faced with a similar dilemma we were told that double glazing could not be made with small panes (and we wanted simple cross bars not colonials) unless we were prepared for about quadruple the basic price so we chose single panes rather than the stick on bars...what about having the colonials in the primary windows and single panes in the others?

What performance is more applicable for your climate? Double glazing will perform significantly better than single glazed whatever in regards to heat loss. You can't beat the air gap factor if you're trying to keep avoid heat loss. Yes there are "Low E" single glazed products such as viridian Comfort Plus which depending upon which side of the glass the absorption coating is placed it will perform in different ways, but bear in mind that since it also will reduce heat gain in winter it can actually work against passive solar building performance if not properly applied. In other words, it's not a "cheap" replacement for double glazing. In Victoria, we generally spec standard double glazing and use external controls such as blinds to mitigate heat gain issues in summer. Thermal Performance Specialists such as an Energy Raters understand the technical nitty gritty around this issue the best, and always good to seek their expert advice when applicable.

Ruth, Supply cost will vary greatly depending the following factors: - Window/Door sizes, if not standard then costs may increase dramatically. - Type of double glazed unit, thickness of the glass, if it has any coating, gas infilled. - Type of windows/doors such as casement/sliding and so on. - Thickness of the aluminium. - Hardware (hinges, runners, handles & locks). - If the site has a wind rating requirement as part of the building code. - If you are in a rural area then this could have a bearing on cost. - The scale of your project; the larger the supply the lower the sqm cost. - The supplier. I don't know much about uPVC, but would expect this to be cheaper than a thermally broken aluminium window. The price for a particular unit may vary considerably, whereby a small 1200 x 500 mm window will be more per sqm than a 3200 x 2400 sliding door. So difficult to provide anything other than a very rough estimate. Suggest you budget at $350/sqm for supply only. If you have not done so already, then take a look at the Australian Window Association website and presuming your desire for a thermally efficient house, review products under the 'WERS' (Window Energy Rating Scheme) section. Recommended that you use a supplier that has had their product WERS accredited. Hope the above get you started. Good luck.

The principle of both is sound, pardon the pun. The secret is no air gaps, so heavy curtains that touch the walls and floor on all edges of window will provide some effect, I had a friend attached Perspex panels to his windows below bench height, both for sound and to stop kids going through them.