[Greenbuilding] Solar Gain from South facing windows

[Ted Inoue]

On 6/13/07, Kat <molasses at speakeasy.net> wrote:
>
> I think - don't know for sure of course, but I think - that Ted meant
> the coating itself would have a sort of... nap... almost like
> microscopic louvers or something.  He said, "tune the coating," not
> "tune the window."


thanks,  that's correct. The way dielectric filters work is they have a
number of layers of  material, spaced appropriately to cause constructive
/destructive interference of the light waves.  If the light comes in
perpendicular to the window, the optical path length between the layers is
less than if it comes in at an angle. So the wavelength rejection /
transmission of the window varies depending on angle.

Of course, as noted, the angle changes throughout the day, so the
transmission will vary as well.

All that being said, I don't know if the dielectric coatings used on windows
are actually working in that manner. One note I saw indicated that the
coating is a thin noble metal coating and the dielectric coating is used to
allow visible light transmission.
http://www.aip.org/pt/vol-53/iss-11/captions/p29box1.html



On 6/13/2007 5:18:02 PM, Keith Winston (keith at earthsunenergy.com) wrote:
> > Well, I don't quite know how they'd "tune the window" with respect to
> > angle of incidence, especially when you really think about how windows
> > are installed and the angle of the sun throughout the day at different
> > times of day....
> >
> > Keith
>
>
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