To Radiant or Not to Radiant

[GARYL]

I am in the planning stages of putting a wood gasification boiler in my chickencoop with storage and supplying my house and barn. My house has an oil fired/baseboard system so that is pretty straightforward. My question is do I use radiant in the barn or an air exchanger. The barn is built into the side of a hill and has dry earth around two sides and under it. I am going to pour a 4 inch floor over the existing concrete floor because of it's poor condition. The stanchions have been cut out but there are still gutters and alot of uneven cement. The existing floor looks to be about 8 to 10 inches thick.( I guess cement was cheap in 1903) Ripping up the existing floor is out of the financial reality realm. My question is: Can or should I install radiant in the new 4 inch layer. I will not be able to insulate as I only have room to pour 4 inches. I should be able to dig around the two exposed sides outside and insulate down a couple of feet with rigid or foam if that would help.
I insulated the barn last year and it had no heat in it all winter but even when it got down to -10 a few nights the barn never fell below 44*. The foundation is layed up stone about 24 inches thick. If I were going to make this a workshop I would use the air excahnger but we have plans to move our preschool into this space and it would be nice to have the radiant heat. I have read horror stories on this site about uninsulated radiant floors and I really don't want to be mowing the grass around the barn in January. :bug: Do you think I should do it or not? Any suggestions would be appreciated.

Gary

 

[Reggie Dunlap]

I would not recommend installing radiant tubing without insulation below, since that 8-10 inches of existing concrete will suck up a lot of heat. Could you pour a 3" slab with 1" of foil faced Celotex below? A 3" slab should be plenty strong. Also remember to install a foam thermal barrier around the perimeter.

 

[Bob Rohr]

What is the barn used for? If it is a shop that you spend a lot of time in radiant heat, in a concrete floor, is the best!
I'd agree without insulation 2" ideal, 1-1/2 OK, 1" if nothing at all.

Hydronic radiant ceilings work nicely in some applications also. While they never get the slab as warm, it is still a clean, comfortable, usually easily reto fitted application. Much quicker response for intermittent use warm ups.

You can get a lot of output from a ceiling do to higher operating temperatures and not many benches or tools up there

A heat load for the space would help define what is do-able.

hr

 

[GARYL]

What is the barn used for? If it is a shop that you spend a lot of time in radiant heat, in a concrete floor, is the best!
I'd agree without insulation 2" ideal, 1-1/2 OK, 1" if nothing at all.

Hydronic radiant ceilings work nicely in some applications also. While they never get the slab as warm, it is still a clean, comfortable, usually easily reto fitted application. Much quicker response for intermittent use warm ups.

You can get a lot of output from a ceiling do to higher operating temperatures and not many benches or tools up there

A heat load for the space would help define what is do-able. hr

Thanks for the ideas. I have never heard of radiant ceiling heat. I have all particle board walls and ceilings painted white with all my electric run in conduit on the surface, so running radiant should be a snap if I can run it on the surface.

How much higher temps can you run with radiant ceiling vs floor?

I will do some research. Can you suggest where best to look?

THANKS!
Gary

 

[Bob Rohr]

Since you won't, or I hope you won't be standing on the ceiling surface temperature is not critical.

As such the limiting factor becomes the materials used. Generally 140F is as high as sheetrock or any manufactured materials as plywood, wafer, etc should see.

A ceiling surface of lets say 100F would put two btu per square foot/ per degree difference 100F surface in a 65F space temperature would be 100-65 X 2 or 70 BTU per square foot, if the entire surface was that temperature. With tube installed 12- 18" on center in aluminum transfer plates, consider 30 - 40 btu per foot. that will handle most shops.

Infrared tube heaters work well for tall ceiling shops, also.

Radiant walls work the same way. Heated walls behind a work bench would be nice. Warm you and the tools!

While this retro fit ceiling at my home wasn't a real crowd pleaser, aesthetically speaking it works great.

I also did a metal ceiling in a body shop a few years back with plates and tube screwed to the metal ceiling panels.

hr

 

[GARYL]

Since you won't, or I hope you won't be standing on the ceiling surface temperature is not critical.

As such the limiting factor becomes the materials used. Generally 140F is as high as sheetrock or any manufactured materials as plywood, wafer, etc should see.

A ceiling surface of lets say 100F would put two btu per square foot/ per degree difference 100F surface in a 65F space temperature would be 100-65 X 2 or 70 BTU per square foot, if the entire surface was that temperature. With tube installed 12- 18" on center in aluminum transfer plates, consider 30 - 40 btu per foot. that will handle most shops.

While this retro fit ceiling at my home wasn't a real crowd pleaser, aesthetically speaking it works great.

I also did a metal ceiling in a body shop a few years back with plates and tube screwed to the metal ceiling panels. hr

hr,
Thanks for the idea. I like your ceiling install. I think you have solved my problem and I will go with 3x8 ceiling radiant panels using rigid insulation and metal roofing. Place the PEX inside the grooves on the metal roofing and cover with the rigid insulation and then screw the whole thing to the ceiling with the metal facing down. Should work. I don't know how to figure the math but I can always add some as I go if the 8 I plan on aren't enough or I can raise the water temp because the ceiling will be seperated from the pipe by a couple inches of insulation.

Thanks again,
Gary

 

[Bob Rohr]

Roth makes a nice product fro that job. 2X4 foam panels with aluminum grooved into it. They ship with the end panels also.

The key is the tube to metal contact to maxumize the conduction transfer. Be sure the tube touches the metal panels, somehow, if you build your own. A good grip would be prefered so the tube doesn't move and make noise or create wear points.

On the shop with metal ceiling I screwed the aluminum transfer plates to the metal, exposed and snapped the tube in. They blew 12" of fiberglass above the metal ceiling from the attic for insulation.

Use a tube with UV protection if it is to be exposed. Viega FostaPex has an aluminum O2 barrier, or their radiant pex is black colored.

hr

 

[GARYL]

The key is the tube to metal contact to maxumize the conduction transfer. Be sure the tube touches the metal panels, somehow, if you build your own. A good grip would be prefered so the tube doesn't move and make noise or create wear points

Use a tube with UV protection if it is to be exposed. Viega FostaPex has an aluminum O2 barrier, or their radiant pex is black colored.

hr

hr,

Good info thanks. I plan on having the rigid foam sqeeze the pex against the metal in the grooves which should give good transfer and no wear. I already have R19 in the ceiling and with the 1 or 2 inch insulation board should give a good insul on top of the pex so the heat should only have one way to go and that is down through the metal. (I hope)

I will check into the UV protection. I am a long ways off from doing this project so I can take my time and do it right. I think I am gonna get a Switzer and Gary said it would probably be next year for delivery by the time I order it.

Thanks again,
Gary