windows- insulating

[Tonyz]

OK another Q re building own home.... with windows and insulation value should I go double glazing or thicker single pane glass ie 8mm plus if money was no object (joke) timber frame or aliminium....
thanks for responces Tonto

[bitingmidge]

If money was no object, I would have thought you'd get better insulation from timber (aluminium is a great conductor of heat) combined with double glazing. However the figures I've just seen say otherwise:

http://www.greenhouse.gov.au/yourhome/technical/fs18c.htm

The cheap double glazing companies used to use plastic extrusions and three mm thick glass, and since the glass contribution to insulation is jigger all I would think you'd be better off with double glazing every day of the week.

http://www.aie.org.au/melb/material/resource/insul.htm


Cheers,

P

[Greg Q]

If the frame is properly constructed, the thermal bridge between panes will be minimalised. Double glazing is the go, as glass has a R value of zero. Low E glass with an inert gas is best.

[Shedhand]

OK another Q re building own home.... with windows and insulation value should I go double glazing or thicker single pane glass ie 8mm plus if money was no object (joke) timber frame or aliminium....
thanks for responces TontoI'm using Pilkington-ACI ComfortPlus Grey Tinted WIndows. They say it is the equal of double glazing.
Have a look here (http://www.pilkington.com.au/building+products/householder/performanceratings.pdf)
Cheers

[Greg Q]

I'm using Pilkington-ACI ComfortPlus Grey Tinted WIndows. They say it is the equal of double glazing.
Have a look here (http://www.pilkington.com.au/building+products/householder/performanceratings.pdf)
Cheers

How can they say that? Equivalent in what regard? Not R value, surely.

[woodbe]

Well, according to Shedhand's linked doc, they are equivalent in 'Summer Comfort', but the double glazing gets 3 ticks for winter while the Comfortplus gets only 2.

The shot with double glazing is to use a frame that does not conduct heat between inside and outside. Wood, plastic, composite wood/aluminium frames do that. There used to be a mob around called Dowell who had a very nice wood/alum frame, not sure if they are still around.

The marketing-speak on Pilkington's site is self-defeating. Every glass they make is just brilliant - how are people supposed to choose? On top of that, most builders and architects seem to be scared to specify double glazing. I can't imagine why...

woodbe.

[Greg Q]

Well, I'll make the point again that the reference books that I have give glass an R value of zero. pilkington can claim anything they want in subjective areas like 'summer comfort' (whatever the hell that means), but as you point out, every one of their products seems to be the greatest thing since...

Given the price of plate glass in this country I'm not surprised at the reluctance to double glaze. Plus, its not well understood here, and it has no WOW value. Construction costs being what they are, I imagine that DG is the first corner to be cut, then proper insulation, then adequate roof over-hangs etc etc.

[ausdesign]

Tonto, there is no single answer to your question.
The type of frame is the easier to start with, with timber generally having the best 'U' value. Aluminuim frames come as - standard; thermally improved & thermally broken with the last the better performer but expensive & fairly limited in availability.
The type of glass &/or double glazing will depend on the direction the window faces, the height to and width of eaves, overshadowing from other buildings and more.
It may be that in some areas of the home standard 3mm glass will perform ok with the addition of say 'low E' glass not improving the comfort levels enough to justify the extra cost.
With some orientation situations of the home, double glazing to say the north windows may be of huge benefit. Fitting double glazed to all windows may be throwing money away.
Just to add to the complexity, double glazed windows themselves are available in many forms with varying glass configurations to suit differing situations.
in summary - a home may have 3 or 4 different types of (windows) glazing to reach an optimum efficiency level.
Most window manufacturers now label their windows under the WERS guidelines (window energy rating system) and this can give a good starting point for your decision making.
"Windows ain't Windows Sol" - as the ad goes.

[mythagoz]

You could always go with UPVC framed windows like those sold by http://www.envirovision.com.au/. By default, they come double glazed. We bought some a few years ago to replace rotted out old timber casements and they have been great.

[Greg Q]

We started using vinyl window replacements on my parents' house in Canada 13 years ago. I was initially opposed, but I was wrong. They still look like new, and the triple glazed (required by law) are warm to the touch inside when its -10 outside. The local supplier now guarantees them for the life of the house. (!)

Greg

[woodbe]

Hi.

The issue is not about comfort level. We will all do what we can to maintain a comfort level in our homes at times of high or low temperature anyway.

The issue is about long term energy costs of running a home. There are so many advisers beating down on things we might add to our homes to improve their long term costs of ownership, that it takes a committed individual, and a lot of luck to achieve reasonable long term cost efficiency.

Everything is geared to the 'minimum', and there is a mindset in the industry that anyone who want better than the minimum is 'throwing money away'. Never mind that a house lasts for 50-100 years, and the windows you install today will probably last most of that. If you come back in 5 years and decide you want to stop throwing your heating dollars out the windows, and therefore install the double glazing you should have been advised to install in the first place, isn't the money spent on the first windows and the wasted energy for heating the sky the money you threw away?

Same story repeats for roof insulation, Hot water services, rain water tanks, weatherseals, heating and cooling systems, appliances, etc. etc. If you spend time in other countries you will see that here in Aus, we squander running costs in the name of cheap purchase and installation costs.

It's usually cheaper to do it right the first time. Perhaps it might help all the advisers if they assumed an energy cost of 10x what it is now when they start calculating the potential savings. Thinking of costs for the life of the building is a good plan too, it get's people thinking long term instead of next week.

rant over... :)

woodbe.

[ausdesign]

i beg to differ woodbe. the primary objective for the majority of home builders (owners) is the 'comfort level' followed by how do we achieve this in the most economical way.(short & long term)
i hear what your saying & the mindset 10 or 15 years ago may have been to build to the minimum, but don't put it on the advisors, put it on the consumer who drives the market place.
My point with window & glass selection is that the best type for a particular part of the home will vary from house to house, depending upon its location, orientation etc.
installing 3mm glass with a low e coating to the internal face in a bedroom facing south in victoria may provide an efficiency level of 80% for heat gain & loss. Installing a double glazed window may result in 82% efficiency.
In the same situation installing the 3mm glass to a west facing wall may be 10% efficient; installing double glazed may be 90%. If the window faces NW then the situation alters.
Just as you wouldn't put external blinds to every window of a home to keep out summer sun it is a fallacy to say one type of glazing is best and use that solely throughout the house.

"end of rant"

[bitingmidge]

i beg to differ woodbe. the primary objective for the majority of home builders (owners) is the 'comfort level' followed by how do we achieve this in the most economical way.(short & long term) I'm pleased to hear that, but it must be the consequence of living in an uncomfortagble climate. I've had one or two clients in four decades who so much as considered these aspects, (which are not optional when dealing with me :D ). Most would save the cost of insulation even!


i hear what your saying & the mindset 10 or 15 years ago may have been to build to the minimum, but don't put it on the advisors, put it on the consumer who drives the market place. Too true. It's all about what the latest glossy ad was about. Every project brief comes with a wad of clippings from New Idea, Belle, or Home Beautiful showing some exotic bath or tap or kitchen exhaust. I've never had someone come in with a picture of the worlds most efficient insulation, or a micro-climate study of their site!

My point with window & glass selection is that the best type for a particular part of the home will vary from house to house, depending upon its location, orientation etc.
As indeed will all other aspects of solar/climatic design. This is the major failure of the method of comuputation set down by the act. Unfortunately it is an improvement for 95% of all situations, the other 5% don't work.

Two of the best houses I've had typically had temperature differentials of up to 8° inside/outside, that is cooler in summer/warmer in winter, yet neither would have received a "rating" due to a lack of northern overhang in the prescribed form!

Cheers,

P (also starting to rant)
:D

[woodbe]

i beg to differ woodbe.
You're welcome to differ :)

I agree that the joe bloggs drive the market, but what sticks in my craw is the general capitulation of the designer community with joe bloggs uninformed values. Maybe you don't see it, but I have been in the situation more than once where I have had to demand that thermal measures including glazing and insulation above the 'minimum' were considered.

If an alternative is not offerred and adequately explained to joe bloggs, of course he is going to go with the cheapest option. Shying away from buying, offering or explaining superior products is like a national disease in Australia.

I agree that there is not one glazing solution for every situation, but I also have to point out that 3mm clear everywhere is not a solution either. that's what seems to be in 99% of the homes I see..:eek:

woodbe.

[MarkV]

Personally I think that you are wasting your dough on double glazing. It doesn't really get cold enough in MOST of this country to justify it. Sensible and decorative use of use awnings ( you can make em removable for winter you know ) and Pelmets on your curtains will please her indoors and really add some style to your whole decorating sheme whilst achieving significant energy savings to your heating/cooling costs. Just my two bob's worth.
Mark

[Greg Q]

Well, you can get a pretty nice double glazed picture window for much less than the price of a nice set of drapes. Also, our climate appears to be entering a different statistical set, with cooler, drier days. (Too soon to tell though). Energy costs, and energy use from non-renewables is going to be a bigger and bigger issue soon. Try retrofitting wall insulation or proper glazing, or sealing between framing and windows before plasteboards go up. A few thousand spent early, with foresight, will pay dividends down the road.

Plus, it sure as hell gets hot enough to warrant double glazing.

Greg

[MarkV]

My point was that her indoors will require drapes/ curtains anyway and you could probably kill two birds with one stone. Incidentally what would a Victorian know about Heat ?? ;)

[woodbe]

Drapes are fine. Most people open them to let light in, and to see out, at which point the energy advantages go 'out the window'.

High energy costs negate arguments about our weather not being extreme. Every bit of heating and cooling costs, and a thermally efficient home needs a lot less of it.

Greg is correct. Retrofitting any of this stuff gets expensive in a hurry, especially if you factor in the perfectly servicable but thermally useless items that are replaced in the process.

woodbe.

[Metung]

If you can accept paying a premium, then I suggest you have a look at the Rylock architectural series. They are a double glazed, timber/aluminium composite window - aluminium outside and Vic ash inside. I have just installed them throughout the house I am building and don't regret one cent of the money spent. They look absolutely fantastic. I was so taken with the timber reveals that I used 140mm framing timber so that I could preserve them. The person who did the energy rating said he was amazed by the difference they made to the overall rating of the house.

[echnidna]

My point was that her indoors will require drapes/ curtains anyway and you could probably kill two birds with one stone. Incidentally what would a Victorian know about Heat ?? ;)

Ahhh sunny ol" queensland

Sunny one day, perfect the next
(bugga the water shortages)

Great beaches,
pity bout the stingers 'n' jellyfish 'n' sharks 'n' crocs 'n' stuff

Where ya don't need heaters,
but ya gotta have air conditioning.

Yep - a real great place...................
for a winter vacation.
:D :D :D :D :D :D :D :D :D :D :D :D :D :D

btw
I'm not even a messican,
born in Ipswitch , just prefer to live in VIC.
y'know - that place that usta be called the garden state.:p

[guym]

Hi Metung,
What did you pay for the Rylock windows and what were the dimensions?



If you can accept paying a premium, then I suggest you have a look at the Rylock architectural series. They are a double glazed, timber/aluminium composite window - aluminium outside and Vic ash inside. I have just installed them throughout the house I am building and don't regret one cent of the money spent. They look absolutely fantastic. I was so taken with the timber reveals that I used 140mm framing timber so that I could preserve them. The person who did the energy rating said he was amazed by the difference they made to the overall rating of the house.

[Metung]

There were 19 windows/doors overall and I just paid the lump sum for the job so I really don't know how much each item was worth. They had prices on their items at the local display centre and a 4.5mx2.4m 4panel sliding double door was around the $4000 mark from memory and a 2.1mx1.5m 2panel sliding window was around the $1200 mark.

[Ashwood]

uPVC double glazed windows nowadays are really good. The reality of the situation is that despite all the "official" recommendations on the benefits of batts & double glazing, the majority of people still are not convinced.

I personally feel double glazed windows are the way to go. Definitely for all West facing windows in warm weather/seasons. Even for other facings in colder climates, double glazing will help lower heating costs, because the thin glass panes (esp. in older homes) in older windows transmit the cold easily (they only block draught, but just touch the windows in winter and they'll be freezing, unlike double glazed ones). But of course, budget rules, and I'd suggest prioritizing and phasing in upgrades as budget permits.

[pharmaboy2]

I personally feel double glazed windows are the way to go. Definitely for all West facing windows in warm weather/seasons..

Double glazing on west facing windows is no better than std glass, because double glazing doesnt stop radiant heat from sun on the glass getting inside the home. Worse still, as the double glazing allows the heat into the home freely via direct sunlight, it holds the heat in as the window insulates the air temp.

Double glazing for cooling purposes should either be done in concert with low e glass, external shading OR in buildings that are fully air conditioned constantly - so office buildings for example would benefit..

I think low e glass is the best of both worlds for Austrlias coastal climates because it slows heat transmission in both directions and more importantly lets less radiant heat throught from the sun. Although this woul;dnt hold for well shaded due north glazing, as these allow winter heat in as well, so double glazing would be perfect for summer shaded, winter sunlight exposed glazing.

[Ashwood]

Perhaps to elaborate further, I am referring to installing double glazing systems in the market, which you will find in the market often include various features like the double glazed sealed system, low E glass, tint, reflective coatings, sometimes inert gases in the double glaze systems.

When we looked at installing these, we were bombarded with technical performance measures (U, E, SC, SHGC) and various overall window energy/star ratings.
I'm no expert on glass, and won't even attempt to talk about the above, but list below a few links which cover these subjects, for interested readers.

http://www.wers.net/
http://www.efficientwindows.org/glazing_.cfm?id=6
http://www.socalgas.com/construction/builders/Builders%20Resource%20Guide/Window%20Energy%20Concepts.htm (http://www.socalgas.com/construction/builders/Builders%20Resource%20Guide/Window%20Energy%20Concepts.htm)
http://www.double-glazing-uk.co.uk/Low_e.asp


I'd agree with pharmaboy2 that low-E glass would be much better if a double glazing system uses it, but would add that most double glazing systems in the market would already reduce heat transmission compared to typical single glazed window systems.

I can say from our own case is that we installed double glazed window systems (slightly tinted, low E, reflective coat on some ie. Western facing) in a new part of the house, and the difference is very distinctly apparent - direct evening sun on hot days are much cooler compared to the old area with similar facing, and it also feels less freezing on cold days compared to the old area. An added benefit is that you hear much less of what is happening outside.

Ultimately, once decides what works best for ones circumstances, but hope the above info/feedback is helpful.

[woodbe]

I agree with you Ashwood. What has caused me a lot of irritation over the last few years is the requirement to understand all this stuff to save yourself from being sold a load of rubbish from people who should know better.

In a hot climate, the number one rule is to keep the sun off the glass. That goes without saying, but it is amazing to see how many new 'designer' homes there are in all parts of Australia with little or no eaves or shading of the windows.

Once we have the sun off the glass, if the climate is such that the interior of the house is still uncomfortable warm and the occupants require lower temperatures than what can be achieved via passive means (that's most of us, unfortunately) the airconditioner gets switched on, and creates a large temperature differential between inside and outside. This is the point at which insulated windows start to pay their way. The cool air inside the house is thermally isolated from the warm air outside the house because their is no direct connection between the glass cooled by the airconditioner and the glass heated by the outside air. Any single-pane glass window will act a thermal hole in the wall. Just put your hand on the window for confirmation. The same principle occurs in reverse when you heat your home in winter.

Low-e glass is a great development, but it is not an insulator. It helps to reduce transmission of heat by radiation, and it's a good option for doing _something_ about those designer houses. A better option would be to say no and find a place with some roof overhang.

woodbe.

[ausdesign]

I realise that it's a complicated subject with as many variables but -
Not everyone in Aus lives in a 'hot' climate.
Windows should be 'shaded' taking into account the climate zone and the orientation of the window.
[thats meant to be constructive not harsh]

[woodbe]

Hi Peter,

Heck yes, I was specifically talking about the hot climate scenario, and I guess I dribbled off into the cold climate scenario with the window insulation as well.

Here in Adelaide, the recommendation is to allow winter sun through north-facing windows, and shade it from all windows in summer. That's a bit hard for us, we would have to cut holes in a wall to achieve north facing windows at all...

Interestingly, even here we have substantial heating needs if we are to maintain a pleasant indoor temperature during winter, so even though we get our fair share of hot weather, we have two energy use peaks per year, and the higher one is during winter. We really have to put measures in place that accommodate both extremes. Variable shading for east and west facing glass to allow the sun in during winter, and suitable insulated windows to trap it inside once it gets there are on the agenda for us.

No harshness taken. Try harder :)

woodbe.

[release r]

g,day new here. Low e glass, been reading replies,curious to know, does any anyone know how it cuts heat transmission

maca

[ausdesign]

[in simple terms]Metal filings reflect the heat back into the room.

[totoblue]

I think it is pretty well summarised on wers.net and on http://www.greenhouse.gov.au/yourhome/technical/fs18e.htm

<table class="tablepassive" summary="" cellpadding="0" cellspacing="0"><tbody><tr valign="top"><th>CITY</th> <th>CLIMATE CLASS</th> <th>HEATING FRACTION</th> </tr> <tr> <td>
Darwin
</td> <td>
Cooling
</td> <td>
0%
</td> </tr> <tr> <td>
Brisbane
</td> <td>
Cooling
</td> <td>
19%
</td> </tr> <tr> <td>
Perth
</td> <td>
Mixed
</td> <td>
31%
</td> </tr> <tr> <td>
Sydney (Airport)
</td> <td>
Mixed
</td> <td>
57%
</td> </tr> <tr> <td>
Adelaide
</td> <td>
Mixed
</td> <td>
68%
</td> </tr> <tr> <td>
Melbourne
</td> <td>
Heating
</td> <td>
80%
</td> </tr> <tr> <td>
Canberra
</td> <td>
Heating
</td> <td>
88%
</td> </tr> <tr> <td>
Hobart
</td> <td>
Heating
</td> <td>
98%
</td></tr></tbody></table>
In a MIXED CLIMATE (temperate) the best results are obtained from windows that insulate well (low U-value), admit plenty of free solar energy (high solar heat gain coefficient) on the north during cooler months, but limit solar heat gain from the east and west (low solar heat gain coefficient). Ideally, northerly windows should be protected by correctly sized eaves. This will provide protection from summertime heat and glare while still allowing sun penetration in winter.

In a cooling climate (tropical, subtropical or hot arid) the best results are obtained from windows that limit solar heat gain on all orientations (low solar heat gain coefficient). Although the first two climates are frequently humid while the last one is not, they can all subject the home to the risk of overheating at any time of the year. Good insulation (a low U-value) is also beneficial, especially if the home is air-conditioned.

In a heating climate (alpine and cool temperate) the best results are obtained from windows that insulate well (low U-value) and admit plenty of free solar energy (high solar heat gain coefficient). In a cold region, large west-facing windows may contribute to short-term overheating in summer, but glazing with a low solar heat gain coefficient must be used with caution on the west because of the energy penalty it causes over the rest of the year.