House too warm in summer, would double glazing help?

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zyo

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#1477372 23-Jan-2016 15:37

Seems to be a lot of conflicting information here. Anyway we are starting to replace all the joinery next week and will see how it goes. We will not have thermally broken windows as the cost does not justify the benifit (we are talking about a 40% increase)

Batman

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#1477436 23-Jan-2016 18:12

I'm just going by experience. In my case, the sun enters the house all day via unobstructed ceiling to floor glass. Without double glazing it was hot, and as soon as the sun is gone the heat will vanish. Then came insulation in ceiling, after that the heat stayed all night and got cool at 5am.

Then double glazing = death by sauna.

kiwirock

685 posts

Ultimate Geek

#1477448 23-Jan-2016 18:38

zyo: ok I guess I am one of those few who have a house with lots of sun during the day.

We are currently replacing all the windows with double glazing (low-e argon filled)

Just wondering if that would help keep the house cool during summer?

Double glazing will help to cut thermal transfer of Convection heat, however unless they are tinted or filtered they will allow Infrared Rays though (the majority of radiant heat from the sun).You should ask your installer about these. However, you may not want to cut to much radiant heat out if it's available during the winter.

Ugly metal venetian blinds will also help reflect radiant heat and you can choose how much light you want let in.

Cheaper than air-con.... switch a fan on so you can feel a draft near doors or windows.

If you have a bathroom extraction fan switch it on. The bathroom one is generally higher up near the ceiling and so will help remove the hotter air inside trapped above the window and door line. I usually leave this on unless I have the air-con on during the hotter summer days. It takes the bite out of how hot the house gets especially when no one is home.

If you have a balanced air to air heat recovery system, ask an installer for a new switch that allows you to only turn the extraction side on.

Cheers.

k1w1k1d

1519 posts

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#1477467 23-Jan-2016 20:12

Our 1950's red brick house has heaps of single glazed aluminium framed windows facing north and no wall insulation. Ceiling has two layers of R1.8 Terra Lana insulation plus the original shrunken Batts.

We have white metal Venetian blinds. The curtains are fairly thick and also have a separate three layer block out lining material behind them.

We leave all the Venetians and curtains shut on hot sunny days. Rooms stay cool and dark.

Jase2985

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#1477565 23-Jan-2016 21:15

joker97: I'm just going by experience. In my case, the sun enters the house all day via unobstructed ceiling to floor glass. Without double glazing it was hot, and as soon as the sun is gone the heat will vanish. Then came insulation in ceiling, after that the heat stayed all night and got cool at 5am.

Then double glazing = death by sauna.

your situation sounds more like poor planning/design/placement of the floor to ceiling windows than anything else

Jeeves

301 posts

Ultimate Geek

#1478088 25-Jan-2016 10:50

Replacing your windows with double glazing will slightly reduce solar gain due to the sunlight having to travel through 2 panes of glass and some gas. But it won't be a huge amount really.

Double glazing will only reduce your house's internal temperature IF the outside ambient temperature is significantly hotter than the interior. Single pane windows will leak the hot air into the house, and allow the cooler inside air out (Exactly the reverse as in winter when single pane glass lets the cold in and the hot out).

You say your house is well insulated already - do you have any cooling devices in the house (Eg: heat pump/AC unit)? If so, the double glazing should make their life a little easier.

You also say that you would rather not close the curtains - well your choice but assuming their thermal curtains with a reflective (Shiny or white) backing - then closing them will make a huge difference as they will reflect a lot of the heat back outside again.

As everyone else said - the best way to keep the house cool is to shade it where possible.

As an interesting comparison - I took these thermal images yesterday of my house. The wall on the right is west facing and catches all the sun from ~12pm onwards. This is what solar gain looks like. (And yes.. it's a very hot house - especially in the kitchen which is above this wall).

zyo

513 posts

Ultimate Geek

#1478120 25-Jan-2016 11:18

Jeeves:

Replacing your windows with double glazing will slightly reduce solar gain due to the sunlight having to travel through 2 panes of glass and some gas. But it won't be a huge amount really.

Double glazing will only reduce your house's internal temperature IF the outside ambient temperature is significantly hotter than the interior. Single pane windows will leak the hot air into the house, and allow the cooler inside air out (Exactly the reverse as in winter when single pane glass lets the cold in and the hot out).

You say your house is well insulated already - do you have any cooling devices in the house (Eg: heat pump/AC unit)? If so, the double glazing should make their life a little easier.

You also say that you would rather not close the curtains - well your choice but assuming their thermal curtains with a reflective (Shiny or white) backing - then closing them will make a huge difference as they will reflect a lot of the heat back outside again.

As everyone else said - the best way to keep the house cool is to shade it where possible.

As an interesting comparison - I took these thermal images yesterday of my house. The wall on the right is west facing and catches all the sun from ~12pm onwards. This is what solar gain looks like. (And yes.. it's a very hot house - especially in the kitchen which is above this wall).

We are starting to replace the windows today. We do have multiple air-cons in the house (one ducted and one split)

Dinning area got vertical blinds which I will close off during the day, otherwise the timber floor is starting to shrink under the heat.

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RUKI

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#1478161 25-Jan-2016 12:25

Windows in New Zealand have wooden or aluminium frames.

Double glazed windows marketed by some are made with plastic frames. They may tell you that that plastic is UV resistant. You can't check that. One company who was installing plastic windows in Auckland with double glazing is no longer on the market.

I had made in Germany triple glazing in Moscow. Although UV there is quite low and I could rarely see the sun - some elements of those plastic windows deteriorated in few years significantly.

So I would stay away from any plastic frame. If they offer aluminium frame - then it is OK.

As for your question - ventilation is important - hence having windows open is important. If you keep them closed - then as you have already been advised - double glazing may not protect you from the heat build-up inside. You'll find that mold may spread as double glazing seals it tight..

zyo

513 posts

Ultimate Geek

#1479531 27-Jan-2016 07:11

In hindsight we should have gone with a tinted float glass rather than clear ones....

Jaxson

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#1479616 27-Jan-2016 09:17

Funny seeing those thermal shots above. I tested laying a foam mat up against the house wall yesterday, underneath my daughters room windows. Massive difference just by shading the bricks. A brick house acts as a giant thermal mass, storing and retaining the suns heat well into the night.

The heat comes from the sun. Doing all that you can to keep that off your house will have the biggest impact. Insulation slows the transfer of heat, but stopping it in the first place is usually more effective. Curtains, blinds, trees, reflective tint etc are all more directly targeted than double glazing.

bfginger

1267 posts

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#1480278 27-Jan-2016 22:17

What double glazing does in summer will depend on many factors like glass specifications, shading, climate, ventilation and climate control. It could make a house cooler but it could make another house warmer.

If household humidity is at the levels it should be we shouldn't see heavy condensation on single glazed glass and solid aluminium unless there's a really large temperature difference between inside and out. Most houses in New Zealand have too much humidity indoors and while better windows may help they aren't a solution by themselves most of the time.

Some companies are going to treat thermally broken aluminium as a premium product and put much larger margins on it. Others have bought it at less than a 40% increase over unbroken aluminium.

Each company selling PVC windows in New Zealand imports from an OEM that should be named on their website which allows further verification of specifications. PVC windows without UV stabilisation would have to be replaced after little more than a decade. It has happened in the past.

pctek

807 posts

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#1483622 2-Feb-2016 15:06

I've tried the film - fail.

Tried pulling the curtains - fail.

what worked - planted a grapevine in front of the deck - this is north facing and in front of lounge.

It made an enormous difference once it grew. Cool and pleasant inside now, and there are no leaves in winter when you actually want the sun in there.

Doesn't have to be a grape - something that drops leaves in winter...vine, tree, whatever.

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