Double glazing ( Dunedin) - recommendation?

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Batman

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#319997 24-Jun-2025 14:39

i am i correct to read that thermally broken UPVC is the best thing to get fashioned and installed for best insulation performance?

the current glass is almost ceiling height and very wide (eg 5-10m)

any recommendation in Dunedin? (price is important)

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#3386663 24-Jun-2025 15:11

Glass is still glass,

Decent thermal lined close fitting curtains should be your first step,( they're also a butt load cheaper than putting in new windows frames)-

kiwifidget

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#3386671 24-Jun-2025 15:24

Is not the first recommendation for double glazing in Dunedin, triple glazing? 🥶

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#3386672 24-Jun-2025 15:25

That's true. Although some windows are difficult or don't suit them.

For reference, single pane glass in aluminum frames R value about 0.15. Thermal drapes add about 0.26 to a window so gets you to say 0.4

Double glazed thermally broken uPVC frames gas filled low e glass up to around 1.0. All that plus drapes almost as good as no window at all!

Drapes with a gap at the top and bottom can create a thermal sink of cold air flowing down. Important that they are tight to the ceiling or in a pelmet and reach the floor or window sill

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#3386673 24-Jun-2025 15:42

kiwifidget:

Is not the first recommendation for double glazing in Dunedin, triple glazing? 🥶

i haven't won the lottery yet. unless it's not much more expensive?

aluminium or upvc?

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#3386688 24-Jun-2025 15:44

johno1234:

That's true. Although some windows are difficult or don't suit them.

For reference, single pane glass in aluminum frames R value about 0.15. Thermal drapes add about 0.26 to a window so gets you to say 0.4

Double glazed thermally broken uPVC frames gas filled low e glass up to around 1.0. All that plus drapes almost as good as no window at all!

Drapes with a gap at the top and bottom can create a thermal sink of cold air flowing down. Important that they are tight to the ceiling or in a pelmet and reach the floor or window sill

upvc or aluminium what's the difference in R value (or something else??)

bfginger

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#3386691 24-Jun-2025 15:50

Aluminium's price is mostly reflective of embodied electricity cost making it financially uncompetitive in most countries especially in Europe. If aluminium became cheaper than plastic then most of the same companies manufacturing and promoting uPVC windows would abruptly turn to manufacturing and promoting aluminium windows. There are positives and negatives to each type of joinery material and no one is the best in every way. I doubt there would be an appreciable difference between uPVC and thermally broken aluminium in typical NZ conditions unless you were on a hill in Central Otago or something.

Could you please tell us what exact it is you're wanting to upgrade? If the window is glass-dominated and the joinery is good quality and not leaking air and water it might be better value for money to just retrofit double glazing with good low-e glass.

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Batman

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#3386694 24-Jun-2025 15:58

bfginger:

Aluminium's price is mostly reflective of embodied electricity cost making it financially uncompetitive in most countries especially in Europe. If aluminium became cheaper than plastic then most of the same companies manufacturing and promoting uPVC windows would abruptly turn to manufacturing and promoting aluminium windows. There are positives and negatives to each type of joinery material and no one is the best in every way. I doubt there would be an appreciable difference between uPVC and thermally broken aluminium in typical NZ conditions unless you were on a hill in Central Otago or something.

Could you please tell us what exact it is you're wanting to upgrade? If the window is glass-dominated and the joinery is good quality and not leaking air and water it might be better value for money to just retrofit double glazing with good low-e glass.

it's a couple of giant windows!

i googled and builderscrack says there are 100 window makers in Dunedin apparently. i don't even know where to start.

lxsw20

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#3386751 24-Jun-2025 16:39

Expect 40k+ for your average home, something to consider if price is important.

Ellisons Aluminium and Aitken Joinery (Doing our new build, good to deal with) are a couple of places you could start.

djtOtago

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#3386752 24-Jun-2025 16:43

Have a look at https://www.retromaster.nz/
I personally haven't used them, but a few of my neighbours have. So far, I haven't heard any complaints.

I have used https://www.thermawoodotago.co.nz/ about six years ago. Retro fitted double glazing into my 100 year old house. No complaints.

fe31nz

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#3386885 24-Jun-2025 23:11

wellygary:

Glass is still glass,

Decent thermal lined close fitting curtains should be your first step,( they're also a butt load cheaper than putting in new windows frames)-

The key thing about using curtains for insulation on windows is not being close fitting, it is preventing the reverse chimney effect. Hot air rises and cold air falls. So when hot air from inside the house hits the window and cools, it falls down the window to the floor and that movement pulls in more hot air at the top and you get continuous air circulation cooling the room. So the idea with the curtains is to stop that circulation, so the air on the windows is still and there is no convection rapidly cooling the room. To do that, you use curtains that touch the floor or window sill without gaps and have pelmets at the top where the curtain also touches. Consumer did a whole lot of experiments quite a few years ago to determine how best to use curtains and they found that if you cut off the circulation, then there is little difference between cheap curtains and special themally lined ones. The distance between the window and the curtains did not matter much either,.

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#3387295 26-Jun-2025 19:40

johno1234:

That's true. Although some windows are difficult or don't suit them.

For reference, single pane glass in aluminum frames R value about 0.15. Thermal drapes add about 0.26 to a window so gets you to say 0.4

Double glazed thermally broken uPVC frames gas filled low e glass up to around 1.0. All that plus drapes almost as good as no window at all!

Drapes with a gap at the top and bottom can create a thermal sink of cold air flowing down. Important that they are tight to the ceiling or in a pelmet and reach the floor or window sill

its been a while and i don't have time to look it up.

to get R1 you really need triple glazing. double glazing is actually not a whole lot better than single. there is quite a jump up in R value from double to triple. granted there is coatings and different gas options.

by mem some of the budget triple glazing is cheaper and better than the top end double glazing.

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#3387356 27-Jun-2025 06:07

tweake:

to get R1 you really need triple glazing. double glazing is actually not a whole lot better than single. there is quite a jump up in R value from double to triple. granted there is coatings and different gas options.

by mem some of the budget triple glazing is cheaper and better than the top end double glazing.

hmm ... really. so no need to double glaze?

so who sells budget triple glazing?

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#3387707 27-Jun-2025 18:00

Batman:

hmm ... really. so no need to double glaze?

so who sells budget triple glazing?

in some cases the gain from double glazing is so small its not worth it. one of the reasons it makes a difference with most nz houses is our love of excessive windows. because of the HUGE glass area (and consequently the lack of insulated walls) the small gain makes a noticeable difference.

no idea who sells triple glazing here. typically that sort of thing is imported and usually high end products. i have seen them overseas but no idea if imported here. a cool one to check out is where they use mylar (i think) clear plastic film as the middle pane instead of glass. that makes a much lighter and cheaper triple glazing.

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#3387711 27-Jun-2025 18:40

Triple glazing sounds expensive. Probably cheaper for you to turn the heater up on max.

bfginger

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#3388452 30-Jun-2025 22:38

Sorry to be contradictory but I don't see reason to think double glazing is of little thermal benefit over single glazing. The law of diminishing returns applies to increases in R values so the cost-benefit of triple glazing over double glazing in moderate climates could be questionable. An extra layer of glass means losing some solar light and heat gain too.

Looking at glass in isolation from a frame this is approximately what thermal losses would be over a 24 hour period for a 10C difference over 10m2

Plain single glazing: 14.4-15kW
Best possible low-e single glazing: 8.4Kw
Worst possible plain double glazing with 6mm air gap: 7.9kW
Best plain double glazing: 6kW
Best low-e double glazing: 2.4kW
Best low-e triple (argon) glazing or vacuum unit: 1.2kW

To fully take advantage of retrofitting double glazing in existing aluminium you need the best double low-e glass because there are still losses from the old thermally unbroken frame. I'd ask about how many mm air gap they do.

Whether it makes sense to do a full replacement, insert or retrofit depends on what's in there and your budget.

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