Selecting the proper windows was a pretty interesting task. When we first started in our planning stage many months ago, we got a price on run-of-the-mill tan vinyl windows, double paned. We thought this was a good plan to use as a base-line to assess for budgeting. Those windows were about $16,500 before taxes. But the type of house we’re building really required triple-glazed windows to achieve the efficiencies we’re after. So we then explored a new triple-paned vinyl window from the same manufacturer. That price came in at about $23,000 before taxes. These windows were pretty nice, to tell you the truth, however, the manufacturer did not offer ‘glass tuning’.
What is glass tuning you ask? Well, for passive solar performance, and to maximize solar gain from south facing windows, not all glass is created equal. First of all, most window glass contains a lot of iron. Iron-free glass increases your solar gain by about 10%. The other big issue is the coatings that get applied to increase U value (or R-value) on glass. Those coatings and gas fills are really effective for north, east and west windows, but they rob up to 40% of your solar gain.
The only window manufacturers that I know of in Canada that will allow you to tune your windows are the high-end fiberglass window folks. We will have triple-glazed windows on all sides, and the south windows are tuned for maiximum solar gain – even though they have a little less insulation value. This is because they let in far more solar heat – the net result is that we gain a lot more energy than we lose with them. And they are still over 2x more insulative than double-paned windows. Our E-W and north windows will have all the fancy coating to keep heat out in summer and in for the winter – and are nearly 3x more insulative than double-paned. The windows are rated at about R5.5, while typical double-pane are about R2, and very leaky.
Fiberglass windows are the best of the best – strong, paintable in any colour, and very efficient. They also have the least embodied energy and are completely recyclable at the end of their life cycle, and are known to last 2x as long as a vinyl window. We approached three well reputed makers here in Ontario and eventually received quotes from two (one maker ignored us despite three telephone conversations – so we eventually ignored them back). Both companies have excellent reputations online and in building forums, and both makers provided excellent service and answered a million questions. In the end, we decided on one manufacturer based on cost savings. It was kind of a hard decision because there were elements we like about both. The end cost is a little over $25,000 – which isn’t much more than the sort-of comparable vinyl product. We’re very happy!!