What windows would you recommend that maximize passive solar but minimize heat loss?
GBA Editor
| Posted in Green Products and Materials on
The standard low-e windows (eg Pella, Anderson, Marvin) on the market now do not appear to allow much solar gain in the winter.
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You're right. The US window industry has conspired with the federal government against passive solar fenestration. The 2009/2010 federal energy efficiency tax credits require that windows have a SHGC of 0.30 or less. Canadian manufacturers, such as Thermotech and Fibertech, as well as some high end US makers as Accurate-Dorwin and Serious Window offer better glazing options. Thermotech seems to be the leader at this point, and they us pultruded fiberglass frames which offer many advantages over other materials.
Suzy,
Two good glazing options are Pilkington LOF Energy Advantage and Cardinal LoE-178. These are high-solar-gain glazings with a relatively low U-factor. If you can find a window manufacturer that understands glazing, ask if these glazing options are available.
Unfortunately, most American window manufacturers have chosen to abandon the market for high-solar-gain glazing. To learn more, read
https://www.greenbuildingadvisor.com/blogs/dept/musings/high-solar-gain-glazing
In general, Canadian window manufacturers do a better job with glazing options than U.S. manufacturers.
Hi,
Cardinal has upgraded their LoE-178 to LoE-179. You can specify Cardinal or Pilkington glazings from most sizable window manufacturers and some smaller ones. Marvin ( and I believe Pella too) will use Cardinal glazing in most of their windows even though it's not their standard glazing. Ask your local distributor and if they don't know off-hand they can check with their manufacturer contact or you can call the manufacturer's tech assistance directly.
In our experience (using Marvin windows) the Cardinal glass increases unit price about 6% from their standard glass (with not much change in U value and nearly double SHGC).
You'll also want to specify the surface on which to apply the low e coating - on a double pane unit, this would be surface #3 (the internal side of the interior pane) for maximum solar heat gain. So tell your salesperson you want whatever window model you've chosen with whatever glazing you've chosen (e.g.: "Cardinal LoE-179 #3"). Hope that helps.
Custom glazing, though, is available only on top of the line windows. The base-line models, like Pella Proline, come with one choice of glazing.
It would be nice if someone would offer Cardinal 179 for the everyman.