I am building a house on the Central California coast, where average temperatures range from about 40 in the winter to about 65 in the late summer/early fall.  The house will be about 2200 feet above ground, about half of which is or will be wooden floors; the other 50% will be mostly slab on grade, with 2 tile bathroom floors.  All of the floors would have radiant heat embedded or underneath, as the case may be.

Most of the people that I've talked to here about radiant heating are sort of set on the idea of using a boiler.  I'm somewhat familiar with how boilers work, and the give and take involved with them, but it seems like overkill.  (The radiant heat hot-water-source would also supply domestic hot water.)

Is there anything prima-facie wrong with a plan that would use 2 small water heaters at different temperatures, one for the slab or bathrooms, and one for the wooden floors and domestic hot water?  Would the savings involved via having one set at a lower temperature, and having a simpler plumbing setup, be offset by having 2 water heaters?

Jeff

Good idea to heat in floor, Bad Idea to use #2 h20 appliances, better to use a 3 way mixing valve and zone with pumps. I am not a fan of open loop systems, problems waiting. Think about a combi boiler, we have a Laars mascot we sell a lot of that isolates domestic from heating, condensing so efficiency is up there. www.blueridgecompany.com . It is not out of the question to heat both floors with the same delivered water temp.
Dan

Bradford White's Combi 1 water heater.

The 2006 International Residential Code prohibits cross connecting space heating and domestic hot water. Thou shan't run the same water through both systems. A water heater that heats both has two separate water circuits in it.