Firewood supply in SE Michigan for those of you low on supplies..

[KeithO]

I just has about 4.5 cords of primarily oak with a little maple delivered this past weekend. I am very late with the firewood this year due to some large scale landscaping going on at my place. I had about 90 yards of fill dirt and county gravel brought in to level an area about 15 ft wide next to the driveway and also to build a level pad at the south end of the property for the firewood. On Thursday evening I had the last 10 yard load delivered and got the firewood pad levellled.

Just before sunset, Todd Fodor from Fodor Timber swung by with 2 large dump trucks with the split firewood. Delivered price is $150/cord split. I have added contact details for Fodor timber to the firewood price report on this site or do a google search for FODOR TIMBER, Grass Lake, MI. I recently bought a Bobcat B200 TLB to cover the multitude of tasks most people get compact utility tractors for, but this machine can lift a ton at the loader bucket and the backhoe will dig down 10 ft. I intend to move out into the mountains in Colorado in the next 18-24 months (just as soon as I can get out from under my current mortgage) and I figure building a home out in a relatively remote area is not something you can do by hiring contractors (at least not on my budget).

I then spent the majority of Saturday 4th of July moving the firewood onto the prepared pad. Because of space constraints and a large number of small neighborhood kids that crawl over everything I decided to make a woodpile instead of stacking. I put down a vapor barrier on the ground, and the surface still slopes downhill about 4" over 15 ft, so I think I will keep the bottom of the woodpile relatively dry. The pile itself is 20ft long at the base, 14 ft wide and 7ft high. I am still working out a "tentlike" cover, since my plan is for a primitive Solar Kiln to speed up the drying process. I have dark grey pvc coated tarps 12ft x 20ft long. The idea is to have a tubular structure to support the tarp about 1ft clear of the wood on all sides. Close most of the sides except for a space about 1sq foot at the peak on both sides. The sun should get the temperatures up to about 170F for a substantial part of the day. Fresh air can enter at the bottom and the system will keep almost all of the rain off the wood. I did this on a smaller scale last year with a "tent" I made using 2" PVC pipe and the same type of tarp. I had no wet wood at any time all season, and we had up to 2ft of snow in a single night at various times last year.

What was kind of amusing moving the wood with the loader was than even though the bucket holds 3/4 yard, I would take load after load and the pile from the dump trucks didn't appear to get any smaller, even though the "new" pile got bigger and bigger. At the end I had to raise the bucket about 11ft high to dump onto the top of the pile and load the last few face cord into the bucket by hand. I had a trailer load of seasoned wood left over from last season, and I would say that maybe 20% of the wood I bought this year was standing dead wood. The rest had been felled last year in September, but left in log form until april this year, before it was put through a firewood processor.

This year 2 of my regular firewood sources have suspended operations (I was getting slab wood for $10/trailer load and hardwood in rounds for $25/trailer load). So this is certainly the most expensive firewood so far, but still better than coal or corn. Corn is down to $3.50/bushel "market price" but the retail price in Michigan still seems to be $6.50/bushel ???? Tough times out there for a lot of folks from automotive companies and suppliers as well as the building industry.

Best of luck to you all.
Keith (near Napoleon, MI)

 

[Todd]

Sounds like you've been busy. Good luck getting that Oak to dry in a pile, I just don't think that large pile will dry as well as stacked even with a solar kiln.

 

[Backwoods Savage]

I agree.

Keith, you are to be commended on all the work you've done to prepare this but it seems as though you are attempting to hinder the drying process rather than speeding it up. It just seems like you are overly concerned with keeping the rain and snow off. We leave our wood piles uncovered completely until snow falls and then cover the top only. We also stack so the wind hits the sides of the piles because you get more drying from wind than from sun and heat.

And for what its worth, all of our wood is dry too and we cover the top only. What little wet any wood gets from rain drys extremely fast; usually within 24 hours or less. As stated, the wood we cut last winter is sitting in a stack completely uncovered and we worry not. We will cover the top of it probably sometime in November. Leaving the sides and ends open still allows for more seasoning even during the winter months.

 

[KeithO]

This chart is from a study on kiln drying wood to speed up drying time. At 140F it needed a bit more than 240 hours or about 1 month (if you consider sunlight hours). There was another study in alaska, but it was pretty flawed. The wood was not split and the vapor barrier was laid directly on the wood without permitting much ventilation at all. Mold formed on the wood whereas regularly stacked wood had none. I do think air circulation is key. My longer term goal is to acquire palletized wire baskets (the type used in industry) and fill them individually and stack them 2 high. I now have a loader backhoe strong enough to lift a full pallet, so that would simplify the handling of the wood substantially throughout the season. It gets rid of all the "cobbled" stacking systems that many non burning types think is unsightly.

Local ordinances are very restrictive regarding outbuildings and even a woodshed has to have an architect design and seal (any "structure"). In my case I could not possibly build a woodshed and meet the setback requirements and have space for my garage. The best I can hope for is a "lean to" on the south side of the garage. I live in a rural area but close to a lake. I'm on a dirt road that the county doesn't plow anytime there is significant snow. My property taxes just went from $3600/yr to $4000/yr while I doubt I could sell for even $160k. What the @#$% is the world coming to ????

 

[woodgeek]

Keith,

Nice table there--would have been useful during the 'hearth drying' thread last year...what's the source? Do they have lower temp data?

As for the solar, my worry would be the wood mass. Even if you collect solar BTU's effectively, will the 6 hour collection period suffice to get the whole pile up to temp? Then you need to have the right level of (probably forced) ventilation to carry away the vapor w/o cooling the stack. I wonder if you could separate the collector (a solar air heater) from the stack enclosure? Requires a blower, but might simplify the engineering/construction of both parts, and the collector could heat your house in the winter.

To get back to your actual situation, I actually think the others had it covered when they told you to keep the stack well ventilated. That is, I also think the wind is more relevant than the sun for most open stack drying. If you had an enclosure with solar gain, you would need to open it up when the sun was not shining (or power vent it) so as to not lose the drying effect of wind at low relative humidity. This (hypothetical) opening and closing is what kills a solar dryer idea--you can heat the wood all you want, but the air still has to carry the vapor away. I agree with you though that I like to keep the rain and snow off the stack with a top cover. Can you get/build a cheap 'tent' type structure with mesh sides--well ventilated but still a visual block to keep the neighbors happy?

 

[KeithO]

The study was conducted in Madison WI.

(broken link removed to http://www.firewoodkiln.com/pdf/fplrn254.pdf)

 

[Dune]

Actualy neither forced ventilation nor vents high in the structure of the tent or cover are needed or desirable. What is important is;
1. That the tent material does not touch the wood any point.
2. That the canvass does not touch the ground at any point.
The operative theory here is the the high temperature causes moisture to evaperate, it then condenses on the inside of the tent material, and gravity conveys it away.

 

[KeithO]

Woodgeek: While it would be great to be able to directly heat the wood, I think the objective of a solar kiln is to raise the air temperature. This drys the air and provides a larger gradient to move the mositure out the wood into the air. In the midwest, outside air can have a 60-90% humidity in summer, so that is not too helpful in trying to dry wood or even evaporate perspiration for that matter.

Dunebilly kind of has the idea, but I think that if you can avoid condensation of the moisture on any part of the structure, so much the better. I think a good strategy is to use a similar principle as is used in solar collectors, where you have a PV collector to provide power and once the solar collector temperature reaches a preset value, you turn on a fan which assists with ventilating the kiln. When the temperature drops back below the pre-set value, a timer keeps the blower running to keep venting moisture and prevent the aformentioned condensation issues (until the sunlight is gone at least). But otherwise, yes, the simple solution is to have the bottom open (vented). A more sophisticated setup would have insulated panels and be sealed tighter, to get the temperatures as high as possible to speed up the process. And yes, such a more dedicated structure would have the entire south side be a high quality solar collector. Provided you have sun, your firewood will keep drying all winter and in fact may dry better in winter than summer due to the low sun angle and low humidity.

 

[Dune]

This is hardly a new idea. I first became aware of this method in the mid-seventies. While I am sure that some kind of fan could possibly improve the system to some degree, not only is it unneeded, but it may not be helpful. Consider the high humidity content of the air. By raising the air temp, and allowing the moisture to condense and drain away, the humidity is lowered. By contiualy importing new air, lower humidity is never achieved. Studies by Mother Earth News in the seventies concluded that the simple arangement I described would reduce drying time by sixty%.

 

[LLigetfa]

Studies by Mother Earth News in the seventies concluded that the simple arangement I described would reduce drying time by sixty%.

I think it is junk science.

Air when heated, lowers the relative humidity which of course allows it to take up more water. Now this is well understood by most folks and is the principle that a kiln works under. If the heated moist air is trapped, it will reach saturation. When it cools it will have more moisture than it can hold and will condense back on any and everything that is cool. The coolest will be the poly on the ground and the wood above the poly near the ground. When the night air finally cools enough for moisture to condense on the poly tunnel, it too will collect moisture, some of which will drip back onto the wood and some of which will run down the sides.

Nature is the best dehumidifier. You will see dew settling on vehicles and on grass when the night air cools. In certain conditions, you will see moisture on just the lower half of vehicles which indicate that there is stratification. It makes no sense to trap the saturated air inside the poly tunnel with the intent of condensing it inside the tunnel. Vent the hot humid air allowing cooler air that when heated allows more moisture to be taken up.

 

[woodgeek]

Thanks for explaining the operative principle, which makes much more sense than before. I'm still skeptical its worth the trouble, though.

I get that heating air will reduce the relative humidity (check), and that one can transport the water away by condensation drainage (check) or alternatively a little ventilation.

But, to get technical, I think the partial pressure of water vapor in the air does not change much when you heat it, and it is the PP that determines the mass transport, not the relative humidity RH. That is, there is a PP for the wood bound water (as a fn of temp) and a PP for the surrounding air (as a fn of temp and RH). It is the difference in partial pressures that drives the (water) mass flow. A kiln operation works not by lowering the RH of the airstream, but by greatly increasing the PP of the wood bound water by increasing its temp. In other words, the wood will rise to the kiln temperature, and I would argue that little drying occurs until it does. This is also why drying is slow in the winter despite really low air RH, the PP of the wood bound water is very low.

Now of course, I am being the worse kind of annoying 'net dweeb, making a theoretical critique of a system not even built yet. Sorry about that. :red:

To summarize: to dry the wood kiln-fast IMO you have to heat the wood, not just the air. Your solar system might well be able to do that, I was just saying if you are 'designing it' you need to plan on heating the entire wood mass to operating temp in less than 6 hours (of useable daylight). I was suggesting you work out the number of solar BTUs collected and compare the BTUs required to heat your wood mass to ~150F or the BTUs required to evaporate two days of desired water loss (assuming half of the days are sunny), whichever is greater. If there is a big mismatch in the BTUs she ain't gonna work (even assuming 100% thermal eff). This will boil down to a maximum wood stack height/depth that can be dried this way.

Of course, if your system is 'hot' for 10 hours every two days, it had better remove water 5x faster than simple wind drying or you won't compete (since the solar collector will trap moisture during the dark periods). My nutty forced air suggestion was to try to have it both ways--to solar heat when the sun shines, but still ventilate at other times.

For the record, I'd be glad to be proven wrong--I'd like to hear how any calcs or expts work out.