Supplementing Solar Kiln Heat In Winter

[Pepe_Silvia]

It's the wrong time of year to implement this, but I was just thinking about it moving forward.

Does it make sense to have a supplemental heat source in the winter, and does a double barrel stove make sense for that purpose?  Or will I still be getting plenty of heat just from the sun?

[scsmith42]

In Plano Texas I would invest first in

• Double pane poly-carbonate greenhouse panels.  These will retain more heat in the kiln than single pane.
• High quality insulation throughout the kiln. 

Coupled together, these two will buy you 2 - 3 months more effective solar kiln use, and minimize the need for an auxiliary heat source.

[GeneWengert-WoodDoc]

I agree that insulating is a key.  However, the clear roof will lose huge amounts of heat, which spread out over 12 or more hours of darkness or low sunlight every day, will make this very inefficient and wasteful, even in Plano.  So, it would be better, if you need winter performance, to build a kiln without a clear roof, or cover the solar roof with insulation.  The small amount of solar in the winter makes the drying slow indeed.

It depends on the species, but kilns do need specific temperatures, humidities and air flow.  The very high RH at night also relieves drying stresses, also called casehardening.

In short, supplemental heat in a solar kiln is likely not the best idea.  If you need year round, reasonably fast performance, consider a DH kiln.

[scsmith42]

I agree that insulating is a key.  However, the clear roof will lose huge amounts of heat, which spread out over 12 or more hours of darkness or low sunlight every day, will make this very inefficient and wasteful, even in Plano.  So, it would be better, if you need winter performance, to build a kiln without a clear roof, or cover the solar roof with insulation.  The small amount of solar in the winter makes the drying slow indeed.

It depends on the species, but kilns do need specific temperatures, humidities and air flow.  The very high RH at night also relieves drying stresses, also called casehardening.

In short, supplemental heat in a solar kiln is likely not the best idea.  If you need year round, reasonably fast performance, consider a DH kiln.

Gene, one thing that I have experience with my double pane solar kilns is that they will retain more heat later in the year, and earlier in the spring - than my single pane kiln.
In general I obtain 2 months more effective kiln use with the double pane kilns than the single.  
As an example, in my area in most Octobers I still see 100 degree+ temps in my double pane kilns, but not in my single pane.  The second layer seems to be good for about 10 - 15 additional degrees in the kiln when it's cooler out.

[GeneWengert-WoodDoc]

Indeed, two layers of clear will add 40% more usable energy to the kiln, compared to a single layer.

[YellowHammer]

Install and use a small Wal Mart style dehumidifier in the winter.  I makes a big difference.  Not so much in the summer.  

[Pepe_Silvia]

Unfortunately it seems I made the wrong call a few weeks ago and just put up single Tuftex Polycarbonate panels.

Would it be effective to just double them up with some amount of space between them?

[btulloh]

Yes. A lot of people have done it that way.

[GeneWengert-WoodDoc]

Yes. Any space is fine. Not critical

[YellowHammer]

I did the same thing, so I attached the other layer to the bottom of my roof rafters, from the inside.  So mine has a 3.5" dead air space between them.