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Community and Q&A

Best integrated system for water heating and radiant floor heating?

Dmitriy Khazansky | Posted in Mechanicals on

I’m looking to remodel my home and install radiant floor heating system. Can anyone provide any information on good heat sources (boiler, water heater, etc) and system arrangement (direct, indirect, closed loop, etc). Is it okay to combine DHW with radiant heat or is there some over arching reason why they should be kept separately?

Home details: Just south of San Francisco, 2500 sqft, two stores, 5 zones, Warmboard S floor board, mostly covered with hardwood flooring.

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  1. GBA Editor
    Martin Holladay | | #1

    You are asking some very basic questions. To start, I recommend that you read some articles from the GBA Encyclopedia, as well as some GBA blogs on the topic.

    Here are some links to get you started:

    Hydronic Systems


    All About Radiant Floors

  2. Expert Member
    Dana Dorsett | | #2

    Since your loads are low an you're micro-zoning the hell out of it a tank-type water heater combi heater will work better, last longer.

    The min-fire output of the low-mass wall-mounted type combi-heaters is probably higher than your whole-house heat load, and more than 5x oversized for your smaller zones, and will short-cycle itself into an early grave. A tank type heater has substantial thermal mass to work with, but it still has to be at least reasonably sized to your loads.

    Doing hydronic design well isn't exactly a plumbing project- you have to do the math, and it helps if you have the software tools. DIY projects are often fraught with expensive errors that A: cost too much up front and B: cut deeply into the operational efficiency of the system. Paying a true hydronic heating design professional (not a "heetin' an' plummin' contractor") to run the design and specify the heat source is likely to come in cheaper and better than a design-by-web-forum approach.

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