Putting a Heated Floor in a Bus (part 1)

I HATE being cold. I hate the thought of being cold. I hate getting out of bed on a cold winter morning to step on a cold floor. Even carpet can't really take the cold out of a cold floor. The most it can do is attempt to mask the cold and it doesn't do a good job of that.

So I decided to install in floor heating in the bus in an attempt to address that concern. I contacted the kind people at Pex Heating They were very helpful in getting this part of the bus build accomplished. They even designed the heating system for me free. They must have thought it was a joke. I had to submit a design request a couple times before I got a response for a heating system for a 300 square foot school bus. They're used to designing systems for houses and office complexes. So when someone emails a request for a little box of a living space, probably smaller than some of the closets in their other designs, it's understandable if they were skeptical.

They submitted their design and even contacted me by phone to see if I had any questions. Being on a budget I began ordering supplies as monies were available. I have still a few more parts to obtain before the system will be operable but I've gotten the main part, the in-floor tubing down. Here's how that went.

Step 1: Prepare Your Floor

I started by stripping the old floor completely to the metal. I treated any rust spots and coated the entire floor with Rustoleum rust inhibitor. I then continued by laying down 1/2" foil faced rigid foam insulation.

Next I began laying out the sleeper sub-sub-floor using 1" X 4" furring strips. The tubing would lay within channels.

I laid out the 1" X 4" strips with spacers to see how the channels would end up. The videos Pex Heat supplies give very detailed instructions. You want to make sure you will have a return channel without having to cross other tubing.

Being careful to round the corners where the tubing will turn.

This is the front section of the bus. Pex Heat designed the system in two zones. This is the front zone. I wanted three zones. Their design tech said because of the size of the system I'd only need two. I'm glad they knew what they were talking about.

Once you have the strips laid out you can start laying in your tubing. As you lay the tubing down it helps to anchor the turns. Otherwise if it pulls up you will find yourself short when trying to lay everything back down. They give very detailed videos on how to install it.

Step 2: Add Transfer Plate

This was an extra step that the tech at Pex Heat suggested. The heat radiated through the tubing will radiate up and out but will concentrate mainly over the tubes. Pex Heat suggested installing a metal transfer plate over the tubing under the sub-floor whereas the transfer plate would spread the heat more evenly heating the entire floor and not just in lines over the channels.

I had metal sheets taken down from the interior ceiling left over and used these for the transfer plates.

Step 3: Install Sub Flooring

You are now ready to lay down the sub floor. As you start to cover the tubing be sure to mark where the tubing is. Once you cover the tubing it is almost impossible to tell where it is. I drew lines the full length of the bus indicating where the tubing is before I began screwing the top sub-floor down. I would not screw anything within two inches of either side of the lines. If you've done construction work before the norm is to draw lines and screw along the lines. Here I had to remember to screw away from the lines.

When laying out the insulation, furring strips and tubing make sure to plan for any through the floor access that may be needed later.

Step 4: Repeat

That was the front half of the bus or the front heat zone. Now I had to repeat the entire process in the back half of the bus or zone two. The plan is to have separate heating zones controlled by separate thermostats. Each zone will have it's own dedicated circulating pump.

This process added 1-3/4" to the floor of the bus (or subtracted that much from the ceiling height inside the bus).

Step 5: Stay Tuned for Part Two

There's just short of three hundred feet of tubing running through the floor of the bus. In all I lost 1-3/4" of floor to ceiling height in the bus. 1/2" rigid foam, 3/4" furring strip and 1/2" OSB. That's a small price to pay for warmed floors.

Here is where all the tubing comes up through the floor. This will be (unlike the European version) my water closet. It will house all the water controls for the entire bus including a tankless hot water heater.

This is just the installation of the radiant tubing that runs through the floor. In a later Instructable I will complete the plumbing phase and report on how it is working.

As always, there is more to come. Check back to see how I'm doing or follow the build at leonardsteward.com and watch me finish the bus.

Thanks for looking,

Leonard