Solar kiln floor insulation??? Edit… my solar kiln project

[caveman]

On our hot box, we have side hinged doors, and they don't sag and the doors seal well.  On our solar kiln, we have two side hinged doors with a large, heavy insulated wooden panel that is put on with the tractor between the doors.  When I was dreaming this thing up, I felt the side hinged doors would sag too much and that putting the panel in would be easy.  The ground is sand, and it is challenging to get the panel to fit just right so the doors on each side of it close properly.

If we ever get around to building another, it will have side hinged doors.  We did not put any vents in our solar kiln.  It can seal up pretty tight, but we usually just leave the doors slightly open and dump moisture for a few minutes each afternoon by leaving the doors open for a minute or so.  At one time we were running dehumidifiers at night in the kiln, but we don't now.  It does a very good job drying wood.

If I recollect, we used one thickness of chicken house foam insulation under the plywood floor of the kiln and two layers in the walls.

[Tom K]

For fans I'm going to run a pair of attic exhaust fans, 1,600 cfm each. 

When I was looking into air flow I ran across a post from Dr. Wegnert with the following 

"For the cfm needed, multiply the thickness of the sticker (inches) times the length of the pile (feet) times the number of layers, divide by 12, and then times 125 feet per minute (desired velocity). Then add 50% to this number to allow for leakage"

[Nebraska]

Unfortunately that was the topic I was researching when I saw the news about Dr Wengert's passing. It kinda took the wind out of the my sails he made a huge contribution to education regarding the lumber industry and this forum. 

So I just guessed to see if it was good enough. 

[doc henderson]

easy enough to add more fans if needed.  I think the big volume is good for things like pine.

[Tom K]

Unfortunately that was the topic I was researching when I saw the news about Dr Wengert's passing. It kinda took the wind out of the my sails he made a huge contribution to education regarding the lumber industry and this forum.

So I just guessed to see if it was good enough.

I do agree that it just seem kind of odd to be in the middle of building a kiln "The Wood Doctor" was such a proponent of, and so instrumental in right now. I feel like I should tag it somehow in his honor.

I do also agree with Doc H. that those air flow numbers are more important for pine, and may be based on green pine. If I remember right I did the calculations for my kiln (13'-6" long x 7' wide sized for 1,000 bf +/-) and I came up with around 3,700 cfm. Based on drying mostly air dried hardwoods I felt comfortable with 2,000 cfm and was going to use a pair of 1,100 cfm fans. When I went to buy them all they had in stock was the 1,600 cfm fans, so that's what I got. I don't know if too much air will be an issue with air dried hardwoods, but if it is I may need to find a way to slow them down.

[YellowHammer]

The general rule is 250 fpm for hardwoods, 600 for softwoods, so 150 is conservative.  

The main thing is to keep the WB/DB bulb depression to more than 10F for any white hardwood and pine and it is a good idea in general for most hardwoods to avoid sticker stain unless the hardwood is green

Remember that the effect of airflow goes way down as the wood dries.