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/yourhom...ical/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 Tonto

I'm using Pilkington-ACI ComfortPlus Grey Tinted WIndows. They say it is the equal of double glazing.
Have a look here
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
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 ). 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)

[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