[Greenbuilding] Source of Combustion Air

[Steve Houlihan]

With all this talk about whether to include a basement in the building 
envelope I wonder where a furnace in the enclosed basement gets combustion 
air.  If it takes it from the conditioned space and the furnace flue 
exhausts to the outside then it creates a negative pressure in the house. 
It could get it from the outside only if it is a high efficiency furnace.

Steve