Glazing factor

http://www.engexp.com/exos/widgets.cfm?selection=78

http://www.reallifeleed.com/2008/06/visible-transmittance-rules-of-thumb.html

http://www.efficientwindows.org/lightview.cfm

http://docs.autodesk.com/GBS/4.2UX/ENU/GBS%20User%20Documentation/index.html?url=WS73099cc142f48755-385a98b0121d1bb015f-1443.htm,topicNumber=d0e2860