I intend on building a solar kiln to hold 10,000 bf, at the same time I will be building a shop and using a wood boiler to heat the concrete floors. My question, has anyone used a heated floor as a secondary heat source in a solar kiln?

You would have to have a solar kiln that is essentially a closed room with a separate collector. The reason is that a solar kiln of the semi-greenhouse design has tremendous heat losses in the evening, night and early morning. So, a separate collector would have to be about 1000 sq ft for a 10 MBF kiln. a sep[arate collector will cost about $30 per square foot, so you would be looking at $30K just for the collector. At that cost, you would be better off with a DH kiln.

Radiant floors are a bad idea in kilns. To work the temperature of the floor always has to be warmer than the air. And you can only get about 100 BTUH per square foot of radiant floor so that isn't much. Also you can damage the bottom courses if it isn't carefully controlled. Some tests have shown that solar kilns use more electricity than dh kilns because the slow drying means the fans run a long time.

Thank you to both of you for your wisdom. I buy timber for a local mill and know logging and timber very well, but when it comes time to turn logs into lumber I am pretty dumb. I am nearing retirement and want a small business milling logs from my tree farm (700 ac.+/-).

Doug,
Your retirement idea is indeed a good one, BUT...

You will get more income and more profit if you do kiln dry the upper grades.

You will find that oftentimes and maybe always, you will spend more time marketing and selling than sawing and drying. In fact, you can saw all day, every day of the week, but you only make money when the lumber is sold.

In your business, there will be times when you need cash (sales are slow; a good deal for some logs comes up; maintenance, etc.). So, always keep as much cash as possible and buy equipment using credit or a loan from the bank. Small business groups in the state may be able to help identify good sources of money; local banks are often excellent too.

Get a business plan that identifies who you are, what you can and will do, what you will not do, markets, and so on. Again, state small business people (often through the county extension agent) can help.

For equipment, buy equipment that someone else has already done all the research and testing. In other words, buy top name brands. Buy "Made in USA" for good maintenance. (For sawmills, choose a big company and the size mill that they sell which will work for you. Then use that piece of equipment to compare to everyone else's equipment. Use a similar approach for a kiln.) Visit someone nearby that has the same equipment and see it running.

Although the upper grades often can be sold easily and with reasonable profit, the lower grades (sometimes 40% of a log is low grade lumber, or more) must also be sold. Profit is less with lower grades, so do not spend lots of time with them in manufacturing or marketing. A business plan forces you to consider all these aspects in advance.

Consider purchasing a kiln first and having all the logs sawn by a contract sawmiller for you. This costs a little bit for sawing, but does mean that you do not have a capital investment and sawmill maintenance...or the mess of a sawmill - - bark, slabs and sawdust. Plus, with a kiln your labor will be less so you can go fishing during the day and then check the kiln at night.

With a kiln, check out a DH kiln that is in a well insulated reefer van. Lots of postings about that here, plus I believe NYLE has some plans (and they credit what the plans cost against any purchase you make). Again, I like something that I know will work, rather than something that I have to do some testing or engineering because the company has this new product, etc.

If you do put in a permanent kiln building, always think ahead and make sure its location is perfect; that is, should you double your size, check that the first kiln is not in the wrong place when you expand.

Contact your power company's business office and they can help you with the best rate for a kiln (which is running 24/7, which means low peak demand). I have heard that because a DH uses a heart pump, that there were some special incentives for that in at least one state.

Finally, join a drying association. Many meet several times a year and have both plant visits and technical presentations. Most have beginners classes too. There are active kiln groups in the Great Lakes, Ohio Valley, PA, New England, Southeast (VA, NC, SC, GA). Of course, you could hire me to come in for a day or two, but that is expensive...the best is always more expensive (LOL).

Attend a 3-day hardwood lumber grading class and also a 3-day drying class. You will also find that within our industry, your competitors are often very willing to share with you.

Questions?

Gene, it is truly great seeing you at work, dispensing wisdom and great advise and all for free, a voice of sanity in this crazy world of online “wisdom”. Thank you much, be well

I agree with Gene, Take 3 day grading and drying courses. I did, you will identify the grade of your boards before they come out of the log. You will start cutting for best grade. That is where the dollars can be made. Leave the knots and defects in your narrow , low grade boards. I am a low volume cutter, purchased a nyle 50 , after I got my mill, You can keep your kiln going ,even if you don't have your own wood to do. There is a steady stream of people that want a few logs cut, then dried, Sometimes you will make just as much this way as they dry all their , boards not just the lower quality. Also I think you should probably undersize your kiln, make it suit what you intend to have for volume, and have it going all the time. If you can't keep up at a later date. add another kiln, rather than having too large a one and have it sit idle some of the time. I think I make more out of kilning as there is none in our area , people will find out, you have one and , come knocking. Good Luck