Hi,
90.1-2007 confuses me a little.
Our project (4 story, 9000 m²/90000 ft²) is located in climate zone 1b. The proposed building is heated by an electrical heatpump. There is no fossil fuel source.

Is the baseline system system 5 or system 6? I would chose system 6 "electric resisstance". Right?

The other point is, that G3.1.2.6 Economizer requests one for system 3-8. Table G3.1.2.6A recommends no economizer for climate zone 1 b. Table G3.1.2.6B instead list a shut-off-temperature.
Do I need to model an economizer?
Probably there is an error in the table, because all climate zones in table A are moist (a) and all climate zone in table B are either dry (b) or marine (c).

Thanks a lot!

Johannes