While hydronic radiant floor systems have become an accepted home-heating method and don't raise as many eyebrows anymore, the particular way we are configuring ours is considered quite unconventional for two primary reasons:
1) Our house will not have a boiler. The system will be powered by a high efficiency Polaris water heater.
2) The same water running under our floorboards to heat the house will be used for domestic hot water (showering, washing dishes, etc.)
The system described above is referred to as an "open direct system." The brainchild behind it are the geniuses at Radiantec, a Vermont-based radiant heat floor company. We're so proud. Here's what it looks like in action.
And here's why the open direct system is the best, according to the Radiantec website:
1 . The open direct system is a combination system getting two uses out of one unit. Stand-by losses of two units are avoided.
2. The money saved from not buying a boiler can be used to acquire a high-quality condensing water like the Polaris.
3. The overall low temperature of the unit improves efficiency.
4. Radiant heating is the most efficient heat delivery system.
5. The overall simplicity of the unit means that parasitic electrical pumping cost is minimal.
6. The flow of cold make-up water through the floor reduces the cooling load in the summer.
7. This nuisance heat is delivered to the domestic water heater where it becomes an energy saving benefit.
8. The open direct system is appropriate for solar energy assistance. (*We are installing two solar hot water collectors.)
While the system makes a great deal of sense to us, it freaks many plumbers out. Like really freaks them out. One, they believe that a radiant heat flooring system without a boiler is blasphemous. What kept running through my head when talking to plumbers about this yesterday (in the process of requesting bids) were the "inconceivable" scenes from The Princess Bride.
[Addition 3/1: I wasted a good 15 minutes of my life watching clips from this movie on YouTube today. Here's a montage of all of Vizzini's "inconceivable" lines. Love it.]
Secondly, they think that anyone with an open direct system will quickly contract Legionnaire's disease. Seriously. I had a plumber tell me yesterday that he was okay with putting in this system if I was okay with Legionnaire's disease. Radiantec has weighed in on this one: "It is our opinion that the risk of Legionnaire's disease in domestic hot water systems is "an emperor with no clothes" that is largely created by special interests groups in the heating industry. Legionnaire's disease is a reportable disease according to law and public health authorities make every effort to determine the cause when it appears. We are not aware of even a single case of Legionnaire's disease that was caused by a domestic hot water based heating system. If it were a real issue, there should be many."
I have to say that my conversations with plumbers yesterday were almost enjoyable. It is exciting to know that we are going to be putting in such an efficient, effective system...and it was fun to convince these folks of our choice...and to have a ready, researched response to their arguments.
Plumber: What type of system are you using?
Me: We're using an open direct hydronic radiant system from Radiantec.
Plumber: With what type of boiler?
Me: No boiler.
Plumber: (Insert some patronizing platitude here). You have to have a boiler.
Me: Actually, you don't. The system is heated solely via a Polaris hot water heater.
Plumber: (Blink, blink) But where's the boiler?
Me: Let's move on. I want to explain to you that all the water for our home will run through this water heater. There will be no separation between the hot water for the floors and the domestic hot water source. Have you ever installed such a system before?
Plumber: Well, that's illegal. You and your family will quickly be stricken with Legionnaire's disease and die.
Me: That's sweet of you to worry but the Radiantec system has been reviewed and approved by the International Code Council, which has been adopted in full by the state of Vermont. In addition, according to the Centers for Disease Control, there has never been a case of Legionnaire's disease in open direct systems. So I think we'll take our chances.
Plumber: (Blink, blink) What type of boiler are you going to use?
Our super efficient, intelligent, innovative heating system: $10,000.
Proving plumbers that a chick like me might know a little more than they think I do about radiant heat and international plumbing codes: priceless.
