I have several questions regarding my Botched HVAC install in NY House is 3500sq ft using 2 gas fired Johnsons Control units - Luxaire 1600csn, 100,000btu 80% efficient - Model# TG8S100C16MP11A. 4ton on first floor and 3ton on second floor - 10 supply lines with (1)6" and (1)8" round return lines

Can R-4.2 Flex Duct be installed in over 15' length?

What is the max length for Flex duct install in one straight line (one connection)?

Can R-4.2 flex duct be used in unconditioned spaces or must R-8 be used (NY area)?

Should flex duct lay on the floor in crawl space running approx 20+' - see pic: http://my.pogoplug.com/share/AmnWTEA9nwKoH-FMcI_HGg/ and see pic here http://my.pogoplug.com/share/5INOBdFUTUgdpqdefGdYCg/.

Should flex duct be installed at the side of HVAC unit - see Pic: http://my.pogoplug.com/share/OouRNHRRi2DJOA1E0CHnaw/

Should Flex duct be installed at elbow (if so under what condition) - see pic: http://my.pogoplug.com/share/o3q8Q65Bqh9FCUgeXwCxWQ/

I have a 4Ton unit with 9-6" supply lines and only 2-8" Round Returns going back to the unit. Is this sufficient?

How much additional Return is needed for this unit or how big must the 2 round returns be (diameter)?

What damage can the lack of adequate returns cause to the unit?

How do you calculate amount of CFM per room (is it 1 CFM p/sq ft)?

Is there a tool to measure amount of inadequate airflow exiting into a room?

Also looking for a good energy auditor or looking to talk to someone that can offer some good repair advice. email nerpny@gmail.com

Many Thanks