What about concrete for Solar Kiln

[Gadrock]

With all the talk about Solar Kiln I am increasing my interest in that operation.

So there has been some discussion about installing insulation in the floor if you construct the kiln in a hollow floored design. First of all I recognize that most people would make a joist and beam floor for convenience to equalize mother nature's terrain problems. Secondly the joist and beam could be insulated, somewhat transportable, and created to a very flat nature.

Now I am giving consideration for a concrete floor in part for flatness. There could be an expedience value to but not in my situation. Construction on top of concrete is quite possible equal in cost to all that heavy joists and beam construction stuff too. I could also have it at near available ground level that could make loading and unloading much more pleasing...given that my stacks of green or semi-dry lumber could be placed neatly on forklift height stickers.

So really what I am asking for is some feedback on the merits of concrete flooring for a solar kiln...with a dehumidifier...with corrugated heat absorbers in the roofing..with adequate air circulation...without additional heat supply.

Of course I appreciate all comments.

David G


Carry on

[thecfarm]

Seem like when I was working for the state insulating low income homes,we was told six inches of concrete has as much insulation value as a single pane of glass.

[goose63]

What if you put floor heat in for when the sun you get that much concrete warm it will stay warm

[GeneWengert-WoodDoc]

There are two issues with concrete.  First, it does conduct heat fairly well, so you will have to insulate it from the soil and also along the sides.  Second, it stores heat, which means you will not get the low humidities that we want...that is, the peak kiln temperatures will not be achieved, but they are critical.

OK?

[red oaks lumber]

my kiln has a concrete floor with 2" high density foam under the crete. i would think a kiln is a kiln and concrete benefits both setups.

[Den Socling]

I think the point is that solar kilns benefit from the alternating periods of high temperature with rapid drying and lower temperature with slower drying. A concrete floor would act as a big heat sink to even the temperature out.

[red oaks lumber]

i've said it before and i'm saying it again, i guess i don't know anything about solar kilns :D

[GeneWengert-WoodDoc]

I would like to modify Den's comment (I did not ask for permission ahead of time however)

I think the point is that solar kilns benefit from the alternating periods of high temperature and low humidity resulting in rapid drying and lower temperature with high humidity resulting in slower or no drying. A concrete floor would act as a big heat sink to even the temperature and humidity out.

[Den Socling]

Not a problem, Gene. I over simplified.

[MILL BRANCH FARMS]

please explain " a big heat sink" and is that a good thing?

[Tom L]

a heat sink is an object place next to something you are heating that absorbs the heat away from the object that you are trying to heat.

[Part_Timer]

With all the talk about Solar Kiln I am increasing my interest in that operation.

So there has been some discussion about installing insulation in the floor if you construct the kiln in a hollow floored design. First of all I recognize that most people would make a joist and beam floor for convenience to equalize mother nature's terrain problems. Secondly the joist and beam could be insulated, somewhat transportable, and created to a very flat nature.

Now I am giving consideration for a concrete floor in part for flatness. There could be an expedience value to but not in my situation. Construction on top of concrete is quite possible equal in cost to all that heavy joists and beam construction stuff too. I could also have it at near available ground level that could make loading and unloading much more pleasing...given that my stacks of green or semi-dry lumber could be placed neatly on forklift height stickers.

So really what I am asking for is some feedback on the merits of concrete flooring for a solar kiln...with a dehumidifier...with corrugated heat absorbers in the roofing..with adequate air circulation...without additional heat supply.

Of course I appreciate all comments.

David G


Carry on

When I do mine it will be done in concrete because the kiln slab will be an extension of the mill shed slab.  However I mostly saw fall-spring and rarely in the summer so the heat sink effect may not be as bad.

[GeneWengert-WoodDoc]

Part_Timer,
How about putting a "false floor" on top of the concrete that is made of wood framing and insulation.  You will find the kiln to work much better throughout the year.

[Sawdust Lover]

I put 2" of insulation in my solar kiln. During the summer months the concrete is still warm in the morning from the day before.

[Gadrock]

so... if we were to think about concrete for simplicity in construction and strength...and then put a couple inches of insulation / styrofoam type stuff...then a heavy duty plywood working floor to support the bunks ...

    Is this what we are trying to really get to?   Is this going to be a satisfactory heat sink resistor?

So I was under the idea that wet lumber when placed into the kiln was heated by convection starting the temp to rise and the humidity to become extremely high. During this circuit the DH would be inoperable because of too high temps. As the sun retreats the convection stops and chamber temps drop...but the humidity is still airborn ready to land and form on any cooling surface. The air still circulates as the DH starts and removes the moisture.

   But here i have a problem understanding that a down town el cheapo DH that removes 60 pints of water a day can remove enough water. I have heard that some people even use less capaicity DH units with satisfaction. My math is not working out at all. The weight of the water collected by the DH is considerably less than the weight reduction of the lumber. Where have I gone wrong?

Thanks

David gaddis

Carry on

[Den Socling]

If I built a solar kiln, I'd vent. But that is just me.

Don't forget that humidity is "relative". Relative to temperature.

[GeneWengert-WoodDoc]

Technical info:  A pint of water weighs one pound.  1000 BF of lumber has a weight of wood (bone dry) that is around 2500 pounds (some heavier; some lighter), and then there is water.  For each 25 pounds of water, that is about 1% MC.  So, a 60 pint DH unit could reduce the moisture of 1000 BF of really wet lumber by a little over 2% MC per day, if the DH unit is running 24 hours and if it warm enough and the humidity is high enough.  As the lumber gets drier and moisture moves more slowly, the rate will slow unless the temperature is raised above 130 F or so.

Most household DH units work up to about 105 F.  The old freon units worked to about 115 F.  None work well under 75 F, with freezing of ice on the coils happening at low temperatures and humidities.

[Gadrock]

Now that is what I am talkin' about. Regular down home head scratching physics.

With that way of thinking so of us inexperienced peeps have a direction to head toward.

NOW:
      WHat if we put a few DH units or a larger one (120 or larger) ?

Right now my desires are toward SYP, which I am directed to thinking gives up its MC very easily? Please ADVISE.....

This is getting interesting.

David G

Carry on

[GeneWengert-WoodDoc]

Because SYP dries so easily and because it has a risk of staining, I would suggest a DH unit and no solar at all.  Insulate the building well, including the floor, as heat losses are expensive with electrical units.  If you are going commercial, then you also need to get a DH unit that will exceed 130 F in order to sterilize and also set the pitch, if required.

[Part_Timer]

Part_Timer,
How about putting a "false floor" on top of the concrete that is made of wood framing and insulation.  You will find the kiln to work much better throughout the year.

Sounds like a god idea.  Thanks