gas hw htr for bb

jersey devil

I am a contractor who got stuck with a family deal.they are installing a 20 x 20 sunroom with 3ft knee wall on all 3 sides .4th side against house with 6ft door way no door.I know i know tried to explain but.I will be installing a mitsu ductless hung over door .2 ton hpump.would love to go larger but price 21/2 x for 3 ton go figure.I wanted to run a bboard loop around perimeter we live in ne us.Can i use a hw heater as my source - gas.Any creative solutions would be much appreciated.Now i know why sunroom installer recommends to use your own hvac guy.youll be married to this thing.and yes radiant is out due to mfg insul floor and hieght of floor.