I am thinking about adding in-floor radiant heat. I have ordered a new wood fired, outside boiler. I am adding a heat exchanger to my forced air furnace, but I want to add floor heat to my garage. Can I cut out cement grooves every 18-24 inches and lay the "pex" tubing and re-cement, or do I need to take out the whole garage floor and start from new? I am trying to save some money by retrofitting, but I am not sure if that is possible or even feasible.

Cutting grooves wioll not work as well as you might picture. Your groove will not be arge enough for the tubing so you need two grooves and chisel out betwee, very very labor intensive. Riping out the floor is an expensive option but can you pour a 2-3" floor on top of the current garage?

Or you could use an electric wire to heat (instead of pex) - would still require an overpour but only 1" at most.

If there is no problem then perhaps you can install all your piping on top of the floor and then raise the floor about 3". This would allow you to put a small insulative sub lining between the pipes and the old floor then cover the floor with new concrete and you will have a new floor without having to dig or make a big mess. I would suggest if you are doing a garage that you go with electric heating as water will freeze if the system is turned off for some time. Hope this helps.

Anybody notice that the poster hasn't been here for two weeks?