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Retrofit double glazing

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Retrofit double glazing

Posted 22 Apr '10 10:12 AM

Hi All,

My home is about 7yrs old & has the standard single glazed aluminium windows (the aluminium frames are not thermally broken). Wall insulation is reasonable & roof has just had further batts added over the existing insulation. I am now considering retrofitting double glazing in the bedrooms to deal with cold & condensation. Cost is about $8K.

Does anyone have experience with retrofit double glazing & do they feel it was worth the effort / cost ?

Re: Retrofit double glazing

Posted 22 Apr '10 10:51 AM

Quite frankly you waste your money. It will be warmer no doubt but you will be very disappointed when all the condensation and mould appears on the frame and perimeter of your double glazing. Double glazing is heavy and the hardware of NZ style aluminium is generally poorly working and it might get far worse with the additional weight. Do it once do it right and get rid of your aluminium windows and fit windows with properly designed insulated frames and properly working hardware.

Re: Retrofit double glazing

Posted 22 Apr '10 12:08 PM

Then the cost goes up to $30 k, bit steep if your on a budget.

Re: Retrofit double glazing

Posted 22 Apr '10 06:06 PM

Especially yhen you can't afford a risk and you need it get right first time. Even in stages if that helps the budget. Those aluminium windows are one of the most expensive mistake (on the longer run)one can do in building/renovating a house.

Re: Retrofit double glazing

Posted 22 Apr '10 08:53 PM

I assume that you would be replacing the insulated glass units and the frames? If as the 2nd poster says you are attempting just to replace the glass then I agree you would probably be wasting your money.

You say you just want to do the bedroom windows, the cost would not be $30K as the 3rd poster has stated, I've recently bought a whole house worth of windows/doors in UPVC for that price, sounds like you've already got a price anyway for the job.

So to answer your question regarding is it worth it. Yes it will certainly make a difference, it will be warmer, less drafty and less condensation (if you steer clear of aluminium). 20-25 years ago when double glazing was beginning to be used in the UK, we did the same thing and just replaced the bedroom windows. The house at that time was approximately 90 years old, so it was not very thermally efficient, but we thought it was worth it. Heating bills and noise levels went down and comfort levels went up.

Good luck Pete

Re: Retrofit double glazing

Posted 22 Apr '10 10:55 PM

Hi original poster

Go for it: I think it is definitely worth it - some energy savings for sure, but more significantly every time you look at a window that used to have condensation but doesn't anymore, you will be reminded of the improvement you made.

(But in any case, get rid of any unflued gas heater you may have!)

Retro-fitting double glazing onto existing aluminium frames offers most households a significant increase in energy performance, without the much higher cost option of replacing standard aluminium frames with thermally-broken aluminium frames. The additional costs include higher labour costs (getting a builder involved) and significantly higher material costs. The suppliers of retro-fit double glazing send their own glaziers in: a one-stop shop.

I have double glaze windows at home, using NZ standard frames, without argon fill: halves the heat loss through the glass area compared with single glazing, no condensation, and in our own limited experience, no mold growth on the frame or perimeter of the double glazing units. Sure the aluminium frames are losing some heat: so does opening windows, kids leaving doors open, uninsulated concrete floors, lack of good thermal drapes, wrong position of heat pump, etc.

A few of the people who post on this forum keep repeating that NZ has junky windows, why don't we do this/why don't we do that - NZ is behind the times, cost is too high, why don't we do it the way they do in Europe, etc.

Importing a house-worth of windows is probably worthwhile to an end customer, without adding up their own time and labour. Our market size (small) dictates our costs structures (higher than elsewhere). The reality is that if it really was HEAPS cheaper or even cheaper-ish for a business to import all these European imports and stay in business and keep their prices down, then someone would do it as a business so the handful of Ecobob posters including the ones on this thread would be able to buy off them rather than have to import their own.

Re: Retrofit double glazing

Posted 22 Apr '10 11:33 PM

If people would smarten up on windows and stop using the junk windows they would disappear very quickly and a competive market for well performing quality windows would emerge in no time. Hey at the end of the day it is still a market of over 4 million. Maybe too small for own extrusion systems but there are well designed (and proven) systems from Europe which could be extruded here under licence.

Re: Retrofit double glazing

Posted 28 Apr '10 03:26 AM

Have you heard of Kristalbond. It is new on the NZ market but has been around for a number of years overseas. It has a very similar rating as a 4/6/4 DG unit but has an advantage of blocking 99.99% of UV rays which is a major in NZ at no extra cost. The other great thing is it is a liquid coating which is applied to your existing windows. You don't have to replace anything and it is about 1/2 the cost of retrofitting double glazing. They can be reached on 0508574782.

Re: Retrofit double glazing

Posted 05 May '10 09:55 AM

Our house in Waikato is 50 years old but the aluminium frames that were retrofitted at some stage in its past are still good and sound. Including the Ranch Slider. Due to a Freshaire ventilation system we had long ago banished condensation but we found the cold downdraft when seated by the windows in winter (and when opening the drapes in the mornings) a noticeable discomfort! Since having retrofit double glazing fitted by Chris Ryan (who replace all opening windows and fit new rollers to the ranch slider) our usable living area has increased and traffic noise significantly lessened in front bedroom and living area. The aforesaid Freshaire ventilation system means the windows don't need to be opened except in the hottest weather and even the shower causes no condensation; since it retrieves heat from the hot-wet air being expelled the running costs are low (unlike the systems that draw air from the loft space and force heated air out through window and door gaps!). Due to future heating costs inevitably rising I regard these more costly additions as an index linked investment and worthwhile in the longer term.

Re: Retrofit double glazing

Posted 05 May '10 07:40 PM

Wonder if he comes back to replace the hardware when it starts to wear off under the weight of DG

UV and uPVC

Posted 06 May '10 10:22 PM

Hi Pete. I'd be interested in how those uPVC frames perform under the NZ UV rays.

uPVC is fantastic for places like the UK, Germany etc, but from what I understand, uPVC hasn't really taken off in NZ because of the UV factor.

It deteriorates when exposed to harsh UV radiation, causing it to become brittle and shrink over time. I don't think WANZ (Window Association) endorse uPVC windows for this reason (but I could be wrong here).

Apparently white uPVC stands up better than darker colours.

For NZ conditions, I'd say timber or thermally broken aluminium are the way to go. Aluminium seems to get a bit of a bad rap on this site, focusing on the thermal properties (or lack thereof).

Re: UV and uPVC

Posted 07 May '10 12:20 AM

UV conditions in NZ are no worse than other areas of the world, the talk of "Harsh NZ Conditions" is a con by sales people selling aluminum products.


Re: UV and uPVC

Posted 07 May '10 01:31 AM

Who also don't tell you that Aluminium is a great conductor of heat/cold so it transfers the cold from outside in the winter and the heat in the summer, bag of sh**

Plus the hardware on then is best used in a greenhouse.

Re: Retrofit double glazing

Posted 07 May '10 02:40 AM

I've installed retrofit double glazing (Dual Glaze) into my kitchen and toilet. It wasn't quite the same situation as yours - I installed aluminiun inserts with low e double glazed glass into the wooden window frames. It cost about $1000 for a very large window and $400 for the toilet window but was really worth it. It makes a huge difference to the ease of heating that part of the house and the reduction in heat loss is noticable. I spent about $6,000 replacing another large window with wooden framed double glazed low e glass french doors and yes they look really nice, and in theory they have a lot higher R value (R 0.48 vs R.31) but to be honest I don't think it was worth 6 times the price.

Re: Retrofit double glazing

Posted 07 May '10 07:46 AM

Hi Anon @ 10:22 you wrote

"Hi Pete. I'd be interested in how those uPVC frames perform under the NZ UV rays.

uPVC is fantastic for places like the UK, Germany etc, but from what I understand, uPVC hasn't really taken off in NZ because of the UV factor.

It deteriorates when exposed to harsh UV radiation, causing it to become brittle and shrink over time. I don't think WANZ (Window Association) endorse uPVC windows for this reason (but I could be wrong here).

Apparently white uPVC stands up better than darker colours.

For NZ conditions, I'd say timber or thermally broken aluminium are the way to go. Aluminium seems to get a bit of a bad rap on this site, focusing on the thermal properties (or lack thereof)."

Yes I'm interested too obviously, but I have seen plenty of PVC down pipes and cladding which seems to be standing up well. I'll let you know in 5 years, although by then I believe the question will be academic as uPVC will be the first choice for most people. uPVC is fantastic in those places you mention and its also fantastic in Spain, Greece, India, Arizona etc.

The membership of WANZ - could not find it on the website, but I would expect its made up of glass vendors and alu window vendors, so they are not likely to be rushing forward to endorse uPVC are they?

White uPVC does stand up better to UV I believe.

Yes, aluminium does get a bad rap here and justifiably so. In manufacture it is much more energy consuming than uPVC, it's thermally rubbish, and the window hardware produced by NZ manufacturers using it is of 1960's designs. If the government were to bring in proper thermal targets for building elements, then I think the alu industry would struggle to compete long term.


Re: Retrofit double glazing

Posted 18 May '10 08:00 PM

Retro fit room by room and do it with thermal broken frames if available at a decent price. However do look at the costs of the full retro fit to moving house into a home with double glazing. It may be the best move as you may not get your money back on the investment.

$30k for a full retro fit=$30k
It may be cheaper to retro fit the windows you need for security site and light and put heavy curtains on the rest.

Re: Retrofit double glazing

Posted 18 May '10 08:43 PM

Hi Preacher, do you look at payback of your investment for your plasma sceen? home entertainment system? for you car? for your spa pool? for your granite benchtop? your beer in the pub? maybe what you eat? A warm and healthy home is much more than a investment with "return" it is first of all a habitat for a human being. Because of the stupid concept of using houses for speculation we have second to third world housing in New Zealand and unrealistic house prices which are beyond the true values. So whoever looks at value for the "investment" should refuse to buy pretty much any of the existing houses.

Re: Retrofit double glazing

Posted 18 May '10 09:54 PM

Hi Anon

Yep. Also looking at the way the costs come into everything in above replies it is a cost issue. I should have started with, If you are worried about the cost of it then you may have a better chance of finding a home with DG. I do agree we should stop buying crappy insulated and cold homes. I wish we could start a campaign today on how to target cold homes properly but that's a big elephant to eat!

Re: Retrofit double glazing

Posted 02 Jul '10 07:56 AM

have a good look at the stick on acrilic sheets magnetite or something comes to mind. they claim a single sheet has better thermal& noise perfomance than double glazing & definately a lot cheaper & less strain on old ally frames. but the first thing to do is get curtains that go to the floor & enclosed in a pelmet & use them

Re: Retrofit double glazing

Posted 08 Jul '10 04:02 AM

Whatever you do, make sure you research the subject as much as possible before you make the decision. Some of the information from the NZ retrofit DG companies is shockingly bad. One on its website says that retrofitting its DG units into existing aluminum frames would provide the same performance as the latest doubleglazed windows - which is a pretty blatant lie.

Re: Retrofit double glazing

Posted 21 Jul '10 10:22 PM

I know of one company, appropriately named the Double Glazing Company who can also include ventilation in their retrofit solution. They have an adjustable vent installed above the glass.

I know some people confuse reducing condensation with reducing moisture levels. Double glazing WILL reduce condensation, but it does this by raising the temperature of the inside glass surface, not by reducing moisture in the home. Only ventilation will do this.

So, considering how well draft sealed windows and homes are these days (a good thing), including some ventilation seems a good idea.

Re: Retrofit double glazing

Posted 21 Aug '11 09:58 AM

Absolutely the cost incurred is about $8k for me too, Look at further more details here:

Re: Retrofit double glazing

Posted 08 Jun '15 09:53 AM

I think you can replace your insulated glass and use quality double glazing which will provides a modern looks with smart design.

RE: Retrofit double glazing

Posted 10 Jun '19 01:02 PM

we got some installed a while back, so far so good - no more crying windows, we live in a old house and recently noticed one of our joinery is fkd! so might have to bite the bullet and get whole new windows for that room. company is local in wellington here is a link

RE: Retrofit double glazing

Posted 12 Jul '20 07:38 PM

Hi everybody
We are a Upvc window manufacturing company based in Dunedin
In response to a number of comments to this thread:
All our windows are rated for NZ conditions (and guaranteed)
They are more expensive than European Upvc because of this
We comply with all WANZ recommendations, NZ and Australian standards
We have very little association with WANZ as by far the vast majority of there members are aluminium
And fair enough, why would they promote products that are in competition to there membership
With regard to retro glazing existing aluminium windows
We have had a number of clients who have had this done and have been very disappointed with the results
To the extent where they have replaced them with Upvc
As far as Thermally broken aluminium goes this works fine providing the thermal break is in the warm zone of your house
Which is to say, if you have a brick, brick veneer house, or if it is on a cavity batten
Thermally broken aluminium is pretty much a waste of money
We started upvc windows into 2010, prior to that I had 25 years experience in the aluminium window industry
While skeptical to begin with, there is no way now I would ever use aluminium

Thanks Dave

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