ones that are directly north facing and they cop an awful lot of sun.

To protect the reveals, I used some heavy duty bugle head screws and fixed them from the stud side where possible so that the fixing can't be seen. The attached pic hopefuly explains.

I am more than satisied with the windows. They look and work superbly. I used 140mm studs and 7mm ply brace on all external walls to preserve the full depth of the available reveals. Rylock mucked up the structural depth of the sliders but carted them all back, replaced the reveals and re-delivered within 4 weeks - and I'm talking a dozen large windows and a round trip of 700km.

Regards

Terry