Spacing 3/4" for Snowmelt

Temblor

Sorry double post

installing Snow melt in North Seattle area using 3/4" Uponor Hepex.



9x24 (216 sq ft) basement garage driveway (Medium grade with channel drain at bottom)



4" Concrete



Using 2" rigid insulation under and around perimeter. 



Manual timer system.



I have a 230' of 3/4" existing material I am hoping to use. So I am

considering putting the heat exchanger near garage (which is about 35'

from boiler)



So I will have to insulate the 35' run?



My main question is:



Would this be a sufficient amount of pipe? Can I use 12" spacing  O.C.?



Thanks in advance!