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Community and Q&A

Glazing options for Zone 3

user-1054948 | Posted in Energy Efficiency and Durability on

We are trying to decide on window glazing options for our east facing windows in San Francisco. Our window manufacturer uses Cardinal glass and offered us two Low-e options.
Low-e 277 and Low-e 180.

If I understand the main difference is in the Solar Heat Gain – we like the idea of getting more warmth from the sun in the winter since we are always cool in San Francisco. Warmer times of the year (mostly in spring and fall) there at most one or two days a year that are too warm inside and a simple fan does the trick and never air condition. In the winter we generally heat in the AM during cold mornings that are often sunny.

Positive on the Low-e 180 is higher solar heat gain (SHGC .69 versus .41) and more clarity at night for our city view with a similar U-factor (.26 verus .25)
Negative is the 8% price premium for the Low-e180 (I guess it is used less and therefore more expensive, hard-coat verus soft-coat).

We aren’t so concerned about the additional cost, but wanted to make sure I am not missing something about the performance difference.

Full specs on the glass are here
I am looking at the first two rows under 3/4″ double pane argon-filled.

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  1. GBA Editor
    Martin Holladay | | #1

    It sounds like these windows are good candidates for high-solar-gain glazing -- as long as the windows aren't huge, and as long as you are accurately reporting the unlikelihood of your house overheating.

    Warmth in winter is certainly desirable; I like high-solar-gain glazing for east-facing windows in Vermont.

  2. user-1054948 | | #2

    Thank you. The east facing windows are large - is the concern about their size heat gain or heat loss? We aren't concerned about being too warm - the coastal fog takes care of that in the summer.

  3. GBA Editor
    Martin Holladay | | #3

    Large east-facing windows can lead to overheating on hot summer days, but if you don't have many days like that, you'll probably be fine.

  4. user-1054948 | | #4

    Thank you so very much. I can't tell you how much GBA has meant to my project. For a homeowner not in the building trade, it is so hard to get unbiased advice on green building, and GBA strikes such a reasonable tone for a "good enough" house. Everyone you talk to generally has some skin in the game, but with some GBA advice and especially the drawing sets have given me the chance to push my architect and builder much green than their general practice without resorting to fashionable "green" builders who quoted me twice the price.

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