Some new windows getting condensation on outside

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Eva888

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#325587 19-Sep-2026 08:39

My new windows installed, double glazed, argon gas and low E. Rained the day after installation. Could see out of them fine.

Last night no rain, windy and dry this morning, woke to some panes with condensation on the OUTSIDE. There is a row of windows facing the same direction and weather but at least half have this condensation on the outside pane and then others are perfectly dry.

I suspect this is some fault but I don’t know what. Would appreciate some advice. Of course it’s the weekend and installer is closed.

WWHB

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#3529106 19-Sep-2026 08:55

This means the windows are doing their job and insulating your house. The outer pane is staying cold and allowing moisture to settle on it.

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Eva888

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#3529113 19-Sep-2026 09:27

WWHB:

This means the windows are doing their job and insulating your house. The outer pane is staying cold and allowing moisture to settle on it.

If this was the case then all the windows would have condensation on the exterior, not just a few. Many are totally clear.

I am wondering if the low E coating which is applied to the interior of the outside pane has had the glass put in back to front with the coating on the outside. The pane directly next to it has no condensation. Same with some of the others.

kiwifidget

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#3529115 19-Sep-2026 09:31

Our windows are the same, some get condensation on the outside and some dont.

Similar specs to your windows.

Whats important is that none have condensation on the inside.

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Eva888

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#3529118 19-Sep-2026 09:46

kiwifidget:

Our windows are the same, some get condensation on the outside and some dont.

Similar specs to your windows.

Whats important is that none have condensation on the inside.

Good to know but my avid curiosity wants to know why only some windows right next to one another and is there a cure. In our case it’s super annoying as it disrupts the view and can only be fixed by going outside in the wind with a blade.

geek3001

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#3529120 19-Sep-2026 09:50

My neighbours double-glazed windows do this in the winter on cold mornings when the dew point / relative humidity is high.

They cannot see clearly out their kitchen windows until the condensation evaporates off the outer pane of glass as it is impractical to clear the glass due to the windows being on the second floor and not easily accessible from the ground.

They have been unable to find a remedy.

k1w1k1d

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#3529124 19-Sep-2026 10:15

The outside story: External condensation with double glazing - RETROGLAZE | Double Glazing NZ Homes

Hope this explains what you are seeing. We get it on the south facing conservatory windows.

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Jase2985

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#3529176 19-Sep-2026 11:19

Eva888:

kiwifidget:

Our windows are the same, some get condensation on the outside and some dont.

Similar specs to your windows.

Whats important is that none have condensation on the inside.

Good to know but my avid curiosity wants to know why only some windows right next to one another and is there a cure. In our case it’s super annoying as it disrupts the view and can only be fixed by going outside in the wind with a blade.

slightly different air flows, temps, thermal bridging from the frames, different spacing from the frames (shims)

sidefx

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#3529178 19-Sep-2026 11:26

Eva888:

If this was the case then all the windows would have condensation on the exterior, not just a few. Many are totally clear.

Surely direction of wind\sun\shadows\temperature inside and out\etc would all affect this?

My understanding is windows are designed with various features to handle moisture (and rain, etc!) on the outside so would not worry about it TBH.

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LostBoyNZ

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#3529179 19-Sep-2026 11:29

kiwifidget:

Whats important is that none have condensation on the inside.

Yeah I'm concerned about ours, where it's appearing between the panes of glass, on all 5 windows of the bedroom and we've seen it on other windows too.

The new build is just 6 years old, and has the Residential ThermalHEART to have thermally broken joinery, the low e glazing and argon gas inside. From googling, it sounds like the gas leaking around 1% a year is normal and so the average life where the gas is still doing a good job is around 20 years. Maybe there's something wrong with the seals.

eracode

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#3529188 19-Sep-2026 12:01

sidefx:

Eva888:

If this was the case then all the windows would have condensation on the exterior, not just a few. Many are totally clear.

Surely direction of wind\sun\shadows\temperature inside and out\etc would all affect this?

My understanding is windows are designed with various features to handle moisture (and rain, etc!) on the outside so would not worry about it TBH.

My understanding is that OP is not necessarily worried from a performance point of view - it’s the disappointment and frustration of not having nice clear windows after an expensive new install and not being able to fully appreciate the view.

Sometimes I just sit and think. Other times I just sit.

sidefx

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#3529189 19-Sep-2026 12:13

eracode:

My understanding is that OP is not necessarily worried from a performance point of view - it’s the disappointment and frustration of not having nice clear windows after an expensive new install and not being able to fully appreciate the view.

Yeah fair enough. Windows are not cheap! Still considering options to replace the "classic" 70s/80s brown aluminium ones most of our house still has.

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Eva888

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#3529199 19-Sep-2026 14:05

@eracode you’ve nailed it. Windows are great but am a bit disappointed since we have a nice view and it was not something I expected to happen. I can see myself out there with a blade when it fogs up. What I couldn’t understand was that the wind was quite brisk and you would expect a drying effect not condensation.

The other interesting thing is when it rained, some windows had rain drops all the way down the glass as you would expect, but others had drops stopping in diagonal lines like stripes, looked quite strange as if the water found a barrier it would not pass - annoying the perfectionist in me. I suspect it may be because of gaps in the E coating that causes it.

@sidefx If you can do them, go ahead soon because the price is going up all the time and especially now with the war, costs will rise. Do as many as you can afford in one go to make it cheaper. Installers will get very busy soon. My guy is already inundated and I waited months to get them done after being quoted in April.

I totally regret putting mine off for so long out of fear that it would be too difficult with the structure of this place. Also regret not doing some of the others and plan to soon. They have made such a huge difference to the temperature and retain heat. Noticing we are using the heat pump far less.

Meanwhile grrr found more specs of black sealant on the carpet.

sidefx

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#3529254 19-Sep-2026 15:12

Yeah, suspect we've left it too long already. There's so many other things needed on the house that what's one more haha.

Take with a pinch of salt as this is another place that sells similar windows, but essentially these folk also reckon it's just because they're working as intended (and perhaps even "too well") similar to the take @k1w1k1d already posted.

https://www.ecowindows.co.nz/external-condensation-on-windows-why-is-it-happening

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WWHB

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#3529389 19-Sep-2026 19:21

My first answer is correct, this is a common complaint after high quality double glazing is installed. Google it and you will get loads of answers but it’s no different to dew forming on your car on colder mornings, I only get it on one side of my car but the whole car will be at the same temperature.

Saor Alba