I am fixing to build a new home with radiant slab heat.. I know how to use two inch extruded styofoam along the walls.,.. But how do you make the thermal break at the two garage door openings? My thought was to use a 2 inch trench drain, plastic if I can find it.. ... Then use styofoam under it? I figure the drain will give a slight break in conductivity... anyone have a sure fire way of doing this? Thanks

You worry about BTU loss? pipe placement? temperature of the cars tyres? are there codes that you feel you would be violating?the transition to the driveway? that is a seperate pour, macadam ,crushed stone.apply at that time according to what you are using for the driveway..might not be much more than an expansion jointmaterial.

I am purely trying to keep my heated slab from transfering heat out into the apron.. You know under the garage door,,Considering I will have an r-10 around the rest of the entire home..slab.. I would hate to think of having 20 feet just wicking in cold

I've never come up with a good insulation method for this application. However; if you just plain kept your tube away from the area near that door; say two to three feet away, you would limit heat loss out that door and I would expect comfort level in the garage would still be good. (unless you lay down right at the door).

Bill

Typcially,you would use and expansion joint at the transition from the garage slab to the apron. Although it is not a major insulator, it is effective. I would give it about an R-4. I don't know your climate because you haven't shared that with us, but, consider the concept that the short 6 or so inches of heated slab between the threshold of the garage door and the expansion joint as a miniature snow melt system. It may not be the most effective radiant heating system, but it has to be the most limited of snow melt systems.

You can do the math. Contact me bc if you want to calculate what you are up against.

good luck,

tom

Well Thanks for all the replies.. I have already had a heatloss ran on it > But just trying to only heat inside not the outside..of central Indiana

Concrete supply shops sell a 1/2" thick expansion strip material. Also they have a H shaped plastic cap for the strip, with a peel strip on top. Slip this over the top of the expansion strip material, pour the slab, then the top portion of the plastic strip pulls off. Next they have a butyl caulk that gets applied in this "space"

It seals and protects the top of the expansion strip, wears much better than just the bare edge of the strip, and allow a very flexiable "connection" between the two slabs should there be any small movement.

I suspect 1/2 foamboard could be used with this plastic cap, also.

As all the other stated, a little loss across this maybe 10 foot opening is not a big deal. Better than a frozen shut garage door

hot rod

Partly depends on whether or not you're going to have a floor drain. If you are in a snow area, when you pull your cars in over the heated slab, you'll certainly get snow melt water. If your slab is drained to the garage doors (as mine is) with no center drain, that water will run under the garage door seal and if you have your tubes in two or three feet, will probably freeze there.

I went with the tubes about 12" in from the slab/apron joint, used expansion strip as advised above, and get a nice snow/ice melt thing going on to about 6" out on the apron. This is in SE MN with plenty of snow and ice and sub zero temperatures. Eve of steel roofed building also drops snow slides on the apron. Slab setpoint is 55 degrees.

Reason to opt out of a floor drain in my case is because I also use the car area as a shop extension for larger projects (stationary power tools on casters) and like the more uniform and level floor you get without a center floor drain.

If it's nothing but car srorage, why not put in a floor drain, slop the slab to the drain, and keep your tubing back away from the apron like you suggest?

Eric,
My workshop has radiant floor heat and we did the installation as your referring to with the trench drain about a foot out from the garage door.It works very well for melting snow and keeping Ice away from the section between the floor and drain.(I have pictures somewhere,if I can find them)However it is a heatloos.

I like the mini snow melt concept. That's how I'm set up for my garage. I was planning on using 2" extruded poly beveled to a 45 degree angle where the two slabs meet but I like the way the snow melts away from the front of the garage. Winters here in Anchorage get down to thirty below occasionally but no worries......

I am curious to find out what that heat loss calculation results were, and to see how Ericjeeper resolved the heat loss under the garage door.

What is available today?

Thanks,
Mike