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Window coatings and solar gain

spenceday | Posted in General Questions on

I’ve got a big window unit I’m replacing. It is 120×66 RO, picture window with 24″ casement flankers. I’m set on a Kolbe fiberglass unit to match the rest of a larger order.
It is located in a north facing covered porch and will never see any sunlight.
As I’m looking at the order specs I question if I should spec this unit as Solar Gain Low-E coating vs the normal Solar Low-E coating to gear the unit toward winter heat retention vs trying to reduce nonexistant incoming solar radiation?

Located in the north part of Zone 4A. Kansas City

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  1. Expert Member
    Michael Maines | | #1

    Spenceday, if it won't see sunlight I would go with whatever they offer for low U-value while maintaining a similar VT (and CRI, if available) as your other windows. That will probably mean a low SHGC but it varies. Maybe someone else will weigh in with specific coating suggestions.

    1. spenceday | | #4

      Thanks. I’m pouring into the table from manufacturer now

  2. tommay | | #2

    If it's a north side window I would want to get as much gain as I could whether it be light or heat rather than trying to reflect it. A simple shade, blind or curtain may make up for the extra cost if you are concerned about heat gain in the summer.

    1. spenceday | | #3

      That’s how I’m leaning. I’m concerned about balancing efficiency. The window will never see sunlight so I’m not necessarily worried about heat gain from summer sun and most of the day a shade is closed for privacy.

  3. Expert Member
    BILL WICHERS | | #5

    Cardinals loE 180 is my favorite for Windows like this. It’s a good balance of VT to other properties for a window that doesn’t have to deal with solar gain.

    Note that if you mix aggressive and non-aggressive coatings (like the loE 180) near each other you will have noticeably different visual tints to the windows when looking through them, or from outside. Try to place different windows so that visual differences won’t be obvious from either inside or outside your home.


    1. spenceday | | #6

      Thanks. The coating I’m considering actually is Cardinal’s loE-180 and it is the only window on that section of house.

      1. Expert Member
        BILL WICHERS | | #7

        You might want to consider i89 too for a bit better U value. It may not be worth it on a full-width triple pane, but on a double pane window it makes sense.


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