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

[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.

 

[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.

 

[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.

 

[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...

 

[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

 

[KenLockett]

Sweet!

 

[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.

(broken link removed to http://www.ebay.com/itm/4-Year-6-Mil-Clear-Plastic-Greenhouse-Poly-Film-24-ft-x-20-ft-/261548827737?pt=LH_DefaultDomain_0&hash=item3ce5866459)

troy

 

[Jutt77]

OK, pictures.
troy

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

 

[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.

 

[Lakeside]

Lots of good information here. Thanks Solar !

 

[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.

 

[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.

 

[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

 

[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!

 

[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

 

[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.

 

[paul bunion]

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.).

 

[Maverik869]

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

 

[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.

 

[BCC_Burner]

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.

 

[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.

 

[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.

 

[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?

 

[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.

 

[weatherguy]

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?