Our Straw House


House - Heating System

October - November 2009

The plan all along has been to have a radiant floor heating system. Since we didn't have a basement and had a humungous concerte slab, the idea of a radiant system made the most sense. The question was, other than the sun what do we use to warm the slab?

Since we have 50 acres of property and most of it is open pasture, we had settled on a horizontal, closed-loop geothermal system like this. We engaged a local heating contractor who we had used at our old house to help us determime the size of the system and give us a quote. The plan was we would take care of putting the radiant system pipe in the floor and the underground pipe in the ground. The contractor would supply the pipe and the heating system and do the final hook up.

He then contacts us one day saying that the underground pipe is in short supply (which it was that year) and we should buy the pipe we need now. We still hadn't gotten a full quote yet (ALARM!) but bought the pipe anyway ($5K). Well, when finally pressured the guy to give us a formal quote so we could get started he waffled, but did say it would be in the neighbourhood of another $50,000.

When we regained conciousness, we decided that since we were doing all of the work, the price was insane (anyone need some underground pipe for a geothermal system? We'll make you a VERY good deal). On top of that, he explained that a geothermal system produces heat very slowly and that we would have to have a 60 gallon tank of water heated at all times in case the system called for heat. Crazy, really, given that we had planned on passive solar gain and the house is super insulated (R40 walls, R50 ceiling). We could heat water for days and never have the system call for heat (we discovered this was true over the following winter).

We decided that an on-demand tankless propane water heater was the way to go in the house since the ONLY time it would be burning propane would be when the system was calling for heat. We found an awesome company in Vermont called the Radiant Floor Company that make a Do It Yourself kit for radiant floor systems. The complete heating system for the house as well as another tankless heater for our potable hot water cost around $7,000. That is a savings of $43,000. That will buy a LOT of propane.

The kit itself is very complete, the instructions are excellent, and there is a supplied video. Not only that, they have a technical hot line you can call up to 8pm Eastern for help (we used it and it was great).The system is straightforward to assemble and make work. Here are some shots of the mechanical bits of the kit.

You can see here that the major manifolds and fittings, especially the heavy duty ones with large brass fittings, come prebuilt for you. Your job is to just mount them on a wall and plumb them together with copper pipe.

Here Linda is wiring up the circulation pumps and you can see we have just started mounting all of the components on the wall.

The way the system works is quite simple: when a thermostat determines it needs heat, it sends a signal to this unit, the controller. The controller then supplies power to the circulation pump associated with the thermostat. The tankless heater senses water moving through it and starts heating the water which then goes through the floor heating it up.

The way the water is distributed throughout the floor is through this manifold. You saw it previously on the concrete page where Mark was pressurizing it with air to test it (the burn marks on the plywood are from removing the test fittings with a torch). This complicated bit of manifold is prebuilt for you as well. You just hook the pipes up to it.

This is the expansion tank (comes out of the box just like this). The expansion tank and the fitting on its top perform two functions: first, the tank itself acts like a shock absorber for the heating system. It absorbs the pressure changes from the pumps turning on and off as well as the changes resulting from the heating and cooling of the water in the floor. The valve on top allows any air trapped within the system to escape (buuurrrrrp...excuse me ;-)

This is early in the hook up process. We have hooked up the south zone completely. Now, a word of warning: ensure you use LOTS of heat when soldering copper pipe together, and that all of the components that are being joined are clean and fluxed. This is especially true of the big brass fittings. Use LOTS of heat or it will leak. A lot. Ask me how I know...

And here is the completed installation. It works absolutely great! Very efficient and quiet.