Radiant floor heat for kiln?

[Faron]

I intend to install radiant floor heat in my new sawmill /wood shop building.  The thought has crossed my mind to install a kiln area as well.  I am wondering whether I should install a separate loop in the kiln  floor, or whether it would be best to install heating loops on the walls of the kiln.  I would be using an outdoor woodburner for heat.  I anticipate the water out of the stove will be about 180°.  I suppose a mixing system will be used to create the correct temperature for the heating system.  Will pumping 180° water through the concrete for the kiln be a problem?  And is that hot enough for a kiln?  As you can probably tell, this idea is just at the hmm, what if, stage.

[fencerowphil (Phil L.)]

I know I remember a thread like this before.

The guys in the serious drying business had doubts as to the capability of floor
radiant to deliver the necessary BTUs.   It was either here on on WoodWeb.
:P  perhaps a search would turn up that old thread.

Yup, here is the thread I remembered:

https://forestryforum.com/board/index.php?topic=22347.0
Phil L.

[Don_Lewis]

Don't have the loop under the kiln on the same circuit as the rest of the shop. Better yet, leave it out. It isn't the a good way to heat a kiln for many reasons.

[Faron]

Don, could you expand on that response a little bit?  I kind of hesitate to leave it out because if I later on decide I don't want that kiln in there, I will have a cold spot in the floor.  While we are talking, would we be better off just to have a kiln apart from the new building?  I am thinking my building will rust quicker having the extra moisture.

[Don_Lewis]

If you are not using the space as a kiln right now, then your idea of putting a separate loop under the floor in that area is a good one. As for radiant floors in kilns, you have to always have the water hotter than the kiln when circulating. In most space heating, like your shop, 100-110F water is about as hot as you want but if you have a kiln running and 140F or higher, and the water is 100F, then the floor will be cooling the kiln, not helping. On the other hand, if you run hot water through the floor (160-180F) and you have a green load, you can damage the lumber in the first courses. So you need to be able to constantly reset the water temperature. It is more complicated than life needs to be but it can be done.

Radiant floors are popular because building heat loss can be reduced to a point where the floor does not have to be too hot to heat the space. Back in the 1950-60' when the first radiant heat fad was going on, most people had poor luck because buildings were so poorly insulated that the floors (or ceilings) had to be too hot for comfort. But a kiln is different. It uses a lot of heat and insulation only reduces the heat consumption by a small percentage of the heat used. You can't get enough BTUs off the flloor to do the job especially when the floor is covered with lumber.

I could go on about this as I have people call who put in radiant heat in their house or their shop and feel that have discovered something that applies to every application and I have heard every reason possible and a lot of impossible ones.

[Faron]

Thanks, Don.  Would hot water radiators with a thermostat controlled fan be the way to use the wood stove for a kiln?

[Den Socling]

We use heat from wood stoves by using a heat exchanger supplied by a 3-way valve. When the fire is hot, a temperature controller allows a small amount of hot water to flow to the heat exchanger. As the fire goes down, the controller allows more water from the boiler into the heat exchanger.