# adding a dehumidifier to a solar kiln?



## Julian the woodnut (Nov 5, 2008)

I have a small solar kiln similiar to the virginia tech one and have already used it successfully, but would like to speed up the process. Is is possible to just seal up the vents and add a dehumidifier in the kiln to essentially turn it into a dh kiln? Is there anything I should or shouldn't do? Cough, cough, Daren.......


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## Daren (Oct 14, 2006)

I'da went d/h in the first place . Without spelling out how to build a d/h kiln in detail on the open forum, since selling plans for them is part of my personal income http://www.woodworkingtalk.com/f23/small-wood-drying-kiln-plans-dry-your-own-lumber-3103/ (and don't _anyone_ take that as greed, I share here plenty) here are my thoughts.

Julian you are just going to have a mutant. A combo solar/dh is not really practical, if even doable (if that is what you are asking). One solar relies on heat and venting the moisture. A d/h is working at lower temps in a sealed environment mechanically removing the water. So you would have to seal your existing kiln very tightly to go d/h. And do away with the solar collection because the d/h unit will keep kicking off on high temp limit over 125 degrees.

But yea, if you have an airtight box a d/h unit and a few other things (which you would have since you already built a kiln) a straight conversion to a d/h kiln would not be that hard.


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## Julian the woodnut (Nov 5, 2008)

Thanks Daren. I figured it would work. I guess I'll just convert the solar collector/roof into an insulated/better sealed roof and see what happens. I wish I would have thought about going this route in the first place since I have a DH that was just sitting in the corner of my shop collecting dust. Now that the season has changed for the better, I plan on getting more logs to mill up and will be needing the kiln to dry wood faster. I am too impatient to wait very long....


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## JP Sinclair (Nov 13, 2006)

Daren's right, you'll need it sealed up much better. I have a kiln that's run off my outdoor wood stove, baseboard heat. The chamber is tight - unvented and I use a DH to bring the moisture down so that the air you are circulating gets progressively drier.


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## Julian the woodnut (Nov 5, 2008)

The top whole kiln was pretty airtight before, with the exception of the vents. I don't know how much tighter the seal can get, since I covered the vents up already. The temp inside was very warm inside it today(over 80 degrees), and its only 50 outside. I'd say that it's working so far. I'll keep watching the mc of the wood and see what happens.


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## bzguy (Jul 11, 2011)

*Solar and D/H*

If your ambient humidity is high at night then run an inexpensive dehumidifier (on a timer?) after the sun goes down.
It's done here and it takes gallons out every night in our humidity, drying the wood 24/7.


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## ETWW (Mar 27, 2011)

I rfealize this is a three year old thread but a word of caution about using a DH with a solar kiln.

One of the attributes of the VT solar kiln is that at night, when the humidity rises, the fans are shut off and the lumber gets "conditioned", relieving the drying stresses introduced during the day. It's not unlike air drying in that regard.

If a dehumidifier is introduced, which runs at night, the conditioning no longer takes place. Yes, the lumber dries faster but then it has to be conditioned somehow at the end of the drying period. The stress has to be relieved. Commercial kilns do this with steam, usually 3%-4% above final MC of the lumber.

If fast drying is required, a solar kiln/hybrid is not the answer. It was never meant for a commercial operation, but simply a way for small-time sawyers or woodworkers to dry their wood safely and more quickly than air drying and with more control over the final product.


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## Picobou (May 30, 2018)

*How to decrease drying time with passive solar kiln*

With a set of dampers, use both. Solar with venting during the day and at night close all vents and go dehumidification. You should speed up by probably up to 30% drying time while keeping the kiln’s environment very constant. 
My son in law has built a solar drier I’m helping him out to design the controls. I knew nothing about your industry. This is why I’m reading forums on the topic. The more I read the more I’m getting a clear picture of how to do it properly. Not knowing much about the wood industry but ri years as a refrigeration technicians with an electronic background has me awake at night programming an inexpensive programable controller to automate this process while improving the quality of finish lumber at the lowest energy use.
PicoBou


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