11 August 2011

Double Glazing in Canberra's new homes?

| Solacecreations
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We all know the benefits of double glazing.

Why are builders still allowed to put single glazed aluminium into new homes in Canberra?

100% of your heat escapes through a single glazed unit.

Maybe they shouldn’t put in wall or ceiling insulation either as the outcome is the same.

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I know I am digging up a really old thread but came across this comment while searching the web. It did make me stop and do further research to understand windows. However after doing this I believe this post is wrong even if it is shrouded in (incomplete) physics.

“double glazing stops heat transfer but not light transfer”

All glass stops light transfer, more specifically it blocks the wavelength of light/heat that is transmitted by the sun. The amount that is blocked is measured using the SHGC. From the WERS website the best single glazed unit has a SHGC of 0.85 – or 85% of this type (or wavelength) radiation gets through. The best double glazed unit has a SHGC of 0.69. Going with a double glazed unit will reduce the solar gain received from a north facing window.

This needs to be offset against radiant heat and its transfer through glass. This is measured by the U value. This is of course where double glazing offers a clear advantage. The lower the U value the better. Gunghalan Al this is what you are referring to in your post.

In theory a window with a SHGC of 1 and a U value of 0 would allow 100% of the solar radiation into the house but not let any radiant heat transfer in or out. Obviously this type of window doesn’t exist.

What Strine is arguing is that the loss in solar heating (SHGC fall) is not made up by the savings in radiant heat loss (U value decrease). I think part of this design also includes insulated window coverings for when the sun isn’t shining – so assumes these are shut at night reducing the heat loss and effective U value of the window & coverings. Keep in mind good window coverings are just as good as double glazing but a lot cheaper.

I don’t think it is right to say one is better in all situations. Its going to depend on the two glazing units you are comparing, the amount of sunshine, as well as the temperature differentials at different times of the year. Rick (from Strine) has run the calculations for Canberra with assumptions on the amount of sunshine etc and thinks it works. These are on his website. Clearly if you had a month of cloud his assumptions would be wrong and a double glazed unit maybe better (I havn’t run the numbers to confirm), but on average we don’t have that issue in Canberra, so on average a single glazed unit would be better using his assumptions and calcs.

The standard approach is to use the same glass throughout the house. But actually we need specific glass for specific orientations. Its never right to say one window is better for every possible situation/orientation/climate. It depends. It is a complicated area and it has been highlighted to me when trying to talk to builders and designers – because generally they don’t know and cant offer advice (which is why I am here).

Gunghalan Al, I do think its a bit rough the way you had a go a Strine without complete information – you have a useful view but I think you played the person too hard particularly when the information you used was incomplete.

And no I am not associated with him 🙂

Gungahlin Al said :

bugmenot said :

Builders also do strange things, like double-glaze only the south facing walls instead of all around.

Unfortunately that comes from certain misinformed architects, the likes of Ric Butt in particular who claim that “you don’t want double glazing on the north windows because it would stop the heat of the sun getting in” (direct quote, to me, by one of his architects). No understanding of the physics of light.

Unfortunately local architect Ric Butt (Strine) also gave the same line to Sanctuary magazine and they printed it http://www.scribd.com/doc/21370093/Sanctuary-magazine-issue-9-The-Millennium-House-Canberra-green-home-profile

I took them to task over it and they conceded that it didn’t sound right at the time but they went with it. As a result, they ran a full feature article about window types next issue, in which they corrected the error http://www.scribd.com/doc/25739197/Sanctuary-magazine-issue-10-Windows-that-work-green-home-feature-article

Just to make it clear: double glazing stops heat transfer but not light transfer. The sunlight pours through double glazing almost unencumbered, hits everything inside and is remitted into the inside airspace as long-wave infrared light = heat. This is radiant heat. This is why double glazing is no help in summer if it is in direct sunlight. The light comes in, everything gets hot, and the heat can’t get out again. You must shade all windows possible from direct summer sun. The EER rating picks this sort of thing up and penalises the rating heavily.

Back to the physics of light/heat. Heat moves from the hotter side (more energy) to the colder side (less energy – where the air molecules can move around with more elbow room and less bouncing into each other if you like). This is mostly by conductivity. If you have single skin glass the heat loss in winter is phenomenal. This is another reason why Ric Butt’s advice is so critically wrong. If it is 40 outside in summer and 20 inside, single skin glass will do a superb job of conducting that heat straight into your home – irrespective of how well shaded the window is. An improved window – as long as it is shaded – will reduce this transfer.

So what happens in some of Ric Butt’s designs is the people have their blinds all draw all day through summer living in darkness to try to compensate for the error. And they don’t get anywhere near the benefit they should from the winter solar access.

Laminated low-e is better than single skin. Double glazing is better again. DG with low-e better still. That plus with argon gas filling better still. And framing with a thermal break will also reduce some 25% heat loss that ordinary aluminium framing has. That’s either wooden frame, two-piece aluminium with a plastic bit sandwiched between, or PVC. It comes down to how much you can afford. Put money into better windows before many other essentials that can come afterwards.

Solacecreations said :

There is a comprehensive ACTPLA publication called: Building Better Homes in Canberra. This is what they say:

Winter heat loss through various glass treatments . . .

Do you realise that the figures you are quoting, as impressive as they are, do not support what you originally posted?

I’m sure you know what you meant, probably everyone here knew what you meant but what you wrote probably wasn’t what you meant to say.

Sure we could correct you but as you have obviously followed this thread and still haven’t spotted the error in what you posted, I get the feeling that attempting to explain what was wrong in the OP would be a frustrating experience.

Besides many people find it amusing to watch “experts” make asses of themselves.

Go back and really read what you originally posted. Sit and think about it, then correct and resubmit.

King_of_the_Muppets9:14 am 20 Nov 12

The EER rating is just a tool which gives a rating for the home as a whole system.

It is far from perfect but its a start. It limits very poor performing buildings but doesn’t neccessarly provide a very accurate reflection of how good a home is.

Another key item to consider is that when high spec glass is used the frame transfers more energy than the glass. If your going down this path make sure you use thermally broken aluminium at a minimum but timber and PVC are far better. There are plenty of sources which you can use to review this – I think the best is the WERS website – http://www.wers.net/ – The U and SHGC values are the values of importance – the lower the better.

Solacecreations12:42 pm 04 Nov 12

I love how you think Gunghalin Al and you clearly know what you are thinking. There are a heap of ways to get your EER to 6 without double glazing and builders and architects know the tricks. What I can’t explain to my clients is the feeling of “comfort” that a well insulated home provides. They have an even temperature, no condensation and no draughts. I have just moved from my lovely insulated home that was double glazed and had hydronic heating. I am now in a rental for 12 months that has no eaves, standard insulation, single glazed aluminium windows and ducted gas heating and cooling. I am having a massive shock to my system. The upshot is that I can see how the less fortunate people live who have purchased a standard project home.

michellecanberra1:49 pm 26 Nov 11

2604 said :

Gungahlin Al said :

At that time the “thermally improved” (read: don’t leak through gaps as much) G James frames and laminated low-e windows cost us $11K more than the standard Stegbar leak-like-a-sieve crap the building offered up.

I’m not convinced that the ROI on double glazing justifies the expense. We could pay our entire annual gas heating bill (for our 70s spec-built house with single-glazed windows and DGH) on the interest earnings from $11,000 invested in an online savings account earning 6.51%.

What you are missing is the comfort that you experience from having an insulated home. Windows need to be insulated also. Next time don’t insulate your walls either and you can save even more. I am a double glazing convert and I wouldn’t go back to single glazing

Solacecreations12:28 pm 07 Oct 11

Spectra said :

100% of your heat escapes through a single glazed unit.

The who to the what now? What in blazes are you talking about? 100% of your heat? Are you seriously suggesting that every surface in your house other than single-glazed windows is a perfect insulator? And that no air could possibly escape or enter? Geeze – I can’t help but wonder what the hell I’ve been breathing, since the oxygen should have run out ages ago.

Seriously, I know you’re truing to spruik your double glazing business under the guise of concern for the environment, but please: at least try to make your ridiculous claims sound slightly plausible.

There is a comprehensive ACTPLA publication called: Building Better Homes in Canberra. This is what they say:

Winter heat loss through various glass treatments
Unprotected single glazing 100%
Vertical or ventian blinds 100%
Unlined drapes or Holland blinds, no pelmet 92%
Heavy lined drapes, no pelmet 87%
Unlined drapes or Holland blinds, pelmets 79%
Double glazing 69%
Heavy lined drapes, pelmet 63%
Double glazing with low-e coating 57%
25mm Polystyrene shutters, good airseal 50%
Double glazing, heavy drapes, pelmets 47%
Single glazed industry typical aluminium 100%
Singe glazed thermally improved aluminium 87%
Single glazed timber or P.V.C 82%
Double glazed industry typical aluminium 72%
Double glazed thermally Improved aluminium 60%
Double glazed timber or P.V.C 54%

I hope this helps those critics of mine. I am frustrated because it is easy to get a 6 star rating in a new home through working around the glazing calculator and using different insulation etc, however, extensions seem to be more under scrutiny. I am seeing more people doing extensions that are unable to get the green tick through using single glazed aluminum windows.

You are right about the Certifier needing to make sure the calculator is correct and they approve the glazing used. If you have selected double glazing then you probably met the requirements and it wasn’t discussed.

As for being a supplier in Canberra and being able to voice my opinion – I am also a consumer and a person passionate about energy efficient homes. I am baffled why project builders don’t see the benefit of building a home that will save money and energy for clients just by using smarter products.

Our uPVC price is getting very competitive with single glazed aluminium windows, however, many builders in Canberra don’t like to use anything other than the products that they know and love. I often have clients coming into my showroom saying that their builder doesn’t believe in double glazing, energy efficient cladding, solar hot water etc etc. Having said that, there are a growing number who are green builders and open minded.

Before everyone criticises me about this, I am married to a builder so I am in the industry already.

With regards to double glazing particular parts of the home, the most important outcome is to seal your whole building envelope so that your precious heat in winter can’t escape. This is through insulating the walls, ceiling, windows and floor and sealing for draughts. If you leave some areas single glazed then it is a no brainer where your heat will go. This includes bathrooms and toilets that don’t seem as important to people.

I replaced my old windows with double-glazed windows and notice no difference in heat/cold proofing. Perhaps the quality of the double glazing in Australia is different from that overseas?

milkman said :

2604 said :

Gungahlin Al said :

At that time the “thermally improved” (read: don’t leak through gaps as much) G James frames and laminated low-e windows cost us $11K more than the standard Stegbar leak-like-a-sieve crap the building offered up.

I’m not convinced that the ROI on double glazing justifies the expense. We could pay our entire annual gas heating bill (for our 70s spec-built house with single-glazed windows and DGH) on the interest earnings from $11,000 invested in an online savings account earning 6.51%.

And this is the issue. double glazing is very expensive, and there are others ways to reduce heat loss. Having decent window coverings (e.g. curtains) goes a long way. Ceiling and wall insulation also make a heap of difference. Also, you should plan to heat only the rooms you use, and keep other doors closed. Do this things and you’ll get a good result. Double glazing is good, but it’s only part of the answer.

Double glazing is expensive and I really feel for people who can’t afford it. However, unless the curtains are open on a sunny day, you won’t get any heat from the sun to heat up any thermal mass in the house. (Even a few minutes of sun can make an extraordinary difference to heat retained in any thermal mass and the overall temperature of the house). With inefficient windows such as single glazing, any heat gained during the day is soon lost back through the windows (ie because the curtains are open). Of course if you close the curtains because it is cold and windy outside then you don’t gain the radiated heat during any sunny moments during the day.

Even on days when it doesn’t even get above 10 degrees (not taking account of wind chill), 30 minutes of sun during a day can easily get a house to well over 20 degrees and keep it there.

2604 said :

Gungahlin Al said :

At that time the “thermally improved” (read: don’t leak through gaps as much) G James frames and laminated low-e windows cost us $11K more than the standard Stegbar leak-like-a-sieve crap the building offered up.

I’m not convinced that the ROI on double glazing justifies the expense. We could pay our entire annual gas heating bill (for our 70s spec-built house with single-glazed windows and DGH) on the interest earnings from $11,000 invested in an online savings account earning 6.51%.

And this is the issue. double glazing is very expensive, and there are others ways to reduce heat loss. Having decent window coverings (e.g. curtains) goes a long way. Ceiling and wall insulation also make a heap of difference. Also, you should plan to heat only the rooms you use, and keep other doors closed. Do this things and you’ll get a good result. Double glazing is good, but it’s only part of the answer.

Gungahlin Al said :

One key downside of single or laminated glass that should be considered is that the thin layer and resulting high tempoerature gradiant across it means you get condensation – a lot of it. A problem that just doesn’t exist with DG. And if your builder uses crappy cheap MDF architraves instead of timber, you just know what that condensation is going to do!

That was one surprise aspect that we hadn’t thought of or expected with our DG. In our previous house our windows were covered in water in winter and the house felt damp from all of the condensation. (I can remember a new ACT resident once saying that they knew they were in trouble when they woke up and found ice on the inside of their windows). Our DG windows don’t get any condensation on them.

I know that a lot of people can’t afford insulating features like DG. I haven’t done the sums but, if possible, I suspect that it might work out cheaper to build a smaller house with as many energy efficient feaures as are affordable and then extend later, rather than build a bigger house initially and then later retrofit features like window frames that can accommodate IGU’s.

The other thing that we have noticed is that the benefits from a solar passive house can’t just be measured by monetary cost. For example, in winter, unless the heating is radiated any artifical heating is not likely to be as pleasant as solar radiation. Heated air which is very temporary is rapidly lost (eg, when the heating is turned off), the movement of air creates a draft which requires additional heating to compensate, heated air is uncomfortably dry and there are hot and cold pockets throughout the house. Artifical radiated heating such as in slab electric is very very expensive to run and hydronic heating is very expensive to install. Coversely, our friends are always surprised when we have to open our windows in winter to cool our house down – which increases the fresh air in our house.

Gungahlin Al said :

At that time the “thermally improved” (read: don’t leak through gaps as much) G James frames and laminated low-e windows cost us $11K more than the standard Stegbar leak-like-a-sieve crap the building offered up.

I’m not convinced that the ROI on double glazing justifies the expense. We could pay our entire annual gas heating bill (for our 70s spec-built house with single-glazed windows and DGH) on the interest earnings from $11,000 invested in an online savings account earning 6.51%.

Gungahlin Al said :

Downlights are your killers. Change the halogens for compact flouros (or LEDS if they are affordable yet – haven’t looked for a while), then also get the plastic cowls that fit over the hole. The cowls stop the draft but you can’t put them over halogens because they are too hot – they chew through enormous juice too. Once the cowls are in place you can stuff a bunch more insulation right up the them.

Ooops – the type of light I meant to describe is a “recessed light” (whatever the proper term is). I’m thinking of the type of units which take a typical light bulb, and have a metal housing up in the roof space (sorry – can’t find a good enough image to link to). Half a dozen of these leaves just as many holes in the roof insulation & hello additional heat loss. I can only assume they are relatively cheap, which is probably why the builder used them. A quick google hinted at recessed units designed to enable insulation to be installed around them.

Anyway, the reported performance difference between my “5*” and your 5.5* is fairly big…

Gungahlin Al3:03 pm 12 Aug 11

ThisIsAName said :

We are renting in one of the newer houses (2 yrs old) with a high EER, but the heat loss is absolutely shocking. The attic has plenty of insulation

Out of interest, what is your EER and heat loss in general terms? (eg. temperature drop overnight)

On paper, my place has a 5* EER, but I think the heat retention should be better (to my untrained eye). The place can be heated to ~19-20, the heating turned off, and it’ll drop to 10-11 by morning. This is only ~2-4 degrees better than a somewhat refurbished 50 year old (?) place I once rented in the inner north. I can’t find the EER, but it would be <= 3. My current place has R4 ? ceilings, R1.5 walls and single glazed aluminium windows (with pelmeted curtains or insulating blinds).

This story appeared recently on the 7:30 report, which may be relevant:
http://www.abc.net.au/7.30/content/2011/s3200765.htm

I've found gaps in the roof insulation:
* 30-40cm squares cut around the drop lights
* cutouts for fans (though the insulation is snug against at least one of the pipes)
* there is an uninsulated gap under a wooden platform that the central heater is mounted on

It'd be useful to know how much heat is lost there & if something similar to the link above is happening.

——

Gungahlin Al: you recently posted here http://the-riotact.com/8-overnight/51151 that your place only dropped to 16 overnight. What is your place rated at?

Only 5.5. But it runs only 11 degrees off east-west, every living space and bedroom is on the north side, which is pretty much a wall of glass. But there is also a large overhang to prevent midday summer sun getting in them.

The south and west sides have much smaller windows, all shaded with very little direct summer sun hitting them – will be zero when the trees get up a bit higher. No windows on the east end – garage.

It should not drop as far as 16 but I have to get some insulation around a heat transfer kit I put in to suck hot upstairs air and dump it down in the laundry/bathroom area. Just been a bit slack.

Downlights are your killers. Change the halogens for compact flouros (or LEDS if they are affordable yet – haven’t looked for a while), then also get the plastic cowls that fit over the hole. The cowls stop the draft but you can’t put them over halogens because they are too hot – they chew through enormous juice too. Once the cowls are in place you can stuff a bunch more insulation right up the them.

Get DraftStoppas to fit over your exhaust fans too – another gaping hole!
Make sure any flues (like where your kitchen exhaust goes outside) have self-closing flaps on the outside too.

matjones said :

Ceej1973 said :

KB1971 said :

On of the reasons the whole EER system is a crock…..

+1. We have double all round, and to think that one of those dual occupancies in the newer areas with hardly any nth/nth wst windows can have the same energy rating as us. Pfft.

We are renting in one of the newer houses (2 yrs old) with a high EER, but the heat loss is absolutely shocking. The attic has plenty of insulation

Out of interest, what is your EER and heat loss in general terms? (eg. temperature drop overnight)

On paper, my place has a 5* EER, but I think the heat retention should be better (to my untrained eye). The place can be heated to ~19-20, the heating turned off, and it’ll drop to 10-11 by morning. This is only ~2-4 degrees better than a somewhat refurbished 50 year old (?) place I once rented in the inner north. I can’t find the EER, but it would be <= 3. My current place has R4 ? ceilings, R1.5 walls and single glazed aluminium windows (with pelmeted curtains or insulating blinds).

This story appeared recently on the 7:30 report, which may be relevant:
http://www.abc.net.au/7.30/content/2011/s3200765.htm

I've found gaps in the roof insulation:
* 30-40cm squares cut around the drop lights
* cutouts for fans (though the insulation is snug against at least one of the pipes)
* there is an uninsulated gap under a wooden platform that the central heater is mounted on

It'd be useful to know how much heat is lost there & if something similar to the link above is happening.

——

Gungahlin Al: you recently posted here http://the-riotact.com/8-overnight/51151 that your place only dropped to 16 overnight. What is your place rated at?

Also, is it really acceptable for someone who states in their profile that they sell double-glazed windows to be starting this topic? And also spreading (apparently) false information in regards to single-glazed windows letting 100% of the heat escape?

Gungahlin Al said :

… If it is 40 outside in summer and 20 inside, single skin glass will do a superb job of conducting that heat straight into your home – irrespective of how well shaded the window is. An improved window – as long as it is shaded – will reduce this transfer.

Hmmm, that might explain why many newer houses also seem to have done away with eaves for shading in summer (because it apparently ‘looks’ nicer), yet they still get a good EER?
What’s up with that? Talk about form over function……

The short answer is that builders want to make a profit, therefore they (shock horror!) spend as little money on a house as they can get away with.

New houses are required to have a 6* EER. How this is achieved is up to the architect / EER assessor. If it is on a good aspect, it will only require single-glazing to get 6*. If not, it will likely require double-glazing, etc.

Gungahlin Al said :

So we had to compromise. At that time the “thermally improved” (read: don’t leak through gaps as much) G James frames and laminated low-e windows cost us $11K more than the standard Stegbar leak-like-a-sieve crap the building offered up.

So it’s not just me. We got cedar Stegbar windows, and right from the very first rain storm, they leaked everywhere. Still do, they are absolutely abysmal. The water in some cases is getting into the frame as well as into the house. The double glazed ones have moisture in between the panes.

They are seriously poor quality windows.

Gungahlin Al9:49 am 12 Aug 11

Innovation said :

#8 Gungahlin Al – Stunning I would never have believed it if I hadn’t read the links that you provided. I had thought that Strine was one of the leaders in environmental design. I’m now glad that we didn’t use them. Some of their clients must now be very annoyed.

I’m not sure why the 6.5 metre wide rooms are so critical. Presumably taller (or clerestory) but well shaded windows would pump solar radiation into wider rooms. Trombe style walls also bring the thermal mass up to the windows to counteract the effect of placing furniture and floor coverings in the path of sunlight.

I don’t know if things have improved but when we built our house about seven years ago we had a lot of trouble getting suitable windows. We didn’t want timber because of the higher maintenance, we couldn’t get thermally broken frames anywhere and we had trouble finding any frames that held an IGU with spacing greater than 10mm. We settled on uPVC but after they were installed we discovered the units were only 10mm.

We also had trouble glazing. Window manufacturers were pressuring us to tint North facing windows and I think they were also recommending other glazing features on the North that were counterproductive to SHGC (I can’t remember now if it was Argon gas, Low E or something else). Tripple glazing was virtually unheard of, would have been cost prohibitive and I doubt that most frames would have accommodated the thicker units.

Yes we were shopping for our house design about 4 years ago and had exactly the same problems with the local glass people. And our budget was really tight after not having any propoerty right through the property boom period. The build almost broke us. So we had to compromise. At that time the “thermally improved” (read: don’t leak through gaps as much) G James frames and laminated low-e windows cost us $11K more than the standard Stegbar leak-like-a-sieve crap the building offered up. To go DG plus low-e would have been another $10K on top of that. Everyone has to draw their own line somewhere according to their circumstances.

One key downside of single or laminated glass that should be considered is that the thin layer and resulting high tempoerature gradiant across it means you get condensation – a lot of it. A problem that just doesn’t exist with DG. And if your builder uses crappy cheap MDF architraves instead of timber, you just know what that condensation is going to do!

Disinformation9:19 am 12 Aug 11

Gungahlin Al said :

Just to make it clear: double glazing stops heat transfer but not light transfer. The sunlight pours through double glazing almost unencumbered, hits everything inside and is remitted into the inside airspace as long-wave infrared light = heat. This is radiant heat. This is why double glazing is no help in summer if it is in direct sunlight. The light comes in, everything gets hot, and the heat can’t get out again. You must shade all windows possible from direct summer sun. The EER rating picks this sort of thing up and penalises the rating heavily.

I think a better reorganisation of what you said is: Radiant energy (short wavelength) from the sun, comes through the window, and heats up the inside of the house.
This heat energy (long wavelength) in the form of hot air and other thermal conduction transfers its energy to places of less energy, at different rates depending on the difference in energy level.
Thermal barriers, such as double glazing are far more effective at slowing the heat transfer from the high concentration to the low concentration. This occurs because the convection currents that are the mechanism by which heat energy is supplied and transfered through the glass surface are prevented from involving a large volume circulating air mass.

Ceej1973 said :

KB1971 said :

On of the reasons the whole EER system is a crock…..

+1. We have double all round, and to think that one of those dual occupancies in the newer areas with hardly any nth/nth wst windows can have the same energy rating as us. Pfft.

We are renting in one of the newer houses (2 yrs old) with a high EER, but the heat loss is absolutely shocking. The attic has plenty of insulation, but the heat loss through the single pane windows & 2 patio doors in the main living area is terrible. The second the heater turns off, you can feel it. I’m highly doubting that there is any kind of insulation in the walls either.

I also feel that ALL new constructions should be required to have solar panels on the roof. It’s a no-brainer really. The only people who would be against this are the energy companies. Last thing they want is all houses producing their own electric, where would they make their profits.

Holden Caulfield said :

EvanJames said :

Holden Caulfield said :

As it happens we will be having double glazed windows, but because we want to, not because we’ve been told to.

Maybe if you hadn’t have, you would have been told to.

Nope, no reference to the type of glazing was made on our plans or building applications.

It was part of the certification process. The certifier had a glazing calculator that the new part of the building had to comply with, and to get the heat transmission target we had to upgrade the glass. The scheme is called WERS — http://www.wers.net/.

KB1971 said :

On of the reasons the whole EER system is a crock…..

+1. We have double all round, and to think that one of those dual occupancies in the newer areas with hardly any nth/nth wst windows can have the same energy rating as us. Pfft.

We all know if you put $50k of PV panels on your roof you won’t pay for electricity any more, so why isn’t everyone doing it?! (stupidity?)

Isn’t it disgusting they allow poor people to have houses built when clearly they can’t afford to ‘Have it all’. I blame under-priced and over-abundant new land…

I hate to be sarcastic, since I understand the benefits of double glazed over single, timber frame over aluminium etc – it’s just that every single aspect of building houses is going up up up and it’s just one more thing to spend another $10k + and I’m wondering how over-priced land encourages spending ever more on the house for essentially comfort features. It is unfortunate.

(I’m indirectly blaming the ACT Labor government btw)

100% of your heat escapes through a single glazed unit.

The who to the what now? What in blazes are you talking about? 100% of your heat? Are you seriously suggesting that every surface in your house other than single-glazed windows is a perfect insulator? And that no air could possibly escape or enter? Geeze – I can’t help but wonder what the hell I’ve been breathing, since the oxygen should have run out ages ago.

Seriously, I know you’re truing to spruik your double glazing business under the guise of concern for the environment, but please: at least try to make your ridiculous claims sound slightly plausible.

DeadlySchnauzer8:52 pm 11 Aug 11

I would suggest two things

1. The overall efficiency of your house in winter is driven by the net heat loss through walls, windows, floors and ceiling. The key word is *net* because it means that you can compensate for one area ( single glazed windows) by increasing insulation in another area ( ceiling ).

2. Double glazed windows are a rather costly way to reduce a relatively small amount of heat loss compared to adding more ceiling insulation and/or insulating blinds.

Hence why builders use single glazed but can still get a reasonable EER. There are many things wrong with the EER system, but this is not one of them. It’s an accurate representation of the physics in this case.

#8 Gungahlin Al – Stunning I would never have believed it if I hadn’t read the links that you provided. I had thought that Strine was one of the leaders in environmental design. I’m now glad that we didn’t use them. Some of their clients must now be very annoyed.

I’m not sure why the 6.5 metre wide rooms are so critical. Presumably taller (or clerestory) but well shaded windows would pump solar radiation into wider rooms. Trombe style walls also bring the thermal mass up to the windows to counteract the effect of placing furniture and floor coverings in the path of sunlight.

I don’t know if things have improved but when we built our house about seven years ago we had a lot of trouble getting suitable windows. We didn’t want timber because of the higher maintenance, we couldn’t get thermally broken frames anywhere and we had trouble finding any frames that held an IGU with spacing greater than 10mm. We settled on uPVC but after they were installed we discovered the units were only 10mm.

We also had trouble glazing. Window manufacturers were pressuring us to tint North facing windows and I think they were also recommending other glazing features on the North that were counterproductive to SHGC (I can’t remember now if it was Argon gas, Low E or something else). Tripple glazing was virtually unheard of, would have been cost prohibitive and I doubt that most frames would have accommodated the thicker units.

Gungahlin Al6:26 pm 11 Aug 11

bugmenot said :

Builders also do strange things, like double-glaze only the south facing walls instead of all around.

Unfortunately that comes from certain misinformed architects, the likes of Ric Butt in particular who claim that “you don’t want double glazing on the north windows because it would stop the heat of the sun getting in” (direct quote, to me, by one of his architects). No understanding of the physics of light.

Unfortunately local architect Ric Butt (Strine) also gave the same line to Sanctuary magazine and they printed it http://www.scribd.com/doc/21370093/Sanctuary-magazine-issue-9-The-Millennium-House-Canberra-green-home-profile

I took them to task over it and they conceded that it didn’t sound right at the time but they went with it. As a result, they ran a full feature article about window types next issue, in which they corrected the error http://www.scribd.com/doc/25739197/Sanctuary-magazine-issue-10-Windows-that-work-green-home-feature-article

Just to make it clear: double glazing stops heat transfer but not light transfer. The sunlight pours through double glazing almost unencumbered, hits everything inside and is remitted into the inside airspace as long-wave infrared light = heat. This is radiant heat. This is why double glazing is no help in summer if it is in direct sunlight. The light comes in, everything gets hot, and the heat can’t get out again. You must shade all windows possible from direct summer sun. The EER rating picks this sort of thing up and penalises the rating heavily.

Back to the physics of light/heat. Heat moves from the hotter side (more energy) to the colder side (less energy – where the air molecules can move around with more elbow room and less bouncing into each other if you like). This is mostly by conductivity. If you have single skin glass the heat loss in winter is phenomenal. This is another reason why Ric Butt’s advice is so critically wrong. If it is 40 outside in summer and 20 inside, single skin glass will do a superb job of conducting that heat straight into your home – irrespective of how well shaded the window is. An improved window – as long as it is shaded – will reduce this transfer.

So what happens in some of Ric Butt’s designs is the people have their blinds all draw all day through summer living in darkness to try to compensate for the error. And they don’t get anywhere near the benefit they should from the winter solar access.

Laminated low-e is better than single skin. Double glazing is better again. DG with low-e better still. That plus with argon gas filling better still. And framing with a thermal break will also reduce some 25% heat loss that ordinary aluminium framing has. That’s either wooden frame, two-piece aluminium with a plastic bit sandwiched between, or PVC. It comes down to how much you can afford. Put money into better windows before many other essentials that can come afterwards.

Doesn’t make sense here either. We are doing substantial renovations, requiring a DA (owner builder), but nowhere does it stipulate double glazing is to be used.

We also have put in double glazed windows, but they weren’t even on the submission for the DA. Perhaps it’s a builder/contractor trying to get one past you.

However, to the main concern of why builders are allowed to single-glaze… It purely comes down to builders not being physicists and having the wool pulled over their eyes by vendors and lousy EER schemes. The vendors want to sell low-E glass and films (and claim they will do the same job as double-glazing) because it’s easy. To *properly* do double-glazing takes a bit of smarts as to the application. The EER scheme doesn’t help as they can make up points with more ceiling insulation etc.

I’ve had a long-standing argument with a builder-friend as to why double-glazing works (and why low-E isn’t). You just can’t win an argument with logic when the person didn’t use logic to get themselves into that opinion in the first place.

Builders also do strange things, like double-glaze only the south facing walls instead of all around.

Holden Caulfield4:45 pm 11 Aug 11

EvanJames said :

Holden Caulfield said :

As it happens we will be having double glazed windows, but because we want to, not because we’ve been told to.

Maybe if you hadn’t have, you would have been told to.

Nope, no reference to the type of glazing was made on our plans or building applications.

Holden Caulfield said :

As it happens we will be having double glazed windows, but because we want to, not because we’ve been told to.

Maybe if you hadn’t have, you would have been told to.

Holden Caulfield3:52 pm 11 Aug 11

mikal said :

I recently did an extension, and was required by the government to put in not only double glazing, but special low-e glass as well…

Huh?

We’re part-way through some renos/extensions and will be replacing all of our windows. ACTPLA has not stipulated any requirements as to what type of glazing we use. As it happens we will be having double glazed windows, but because we want to, not because we’ve been told to.

I recently did an extension, and was required by the government to put in not only double glazing, but special low-e glass as well. Additionally, R4 for ceilings and R2 for walls are now minimum standards. So, I’m not sure what you’re talking about? Surely new buildings have to comply with the same standards (or better) than extensions?

On of the reasons the whole EER system is a crock…..

“100% of your heat escapes through a single glazed unit”.

Only if some idiot has left the single glazed unit open.

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