Hi
I am looking at putting a small radiant heat system under the concrete floor in my garage
I live about 1 hour north of Detroit Michigan so great lakes area of Ontario
Garage is 28x28 foot dimensions attached to house fully on one side.
2x 9x8 overhead doors and relatively high ceiling facing South West so the doors do provide some radiant heat through them today.
Questions I have are:
Can I bury the perimeter insulation on the inside of the garage footings rather than outside as garage is now 20 years in place but no floor yet. Outside escavation is very difficult now as drive way and parking area on two sides and wooden deck across the back.
Since the garage is attached considering putting the heat source in the basement of the house. I have the space and a logical location. (Where my old well pump and storage tank are) Likely a Propane or electric fired hot water heater. (No natural gas where I am in out in the country) Will I have head issues because of the elevation difference between basement and garage floor?
I would likely mount the manifold inside the garage space
What size and type of tubing should I use for this type of application? Is pex the best?
I would like to have a cement contractor do the grade leveling and then install the under slab insulation myself and the tubing
Trying to keep cost down as the better half is wondering why I need the heat out there!
Thanks
Rob M 

there are no head issues in a closed system. falling water pulls up rising water.

if you trace a line from your slab to the outside, it must pass insulation before it gets there no matter how you trace the path. if that insulation is inside the footers, no problem, as long as it's full coverage. garage doors are a tough detail though.

what is your existing heating system?

Can I bury the perimeter insulation on the inside of the garage footings rather than outside as garage is now 20 years in place but no floor yet. Outside escavation is very difficult now as drive way and parking area on two sides and wooden deck across the back.

You are leaving a cold zone under the footingwhich and with ground water under the perimeter insulation puts you in danger of water migrating under the footing, freezing & lifting footings I would not do it.

Since the garage is attached considering putting the heat source in the basement of the house. I have the space and a logical location. (Where my old well pump and storage tank are) Likely a Propane or electric fired hot water heater. (No natural gas where I am in out in the country) Will I have head issues because of the elevation difference between basement and garage floor?

Propane is expensive - are your walls & doors well insulated?

Heated garage is nice comfort but corrosion kills your vecheicles

Radiant is slow to react so you must heat all the time . I don't know your usage plan but I would not consider this a good application for radiant floor heat. Take a look at infra red propane overhead heaters fast heat up economic as air is not heated directly only objects Can be zoned for all heat in one working area



I would likely mount the manifold inside the garage space
What size and type of tubing should I use for this type of application? Is pex the best?
I would like to have a cement contractor do the grade leveling and then install the under slab insulation myself and the tubing