I am designing a house Central West NSW (latitude 33.5 South) and wonder whether double glazing is worth the extra expense. This area gets hot - 40+ summers and fairly cold to zero maybe in winter so there is certainly a need to keep heat out in summer / warmth in during winter BUT isn't it true that double glazing on the north side (onto a north facing polished concrete living room / kitchen floor) would act to REDUCE the amount of heat entering on a cold winters day?
I was thinking from various readings that cold bridging - from lintels, aluminium frames, draughts from poor sealing, lack of pelmets, inadequate wall insulation - may be contributing a lot more to poor performance than single glazing.
Wanted to know people's opinion/observations on double glazing before going down that (more expensive) path.
single or double glazing for new home?
(88 posts) (24 voices)-
dubbo teacher
MemberPosted Sunday 2 May 2010 @ 4:30:38 am from IP # -
ghostgum
MemberSome rough figures:
Standard aluminium frame, single glazing, U=6
Standard aluminium frame, double glazing, U=4
Improved frame, good double glazing, U=2I've got the U=4 variety (which reduced heat loss through windows by 33%), and the windows are still responsible for over 50% of the heat loss in winter. Changing 75% of the windows to double glazing cost $10k. I'm pleased we did it.
Yes, double glazing on the north reduces heat gain in winter. Look at the SHGC (Solar Heat Gain Coefficient) for the windows. Window ratings are at
http://www.wers.net/House star ratings are calculated assuming no window coverings, for the purpose of determing if a house meets the 4/5 star minimum.
Posted Sunday 2 May 2010 @ 5:04:04 am from IP # -
dymonite69
MemberDT,
I would study this very carefully before your build. It is full of good advice on energy efficient building. If you want to ensure the DG doesn't go to waste you should attend to a range of issues beforehand including good orientation, insulation, shading and internal thermal mass.
http://www.yourhome.gov.au/technical/
In your area DG would be a reasonable thing to do.
Although it slight decreases solar heat gain, the net energy balance would still work in favour of DG considering your climate.
Posted Sunday 2 May 2010 @ 6:13:39 am from IP # -
gmccall
MemberHi DT
I have just today received a price for a Solar efficient house construction near Wagga (Coolamon) NSW
House area 226 sq m
Garage area 50 sq m
North Paving 74 sq m
Total roof area 453 sq m, light coloured colorbond
Total glass area all basic double glazed Al framed 62 sq m
All walls and roof as much insulation as possible
Ceiling space well ventilated
True North access
Approx 10 m of 400mm thick brick, concrete filled thermal mass walls (3400 bricks)
House price including paths and drive $380,000.The builder made the following comparisons with a typical construction of around 300sq m
Solar passive Standard house
Windows $20,836 $9000
Frames&Trusses $27,000 $19,000
Concrete floor $39,000 $35,000I have not yet priced timber or PVC and e glass windows as the price quoted was too see if I can afford such a house. I believe better options will be much more expensive.
I plan to put heavy drapes and pelmets on all windows and doors.
I have lived in similar house concept previously and believe the extra cost to be worth it.
The is no solar power or water in the price, provision for both in the construction.
This is my retirement house so has to have a reasonable payback and resale value.
Posted Monday 3 May 2010 @ 8:57:59 am from IP # -
DT,
Sounds to me like your climate is similar to that 'enjoyed' by gmccall in Coolamon, and therefore a similar style of building may well be helpful. Of course, it depends on what type of site you have.
You can see from the numbers in gmccall's list that the roof area is about twice the interior house area, another reason for the increased cost. On a small block there may not be space for this style of building.
The window or glass door area is also quite high (for a difficult climate) at approximately 27% of floor area, which also increases the window cost further. A 'typical' house will often have a window area of more like 15 - 20% of floor area.
The last time I was in Dubbo I was quite surprised that most newish houses looked like standard Sydney suburban places, except that they had evaporative cooling units on the roof.
I would be interested to know what the 'normal' power bills are in a 'normal' house in Dubbo's climate.
Posted Monday 3 May 2010 @ 1:32:53 pm from IP # -
dymonite69
MemberDubbo weather data:
http://www.bom.gov.au/climate/averages/tables/cw_065012.shtml
similar to Mildura:
http://www.bom.gov.au/climate/averages/tables/cw_076077.shtml
and NATHERS starbands for Mildura:
http://www.nathers.gov.au/about/pubs/starbands.pdf
show that heating/cooling
3 star (average): 256MJ/m2/year
5 star (new standard): 143
7.5 star (high efficiency): 67Posted Tuesday 4 May 2010 @ 4:25:55 am from IP # -
ptd
MemberHave you looked at R Control Structural Insulated Panels? They are manufacturing in Wagga for the first time in Australia. A home currently being built in Canberra using the panel will achieve clost to 10 star. A preliminary blower door test on the house, the doors of which were only sealed with 'packing' showed an air exchange rate of 4.2. The company who does the testing were in awe, saying that a standard Canberra home registers between 20 and 30 and a brand new home, built according to standard registers between 10 and 13. The BEST he had ever seen before was a 6 and that was in a one off sustainable building.
SIPS are used for floor, internal and external walls and the roof and require no framing. They are as structurally strong as steel and are fast to build with. They are used to build with in all climates from scientist research stations in Antarctica, to Canada and the Arizona desert.
Their website is: http://www.au.rcontrol.com
I strongly recommend you look at the site which has all technical details on it, including R Values. A thermally insulated envelope provides the most effective energy savings and the house in Canberra can be viewed. Very little heating or cooling is necessary in a house built from SIPs. It is THE product of the future, growing dramatically in use in both the USA and UK. It has been around for many years, but government mandates are forcing builders to rethink the material they build with and the cost of energy and rating attached to new homes for sale are making owners really think about the running costs of their homes and their long term value being retained.
I would build with SIPs absolutely.
R Control SIPs have an excellent reputation and the panels come in a range of sizes. The house is cut in situ and delivered ready to assemble without fill waste!! It is the lowest embodied energy product on the market too.No negatives at all. The site will confirm this.
Posted Wednesday 5 May 2010 @ 9:44:37 am from IP # -
dymonite69
MemberPre-fabricated SIPs sound very appealing in terms of quality control of insulation and weatherisation. What are the highest R-values available and at what thickness? What is the comparative cost per m2 (materials and labour) wall to brick veneer or weatherboard?
Can you affix masonry veneer to the outside? How do you prevent moisture damage to the outer skin?
Posted Wednesday 5 May 2010 @ 10:36:30 am from IP # -
ghostgum
Memberptd, we are talking about glazing, which with well insulated walls will dominate the heat loss in the building. It doesn't matter how well insulated are your walls. I've got R4 ceiling, R2 walls and most of my heat loss is through the windows.
You wrote "Their website is: http://www.au.rcontrol.com", when you should have written "My website ..." I don't mind you mentioning an energy efficient building product, but you should declare your interest in it, rather than write like a potential customer "I would build with SIP".
Sounds like a similar product to Green Energy Bricks, but done with large sheets instead of blocks.
Posted Wednesday 5 May 2010 @ 12:19:42 pm from IP # -
Hi dubbo teacher
When I researched double gazing twelve years ago, by far the best bargain was Rylock windows with concealed aluminium frames. See the letter published in Renew, Issue 66,Jan-Mar 99, p 12, and replies in subsequent issues.
I live in Manilla, NSW in a climate similar to that of Dubbo and Coolamon. These sunny places have daily temperature ranges that are extremely wide: about 16 degrees. Double glazing is essential. However, Australian climates are benign compared to those of most other continents. I doubt that more expensive options, other than low-emissivity glass, are worth while here.
I now have a lot of data on the performance of my house. All windows in living areas are double-glazed. Together with insulation, solar orientation and very high thermal mass, the double glazing brings the indoor daily temperature range down to 3.2 degrees.
I estimate that double glazing my house cost (in 1998) about $5000 more than single glazing in frames of equal quality. (Cheap frames won't do.) With heating and cooling costing me less than $20 per year for fans and blower heaters, I think I am well on the way to covering the capital costs.Posted Wednesday 2 Jun 2010 @ 5:17:05 am from IP # -
dymonite69
MemberIn order of payback time - draughtproofing, ceiling insulation, slab edge insulation, wall insulation and lastly double glazing
Catopsilia, don't tell me you don't even use wood heating in your house?
Posted Wednesday 2 Jun 2010 @ 1:10:12 pm from IP # -
No, dymonite, not using firewood was part of the motivation:
http://www.cyberspeights.com/index.php/en/sustainable-living/housing/13-comfort-in-an-unheated-solar-passive-housePosted Thursday 3 Jun 2010 @ 4:32:46 am from IP # -
dymonite69
MemberCatopsilia,
Thank you for a well documented report on the performance of your passive solar house. We need more detailed data like this.
We get a similar range for our free running internal temps. Our house is 6 deg west of north, slab only for mass (not insulated), R 3.5 ceiling, R 2.5 walls and 19% north windows (double glaze). Our winters are milder than yours but our insolation is 25% less for the winter period.
Sun makes such a big difference to how much free heating we can get.
Posted Thursday 3 Jun 2010 @ 5:13:24 am from IP # -
Thanks for the kind words, dymonite69 and Frateco.
My manuscript on the topic for "Renew" did not make it. Maybe I could have written it better.
For the time being I'm writing in a "weatherzone" Indoor Climate forum thread.Posted Friday 4 Jun 2010 @ 11:42:24 pm from IP # -
Magnetite
MemberHi guys, I manage a retrofit double glazing company in Sydney.
If you can afford it I think it is better to double glaze from the start rather than as an after thought. A good source of information is the Australian Window Association (awa.org.au) as they are impartial to suppliers.
As mentioned by Ghostgum you would want to get the type of double glazing correct for the orientation of the window. If you are building i think it woudl be important to consier awnings as these are an excellent way of shading a window in summer and allowing sun during winter.
gmccall you mention it is your retirement home adn you don't want to over capitalise. Keep in mind that even with increasing energy costs insulation is about comfort. If you plan on spending a lot of time in the home you want to be comfortable.
Posted Wednesday 9 Jun 2010 @ 2:00:26 am from IP # -
Magnetite makes an interesting point about planning to be housed comfortably in retirement.
People who commute to work do not benefit from the comfort built in to their home (always at some cost) during the time that they are out of the house. In retirement it is likely that they will be in the house during most days, for better or for worse.
A retirement complex near here was built recently in complete denial of the idea of affordable comfort. I wrote a futile letter of complaint about it. I thought it was scandalous that people with little choice in the matter should be housed in a place that would be miserable to live in if the managers should ever be forced to economise on fuel or power.Posted Wednesday 9 Jun 2010 @ 11:15:32 am from IP # -
Just to add a little to what others have said...
I have different styles of double glazing installed. All of it was retrofitted in a house that was built 25 years ago as a solar passive house. Windows are all stained timber (cedar).
On the long north facing windows, I have a special glass called starphire. The people who helped me suggested it and I am very happy with it. The glass is high transmission so that it lets a higher proportion of light in. In Winter this is ideal because it heats up my dark slate floors so that it reaches 25+ degrees and more than that in early spring. In Summer, I make sure that no direct sunlight hits the windows. This means that the double glazing works to keep the house very cool. We are talking about Canberra where it is cold in the winter and hot in summer. The heat flow for the starphire is higher than for the low-e varieties but the benefits of more energy input in winter outweighs that - IMHO.
On the south side I use the low-e glass that is setup to reduce heat flow through the glass. Again that is useful in both winter and summer.
My gas heating bill is down by 40% since double glazing but that is not the full story. On one hand I removed a slow combustion wood heater that was used 2-3 days of the week so that would mean I am no longer supplementing the gas heating with that. The other thing is that I have a solar heating panel that provides significant warmth when the sun shines. Since the double glazing I have the heavy curtains open more as well.
The gas heater is a small rinnai "room heater" that does the whole house of 3 bedrooms and large living areas.
It is pretty clear to me that there is a significant improvement I notice a much more stable overnight temperature. I measured a low overnight about 5 years ago of 3 degrees in a living area and the lowest overnight temperature there since the double glazing has been 13. I do not find the low overnight temperatures a problem because it only takes a short time to warm up with the gas heater.
I am sure that the $5-6k I spent on the double glazing will pay for itself in the next 20 years. That is not really the point. Why consume fuels to keep a house at a livable temperature when you can do better with good design and construction? I happen to think that the whole concept of "over capitalising" is a Furphy ... it is more a matter of doing what is sensible and sustainable.
The best thing of all is that I enjoy the view all year round - instead of having the curtains closed during the day for at least 5 months of the year to keep the heat in and out!
Posted Friday 2 Jul 2010 @ 4:01:45 am from IP # -
solar_star
MemberI can recommend the following (north american) book which has very detailed discussions of which kind of glass to get when you are in different heating and cooling regions. Just map the kind of climate you live in to one of their climate examples and it should give you a good idea which would be the best glazing to get.
Its quite technical but I found it very useful. If you go on amazon you do the see in side on a previous issue and see the index of what is discussed.
If you are in the Eastern Suburbs of Melbourne they have a copy in Box Hill library.
Residential Windows: A Guide to New Technology and Energy Performance [Paperback]
John Carmody (Author), Stephen Selkowitz (Author), Lisa Heschong (Author), S. Selkowitz (Author)Posted Wednesday 7 Jul 2010 @ 8:59:28 pm from IP # -
oldfossil
MemberPetacat,
We also have a solar house with 20 metres of north facing, full height single glazed cedar windows. Did you have to replace yours or were you able to just replace the glazing? I haven't been able to find out if that is do-able. Seems to me it would be ideal if it was possible to get double glazed panels with the outside pane 10mm larger all round to fit neatly in place of the old glass.Posted Wednesday 7 Jul 2010 @ 10:27:34 pm from IP # -
dymonite69
MemberPosted Thursday 8 Jul 2010 @ 2:42:38 am from IP # -
termite
MemberI'm new to this forum, so please excuse me if my comments are naive or too wordy.
My experience:
7+ years ago, I got a bank of double-glazed (thermo-sized gap, not sound) w.r.c. timber casement windows (17 panes of which 3 were fixed) down the eastern side of my house, replacing mostly fixed 3mm glass with just 2 awning windows. Didn't notice too much of a difference. It cost over $10k then.
However, that may have been swamped by the heat transfer through the southern wall of the living area (raked 2100mm at side to 3600 at peak), which was still just plain 3mm glass in oregon frames.
Finally had to change that (the oregon support beam had rotted badly), and elected for 6mm "comfort plus" single glazed glass, installed just last month. Though the place is currently rented, the chippy who installed it says there was an immediate improvement in the warmth of the place. The new wall of glass has a standard powder-coated aluminium frame (though it's white, whereas the original timber frames were mission brown). Total cost was $15k, though I get the impression the type of glass didn't add all that much to the overall cost.Posted Friday 9 Jul 2010 @ 4:57:38 am from IP # -
oldfossil,
I was able to install retrofit double glazing for most of the windows. That meant it was cheaper and kept perfectly good timber windows. What I had to replace were opening windows because they needed to be more robust. I decided to remove some of the opening windows and make them sealed (closed) to reduce leakage. I only made that decision because I am happy with the level of ventilation I have.Posted Friday 9 Jul 2010 @ 10:46:07 am from IP # -
renovatingforbaby
MemberHi everyone,
Don't be lured into a false sense of security by magnetites comments about AWA and its apparent impartiality! If a company is a member of AWA they can still rip you off and AWA wont do anything about it! We bought double glazing from a company in Sydney that we later found out imported pvc windows from China and everything went wrong that possibly could have. My advice don't trust only buy from local suppliers after you actually go to the factory and verify that it exists and that it makes windows. We got a bad quality product, made worse by incorrect installation and had to wait endlessly while being fed empty promises and had to pay additional money many times. AWA did not do anything, they didn't help at all and didn't even remove the company from membership. Just because a company is a member of AWA doesn't mean they are a reputable business - you need to examine the quality yourself.
about low-e glass...it's not all that good - our friends have it on the east and north facing area of their home and sure its better than clear glass but they are saying they should have got tinted.Posted Saturday 31 Jul 2010 @ 6:22:20 am from IP # -
dymonite69
MemberThere is more to windows than just the glass.
Frame material, construction and hardware significantly affects price and quality. None of this is assessed by WERS or AWA. The shake/rattle test is the best one.
Double glazing is after all just another piece of cheap glass.
Good shading of sun-exposed windows is better than any tint or coating that you can place on them.
Posted Saturday 31 Jul 2010 @ 1:30:55 pm from IP # -
norbert
MemberWe had double glazed 4-20-4 windows with PVC frame in two consecutive houses.As dymonite pointed out the frame is equally important. Plastic doesn't expand or shrink and doesn't conduct heat or cold. Temperature wise the frame feels the same in summer or winter. PVC frames are the most common used in countries such as Germany for the very same reason.I don't see much point in double glazing an aluminium frame achieving a max air gap of some 8mm while the frame itself gets boiling hot in summer and freezing cold in winter.It puzzles me hearing people whining about the cost of double glazed windows when they then spend $10000 on insulating curtains to keep out the cold and another $ 5000 for aircond so they don't fry to death in summer.As far as I'm concerned double glazing should be mandatory for every new house built.It reduces greenhouse gases and saves you money in the long term.It also increase the livabillity in the house by heaps. Once you had double glazing you would never go back the other way.
Posted Sunday 1 Aug 2010 @ 12:37:48 am from IP # -
dymonite69
MemberYou still can get dodgy PVC window frames that are made of inferior materials and poorly constructed.
We invested in both DG and insulating blinds! After all even triple glazed windows are less insulating than a standard insulated wall.
We did this in addition to getting the right orientation so that a sunny cold winter day keeps the house warm without any heating.
Posted Sunday 1 Aug 2010 @ 12:43:15 am from IP #
