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Senior Contributor

Floor heat

We are building a small shop with tubes in the floor for heating.
No decision has been made on how to heat the fluid in the pipes.
Any suggestions and what are the pros and cons of the source?
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7 Replies
Senior Advisor

Re: Floor heat

What are all of your options?
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Senior Contributor

Re: Floor heat

I only have the tubes in the concrete floor so far.
Electricity is available. Propane is a possibility. Natural gas is not.
Those two energy sources make a boiler (or water heater) a method of providing heat to the floor.
My plumber mentioned a water source heat pump. Not sure how that would work through the floor.
Any suggestions or other ideas are welcome.
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Senior Advisor

Re: Floor heat

I would imagine electricity will be cheaper than LP, but if you lose power than you lose heat as well. Would you have standby generator? Not sure if a wood fired burner would be an option, but I know geothermal is. Initial cost of GT is frightening, but I've been told they are cheaper in the long run if you've got the ground space to bury it.
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Senior Contributor

Re: Floor heat

We have a water heat pump in our house and yes it is very inexpensive to run.
What we do now is use our house well for the source, run it through the furnace/air conditioner. Then dump the discharge into a pond which is between our house and this new shop. So this is a possible solution for the shop. What I'm not sure about is how it works to transfer the output from the heat pump to the tubes in the floor. You think the output will be hot enough to not only heat the floor, but the entire shop (48' x 42')????
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Senior Advisor

Re: Floor heat

You're asking the wrong person, I have no idea.
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Senior Advisor

Re: Floor heat

A propane hot water heater like I use in my shop is much cheaper to install than a water to water heat pump, but the heap pump is probably cheaper over the long run.

 

I don't worry about power outages of a day or two because the concrete is such a heat mass that it will take several days to cool to whre there is a danger of freezing the pipes.  Time to get emergency power in to do something if it's that bad.

 

I'm thinking about some remodelling so these questions are on my mind but I'm not far enough along to help yet.

 

 

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JHaydenO
Friend

Re: Floor heat

    A water to water heat pump works the same as the one in your house, except instead of heating and cooling the air it heats & cools a water loop running in your slab.  One small little circulating pump and some balancing valves and you are set!

 

    The pump and dump method you've got is the least expensive to install of the geothermal options, but if you eventually run out of water you are out of luck!  The other trouble we see in the eastern US is dirty water clogging up the heat exchangers, which is why we often design using an indirect sink source, like a slinky in the pond or geothermal wells.

 

    Water temps in the slab should never be more than 115F, or you run the risk of cracking it.  You would be better served running more pipe in the floor (closer centers) than overheating the water.  Lower water temps also increases the efficiency of the heat pump too.  More pipe in the floor doesn't mean longer circuits either, it means more circuits of the same length (250-300' depending on diameter)

 

    The idea of the heated floor is not to heat the air as much is it radiates to heat objects, reducing the air temperature (and reducing the hot air leaving the building).  For example, a shop that you might heat to 70F with forced hot air would be just as comfortable, if not more so, with hot floors and an air temperature of 65F.  Be aware heated floors are not something you can just turn on and they warm up in a few minutes.  It can take days for the floors to absorb enough heat and heat up (thermal mass) and likewise, if you get a warm day in February your shop may overheat, even if you turn the heat pump off that morning!

 

    I'm no expert, but an engineer and farmer who dabbles in this stuff and built my own house with a WWHP and a pond loop.  I'm very happy with the result.  Good Luck!

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