HVAC questions
 

Three questions: 1) installing a bathroom exhaust fan in my basement
and *think* I remember hearing that the outside exhaust vent needs to
be 4" horizontally from the nearest window. Unfortunately I only have
7 feet of space between my windows, and 7 feet between one of those
windows and my kitchen sliding glass door. Am I remembering this
requirement right, and if so, is there anything I can do - such as
install a diverter to force the exhaust air downward? Does the
kitchen sliding glass door count as a "window"? I can't really go any
other direction since this is a townhouse with neighbors on either
side and the fourth wall of the basement is the garage. Any chance an
inspector would let me get away with 3.5 feet on each side? 2) for
extending duct runs to heat the basement is the flexible metal ducting
material as good as the ridgid tin? I'll have a few runs that have
multiple 90 degree bends, so the flexible would just be way easier for
those (which will only be about 10 feet in length). 3) Do I need to
be worried about return air lines AND combustion air calculations? I
had done the combustion air calcs and had planned to just connect the
mechanical room to the rest of the finished basement with two grates
exceeding the requirement, but now I'm thinking if I add 3 heat supply
lines at 6" each, I'll need to add a return air grate/duct to the
return air line of about 10" diameter. Do I really need to do the
return air for this (I ask because the permit was issued without any
note regarding return air)..

Thanks so much.

HVAC questions