# Heating wood shed to dry faster?



## jpowell1979 (Sep 28, 2009)

I have a 12x14 shed that houses my Greenwood boiler.  I usually store 3 cords of wood in there as well.  I burn mostly birch and it does not dry very fast.  Would it be worth it to heat the shed to speed up the drying.  The shed is insulated with R-14 and usually stays around 50-65 from the heat coming off the boiler.  How hot would I need to heat it and would it be worth while?


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## DeePee (Sep 28, 2009)

I've been researching a similar tangent of recent. I'm sorry this won't directly answer your question, but perhaps will be helpful none-the-less.

Estimating Air Drying Times of Lumber With Multiple Regression

The other factor is the 'cost' to increase the temperature in the shed. I was curious, so I plugged some numbers into a BTU calculator, calculated BTU per month and referenced that against the species listing ( in the Heath.com article section ). In my worst case scenarios, and assuming a softwood fuel like pine or fir, I'd bet the cost would fall somewhere between 0.75 and 1 cord per month. Unless the issue is that the 3 cords are completely green, you're likely getting the most benefit right now passively, from the 'free' waste heat.

Best regards.


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## maplewood (Sep 28, 2009)

Hi to my old University town - Fairbanks!
I remember when the only hardwood was white birch (Anchorage for 9 years, Fairbanks for 1.5). We burned a lot of softwood in those days, too.
If you are at about 60F now, you're drying your wood. I don't think raising the temp a little more would make a drastic difference.
What's your C/S/S schedule? Do you have unsplit wood? There are a lot of threads to discuss time and size for seasoning. The consensus is at least a year, and reasonable splits (6" across max or less). Do you dry the wood outside for at least a year, then put it in your shed?
The shed is an excellent idea. If it can stay warm all through your winter, it's a fantastic shed. Most of us loose drying time over a year because our wood is outdoors, and it ain't dryin much from Dec. - March. But if you store it in a warm dry shed all winter, you're probably getting at least 2 years drying in less than one year.
Pics would help!
Happy burning.


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## jpowell1979 (Sep 28, 2009)

My wood hauling truck was broke down for a while and I did not get this years wood cut when I wanted to.  I have several cords of good dry wood but most of the wood that I want to burn this spring is in the range of 27-35% moisture content right now.  

Right now I do not have water storage but I have a 1200 sq ft slab in the garage and basement that is 6" thick.  When the house is not calling for heat I dump the extra heat into the slab which seems to work fairly well.  I was thinking of plumbing in a heating loop with a magnetic valve in the shed for overheat protection in the event of a power outage.  If I did this then I could easily divert some of the extra heat to drying the wood if it would be of any incremental benefit.


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## DeePee (Sep 28, 2009)

Increasing the temperature and maximizing the differential in humidity would certainly help speed things up. If the energy used is waste in the first place, why not?


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## rotaxman (Sep 28, 2009)

I grew up with wood that was always too green to burn in the fall. 60 degrees will definately dry your wood somewhat but you absolutely need good air flow, so get one or more fans in there and provide an escape for the moisture. If you can measure the moisure in the room, that would help maximize your setup


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## stee6043 (Sep 29, 2009)

I have to believe someone out there has done at least some math on the cost of drying wood "mechanically" vs heating with the energy you used to dry your wood.

I tend to think it would be cheaper and more efficient to heat your home (for sure in the shoulder seasons) with the energy you would be using to dry your wood.  At the end of the day I'd suspect you're going to spend more to get your wood into suitable burning condition than you would just to fire up the furnace and burn some good ole fossil fuels.

Save the non-seasoned wood for next year...


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## yknotcarpentry (Sep 29, 2009)

I used to work in a place where we built post and beam modular cottages. we would mill all our lumber from rough pine timbers, occasionally when we got some wet timbers we had a small old trailer container that was attached to the workshop. we would stack the timbers in there on bunks and set up a few box fans for air circulation and had electric baseboards that we would crank to 80*. It was a bit slow but yes it worked, we where able to finish drying down to 7-8% and at times the water would be running out the bottom of the trailer, I was kinda of impressed that it worked the first time I saw it. I would think you needed more heat than what you get. I would say it took about 2 weeks for 5"x10"x12' timbers to dry out 3 or 4%? it was 6 or so years ago so my memory may be off a bit.
good luck!


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## jpowell1979 (Sep 29, 2009)

My alternative to free wood is heating oil which is going for $2.70 a gallon today so I need to burn this wood this winter.  I know that I could get by by mixing the wet wood with my dry wood.  I think that speeding up the drying process a little would give me better results.  I found some kiln drying manuals and they heat the wood to 140 degrees for 10 days to get from fresh cut to >30%.  Since the shed gets to 60-70 this time of year from latent heat from the boiler and chimney pipe it would not take too many BTU's to get to 100+ for a week or two with a couple of box fans circulating the air.  

I need to build a dump zone for safety purposes anyways so I might as well make an experiment out of it.  I ordered a automag zone valve today.  I have an idea to build a DIY heat exchanger with a couple of sections of old baseboard and some 3/4" tees.  I was going to put it together so you could tye-wrap a box fan too it and you have a 3-speed heat exchanger.


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## lexybird (Sep 29, 2009)

i have found anything near room temperature isnt going to season wood faster by much ,a kiln heats with hundreds of degrees 
it takes time and theres no true easy shortcut in my experiance


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## sdrobertson (Sep 29, 2009)

Last year I had the same problem with my wood supply.  What I ended up doing was split the wood down to 2" splits and stack as much as I could in my boiler room.  When I'm burning the boiler it gets up to around 90 degrees or so and it seemed to help a little bit.  I bought a electric splitter so I could resplit all of my wood down this far as what I thought was dry wood, wasn't even close.  Small splits and mixing with dry wood will get you through but its a pain and not much fun.


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## jpowell1979 (Sep 29, 2009)

http://www.firewoodkiln.com/firewood/Firewoodkiln.html

These guys sell kits to convert a shipping container into a kiln using a central boiler for heat.

If you break it down my shed is basically putting the boiler inside and I have better insulation than any container would.  It is R-14 with 6mil vapor barrier and sheet metal siding inside.


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## jpowell1979 (Sep 29, 2009)

I found a study using Oak, it looks like it makes a big difference if you can get the temps up.

The drying times for the experimental conditions are shown in figure 2. The
average initial moisture content was 52 percent (dry basis). As expected, the
drying time decreases as temperature increases. The times required to reach 20
percent moisture content were as follows:

Loading method Drying temperature (hours)
                      140 °F 180 °F 220 °F
Parallel stacks 226     97       34
Random stacks 287    87       29
Average           257    92       32

Times ranged from a low of slightly more than 1 day (29 to 34 h) at 220 F to a high of 11 to 12 days (226 to 287 h) at 140 F. An analysis of variance showed that the effect of drying temperature on drying time was statistically significant, but that the differences in drying times observed for stacking versus piling were not statistically significant. Parallel stacking is more efficient than random piling because of kiln capacity and energy parallel should also be considered. use, but the increased effort required to stack


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## flyingcow (Sep 29, 2009)

My only observation would be is when you get 2 yrs ahead, don't put it in to the garage until late fall. I have a insulated garage I keep my wood in. Once wood goes inside garage, the drying slows to a crawl. Wood stacked on pallets and have pallets against walls. Nothing beats outside in the open. You'd have a hard time convincing me that heating a woodshed to help drying the wood will save $$. As pointed out above, split it small. Maybe build a rack or two to hang over boiler. Or store directly beside boiler, on a pallet. Keep rotating a couple of days of wood. Moving air would be a big plus, especially without sucking up electricity.


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## mole (Sep 29, 2009)

I have a Seton, similar to the Greenwood.  I have found that I can get the big rounds to drop from 20-30% moisture to 10-20% in about 2-3 weeks by  stacking them in front of the boiler door, maybe 4-5 feet away so it isn't a fire hazard.   I'll stack a 5-6ft high row by maybe 10-12'long.  The radiant heat coming off the door is pretty  good for drying wood.  If you check the end of the log facing the boiler, you might get 3-10% moisture, but if you check the back of the log, more like 10-20%.  I think the water wicks out slowly and there's a moisture gradiant from the center of the log outward.   

I strive to get my wood down under 15%.   After drying the wood in front of the boiler for 2-3 weeks, I move the dry stuff to the side of the boiler (where there is a little radiant heat.) I use this stack to burn  while the next "batch" is drying.  No doubt it's some extra handling, but I think I get a bit more heat out of the wood this way.    It  helps that I only burn about 4-1/2 cords/yr.  I think if my consumption were higher, there might not be enough time to dry it as well.

JR


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## Huskurdu (Sep 29, 2009)

AlaskaWoodburner said:
			
		

> My alternative to free wood is heating oil which is going for $2.70 a gallon today so I need to burn this wood this winter.  I know that I could get by by mixing the wet wood with my dry wood.  I think that speeding up the drying process a little would give me better results.  I found some kiln drying manuals and they heat the wood to 140 degrees for 10 days to get from fresh cut to >30%.  Since the shed gets to 60-70 this time of year from latent heat from the boiler and chimney pipe it would not take too many BTU's to get to 100+ for a week or two with a couple of box fans circulating the air.
> 
> I need to build a dump zone for safety purposes anyways so I might as well make an experiment out of it.  I ordered a automag zone valve today.  I have an idea to build a DIY heat exchanger with a couple of sections of old baseboard and some 3/4" tees.  I was going to put it together so you could tye-wrap a box fan too it and you have a 3-speed heat exchanger.



Your sig says you're burning ina 'Greenwood' so didn't they tell you that green/wet wood is ok?  

np


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## iceman (Sep 29, 2009)

make sure you have an exhuast fan.... if you dont get humidity out you will ruin your shed and the wood will take longer to dry...


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## mike1234 (Sep 29, 2009)

I have 20 or 25 splits in the house, cut from live trees last winter, that are in the fireplace wood bin just because they look good sitting there.  Over 30% on the moister meter.  The same wood sitting outside is more like 22 - 25%.  I think unless there is a way to get rid of the humidity, the heat of being inside isn't helping.  At least put a fan in front of the stack and blow air across the wood when you heat the room.


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