# I built a 12.5' x 28' greenhouse to store and dry wood--working awesome.



## solarguy2003

We bought a new blaze king for this fall.  I figure to get the most out of it, we should give it very dry wood.  We have heated with wood for a long time.  Up until now, we stored our cut/split wood under tarps that are on frames to keep it (mostly) off of the wood.  That mostly worked, but it was hard to get the wood under 14-15% moisture content.


You will get long term reports of course, but the short term report is awesome!  

This is a hoop house type greenhouse, made of 3/4" emt.  It was relatively inexpensive to put up (well under a thousand dollars).  It has plywood/framing walls for the ends, and 5 year greenhouse plastic for the roof/covering.  You don't get much of a wood framed shed for a thousand bucks any more...

I think the key is that I put vapor barrier plastic down on the ground, because the ground can pump mass quantities of water vapor into a hot greenhouse.  I put black tar paper over that, to give the sun something black to hit, and to protect the integrity of the vapor barrier somewhat.  The second key is the 18 dollar box fan on a timer.  There is a 21" window on each end, one holds the box fan and the other allows the hot humid air to leave.  And man is it hot and humid. 

I set the timer so the fan doesn't come on until 2 pm and the greenhouse is already quite hot.  And it shuts off at 6:00, so I'm not spending a ton on electricity, and the fan runs when the moisture is removed most efficiently.

The greenhouse has a door on each end, so no old dry wood gets trapped by new/wet wood.

The wood is stacked on pallets.

I'll try to post a picture this week sometime.

Water can't get on the wood at all, and water (vapor) is being pumped out in a hurry by heat and forced circulation.


I know that more moisture = more wasted BTU's in my firewood. But how much?  I thought I had seen a chart with moisture content on one axis and energy or efficiency lost on the other axis.  

Any hard data laying around???


thanks!

troy


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## velvetfoot

The metallic conduit can bend so that the diameter is 12.5'?  I've got no experience with hoop houses, only that my wife has said she'd like one.


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## solarguy2003

Most EMT is made of soft annealed steel so it will bend nicely for wiring purposes.  Wire never just runs in a straight line.  So yeah, a 12 foot radius is super easy.  Tons of youtube videos on how to make a hoop house.  The special greenhouse plastic cost more than anything else.

troy


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## Woody Stover

solarguy2003 said:


> I know that more moisture = more wasted BTU's in my firewood. But how much?  I thought I had seen a chart with moisture content on one axis and energy or efficiency lost on the other axis.


Yeah, I thought there were some posts with some of that info. I don't think it's a huge amount of wasted BTU if it's not sopping wet, but keeping the creo at a minimum might be the even greater benefit.


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## DanCorcoran

velvetfoot said:


> The metallic conduit can bend so that the diameter is 12.5"?  I've got no experience with hoop houses, only that my wife has said she'd like one.


Presumably you meant 12.5 feet, not 12.5 inches.


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## velvetfoot

Yes.  Sorry.


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## mustash29

The weight of water varies with temperature, about 8.3 to 8.0 lb/gal from freezing to boiling.  Lets use 8.0 lb/gal for arguments sake.  So 1 lb for 16 ounces of fluid water.

http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html

BTU = amount of heat to raise 1 lb of water 1 deg F.

If the (wet) wood is frozen - You have to heat it up to 32, then change the state from ice @ 32 to water @ 32 (latent heat of fusion), then heat it up to 212, then change the state from water @ 212 to steam @ 212 (latent heat of vaporization).

Lets say our "wet" wood contains an extra pound (16 ounces) of water that is frozen to 0 deg F.

32 BTU to heat it up to 32 deg.
144 BTU to change it to water @ 32.
180 BTU to heat it up to 212 deg.
974 BTU to change it to steam @ 212.

= 1330 BTU wasted up the flue getting rid of that pound of water.

http://en.wikipedia.org/wiki/Latent_heat

http://www.onlineconversion.com/


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## solarguy2003

My back of the napkin calculations based on the pure thermodynamic/phase change numbers above,  suggest that if my previous wood storage method produced wood at 15% moisture content, and my new method produces wood of 10% moisture content, I will improve my BTU output by 1%.  

Humphh.  Dropping the moisture by a third only improves efficiency by 1%.

That seems low to me, but that's what the math says, unless I have dropped a decimal place somewhere.

This site suggests that dropping the moisture from 20% to 10% improves the BTU content from 6660 per pound to 7,300 per pound.  That's a 10% improvement by moving the water content down 10 points (cutting it in half)

http://mha-net.org/docs/v8n2/docs/WDBASICS.pdf


So the truth must lie somewhere in between 2% and 10% more BTU's for cutting the water content by 10 points, (20% to 10%, or 15% to 5%).

troy


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## STIHLY DAN

I have done kind of the same thing with a shelter logic shed. Although its dark green and both ends are always open. Tarps on the ground for vapor barrier. This has worked very well, the red oak was ready in a year, its been two now and I know the wood is premo. Plus it looks as new as when stacked with no none bugs. That also gets very hot in there when the sun is out.


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## Auzzie Gumtree

solarguy2003 said:


> Humphh. Dropping the moisture by a third only improves efficiency by 1%.


All i know is that there is a sweet spot regards moisture levels. Once you get there (in my case ~ 18-19%) there is not as much gain once you go lower but there is a massive difference if you go higher. ie its not a linear benefit.


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## Jutt77

solarguy2003 said:


> We bought a new blaze king for this fall.  I figure to get the most out of it, we should give it very dry wood.  We have heated with wood for a long time.  Up until now, we stored our cut/split wood under tarps that are on frames to keep it (mostly) off of the wood.  That mostly worked, but it was hard to get the wood under 14-15% moisture content.
> 
> 
> You will get long term reports of course, but the short term report is awesome!
> 
> This is a hoop house type greenhouse, made of 3/4" emt.  It was relatively inexpensive to put up (well under a thousand dollars).  It has plywood/framing walls for the ends, and 5 year greenhouse plastic for the roof/covering.  You don't get much of a wood framed shed for a thousand bucks any more...
> 
> I think the key is that I put vapor barrier plastic down on the ground, because the ground can pump mass quantities of water vapor into a hot greenhouse.  I put black tar paper over that, to give the sun something black to hit, and to protect the integrity of the vapor barrier somewhat.  The second key is the 18 dollar box fan on a timer.  There is a 21" window on each end, one holds the box fan and the other allows the hot humid air to leave.  And man is it hot and humid.
> 
> I set the timer so the fan doesn't come on until 2 pm and the greenhouse is already quite hot.  And it shuts off at 6:00, so I'm not spending a ton on electricity, and the fan runs when the moisture is removed most efficiently.
> 
> The greenhouse has a door on each end, so no old dry wood gets trapped by new/wet wood.
> 
> The wood is stacked on pallets.
> 
> I'll try to post a picture this week sometime.
> 
> Water can't get on the wood at all, and water (vapor) is being pumped out in a hurry by heat and forced circulation.
> 
> 
> I know that more moisture = more wasted BTU's in my firewood. But how much?  I thought I had seen a chart with moisture content on one axis and energy or efficiency lost on the other axis.
> 
> Any hard data laying around???
> 
> 
> thanks!
> 
> troy



Here's an interesting study.  Seems to suggest that without proper ventilation and/or a large volume of drying area to wood ratio, there are no gains using a solar kiln or greenhouse vs traditional split stacks.  Good ventilation seems sort of like a no-brainer so good call on the fans.

http://www.familyforests.org/research/documents/DryingFirewoodinKiln.pdf

Also, 15-20%MC is pretty darn good and that's what I shoot for.  Although its nice if it gets a bit lower but really it's somewhat unnecessary to strive for under 15%. 

One other thing, I couldn't find the study I read before but I thought MC bottoms out somewhere around average relative humidity?

Edit: Found the chart: http://www.woodworkerssource.com/moisture.php


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## solarguy2003

When I was researching the idea, I ran across that paper.  My conclusions were:

1.  Has to be sealed from the ground, their's was not.

2.  Needs some active ventilation, aka: a fan, theirs did not include a fan.

3.  Split your wood, they didn't.


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## Jutt77

solarguy2003 said:


> When I was researching the idea, I ran across that paper.  My conclusions were:
> 
> 1.  Has to be sealed from the ground, their's was not.
> 
> 2.  Needs some active ventilation, aka: a fan, theirs did not include a fan.
> 
> 3.  Split your wood, they didn't.



Yep, splitting wood is a no-brainer but regarding the test: both uncovered _and_ covered stacks were unsplit similar sized rounds in order to compare deltas between the two.

Higher humidity levels in the greenhouse relative to humidity levels outside will offset even a significant rise in temperature.  This is pretty easy to extrapolate from the below chart, but if its 80F/50%RH outside then the EMC is 9.1.  At 120F/60%RH then the EMC is 9.7, the wood would actually be taking on moisture even though its 40 degrees warmer due to the bump in relative humidity.  Even with good ventilation to at _least_ match outside RH (a large fan(s) running 24/7) it seems you would need some sort of additional dehumidification process in the greenhouse to actually see a benefit.

This is an interesting long-term experiment though.  Could you measure the temp/humidity levels in the greenhouse at various times and compare them to outside temp/humidity levels?


EDIT: As PB pointed out below, I forgot to account for the drop in relative humidity as temp rises.


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## solarguy2003

Yes.  I have a quality hygrometer and thermometer, so long term data will follow.


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## paul bunion

Jutt77 said:


> Yep, splitting wood is a no-brainer but regarding the test: both uncovered _and_ covered stacks were unsplit similar sized rounds in order to compare deltas between the two.
> 
> Higher humidity levels in the greenhouse relative to humidity levels outside will offset even a significant rise in temperature.  This is pretty easy to extrapolate from the below chart, but if its 80F/50%RH outside then the EMC is 9.1.  At 120F/60%RH then the EMC is 9.7, the wood would actually be taking on moisture even though its 40 degrees warmer due to the bump in relative humidity.  Even with good ventilation to at _least_ match outside RH (a large fan(s) running 24/7) it seems you would need some sort of additional dehumidification process in the greenhouse to actually see a benefit.
> 
> This is an interesting long-term experiment though.  Could you measure the temp/humidity levels in the greenhouse at various times and compare them to outside temp/humidity levels?
> 
> View attachment 135773


I believe you are missing one thing.  A rise in temperature with air pressure and actual moisture content held constant causes the relative humidity to fall quite significantly.   If you take 80 degree air at 50% RH and raise it to 120 degrees the RH falls to 15%.  Then you let some moisture evaporate from your wood to raise the humidity.    Your wood just got drier, that's where the additional humidity came from.   Vent the humidity and the moisture is gone, permanently.

If you can get your greenhouse to gain 40 degrees along with a gain of 10% RH you have gassed off a good deal of water out of your wood.   You are pretty much going to have dry wood wood in a matter of months. As long as you can jack up the temperature significantly I don't think that rapid ventilation is that important, and it becomes progressively less important as the wood gets drier because the will be less moisture to vent.


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## Richie

I have a green house that was professionally made.  It is contructed from wood and has about 12 windows and has a clear plastic roof.  I have six of the the windows cracked.  I recently cut a red oak fresh.  After about a month it is down to 27%.  I would say after another two months it should be ready.  I would guess it gets about 130-140 degrees in there.


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## solarguy2003

Ok, got around to collecting some data.  Today is wednesday, july 30.  It's 12:30 (11:30 not counting DST) 

Outside temperature and humidity are 76* F and 62% RH.

The box fan has not kicked in yet.  The greenhouse has had less than 2 hours direct sunlight.  It's shaded by trees on the east.

Inside temp and RH are:          98*F and 6% RH!


I'll post the numbers once the fan kicks on and the sun heats things up.


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## Jutt77

paul bunion said:


> I believe you are missing one thing.  A rise in temperature with air pressure and actual moisture content held constant causes the relative humidity to fall quite significantly.   If you take 80 degree air at 50% RH and raise it to 120 degrees the RH falls to 15%.  Then you let some moisture evaporate from your wood to raise the humidity.    Your wood just got drier, that's where the additional humidity came from.   Vent the humidity and the moisture is gone, permanently.
> 
> If you can get your greenhouse to gain 40 degrees along with a gain of 10% RH you have gassed off a good deal of water out of your wood.   You are pretty much going to have dry wood wood in a matter of months. As long as you can jack up the temperature significantly I don't think that rapid ventilation is that important, and it becomes progressively less important as the wood gets drier because the will be less moisture to vent.



Yep, I forgot to account for that, good point.


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## Jutt77

solarguy2003 said:


> Ok, got around to collecting some data.  Today is wednesday, july 30.  It's 12:30 (11:30 not counting DST)
> 
> Outside temperature and humidity are 76* F and 62% RH.
> 
> The box fan has not kicked in yet.  The greenhouse has had less than 2 hours direct sunlight.  It's shaded by trees on the east.
> 
> Inside temp and RH are:          98*F and 6% RH!
> 
> 
> I'll post the numbers once the fan kicks on and the sun heats things up.



Very nice!  I might have to try something similar.


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## solarguy2003

It's now 3:40 in the afternoon (2:40 without DST).

Ambient temps are 84F, RH 59%


Greenhouse, the tar paper floor measures 155F.  Air temperature 141F.  

Wood on the surface of the pile varies between 123 and 145, depending on how black it is.

RH measures 2%.  Fan has been on since 2:00.


Totally enthused with the performance and cost of my new wood "shed".

troy


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## JCrean

You've got a heck of an idea there!  You're gonna have all the "kiln dried" wood you need .  141 degree air temp is ferocious!


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## Auzzie Gumtree

How much wood do you have in the greenhouse kiln? is there going to be enough for a winter?


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## Lakeside

solarguy2003 said:


> I'll try to post a picture this week sometime.



Solar,
Any chance of getting those picture's posted


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## paul bunion

With humidity that low you probably don't need to worry about venting at all when the sun is on it.  Increasing the temperature gain will significantly reduce your drying time.  See http://www.firewoodkiln.com/pdf/fplrn254.pdf Dry wood in 2/5 the time by raising the temp from 140 to 180 in a closed (but not sealed) kiln.  You obviously can't maintain that temp 24 hours so venting the moisture as greenhouse cools off in the evening might be the thing to do.   Note that no where in that report do they claim the oak to have been cut-the-day-before-green, starting at 52% it certainly wasn't.


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## Hoozie

It would be very interesting to take some splits from the same round, weigh each one, and throw some in the greenhouse and some outside.  Weigh them every week or 6 and note the difference, hopefully showing the kiln drying them much faster (and see if the outside ones catch up by Fall).

I was going to do this when I got some wood delivered, but got too busy stacking


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## cptoneleg

Should have spent all this time c/s/s and get 3 years ahead instead of trying to bring firewood as low as hardwood flooring.  I thought most modern stoves had a sweet spot of about 20% give or take a bit.

All this high teck is great, how about good old fashion picture.


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## Christopix

As the start of August approaches, thoughts about burning are entering our minds again - cooler nights have begun again - and I thought I'd pay a visit to hearth.com.  This thread caught my attention!  Really interested in seeing a photo if you have time to share.


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## solarguy2003

I will try to get pics up this week.

I currently have 240 cubic feet of wood, so just a hair under 2 cords.  We expect to double or triple that before fall.

I believe the fan to be an essential part of the method.  If it gets really hot, the moisture will leave the wood and go into the air, but the air will be (mostly) confined to the green house.  When it cools off, the moisture will go back in the wood, or condense on the cold plastic and stay inside the greenhouse.  The fan physically removes the moisture from the greenhouse.


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## Knots

I had a greenhouse at the last place I lived that used for fire wood and occasionally - as you can see from the pics (greenhouse in background on the first one) - for drying paint.  It was good, however mine could have used more ventilation.  It would bake the wood during the day and the hot air would hold lots of moisture.  At night the moisture would accumulate on the glass and then rain down again.  The bottom line: the moisture needed some way to get out when the air was warm.  It was good, but not great the way mine was set up.

Side note: mice loved the place.  Mouse-trapping in the fall was a job...


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## solarguy2003

OK, pictures.
side view:   
	

	
	
		
		

		
		
	


	




interior 
	

	
	
		
		

		
		
	


	




east end 
	

	
	
		
		

		
		
	


	




Note that both ends have a door and a window.  This is the passive window that lets the humid air out when the fan at the west end is running.  Both windows will end up with a plywood awning and some 1/4" screening to attempt to keep the mice out.


West end
	

	
	
		
		

		
		
	


	




Note that a box fan -just-  fits between two studs.


floor plastic sealing
	

	
	
		
		

		
		
	


	




I made the dirt floor pretty smooth.  Wacked and pulled all the weeds and grass.  Raked it smooth and removed all the significant sharp rocks.  Laid 6 mill black plastic on the dirt and used  sealant made for polyethylene vapor barrier to seal it to the framing around the edges.  This is called acoustic sealant and I had to special order some.  Then laid tar paper over the plastic to protect it from the wheel barrow and the pallets, etc.

Each rib is comprised of two pieces of 1" emt.  They cost about $6.xx each.  I used a piece of 3/4" emt inside at the joint at the top. The joiner piece is just long enough it can't really slide any further and is trapped.  It's straight.

Note that many plans and youtube videos tell you to put the ribs every 4'.  That will work fine if you don't get much snow or too much wind.  Since we get several to many feet of snow, I put the ribs every 2'.  If it's worth building, it worth over building.

I used 1 1/8 emt that is pounded into the ground, then got screwed to the 2x6 base boards by angling the screw in from the top.  You could also do it by drilling a big hole on the inner surface and small 1/8" hole for the screw to attach it to the 2x6.

The wood base boards are pressure treated 2x6's.  I pounded a 16" length of 1 1/8" emt into the ground to receive each rib.   The rib just slips inside and then gets screwed to the emt.    I attached the emt with various self tapping tech screws in predilled holes.  There are two purlins that run the length of the greenhouse, and every corner got a piece of 3/4" emt for diagonal bracing to resist shear/wind.  I weight 200 pounds and can do pullups on the ribs.   It is a sturdy structure.

Don't forget, you have to use plastic that is rated for greenhouse/outdoor use, or it will be trash in a year.  This stuff is rated for 4 or 5 years, and might last 6 or 7.

troy


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## KenLockett

Sweet!


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## solarguy2003

A 24' x 20' piece of 6 mil greenhouse plastic is about a hundred bucks on ebay.  Guaranteed 4 years, will often last longer if properly installed.

http://www.ebay.com/itm/4-Year-6-Mi...737?pt=LH_DefaultDomain_0&hash=item3ce5866459

troy


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## Jutt77

solarguy2003 said:


> OK, pictures.
> troy



I like it.  I was planning on building a wood shed and greenhouse.  Hmmmm... What are your costs at?


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## solarguy2003

The plastic is about a hundred bucks (more if you have to pay shipping)

The emt for the arches is  1"  x 10'.  It takes two to make an arch.

(36) x $6.49 = $233.64

The emt for the purlins and corner braces is 3/4" x 10'

(10) x 4.06 = $40.60

There are 10 pressure treated 2x6's

4 or 5 sheets of 5/8" plysood at $16 per sheet.

Maybe a dozen 2x4s, pressure treated.

Hinges, a fan.

Oh yeah, and wiggle wire.  That's the slickest and most durable way to attach the plastic:

http://www.poly-tex.com/wiggle_wire.html#.U9wBQvldWSo

I think that was the most expensive single component.

You can restrain the plastic with 1x2's and screws, but the wiggle wire is better.

I think about 700 bucks, give or take a hundred.

If you build a shed, you don't get much shed for $700.

This is 12 x 28 with 6 1/2' high in the middle.


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## Lakeside

Lots of good information here. Thanks Solar !


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## Auzzie Gumtree

Excellent report. How do you test the moisture of the wood which is in the bottom middle of the stack? Just trying to work out how the moist heavy air at the bottom of the stack is going to get moved / circulated. 

Very impressed.


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## solarguy2003

As it comes out of the stack it will get measured.

But it has to come out better than what I've been doing.  Zero water gets on the wood, top, bottom, middle or anywhere else.  And it has regular ventilation with very hot, dry air.


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## renewablejohn

We use solar kilns commercially in UK and have found using IBC container frames ideal for drying bulk split logs inside the solar kiln


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## maple1

I think I would have not sealed the bottom edges of the plastic but rather left a space there for convection to pull cool air in at the bottom, and also maybe to give a spot for moisture that might condense on the inside of the plastic to run down & drip off of & away from. Maybe together with openings at the tops of the ends that might give quite a bit of natural airflow as it heats up? And maybe also check out a solar attic vent fan thing for a fan - no idea what they cost though. Just my initial thoughts - I've never done anything like this though. Do you get any condensation? I'll go back & read the first page, maybe you already posted. Looks good!


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## solarguy2003

When we first put the wood in, there were some conditions where there was some condensation.  Now that the wood has already dried down significantly, there is (so far as I have noticed) none.  Even when we add a batch of newly split stuff, no noticeable condensation.

Yes, it may be possible to design an elegant greenhouse/woodshed that works well passively without the need for a fan.  I leave that for the next guy/gal.

A solar driven fan was considered, but they are expensive and don't move a lot of air compared to the $18 box fan.

http://www.amazon.com/Solar-Attic-Fan-25-year-Warranty/dp/B0002YWVJM

$300 by the time you pay shipping.

troy


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## renewablejohn

Our commercial solar kilns are 8mtr x 25mtr with no fans. Instead it is designed 90 degrees to the prevailing wind open at each end but the important part is the ridge is not horizontal but has a 1 mtr slope over the 25mtr length. This is important as it can give a a 10C to 15C difference in temperature from one end of the tunnel to the other creating a strong convection current taking the moisture out of the tunnel.


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## paul bunion

Auzzie Gumtree said:


> Just trying to work out how the moist heavy air at the bottom of the stack is going to get moved / circulated.




Quite contrary.   Moisture saturated air is lighter than dry air.   (With temp and air pressure and all those other things held constant.).


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## Maverik869

solarguy2003 said:


> The plastic is about a hundred bucks (more if you have to pay shipping)
> 
> The emt for the arches is  1"  x 10'.  It takes two to make an arch.
> 
> (36) x $6.49 = $233.64
> 
> The emt for the purlins and corner braces is 3/4" x 10'
> 
> (10) x 4.06 = $40.60
> 
> There are 10 pressure treated 2x6's
> 
> 4 or 5 sheets of 5/8" plysood at $16 per sheet.
> 
> Maybe a dozen 2x4s, pressure treated.
> 
> Hinges, a fan.
> 
> Oh yeah, and wiggle wire.  That's the slickest and most durable way to attach the plastic:
> 
> http://www.poly-tex.com/wiggle_wire.html#.U9wBQvldWSo
> 
> I think that was the most expensive single component.
> 
> You can restrain the plastic with 1x2's and screws, but the wiggle wire is better.
> 
> I think about 700 bucks, give or take a hundred.
> 
> If you build a shed, you don't get much shed for $700.
> 
> This is 12 x 28 with 6 1/2' high in the middle.



http://www.amazon.com/ShelterLogic-...7427483&sr=1-2&keywords=firewood+shelterlogic

Not knocking on what was done, but the costs makes this product look like a good investment


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## solarguy2003

If that's big enough to store what you want to store, it's not a bad deal.

However, their cost per square foot is at least $2.88.  My cost per square foot is$2.43, and I have more than double the ribs that they have. 

They have a rib every 4 or 5 feet, I have a rib every 2 feet.  I have seen those collapse under snow load around here.

I looked at a lot of kits before I decided to roll my own.

The kit is less work.  

The one you build yourself will give you a more robust structure for the dollar.


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## BCC_Burner

solarguy2003 said:


> If that's big enough to store what you want to store, it's not a bad deal.
> 
> However, their cost per square foot is at least $2.88.  My cost per square foot is$2.43, and I have more than double the ribs that they have.
> 
> They have a rib every 4 or 5 feet, I have a rib every 2 feet.  I have seen those collapse under snow load around here.
> 
> I looked at a lot of kits before I decided to roll my own.
> 
> The kit is less work.
> 
> The one you build yourself will give you a more robust structure for the dollar.



Are you considering your time to be free to get that number?  People so rarely factor in the worth of their time when doing these calculations.  I don't think of myself as a slave, and I know my time has value.


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## solarguy2003

Yes, since I enjoy the work and have the time, I do not account for the cost of the labor. 

 Also, I would have to buy the kit and assemble it, every year.  We get multiple feet of snow, and that just won't hold up. 

 So, my other choice is a much stronger wooden structure, which would take a lot more time and effort, either mine, or someone that I pay.  And considerably more expense.

Do it yourself is not for everybody, but it has worked out well for me.


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## solarguy2003

OK, time for an update.  

Still awesome.

I set the fan to come on at 90-95F, and by then there's plenty of moist humid air ready to get pumped out.

Some of my 1 year old wood got moved into the greenhouse.  It measured 14-16% when I moved it into the greenhouse.  It was split pretty small, and always stored in a tarped stack on pallets.

Within 3-4 weeks, my carefully marked samples measure 0-3% moisture.  The newly split stuff had dropped from high 40's percent moisture to middle 20's percent moisture.

I'm never going back to open stacks with tarps.


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## Poindexter

I am impressed.  I didn't notice weight/mass calcs on page one.

I have to carry my cordwood from the shed, across the back yard, through the garage, up the stairs and across the living room to get to the stove.

If I can get a cord of wood from say 17% down to 16% how much less motrin will I need to take?


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## solarguy2003

Oh yeah, since the pallets will never get wet, and never touch the soil, they will never rot.  I must have hauled half a dozen totally rotten pallets to the dump from my previous wood pile.  Nice little added benefit.


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## weatherguy

solarguy2003 said:


> OK, time for an update.
> 
> Still awesome.
> 
> I set the fan to come on at 90-95F, and by then there's plenty of moist humid air ready to get pumped out.
> 
> Some of my 1 year old wood got moved into the greenhouse.  It measured 14-16% when I moved it into the greenhouse.  It was split pretty small, and always stored in a tarped stack on pallets.
> 
> Within 3-4 weeks, my carefully marked samples measure 0-3% moisture.  The newly split stuff had dropped from high 40's percent moisture to middle 20's percent moisture.
> 
> I'm never going back to open stacks with tarps.


How are you measuring the MC? Are you splitting a piece of wood and measuring on the fresh split face?


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## mark cline

Didn't notice but is there a door at both ends? So the wood that was put in first can be taken out first?


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## RobertNH

solarguy2003 said:


> OK, pictures.
> side view:
> 
> 
> 
> 
> 
> 
> 
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> 
> 
> 
> 
> 
> 
> interior
> 
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> east end
> 
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> 
> 
> 
> 
> 
> 
> 
> Note that both ends have a door and a window.  This is the passive window that lets the humid air out when the fan at the west end is running.  Both windows will end up with a plywood awning and some 1/4" screening to attempt to keep the mice out.
> 
> 
> West end
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Note that a box fan -just-  fits between two studs.
> 
> 
> floor plastic sealing
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> I made the dirt floor pretty smooth.  Wacked and pulled all the weeds and grass.  Raked it smooth and removed all the significant sharp rocks.  Laid 6 mill black plastic on the dirt and used  sealant made for polyethylene vapor barrier to seal it to the framing around the edges.  This is called acoustic sealant and I had to special order some.  Then laid tar paper over the plastic to protect it from the wheel barrow and the pallets, etc.
> 
> Each rib is comprised of two pieces of 1" emt.  They cost about $6.xx each.  I used a piece of 3/4" emt inside at the joint at the top. The joiner piece is just long enough it can't really slide any further and is trapped.  It's straight.
> 
> Note that many plans and youtube videos tell you to put the ribs every 4'.  That will work fine if you don't get much snow or too much wind.  Since we get several to many feet of snow, I put the ribs every 2'.  If it's worth building, it worth over building.
> 
> I used 1 1/8 emt that is pounded into the ground, then got screwed to the 2x6 base boards by angling the screw in from the top.  You could also do it by drilling a big hole on the inner surface and small 1/8" hole for the screw to attach it to the 2x6.
> 
> The wood base boards are pressure treated 2x6's.  I pounded a 16" length of 1 1/8" emt into the ground to receive each rib.   The rib just slips inside and then gets screwed to the emt.    I attached the emt with various self tapping tech screws in predilled holes.  There are two purlins that run the length of the greenhouse, and every corner got a piece of 3/4" emt for diagonal bracing to resist shear/wind.  I weight 200 pounds and can do pullups on the ribs.   It is a sturdy structure.
> 
> Don't forget, you have to use plastic that is rated for greenhouse/outdoor use, or it will be trash in a year.  This stuff is rated for 4 or 5 years, and might last 6 or 7.
> 
> troy



Oh My God Mon!! You went BIG!
Good for you!

I've debated this direction, it's just too simple and works, not to debate it.

I'll read more to see how much wood and how long.
Of course I'll be looking for temps and region to evaluate compared against mine.

Single stack is 'my' current thought.
I'm having a hard time passing 140F
If you're beyond that, then I'm very interested in what you've done!
If so, you've gone beyond what I believed possible.

Love it!
Talk to me!


----------



## RobertNH

renewablejohn said:


> Our commercial solar kilns are 8mtr x 25mtr with no fans. Instead it is designed 90 degrees to the prevailing wind open at each end but the important part is the ridge is not horizontal but has a 1 mtr slope over the 25mtr length. This is important as it can give a a 10C to 15C difference in temperature from one end of the tunnel to the other creating a strong convection current taking the moisture out of the tunnel.



Very interesting aspect that others may not have caught John!
Please explain further!

Here in the 'Colonies' we're not familiar with "mtr", we still resist (have no reason why myself) to working in a simpler fashion.
It's your 'slope' ideal that fascinates me!
It just makes sense, from a naturalist point of view (hmm, simplicity as well).

Please explain further!
Pm me, if indeed I'm the only one interested..


----------



## RobertNH

solarguy2003 said:


> When we first put the wood in, there were some conditions where there was some condensation.  Now that the wood has already dried down significantly, there is (so far as I have noticed) none.  Even when we add a batch of newly split stuff, no noticeable condensation.
> 
> Yes, it may be possible to design an elegant greenhouse/woodshed that works well passively without the need for a fan.  I leave that for the next guy/gal.
> 
> A solar driven fan was considered, but they are expensive and don't move a lot of air compared to the $18 box fan.
> 
> http://www.amazon.com/Solar-Attic-Fan-25-year-Warranty/dp/B0002YWVJM
> 
> $300 by the time you pay shipping.
> 
> troy



Just tell me you're running them from the batteries charged by the panels...


----------



## solarguy2003

The mc is measured by splitting and measuring the fresh split face.  I also checked my cheap ebay chinese meter against

the weight/bake/weigh/bake/weigh method, and it was surprisingly accurate.

The test pieces of my 1+ year old stuff that got moved into the greenhouse were of various sizes, not just the small stuff, or the bigger stuff.



The 120V box fan is operated from uranium at the cook nuke plant.   I have plans for getting away from that, and I optimize/minimise  the use of this precious refined energy


----------



## paul bunion

Did you get your test specimen from the very bottom of the middle row or did it come off the top?


----------



## solarguy2003

I tested several, from several spots. .  I don't think there was any pattern from top or bottom.  They were all 3 or 4% and less in the one year old wood.

They all sit up on pallets, the fan keeps the air moving, the heat just keeps cooking the water out.


----------



## solarguy2003

Yes, there is a door on both ends, so dry seasoned wood won't get trapped by the new green stuff.


----------



## gzecc

solarguy2003 said:


> OK, pictures.
> side view:
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> interior
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> east end
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Note that both ends have a door and a window.  This is the passive window that lets the humid air out when the fan at the west end is running.  Both windows will end up with a plywood awning and some 1/4" screening to attempt to keep the mice out.
> 
> 
> West end
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Note that a box fan -just-  fits between two studs.
> 
> 
> floor plastic sealing
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> I made the dirt floor pretty smooth.  Wacked and pulled all the weeds and grass.  Raked it smooth and removed all the significant sharp rocks.  Laid 6 mill black plastic on the dirt and used  sealant made for polyethylene vapor barrier to seal it to the framing around the edges.  This is called acoustic sealant and I had to special order some.  Then laid tar paper over the plastic to protect it from the wheel barrow and the pallets, etc.
> 
> Each rib is comprised of two pieces of 1" emt.  They cost about $6.xx each.  I used a piece of 3/4" emt inside at the joint at the top. The joiner piece is just long enough it can't really slide any further and is trapped.  It's straight.
> 
> Note that many plans and youtube videos tell you to put the ribs every 4'.  That will work fine if you don't get much snow or too much wind.  Since we get several to many feet of snow, I put the ribs every 2'.  If it's worth building, it worth over building.
> 
> I used 1 1/8 emt that is pounded into the ground, then got screwed to the 2x6 base boards by angling the screw in from the top.  You could also do it by drilling a big hole on the inner surface and small 1/8" hole for the screw to attach it to the 2x6.
> 
> The wood base boards are pressure treated 2x6's.  I pounded a 16" length of 1 1/8" emt into the ground to receive each rib.   The rib just slips inside and then gets screwed to the emt.    I attached the emt with various self tapping tech screws in predilled holes.  There are two purlins that run the length of the greenhouse, and every corner got a piece of 3/4" emt for diagonal bracing to resist shear/wind.  I weight 200 pounds and can do pullups on the ribs.   It is a sturdy structure.
> 
> Don't forget, you have to use plastic that is rated for greenhouse/outdoor use, or it will be trash in a year.  This stuff is rated for 4 or 5 years, and might last 6 or 7.
> 
> troy


 
Keep the mice out. Thats funny. Its going to be club med for mice. Nice and warm at night.


----------



## solarguy2003

In the other half of the greenhouse, I keep tomatoes and fig trees in pots.  Mice are BAD for fig trees, so I trap aggressively and they are getting thinned out pretty good.  The couple tons of firewood provide some thermal mass to keep the greenhouse warm at night for the plants.


----------



## RobertNH

Thermal mass.. This is something I really didn't catch when I started into this..
It's amazing how much thermal mass is involved with wood (and directly to what we hope to dry).

At some point I will get down to the numbers (math doesn't lie) and figure some of this out.

One of my 'experiments' was the Black Cover.
Thought was collected more heat and transference of such would be great.
Reality is seeing clear allows more to come in contact with subject (wood) and the mass (wood) does collect quite a bit!

I'm rather impressed!

I'm looking at doing something very close to what you have.
The difference comes from an article I read about curvature of the top in induce air flow.
Basically, if ends are higher than mid, then natural air flow is induced.
Of course there is some math involved to get it right.. But.. Very nice concept.

Cut your mid supports shorter and possibly remove the fans?
I'm liking the concept, has warrant and should be looked at.


----------



## renewablejohn

RobertNH said:


> Very interesting aspect that others may not have caught John!
> Please explain further!
> 
> Here in the 'Colonies' we're not familiar with "mtr", we still resist (have no reason why myself) to working in a simpler fashion.
> It's your 'slope' ideal that fascinates me!
> It just makes sense, from a naturalist point of view (hmm, simplicity as well).
> 
> Please explain further!
> Pm me, if indeed I'm the only one interested..



Sorry about the mtr I am of the age that I use both mtr and yds but the younger generation are all metric so I have had to convert but still enjoy a pint at the local. we also sell timber by mtr cube rather than cords.
As for polytunnels I am from a horticulture background so used to polytunnel design. Our normal horticulture tunnels are 40 mtr long and again use a slight slope on the roof line as we suffer frosts in the winter and require heat for frost protection. Having the slope allows a sawdust burner at one end heat the whole tunnel by natural convection of heat rising.
When we came to designing the solar kiln we just applied the same technique. The only additional requirement was bog mats on the polytunnel floor to allow the 2 tonne free lift forklift to operate within the tunnel stacking the IBC container frames which each hold 1mtr cube of split logs. The bog mats also provide additional thermal mass but I have not bothered to paint them black as yet as the tunnel is hot enough without.


----------



## RobertNH

renewablejohn said:


> Sorry about the mtr I am of the age that I use both mtr and yds but the younger generation are all metric so I have had to convert but still enjoy a pint at the local. we also sell timber by mtr cube rather than cords.
> As for polytunnels I am from a horticulture background so used to polytunnel design. Our normal horticulture tunnels are 40 mtr long and again use a slight slope on the roof line as we suffer frosts in the winter and require heat for frost protection. Having the slope allows a sawdust burner at one end heat the whole tunnel by natural convection of heat rising.
> When we came to designing the solar kiln we just applied the same technique. The only additional requirement was bog mats on the polytunnel floor to allow the 2 tonne free lift forklift to operate within the tunnel stacking the IBC container frames which each hold 1mtr cube of split logs. The bog mats also provide additional thermal mass but I have not bothered to paint them black as yet as the tunnel is hot enough without.



Ya killin' me here.. Yet Loin' it..
I do prefer my 'glass' chilled, but that as side for further conversation, it comes down to a swallow of preferred and explanation of 'MTR'?
Curvature of design comes down to degrees, again another shallow, and we continue..
M(assumed meters) 'of'(T, assumed 'to') to what (R)'?

Degrees of inclination?
Have you charted what you have seen, according to what you have done?
Have you reached a point of which X does vs, What Y dies?
Yet another shallow and hopefully the conversation continues,,,

I'm enjoyin' my chilled.
Hopefully, while enjon' your warm..
We'll get down to the bottom of this, aye?

Clink! Here's to you!
Tell me some more.


----------



## Pellet_Pete

Reading this thread reminded me of something I read this past summer - not a how-to, but reinforces a lot of what you folks have been finding in your "experiments".

http://northernwoodlands.org/knots_and_bolts/passive-solar-firewood-dryer


----------



## DanCorcoran

RobertNH said:


> Ya killin' me here.. Yet Loin' it..
> I do prefer my 'glass' chilled, but that as side for further conversation, it comes down to a swallow of preferred and explanation of 'MTR'?
> Curvature of design comes down to degrees, again another shallow, and we continue..
> M(assumed meters) 'of'(T, assumed 'to') to what (R)'?
> 
> Degrees of inclination?
> Have you charted what you have seen, according to what you have done?
> Have you reached a point of which X does vs, What Y dies?
> Yet another shallow and hopefully the conversation continues,,,
> 
> I'm enjoyin' my chilled.
> Hopefully, while enjon' your warm..
> We'll get down to the bottom of this, aye?
> 
> Clink! Here's to you!
> Tell me some more.




I think he was referring to meters and yards ("mtr and yds")...


----------



## renewablejohn

Okay I will start again. Yes mtr is indeed meter or for you in the US 1 yard and 3 inches. Our solar kilns are all measured in mtrs being 8 mtrs wide and 25 mtr long with hoops at 2.5 mtr centers. The hoops slide over a ground anchor which is just a smaller diameter tube with a bucket of concrete attached to the bottom. (We have to do this in UK to keep the structure as a "temporary" structure to avoid the strict planning laws on permanent structures). With a spirit level and string mark horizontal on first and last tube then decide which direction you want the heat to go and then move the string up 1 mtr at the hot end. Where the string crosses the tubes attach a car exhaust clamp of the right pipe diameter repeat on both sides then slide hoops onto the anchors and you have your solar kiln frame with gradual slope ready for covering with plastic. Remember to grease the exhaust clamps as you can tighten the plastic if it goes slack using the clamps.
Performance wise it takes 3 months to get split logs below 20% MC during the summer and 6 months in the winter. Our D shaped tunnel holds 80 IBC containers and the straight sided although the same size holds 120 IBC containers. Each IBC container holds 1.2 meter cube of loose fill logs.


----------



## renewablejohn

This is how we fill our IBC containers although it is now located within the polytunnel as I hate being cold and wet.


----------



## RobertNH

renewablejohn said:


> Okay I will start again. Yes mtr is indeed meter or for you in the US 1 yard and 3 inches. Our solar kilns are all measured in mtrs being 8 mtrs wide and 25 mtr long with hoops at 2.5 mtr centers. The hoops slide over a ground anchor which is just a smaller diameter tube with a bucket of concrete attached to the bottom. (We have to do this in UK to keep the structure as a "temporary" structure to avoid the strict planning laws on permanent structures). With a spirit level and string mark horizontal on first and last tube then decide which direction you want the heat to go and then move the string up 1 mtr at the hot end. Where the string crosses the tubes attach a car exhaust clamp of the right pipe diameter repeat on both sides then slide hoops onto the anchors and you have your solar kiln frame with gradual slope ready for covering with plastic. Remember to grease the exhaust clamps as you can tighten the plastic if it goes slack using the clamps.
> Performance wise it takes 3 months to get split logs below 20% MC during the summer and 6 months in the winter. Our D shaped tunnel holds 80 IBC containers and the straight sided although the same size holds 120 IBC containers. Each IBC container holds 1.2 meter cube of loose fill logs.



Thank you John for your patience and explanation!
That's one heck of a lot of wood placed in there!

No other source of heat..
That much wood..
And, not insulated on the backside??
And you can turn it over in 3 months..
I'm impressed!

It's the curvature of the top that strikes me the most.
Very inventive!


----------



## DanCorcoran

RobertNH said:


> Thank you John for your patience and explanation!
> That's one heck of a lot of wood placed in there!
> 
> No other source of heat..
> That much wood..
> And, not insulated on the backside??
> And you can turn it over in 3 months..
> I'm impressed!
> 
> It's the curvature of the top that strikes me the most.
> Very inventive!



Looks like a Hearthstone Shelburne...is it?


----------



## renewablejohn

RobertNH said:


> Thank you John for your patience and explanation!
> That's one heck of a lot of wood placed in there!
> 
> No other source of heat..
> That much wood..
> And, not insulated on the backside??
> And you can turn it over in 3 months..
> I'm impressed!
> 
> It's the curvature of the top that strikes me the most.
> Very inventive!



You must remember this is a commercial operation but you can apply the same techniques on a smaller scale. Part of the reason why it works so well is the timber is not stacked but loose fill within the IBC containers allowing the air to circulate around the logs this is particularly important when drying "wet" timber such as willow and poplar to avoid it going mouldy.


----------



## RobertNH

DanCorcoran said:


> Looks like a Hearthstone Shelburne...is it?



Why yes it is!
Love it!


----------



## RobertNH

renewablejohn said:


> You must remember this is a commercial operation but you can apply the same techniques on a smaller scale. Part of the reason why it works so well is the timber is not stacked but loose fill within the IBC containers allowing the air to circulate around the logs this is particularly important when drying "wet" timber such as willow and poplar to avoid it going mouldy.



I'll be able to look up Bolton and get some historical weather info to compare to mine.
Some temperature readings inside the kiln would be very nice, as well as time of season.
Is Willow and Poplar your main wood?
Willow having a density of 54lbs per cubic ft and Poplar @ 38lbs (considered @ 50%), the Willow comes closest to what I'm drying.
I'm working in the 54-63% range.

I'm liking what both you folks are doing!
The system has much merit and dual purpose for me.


----------



## mellow

Bump, any updates on how long it is taking you to season fresh split wood down to below 20%?


----------



## RobertNH

mellow said:


> Bump, any updates on how long it is taking you to season fresh split wood down to below 20%?



Who is Bump??
Interested in whom your following.. and what he has.

Both John and Solar are running the same basic way, and from what I've learned from my experiments, I'm really liking the direction.
I own 2 'round tops' I use for storage and here in NH, with the snow, they've held up great.
I see one more more in my future to dry my wood.

I have no doubt that it will dry my wood from fresh cut to burnable (seasoned >20%) in half the summer.
My little 'face cord' solar kiln is still drying wood wonderfully.
Saw a 90* temp out there as I was reloading in 30* weather.

Size I do believe matters, but in this case, smaller is better.
IMHO, size your unit to what you need to dry and how often you wish to re-load.

I'm probably going to buy a 20' unit.
This way I can load once (for my needs 2+ cords) and have it all in the direct sun (the second thing I learned about expediting drying).
I plan to only use half the season (mid-summer) to complete my loading.
From what I've learned so far, that may even be too early.

So... Who is Bump and what does he have?


----------



## mellow

RobertNH said:


> Who is Bump??
> Interested in whom your following.. and what he has.
> So... Who is Bump and what does he have?




Bump is a term meaning to bring the thread back to the top again to try and revive it.


----------



## RobertNH

Well then, I hope I did!


----------



## RobertNH

Here's a link to my experiments with drying: https://www.hearth.com/talk/threads/expeditided-wood-drying-solar-kiln.131537/page-2

All three work, just some better than others.
The Big Black Box shown was changed (and I show this) to a clear cover.
Made quite the difference.

The S&G (just a clear plastic over the pile) worked quite well!
For just the cost of plastic, very  inexpensive way to go.

My Display Case (the Solar Kiln) works the best.

We just had a bad heavy snow storm and I've cleared some of the downed limbs and added them to the small kiln.
Largest piece being 5" round.
I'm curious how long it will take to get to 20%, especially with this being winter now and no more ambient temps being over 35*..
I read 90* in it just the other day!
So it still gets hot enough!


----------



## solarguy2003

Just a little fall update with some more data.  The greenhouse/solar dryer continues to perform well.  The wood rounds that have been cut and stacked outside all read 41-45%.

The four random splits that I checked on the east end (it's been split and stacked in the greenhouse 3-4 weeks read:  22, 23, 34, and 25%

The four random splits that I checked on the west end (it's been split and stacked in the greenhouse ~3 months read: 17, 23, 16 and 21%

The old stuff that I could still reach (been in there a year or so) read; 9, 11,  9 and 7%

All moisture readings done on a freshly split face across the grain with an inexpensive but verified (fairly) accurate 4 pin chinese moisture meter.

And the tomato plants and fig trees seem pretty happy too.

Since I had plants in the greenhouse this summer, I added a second cheap box fan to insure the plants didn't overheat.  It worked, the plants never overheated.  But it was also not as hot and steamy as last year with just one fan.  The wood still seems to be drying nicely and next year I'm going back to one fan and see if the plants tolerate the additional heat ok.  I'm sure there is some optimum ventilation rate that balances top temperature with rapid moisture removal.


----------



## HisTreeNut

I just read through the thread and that's impressive.
Has me thinking...


----------



## BlueRidgeMark

It's been interesting reading  this thread and seeing the initial skepticism that was expressed.   The science of this is undeniable, and not at all complicated.

I did something like this on a very small scale one year when I was short of dry wood. I just stacked a pallet with wood, and wrapped it in clear plastic food wrap, including the top.  I used a 12" duct elbow as a vent in the top, and wrapped it into place.  Pure convection.  Within a couple of hours there were drops of condensation visible on the inside of the plastic.  I got a pallet fully of nicely dry wood in a matter of a couple of months.  I don't have a moisture meter to provide a number, but it sure burned well a few months after being wrapped up.

Now that I've seen the hoop kiln in all its glory, my wife is going to hate this forum.  I have another project in my future!


----------



## RobertNH

solarguy2003 said:


> Just a little fall update with some more data.  The greenhouse/solar dryer continues to perform well.  The wood rounds that have been cut and stacked outside all read 41-45%.
> 
> The four random splits that I checked on the east end (it's been split and stacked in the greenhouse 3-4 weeks read:  22, 23, 34, and 25%
> 
> The four random splits that I checked on the west end (it's been split and stacked in the greenhouse ~3 months read: 17, 23, 16 and 21%
> 
> The old stuff that I could still reach (been in there a year or so) read; 9, 11,  9 and 7%
> 
> All moisture readings done on a freshly split face across the grain with an inexpensive but verified (fairly) accurate 4 pin chinese moisture meter.
> 
> And the tomato plants and fig trees seem pretty happy too.
> 
> Since I had plants in the greenhouse this summer, I added a second cheap box fan to insure the plants didn't overheat.  It worked, the plants never overheated.  But it was also not as hot and steamy as last year with just one fan.  The wood still seems to be drying nicely and next year I'm going back to one fan and see if the plants tolerate the additional heat ok.  I'm sure there is some optimum ventilation rate that balances top temperature with rapid moisture removal.



Very well done!
The Solar Kiln (display box) gets the same results. Last time though I ran some larger splits than I usually do, just to see the results. Mid-High 20's in a month. This from a Red Oak I just took down the week previous.

If you have a decent sized gram scale (bought mine online for $15), try weighing a piece and compare your MR to the scale shown here.
http://www.engineeringtoolbox.com/weigt-wood-d_821.html


----------



## Poindexter

I dunno how many times I have read this thread and followed the links, but it's a lot.

I sent pencil sketches off to a local engineer today, I am going for a passive unit that doesn't need a fan.  I hope to have good results about a year from now...

Thanks for the inspirational ground work.


----------



## 3fordasho

I've been stacking wood on pallets to about 5.5' high and then wrapping with stretch netting.  Holds it together well enough to move with the bobcat. 
Last night I tried a little different version with stretch film, then netting (in case the sunlight degrades the film) and then a short scrap of 5" duct for a vent on top.


----------



## Poindexter

3fordasho said:


> I've been stacking wood on pallets to about 5.5' high and then wrapping with stretch netting.  Holds it together well enough to move with the bobcat.
> Last night I tried a little different version with stretch film, then netting (in case the sunlight degrades the film) and then a short scrap of 5" duct for a vent on top.
> 
> 
> 
> 
> 
> 
> 
> 
> 
> View attachment 164492



That will probably work pretty good for ya.  Did you close the bottom, or have you got the pallet sitting on something that doesn't let groundwater through?


----------



## solarguy2003

I'm not sure I ever mentioned, the long axis of the greenhouse runs east/west for optimal exposure to the sun.  It's not an absolute requirement, as greenhouses still work when the long axis is north/south, just not as much heat input.


----------



## renewablejohn

mellow said:


> Bump, any updates on how long it is taking you to season fresh split wood down to below 20%?


Apologise if this bump was for me but I thought I had already answered the question at post 66. Anyway to repeat if you missed it it takes approx 3 months in summer for green wood 50-60% MC to be below 20% MC and approx 6 months over the winter period.


----------



## renewablejohn

solarguy2003 said:


> I'm not sure I ever mentioned, the long axis of the greenhouse runs east/west for optimal exposure to the sun.  It's not an absolute requirement, as greenhouses still work when the long axis is north/south, just not as much heat input.



I am actually on a very windy hill top site the prevailing wind is West to East so the spine of our tunnels are North to South allowing the prevailing wind to flow over the tunnels like an aircraft wing.


----------



## solarguy2003

renewablejohn said:


> Apologise if this bump was for me but I thought I had already answered the question at post 66. Anyway to repeat if you missed it it takes approx 3 months in summer for green wood 50-60% MC to be below 20% MC and approx 6 months over the winter period.



Yes, just to confirm, lots of the wood is below 20% in 4-6 weeks.  Nothing takes longer than 6 months. 

I just went out and split a few.  The older stuff almost all reads 4-7% on the 4 pin chinese moisture meter.  One piece at the old/dry end read 17%.  ???  Meh...an outlier.  data is data...

The newest stuff reads 16-18%.  The newer stuff got split and put in the greenhouse in late september.  It is currently being run in a somewhat compromise fashion.  I still have tomatoes and fig trees at one end.  So the windows are totally blocked, and I'm still watering them both.  I get condensation on the plastic most nights.

If I were running it just for the firewood, I would still be opening the windows and turning on the fan on sunny days.

Despite that, it's still awesome.


----------



## Rustyreel

solarguy2003 said:


> Yes, just to confirm, lots of the wood is below 20% in 4-6 weeks.  Nothing takes longer than 6 months.
> 
> I just went out and split a few.  The older stuff almost all reads 4-7% on the 4 pin chinese moisture meter.  One piece at the old/dry end read 17%.  ???  Meh...an outlier.  data is data...
> 
> The newest stuff reads 16-18%.  The newer stuff got split and put in the greenhouse in late september.  It is currently being run in a somewhat compromise fashion.  I still have tomatoes and fig trees at one end.  So the windows are totally blocked, and I'm still watering them both.  I get condensation on the plastic most nights.
> 
> If I were running it just for the firewood, I would still be opening the windows and turning on the fan on sunny days.
> 
> Despite that, it's still awesome.[/QUOT
> Excellent. How well does it hold up to the snow load? I live in the snow belt along lake superior.


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## solarguy2003

The snow hasn't bothered it a bit.  I have noticed several commercially available kits for quicky garages and the like, and the snow just trashes them in a heavy year.  We get a fair amount of lake effect snow.  I occasionally run the snowblower around it (maybe twice last winter) just so the snow has a place to shed better.  I'm not sure it was even necessary.  The cheap commercial units have a rib every 4 feet, and mine has a rib every 2 feet.  Plus a big diagonal brace on every corner.  No complaints so far.


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## drz1050

The windows in the ends: are they always open, or do you seal them up in cold weather to hold as much heat in as possible?


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## solarguy2003

Since I had fig trees and tomatoes, I would close it up any time it dropped below freezing.  I got another 6 weeks out of the tomato plants.

Now I just leave it closed up.

Last year (no plants) I left them open and we got a little snow blow in and drift in through the windows.


It's such a treat to park the wheelbarrow outside the door and not have to fart around with tarp and dig stuff out of the snow.

Once we get one more row of firewood inside, we can push the wheelbarrow right inside to load up.


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## drz1050

I like this thing a lot, and might try to copy you in the springtime here.. have to just figure out a place to put it first.

What type of wood were your figures based from? Oak? Maple? Pine?


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## solarguy2003

It was a mixed lot of everything.  I have 7 acres and there's an oil pipeline in my pasture.  They replaced it and had to cut down about 80 good sized trees as part of that process.  It was all mixed hardwoods, the most common species being maple.  After spending a lot of tedious work getting it all in writing that they were to chip everything smaller than one inch (and nothing else), and stack all the logs in a pile in a certain place...I came home to a pile of chipped mulch the size of my house.  All of it.   I was soooooo mad.

So anyway, they had to replace my hardwood trees/log and brought in a truckload of stuff which turned out to have a little bit of everything.  Quite a bit of oak, -pine-, -fir-, some of that stuff that smells like urine when you split it (cottonwood maybe), some shirt that dulled my freshly sharpened chain in two smoking cuts., maple, etc etc etc.  

I was so sick of them screwing up, I just told them to go away and stay away.  


There...got it off my chest.


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## neverbilly

solarguy2003 said:


> It was a mixed lot of everything.  I have 7 acres and there's an oil pipeline in my pasture.  They replaced it and had to cut down about 80 good sized trees as part of that process.  It was all mixed hardwoods, the most common species being maple.  After spending a lot of tedious work getting it all in writing that they were to chip everything smaller than one inch (and nothing else), and stack all the logs in a pile in a certain place...I came home to a pile of chipped mulch the size of my house.  All of it.   I was soooooo mad.
> 
> So anyway, they had to replace my hardwood trees/log and brought in a truckload of stuff which turned out to have a little bit of everything.  Quite a bit of oak, -pine-, -fir-, some of that stuff that smells like urine when you split it (cottonwood maybe), some shirt that dulled my freshly sharpened chain in two smoking cuts., maple, etc etc etc.
> 
> I was so sick of them screwing up, I just told them to go away and stay away.
> 
> 
> There...got it off my chest.



Did your contract provide for 'liquidated damages' in the event of a screwup? Meaning that a dollar amount they would pay, agreed beforehand? Whatever... they should be contractually liable for the screwup. Meaning, they should replace your wood with like kind, or pay you. I know that was disappointing and disheartening. The supervisor is a bonehead.


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## solarguy2003

neverbilly said:


> Did your contract provide for 'liquidated damages' in the event of a screwup? Meaning that a dollar amount they would pay, agreed beforehand? Whatever... they should be contractually liable for the screwup. Meaning, they should replace your wood with like kind, or pay you. I know that was disappointing and disheartening. The supervisor is a bonehead.



Yes, I got some extra money out of the deal.  That did make me feel somewhat better.  I never thought to include a clause that gave me financial remuneration for them pissing me off.  And I now have a lifetime supply of mulch, which I can actually use...eventually.


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## Kristen

solarguy2003 said:


> I now have a lifetime supply of mulch, which I can actually use...eventually.



Is the pile generating heat - enough that you could harvest that heat perhaps?


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## solarguy2003

Kristen said:


> Is the pile generating heat - enough that you could harvest that heat perhaps?


Short answer, no.  That surprised me.

Longer answer, they put the pile in the wrong place (where I would get stuck driving across the disturbed wet swampy spots).  So I made them move it.  When they did that, they mixed a bunch of dirt in with it.  That's the only reason I can think of that it didn't heat up.


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## solarguy2003

Spring update on the solar heated firewood dryer.  Still working awesome.  Over the winter, I kept everything closed, since we got some snow drifting in through the open windows last winter.  We had no snow inside, which is a plus, but the wood didn't stay -as- dry as the previous winter with ventilation.  Various pieces measured from 12-16% mc, which is still fine.

I also added a second "window"  (a hole that I can open or close) on both ends, so now a door and two "windows" on each end.  With two box fans.  The additional ventilation was to reduce the daytime highs to make the tomatoes and tomatillos and fig trees happier, not necessarily to make the firewood happier.  Next year I'm building a second one for exclusive use by the plants.  When we put the fresh green firewood in this year, I'll see what double the ventilation, but at reduced temperatures does.


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