radiant floor heat

[black4x4]

I'm looking to do the pole barn with living built into it here in the near future. I was hoping to do something along the lines of a 80x50 with a 30x50 area of that being living and 50x50 being shop the pad would most likely be 5"s thick. for the living area I plan to just do stamped and stained concrete, so I was looking at doing radiant heat. so if I were to go with radiant could I just put it in the living area and it be affective, or will the shop area want to draw heat from it till it heats the whole 80x50 pad.

I've also been hearing about geothermal alot and was wondering if I could use it to keep the pad at a constant 50-60 whatever the earth stays at or would it not work like that. I've also looked at wood boilers and was wondering if I could use one of those to heat the water for the radiant heat and also use it as a source of convection type heat?

[dopeassjackson]

it would probaly be best to isolate the living from non living area. even if its a 2-3in gap in the cement. it is possible to heat the floor with the wood burning idea you said. if you have a pond or big stream you can also cool the water in the summer if nessary.

[Slowzuki]

I've got the same setup, no need to separate the slab, just put a deep sawcut or plastic zip strip where you divide it. Insulate under the living area. A ground temp slab is too cold in most areas and you'll get condensation in a living area. For the same reason don't cool a slab in the summer.

I've got a wood boiler in the process of being hooked up to the slab. You can't put the full temp of the boiler into the slab. You need a mixing valve and a few other things. My boiler is hooked to an old 800 gallon ss milk tank that stores enough hot water to keep me going a day between burns at -15 C, keeps me about a week in the summer just using for hot water. Slabs have so much mass you need cold water return protection on the boiler too or the boiler will run too cold making corrosion and smoke.

[XtremeJ]

A ground temp slab is too cold in most areas and you'll get condensation in a living area. For the same reason don't cool a slab in the summer.

.

Please explain cooling a slab in summer. I designed and built a solar home in Colorado, and a large amount of the thermal mass is in a concrete slab. This slab is cooled in summer, and there are zero condensation problems.

Does it only apply where ground temp is pretty cold? Canada?



I would make every effort to put radiant heat into your shop slab, you cannot believe how nice it makes the shop in winter time. But expensive to build, and expensive to run.

[Slowzuki]

Its all to do with the relative humidity levels. Its fine in low humidity areas. More areas in NA are high humidity though and I didn't see where he lives.

At our place, its say 90 F and 85% humidity on a normal summer day, the slab in the shop is about 65 F and gets soaked since the dewpoint is like 70 something.

[XtremeJ]

thanks for the explanation, Colorado is very dry, and we are at 6000 ft, so that likely explains it.

The only time we get condensation issues is winter if we have the humidifiers running a lot. Du'h. And that is humidity on cold windows not anything to do with the slab.

[blackrider]

on a radiant floor;1"x2' foam is placed on the ground around the perimeter of the stem wall(inside)in really cold climates on the out side also.
and on the stem wall up as high as the slab thickness.

[Slowzuki]

My slab is a frost protected slab design. The design frost depth here is 4-5 ft in places where snow accumulates, its like 8 ft for places kept plowed off.

I have 3" of XPS on the slab perimeter extending to about 1.5 ft below grade, at that point 1.5" XPS extends 4 ft outwards underground.

In my shop I left the slab uninsulated, poured on top of 2 ft of coarse sand. In the living quarters I used 1" XPS under the slab, on top of the sand.

The living space needs to change temp more quickly. I don't care if the shop gets cool and I need to wear a jacket as long as the floor is warm. Not ok in the living space. The shop floor takes a long time to change temp since so much mass is touching it underneath.

The reason this matters is cause on a cold day you need to make the slab hotter to heat the room to the same temp.

[XtremeJ]

OK,

my house slab is also frost protected, the entire perimeter of the foundation is lined with 2" EPS. The slab itself is on the very top of 2" EPS, with rocks and sand, then crushed compacted rock, then a layer of concrete block, then the slab. Also insulated around the entire perimeter. The concrete block layer forms a series of tunnels under the slab, and air if forced through those tunnels to carry heat to the crawlspace (in winter) or to carry cool air under the slab and force a convection cycle (in summer)

At my shop, the radiant floor heating takes a day or two to come up to temp, and stabilize. I keep it around 58 or 60 degrees in winter and use a small heater placed where I am working if it feels cold. Really nice to have warm floors to work on. The slab at the shop is not nearly as well insulated as the one at the house.

[Slowzuki]

That is a neat idea with the blocks, I'd not seen a good method to heat a slab with air. Do you get problems with mice etc getting into the floor? I get dead mice in the walls all the time and talk about stink. I also get them in my 4" pvc piping runs under the slab. Haven't had any stuck in there yet though.

[XtremeJ]

We live out in the foothills, and the wife feeds the birds, so mice can be a problem in the outbuildings, garage, under the hood of my truck, but so far (12 years plus) no problems with them in the "tunnels" under the slab.

Perhaps the "blades of death" (the 2 way fan in the plenum) is enough deterrent.

No problem with them in the walls, because the house has poured concrete walls to the top of the second story. (poured in EPS forms, which remain in place and then are stucco'd), but I did have a mouse die in one of the heating ducts once, and whew what a stink.

The thermal mass of the slab is very effective, we use approx 1/3 of the heating propane our neighbour uses in winter, and he is in a pretty efficient log home.

[gte718p]

My uncle has radiant heat in his house in Seattle. I lived with them for a while and can honestly say its incredible. Their house is all tile and stone floors. Even on the coldest morning its nice to wake up and walk to the bathroom.

Once you've worked on headed floors it really hard to go back to working on a freezing slab.


You can use about anything to heat the water. I'm lazy I don't want to build and maintain a fire so I'm going with gas when I build. The controls are also much simpler. Its very easy to use a geothermal well to preheat water for the system. The well, control system, and mixing valves add a good bit to the upfront cost. Last time I looked it was almost 8k~20k depending on well depth and cost. You can also design your own control system fairly easily and save big bucks. Depending on where you are solar is another good option for preheating water before it goes into the hot water heater.

[unimogken]

My buddies dad has a shop with radiant heat installed with PEX-like pipes and he uses a propane hot water heater and a pump to cycle the water thru the lines.

I am going to do electric radiant heat in my basement on top of the slab in self leveling cement followed by tile.

It may be a bit more expensive initially but totally worth it!