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Radiant floor heating Zone 4a – yes or no?

mikeysp | Posted in General Questions on

Hi everyone.

Is radiant floor heating is a good idea for me?

If yes, where is a guide, so I can design my system?

I am in zone 4a. I am building a 28×80 house/shop 1120 sq ft for house and 1120 sq ft for shop.

I have a ton of recycled 25psi high density XPS in 1″x4’x26′ pieces. Enough for 3layers/3″ if I want.

Since I will be operating a home based manufacturing business in my shop side of house, I thought it would be a great comfort in cold times of year to have the floor warmed for my aging and aching body.

Since I also have a ton of recycled polyiso also, I plan to utilize the perfect wall concept for insulating the house and shop where the polyiso layers are outside of the roof and wall sheathing with a rain screen behind finish siding/roofing.

I am a materials scrounger, so I will not utilize a company to design a radiant system. DIY is my only option. However, I need to to be intelligently done, as I can much less afford errors under a slab. 🙂

Thank you. 


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  1. Jon_R | | #1

    Lots of elements to a full answer, but a few general points about hydronic radiant:

    1) is easy zoned for superior per room temperature control
    2) makes heat pumps somewhat more efficient
    3) is more expensive and complex
    4) doesn't dehumidify

  2. Expert Member
    Akos | | #2

    Floor heat adds an extra system for any climate where you need airconditioning. You are esentially doubling your mechancial cost.

    About the only way for this to be worth it is that you have an outdoor wood boiler so you can heat for free (if you have enough forest on your lot). Even then, you are better to go with a couple of hydronic air coils as they are way cheaper to install.

    Generally, a well insulated building all surfaces are at the same temperature as the air, there is no comfort benefit to heated floors.

    You probably get more "aching body" benefit by putting a compliant floor over the concrete (plywood over 1/2" cork is pretty nice).

    1. mikeysp | | #3

      Thanks. I do have all the wood waste I can use, so it does become viable. However, your point about the room being so well insulated and the slab being inside that envelope makes a lot of sense. If I was further up north, I think it would be easier to lean that way. But Nashville is very strange. 20 degrees F one night, and 75 F by lunch. That makes a slow changing heat system like a loaded concrete floor even less desirable I think.

      Since I will be working with steel, welding, etc.. I need to operate on concrete. My only option for surface comfort is to place work mats at certain machinery and wear comfortable footwear.

      I am thinking I will forgo the radiant idea to save some pennies and the need to study one more skill for my build.

      If I use wood to heat, I guess I can use the hydronic air coil or a woodstove.

      I need to chew on this. Though it has some appeal to have heat emitting with no air circulation.


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