Retrofit double glazing

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TomHenshall

5 posts

Wannabe Geek

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#3173499 19-Dec-2023 17:30

johno1234:
TomHenshall:

We've just had a quote through a Veridian Glass supply in Auckland (North Shore) and the cost was ~$15,000 for about a dozen windows.

The plan was to cut the old windows out of our existing wooden frames and insert new glass in, add some draft excluder, foam beads.

Thanks. Roughly how many m2 of glass was that?

It is about 8 square meters.

Struikrover

3 posts

Wannabe Geek

#3179382 9-Jan-2024 14:41

Registered for this (hi everyone), though not sure how far you've gotten along with this. As it happens, I am going through this double glazing process now. We decided against secondary glazing (foil, magnets etc.) as this wasn't really a solution to our problem. From what I gathered there's 3 options, or 4 if including reglazing. I was told reglazing may require work on the entire window frame, which would be very expensive, possibly making it not worth it for existing houses. I did not investigate further, but i can imagine there may also be consent issues, given it would be structural. I don't actually know, so consider this speculation and perhaps someone more knowledgeable can comment on this?

Regarding the other 3 options, its possible to have retrofitted 1) double glass in your existing wooden frames, or have double glazed IGU's based on 2) uPVC or 3) aluminium frames. I believe the glass is produced overseas, imported and assembled into IGU's here. In the end, we chose aluminium double-glass inserts in existing wooden subframes, for reasons below. Essentially, it entails removing the casement and fixed windows including their frames, which for casements is the entire window, and for fixed windows the glass plus the small wooden strip its fixed in. They then fit aluminium inserts holding the double glass in the subframes that remain. I suspect the process is the same for uPVC frames whereas for wooden retrofit they just remove the single glass and replace with doubles. They won't / shouldn't install over rot in subframes, though painting is generally not included. Our 50s house has 15 windows, most of which casements, and all are held in place with putty and a nailed wooden strip. Seems to be common.

Wood and uPVC are good insulators, and the same is true for thermally broken alu. In older houses alu windows generally are not thermally broken, and thus superconductors that allow substantial heat leakage regardless of glass. Installing DG in this would partially defeat its purpose. In western Europe where I'm from, TB alu and uPVC has been the norm for a long time, > 40 years. Though surprisingly, I was still offered traditional non-TB alu DG here. In our case, the wooden casement windows would warp in summer to winter and so not close or seal properly. Retrofitting in this, installers plane few extra mm of the window and fix sealed draft beads. AQ21, Schlegel, 8 mm acoustic seals seems to be gold standard. However, it does not eliminate warping and so, over time, this might still compromise the window seal. If just fixed windows this may not be an issue

uPVC is common in Europe for IGU's, mainly because its cost-effective and a good solution. I would say uPVC in NZ is still in its infancy. From what I've read / been told by glaziers its first generation had severe longevity issues, due to material breakdown from high UV. Its unclear to me whether this problem has been solved now. I imagine it has, but there's not enough people that can comment on this long-term. From homework that I did, alu retrofit is ~30% more expensive than wooden or uPVC retrofit. There's a fair number of companies in Aucks that provide wooden and uPVC retrofit, and few that provide alu retrofit. I figured for us, given the significant expense, it was not worth not going with aluminium and NZ has lots of experience with it. Of course, its purely based on personal situation. I should warn, none of this comes cheap. Altogether we paid 35k but it was justified as being from Europe I wasn't going to put up with single glass. The install had complementary TB framing / Argon included, but low-E and 6 mm lamination was an extra 3k (35k total). Glass is hardened, which is closer to safety glass and quite effective at reducing outside noise.

Being a young family, this expense also came with consideration on how long we intend to live in our house vs. selling / keeping as kids grow up. I think it was the right choice health-wise, but on the fence investment-wise. Sadly, it appears houses also appreciate by just mowing the lawn. Would be interested what others think about this...

Sorry, long story, for what its worth. Hopefully this is helpful. Feel free to shoot if other questions =)

MikeAqua

7779 posts

Uber Geek

#3179387 9-Jan-2024 14:58

Something I've always wondered about argon filled DG is how you know it actually has argon in it? It's a colourless, tasteless, odourless, inert gas, so there is no way for the consumer to really know. It could all be a giant scam. Like those beans I exchanged a cow for last week.

Mike

wellygary

8321 posts

Uber Geek

#3179430 9-Jan-2024 16:25

To the OP.

I know you didn't want to "ruin the look" with Curtains or blinds,

But a good set of good fitting Thermal curtains is likely to give you a better R outcome than DG, (although its even better if you do both)

There are ways to tie them open so they are not too intrusive,

mattwnz

20155 posts

Uber Geek

#3179438 9-Jan-2024 16:43

wellygary:

To the OP.

I know you didn't want to "ruin the look" with Curtains or blinds,

Curtains can be really expensive, and won't work during the day when you want natural light.

johno1234

2803 posts

Uber Geek

#3179485 9-Jan-2024 20:10

I know it’s not very green, but am starting to think it will be cheaper to get a powerful heat pump and run it s long and hard as necessary than to touch the glass.

timmmay

20580 posts

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#3179487 9-Jan-2024 20:22

Struikrover:

uPVC is common in Europe for IGU's, mainly because its cost-effective and a good solution. I would say uPVC in NZ is still in its infancy. From what I've read / been told by glaziers its first generation had severe longevity issues, due to material breakdown from high UV. Its unclear to me whether this problem has been solved now. I imagine it has, but there's not enough people that can comment on this long-term.

I have one 12 year old uPVC Window from Thermal Frame in Wellington. It looks as good as the day it was installed. I had the rest of the house done in 2016, they also all still look good. You should wash the frames once or twice a year, just soap and water.

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ratsun81

508 posts

Ultimate Geek

#3179537 10-Jan-2024 08:41

timmmay:

Struikrover:

uPVC is common in Europe for IGU's, mainly because its cost-effective and a good solution. I would say uPVC in NZ is still in its infancy. From what I've read / been told by glaziers its first generation had severe longevity issues, due to material breakdown from high UV. Its unclear to me whether this problem has been solved now. I imagine it has, but there's not enough people that can comment on this long-term.

I have one 12 year old uPVC Window from Thermal Frame in Wellington. It looks as good as the day it was installed. I had the rest of the house done in 2016, they also all still look good. You should wash the frames once or twice a year, just soap and water.

We had all our windows replaced in 2013 with uPVC. Same thing for us they still look like they did when they were installed.

tweake

2391 posts

Uber Geek

#3180122 10-Jan-2024 17:08

johno1234: I know it’s not very green, but am starting to think it will be cheaper to get a powerful heat pump and run it s long and hard as necessary than to touch the glass.

i much prefer insulation first, heating equipment 2nd. but there is a cost to it all. it depends a lot on the actual house. how many windows, how big they are etc. double glazing doesn't give a big increase in insulation value, but with many kiwi homes that have lots of glass, it can make a sizeable improvement.

the other factor is IF you are used to heating a house properly. many (dare i say most) do not heat homes properly and are shocked at the cost of doing so.

Struikrover

3 posts

Wannabe Geek

#3180813 12-Jan-2024 09:43

I have one 12 year old uPVC Window from Thermal Frame in Wellington. It looks as good as the day it was installed. I had the rest of the house done in 2016, they also all still look good. You should wash the frames once or twice a year, just soap and water.

We had all our windows replaced in 2013 with uPVC. Same thing for us they still look like they did when they were installed.

Thanks, these experiences are incredibly valuable information. Had I know I might have changed my decision-making process =) If you don't mind me asking, have you found a difference at all between your north vs. south-facing windows?

timmmay

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#3180816 12-Jan-2024 10:03

Struikrover:
Thanks, these experiences are incredibly valuable information. Had I know I might have changed my decision-making process =) If you don't mind me asking, have you found a difference at all between your north vs. south-facing windows?

Nope, all fine. Maybe in another 20 or 30 years there may be a difference, but not after a decade or so.

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