radiant heating design for 2-car detached garage

Al Letellier_9

We did a similar project last fall and it was more cost effective to use a new heat source in the garage. With that small a load, and with glycol (use it in this application) it simply was less expensive to do it that way. With gas available, there is a multitude of boiler options for you to consider.

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David Balaj

radiant heating

Hi Everyone,

I am in the Real Estate business in and around NYC and i am familiar steam systems. I am have been following a lot of good information on this site and started reading Dan's book "Lost art of Steam..." My question is regarding a home project, where i am renovating the garage and want to install radiant heating in the new concrete. Based on the parameters which i will further detail below, what is a better design, a stand alone system with separate heat source located within the garage or tap into the exisitng steam boiler within the house? I am thinking of tapping into the exisitng home boiler because space is an issue in the garage. Hopefully i can provide enough specific detail below to get helpful feedback. I apologize for my inexperiance, but the very informative and knowledgeable people on this site is VERY MUCH appreciated. So onward...
The Garage:
a) its a detached 2 car garage
b) new slab on grade will be 5-6" thick, area= approxiamtely 400 sq ft
c) garage will be insulated R-19 in the ceiling rafters; R-13-15 in the 3 exterior walls; garage doors are 8' wide by 7' high 2" thick insulated.
d) no windows in the garage
e) 1" natural gas line feeds the garage
f) radiant system will run with glycol
The House:
a) house is a 90-100' run to the existing steam boiler
b) Boiler is a old Arcoliner with a Beckett #2 oil burner with 1.25 nozzle (i am still trying to get specs on boiler and will post later)
c) Boiler has a tankless coil (currently not in use because i installed domestic nat. gas hot water heater for hot water)
d) oil tank size that feeds burner is 275 gal.

So the main question is: should use a point of use heat source within the garage to heat slab, or will it be more efficient and cost effective to run a main supply and return under ground from garage to the steam boiler tapping into either the tankless coil or heat exchanger as i will run glycol in the radiant system.

Any advice, feedback, or constructive criticism (my thinking may be way off on these methods) would be very helpful...