iDRY Vacuum Kilns

Sponsors:

Shed.... build green or air dry?

Started by wfcjr, January 09, 2015, 01:40:45 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

wfcjr

Will be building a machinery/equipment shed, probably 30' x 40'.  High clearance, but only
single story.   Would like to use lumber from some logging that we will do on the property this winter.

Don't have access to a kiln, so the best we can do is either to build green, or sticker & air dry.
Will be mostly softwoods, spruce with some pine & hemlock.

Does is make a big difference if we build green or air dry? 

kderby

I say go green!  In the old days they did not have kilns.  There are design considerations.  It is an equipment shed.  What could go wrong? 

Stradivarius did not have a kiln.  His woodwork is worth millions!

I get impatient with customers.  They act like they are building a piano.  Please!  It is a chicken shed behind the house on the end of the county road.   :snowball:  end of rant. :new_year:


Ianab

I think the general consensus for a shed will be to build green and let it dry in place.

Wood doesn't change in length as it dries, and being nailed into a structure tends to keep it straight enough. A shed being open allows the wood to dry out, rather than a house where the walls get totally enclosed, and if something doesn't stay 100% straight, it's a shed, and not a fancy interior wall we are looking at.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

wfcjr

Quote from: kderby on January 09, 2015, 02:08:55 PM
I say go green!  In the old days they did not have kilns.  There are design considerations.  It is an equipment shed.  What could go wrong? 

Stradivarius did not have a kiln.  His woodwork is worth millions!

I get impatient with customers.  They act like they are building a piano.  Please!  It is a chicken shed behind the house on the end of the county road.   :snowball:  end of rant. :new_year:

... a beautiful rant that speaks to some of the ridiculousness of our lives & expectations... rant on...

AnthonyW

I recently cut up 1k bdft of white pine for my brother to use to build a shed come spring. It is stickered in his non-car-used garage. It appears that being just above freezing in the dry winter air, the water (and pitch) is making a collective puddle on the floor. His lumber will only be dried during the winter and come spring, up the shed goes. We all hope this plan will work.
'97 Wood-Mizer LT25 All Manual with 15HP Kohler

beenthere

Unless this shed is heated, the air is not dry in the winter. It is likely pretty high relative humidity which slows the drying of the wood. Hope that makes sense.
Cool air holds less moisture than warm air, so the relative humidity percentage is higher (however less amount).
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

AnthonyW

Not as though I'm expert, but that actually does not makes sense. Cold air hold less moisture but air is not drier in the winter?

The RH gauge on the weather station we moved into the garage was reading 18% on Saturday before we cut the second half. It was up to 24% on Wednesday when he called to mention the garage felt like a "cold sauna". I can only imagine being in a damp humid room at 40 degrees. Yuck. It appears that under these conditions the wood is drying, and drying quickly. The physical evidence in his garage (wet floor under the wood, pitch oozing out, feels like a cold sauna opposed to just cold, and a very strong almost unbreathable pine smell) lends itself to that. I hope it is not drying too fast. But again I'm still learning.
'97 Wood-Mizer LT25 All Manual with 15HP Kohler

wfcjr

Relative Humidity...

The air in the winter cannot hold as much water as the air in the summer.  Heating the shed will actually increase the amount of water vapor that can be suspended in the air, in the shed.

A given volume of warm air can hold more moisture, in the air, not condensing out, than
a given volume of cold air.  So yes, the relative humidity can be higher in the winter, but it is
relative to the max amount of water the air can hold at that given temperature.  So it is possible to have a higher ratio, but the denominator, the max water at that temp, is smaller.  It is possible to have higher relative humidity in the winter, but it is a lower overall volume of moisture because cold air cannot hold as much moisture as warm air.  It makes complete sense that there is puddling on the floor.

Bottom line, the wood will not stay wet longer in winter due to relative humidity.  The humidity is "relative" to the max moisture the air can hold and cold air cannot hold as much moisture as warm air.


Why do folks get chapped, wind burned & cracked hands in winter?  There is not as much moisture in the air.....

thecfarm

With all my buildings,I have cut down the tree,hauled it to the mill,sawed the log into lumber and pounded nails into in a few hours of when the tree has hit the ground.
Looks pretty good,don't it?



 
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

wfcjr

Quote from: thecfarm on January 09, 2015, 08:25:40 PM
With all my buildings,I have cut down the tree,hauled it to the mill,sawed the log into lumber and pounded nails into in a few hours of when the tree has hit the ground.
Looks pretty good,don't it?



 

Looks real good.. any issues over time as the structural lumber & boards dry?

thecfarm

That one has only been up a few years. I built a horse run in about 10 years ago using all green hemlock. I did the same thing with that one too. No problems at all. I don't expect any from the building pictured either.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

Ianab

Quote from: AnthonyW on January 09, 2015, 04:30:47 PM
Not as though I'm expert, but that actually does not makes sense. Cold air hold less moisture but air is not drier in the winter?

The RH gauge on the weather station we moved into the garage was reading 18% on Saturday before we cut the second half. It was up to 24% on Wednesday when he called to mention the garage felt like a "cold sauna". I can only imagine being in a damp humid room at 40 degrees. Yuck. It appears that under these conditions the wood is drying, and drying quickly. The physical evidence in his garage (wet floor under the wood, pitch oozing out, feels like a cold sauna opposed to just cold, and a very strong almost unbreathable pine smell) lends itself to that. I hope it is not drying too fast. But again I'm still learning.

Basically you can't dry pine too fast. You can dry it too slow, and that allows fungus and mould to get into it before the wood gets dried out.  Now wood will still dry in cool conditions, that moisture vaporises  into the air, and unless it's vented the humidity has to go up. Pretty soon you get to the dew point of the coldest part of the room, and that water vapour condenses out again. If it's cold enough you may slow up the fungus, but once things warm up it's going to start to form a mushroom farm in there.

I'd suggest opening the doors and a running couple of fans. Get the air moving, get the moisture out, and things are going to be a lot better.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

AnthonyW

Good to know I can't dry pine too fast.

I did not describe the premise well. RH is the measure of the amount of water vapor in the air relative to what it can hold. At 100% RH it is raining out. As long as the RH of the air is lower than the moisture content of the wood it will dry as long as it is not frozen. Based on information from NOAA, it is easier to get a RH less than the wood in the winter than in the summer. The trick is to keep the wood above freezing so the water can come out.

Unfortunately, I don't have a moisture meter (on the to get list) but the garage reached 35% today. He He said when he opened the garage door he could feel the moisture in the garage. He propped open the door and opened window and will close it at night to help keep the wood above freezing.
'97 Wood-Mizer LT25 All Manual with 15HP Kohler

wfcjr

Quote from: AnthonyW on January 09, 2015, 09:24:19 PM
He He said when he opened the garage door he could feel the moisture in the garage. He propped open the door and opened window and will close it at night to help keep the wood above freezing.

The other thing to keep in mind is that it is air flow and not heat that dries things.  The more air that flows across something, all else being equal, the faster it will dry.   More MCF of air flow equals more ability to carry moisture away.  Pick flow over heat.

I remember learning that lesson the hard way many years ago in a printing plant.  The guys would turn up the gas heaters in the drying stations as the web of paper flew past.  The only thing it did was cause fires, as the paper board dust would ignite.  It was certainly entertaining, but did not add much to productivity.  Once they increased the air flow by installing larger blowers, the ink dried much faster at much lower temps, without the accompanying incendiary festivities.


AnthonyW

Quote from: wfcjr on January 09, 2015, 09:37:30 PM
The other thing to keep in mind is that it is air flow and not heat that dries things.  The more air that flows across something, all else being equal, the faster it will dry.   More MCF of air flow equals more ability to carry moisture away.  Pick flow over heat.

Agreed. To an extent. As much air flow as he can get while staying above freezing. That was the instructions I passed along. Hopefully I can get a meter before spring, all this discussion is making me wonder where they will end up.
'97 Wood-Mizer LT25 All Manual with 15HP Kohler

Ianab

Don't worry, I know about cold and high humidity  ;) :D

And yes you can get 100% humidity and -8C. It's an interesting combination of freezing fog and hoar frost. Not good for drying wood of course.

35% feels "damp"?  I think I've seen ours down to ~50%, and it started feeling a bit dry. 70-80% is more normal.

Worry you have about the shed is when the weather warms up. When things get above freezing, open it up and get some air flow happening.
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

thecfarm

I never had the mositure problems,my cut the tree and build would give it time to dry. Work and life would get in the way too. I worked on it alone too. So it was that much slower. Doors and windows would be put in weeks afterwards too.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

AnthonyW

Quote from: Ianab on January 10, 2015, 03:03:12 AM
Don't worry, I know about cold and high humidity  ;) :D

And yes you can get 100% humidity and -8C. It's an interesting combination of freezing fog and hoar frost. Not good for drying wood of course.

35% feels "damp"?  I think I've seen ours down to ~50%, and it started feeling a bit dry. 70-80% is more normal.

Worry you have about the shed is when the weather warms up. When things get above freezing, open it up and get some air flow happening.

LOL. It's all relative. When walking in to the garage from outside where it is 18% into 35% it might feel high, higher, to some. On the other hand he could have just been pointing out (exaggerating?) the fact that he could feel the dampness in the air from the wood drying and showing that his plan was working. Unfortunately, I don't have a garage. So all my wood is outside stickered on pallets under tarps in the freezing weather and will like be that way until June (hahaha).
'97 Wood-Mizer LT25 All Manual with 15HP Kohler

Verticaltrx

All the buildings on our farm were built green, including our house I would assume (built in 1927, all full dimension oak for framing).

The only thing I use dry lumber for is interior projects like furniture, everything outside gets put up green. Try driving a 20D nail into dry 8/4 white oak or black locust and you'll see why pretty quickly.   ;D
Wood-Mizer LT15G19

GeneWengert-WoodDoc

Wood dries because of the temperature, relative humidity and air velocity.  All three are important. 

As a rule of thumb, every 20 F hotter results in 30% faster drying.  Another rule is that under 50 F, drying is very slow.  Hotter means more chance of defects in many species due to the strength loss in the wood due to this heat.  Heat also has other effects including color changes.  Over 130 F will kill insects, eggs and fungi.

Relative humidity drops increase the drying rate.  Actually, the key is (100 - RH).  This means that 80% RH (or 100 - 80 = 20) will dry half as fast as 60% RH (or 100 a 60 = 40).  Further, our bodies do not estimate the RH well, as heat confuses them.  The truth is that for most of the USA, the outside daily RH, summer and winter, is 65% RH average.  It is not higher RH in the summer or winter (maybe a few percent difference at most and that is not important).  This means that wood outside in most of the USA will dry to 12% MC if protected from rain or other water. As mentioned colder air can carry less moisture, but if there is circulation, and the air that is doing the drying and increases its RH therefore, is exhausted to the outside and fresh 65% RH air is brought in, this is not an important factor unless we have a big load and so the RH within a pile is changing as the air moves through.  Of course, we do have foggy  mornings and days 100% RH), but afternoons are oftentimes under 50% RH (even though on a hot day our body says it is hot AND HUMID).  In terms of quality, lower RH means whiter or lighter color and flatter wood, but more risk of checks, and a few other ef.fects for some species.

The velocity will dry wood faster if there is moisture near the surface.  As a rule of thumb, when lumber is over 40% MC, increasing airflow makes wood dry faster...going from 200 fpm to 500 fpm will roughly double the drying rate.  In a kiln or similar situation with fans, the cost of doubling air speed is maybe four times more expensive for electricity, plus larger motors, electric circuits, etc.  However, at 20% MC, and lower, velocity has little effect on drying rates as we are waiting for the water to wiggle its way to the surface and not for the air to scrub the water off the surface.

Note that the drying rate is affected by all three.  All are very important.

Want to know the average EMC for your location?  (Note that 12% EMC is 65% RH.  Other values are in Table on page 3 in the report below.)  Check out
http://www.fpl.fs.fed.us/documnts/fplrn/fplrn268.pdf
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Glenn1

Gene,

As usual,  your  explanation is very helpful.  I have been reading your book (also  Joe Denig and William Simpson) and this explanation makes things easier to understand.  Thank you!

Glenn
Vacutherm IDry, Nyle 53 Kiln, New Holland Skid Steer, Kaufman Gooseneck Trailer, Whitney 32A Planer

Al_Smith

With regard to green lumber in this area a good many of the post and beam huge dairy barns were framed with same using white oak .White oak as many know takes almost decades to air dry .Because of the type of construction ,old school those structures stood for over 100 years .Unfortunately they fell by the way side because those old dairy barns would not house the huge machinery used in todays farming .There are a few left but not many .

Thank You Sponsors!