Sounds like we could benefit from an updated DOE-2 window library based on Bruce?s observations.
As to the meaning of ?e3=.4?, per Table 7 in the DOE-2 help entry for ?WINDOW Library?:

Low-E:

A low emissivity metallic coating is applied in order to increase thermal IR reflectance. The coated surface is indicated by en = v, where n = 1 is the outside of the outer pane, n = 2 is the inside of the outer pane, etc., and v is the emissivity (see, for example, G-T-C = 2635, where e2 = 0.1 indicates a coating with an emissivity of 0.1 on surface #2).

So, ?e3=.4? describes an assembly with a low-e coating of emissivity 0.4 on the inside surface of the inner pane.
Syracuse Glass has a good list of considerations for low-e coatings and whether to have them on the #2 or #3 surface. Generally, coat the #3 surface if heat loss is the primary consideration, and the #2 surface to limit solar heat gains.
http://www.syracuseglass.com/E-DOCS/Insulating%20Glass/EDOCS/LOW-E%20Coating%20Orientation.pdf

Regards,
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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