We ultimately choose above the subfloor in floor heat. This is what the final install will look like. Over this heat system, we will place 1/8" thick underlayment plywood, followed by flooring. The heated tubes will be within 1/2" of the bottom of Mom's feet!

We choose this method because it will allow us to run the boiler temperature much lower, resulting in lower heating bills. And because we are putting a heat system in so late in the game, this was actually one of the easiest methods. It's always easier to work on the floor as opposed to over your head on a ladder.

As you recommended, we worked with Radiantec to have a DIY kit sent up to us. We sent them a floor plan and they sent us a diagram of the tubing layout and the parts and pieces to hook it all up to a boiler system.

Because we have only about an inch to work with, we can't pour concrete or gypcrete on the floor, as some installations do. So we are filling the gaps between the pipes with 3/4" plywood.

We've gotta rip 50 sheets into strips 10" and 4" wide. 50 sheets. Of 3/4" plywood. Each weighing oh about 60 pounds.

We could run the 50 sheets each 5 times through the tablesaw. That's about 15,000 pounds of plywood being pushed through a tablesaw. Anyone eat their Wheaties today?

The Ram had a better idea. Why not run the 10 pound circular saw through multiple sheets of plywood at once?

We have a Kreg Rip Cut (awesome tool BTW!) and we just set it to the width needed for ripping the plywood ...

And kept on ripping.

John and Junior are helping us out (something about making a Mother's Day moving date has us begging for help) and did most of the ripping. The plies of plywood strips piled up, and the sawdust had to be shoveled up at the end of the day.

Most strips are ripped for 10" spacings (9 1/4" widths) but 4" strips are cut as well.

In the rooms, the 4" strips are used to picture frame the walls. This enables the heat transfer plates to sit off the wall.

Once the rooms are picture framed, we do a quick layout with chalk lines.

And then the 9 1/4" strips are cut down to length.

And layed in the room.

Then you just load up with screws ...

After we got into the groove of things - as in using plywood spacers in the grooves - things started going pretty fast.

We found it was better to use the spacers to line up the strips than keeping in line with chalk lines. Our big worry is the spacing would be too tight to fit the pipe.

Noticed the square ends that we leave open on every other row?

These are for the 180 degree bends where the pipes loop back around to the next row.

On some rows, we'll need to make a 90 at the ends, for transitioning between rooms or back to the main manifold.

We used a jigsaw to cut out a pattern of an arched 90 degree turn.

And then screwed those down.  We save the scrap piece for filling in the void on the end.

You have to be careful with tubing to not bend too sharply or it will kink and eventually leak.  So in a few spots, we did have to do some fancy cutting, like this sharp 90 near the stairs.

But for the most part, it's just long strips.

Attaching the plywood spacers to the floors was actually pretty easy and went fast.  Once one side was done, the other was a mirrored copy, so we could reference the finished side when doing the unfinished side.

Here's our first room done!

Once the plywood spacers are screwed down to the subfloor, we'll just need to add the heat transfer plates and piping, and then hook it all up to the boiler to be done with the heat system!  We can't wait to see how this heat system performs.

So what do you think?  Did we make the right decision with radiant heat above the floor? Have you installed radiant heat?  Did you do anything different?

Thanks again for helping us out on this one!