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Author Topic: Proper Humidity for Storage  (Read 703 times)

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Offline Stephen1

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Proper Humidity for Storage
« on: June 02, 2019, 10:45:55 AM »
I have a dehumidifier running in the my building holding the kiln and my dried lumber/live edge wood
Right now I have the dehumidifier running full blast and it is keeping the shop at 38%
Is this to low?
Wha do the rest of you keep your storage area/shop at?
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Offline firefighter ontheside

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Re: Proper Humidity for Storage
« Reply #1 on: June 02, 2019, 05:50:55 PM »
Read the thread about where to store slabs.  Your question is addressed in there.
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Offline WDH

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Re: Proper Humidity for Storage
« Reply #2 on: June 02, 2019, 07:53:13 PM »
I shoot for 35% to 40%.  That is just a bit less than 8% equilibrium moisture content. 
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Online GeneWengert-WoodDoc

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Re: Proper Humidity for Storage
« Reply #3 on: June 02, 2019, 08:28:07 PM »
Because you are in Canada, at the same latitude as Minneapolis, MN and similar in climate to most northern states, your local customers will be using much of what you dry in inside locations.  The inside living environment in your area will be between 25 to 35% RH average, with a humidifier if it gets much drier than 25% RH in the winter.  This is 5.5% to 7.0% MC in wood, called 5.5% to 7.0% EMC.  It is fairly critical to avoid much shrinkage in most wood products, so it is best for you to dry to 6.8% MC target, with no pieces over 7.5% MC, and store the wood at 30 to 33% RH.i
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline YellowHammer

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Re: Proper Humidity for Storage
« Reply #4 on: June 02, 2019, 11:01:59 PM »
It also depends on how fast you cycle it.  We run multiple dehumidifiers but the dead stacked wood doesnít stay long enough to pick up much moisture, anyway.
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Offline Stephen1

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Re: Proper Humidity for Storage
« Reply #5 on: June 04, 2019, 09:26:58 PM »
thank you ,I have mt dehumidifier running around 35% now, and I am noticing action in  the green wood.
The questions keep coming up as I learn more and more.
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Offline bobborneman

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Re: Proper Humidity for Storage
« Reply #6 on: August 13, 2019, 01:57:50 PM »
Has anyone tried storing their lumber after drying in a greenhouse or solar kiln type building?  I am wondering if it will keep warm enough to keep the RH down.  Though the mornings before the sun comes up may be a problem.
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Offline Ianab

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Re: Proper Humidity for Storage
« Reply #7 on: August 13, 2019, 04:02:51 PM »
I know one of the features of a solar kiln is that you can store your wood in there once it's dry. It will still go though a RH cycle every day, but the average EMC over the 24 hours will be the same ~8%, which is what matters.

It's also important not to over dry wood or it gets difficult to work, hence the guys trying to keep storage humidity in the 30-40% range. It doesn't have to be steady, just average that, and the solar kiln designs wont dry to much less than 8% because of those daily swings. 
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Re: Proper Humidity for Storage
« Reply #8 on: August 13, 2019, 04:11:45 PM »
Iíd be careful with that. Maybe ok with the vents open full. 

I have over dried lumber in the solar kiln. Itís never good after that happens. As YH said, once the cookies are burnt they stay burnt. 
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Re: Proper Humidity for Storage
« Reply #9 on: August 13, 2019, 10:38:12 PM »
 smiley_thumbsup smiley_thumbsup

 
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Offline bobborneman

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Re: Proper Humidity for Storage
« Reply #10 on: August 14, 2019, 08:50:59 AM »
sounds like it would just be better to build an insulated shed and put a cheap dehumidifier in there.  thanks for the help guys.
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Re: Proper Humidity for Storage
« Reply #11 on: August 14, 2019, 09:09:23 AM »
The easiest storage is to get an old truck trailer that does not leak when it rains, paint the roof a dark color and then add a little heat for cloudy days, with the heater being controlled by a humidistat.  When the RH is too high, the heat comes on.  The key is to make sure that the lumber's MC is correct when it goes into storage, as a storage facility is not a drying operation.

A VT solar kiln with dry lumber may reach low EMCs in the afternoon because the energy is no longer being used for evaporation but is then used for heating only, but at night, the humidity is close tom100% RH or over 20% EMC, so it does average out.  The concern is that the heat can build up on a sunny day and melt or damage the fans, so you might run the fans  or keep the top vents open.

As indicated, the daily average RH or EMC is the key rather than the single reading in early morning or afternoon.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

Offline bobborneman

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Re: Proper Humidity for Storage
« Reply #12 on: August 14, 2019, 09:10:11 PM »
Doc, is it possible that trailer could get too hot?  Today, where I am in West GA, its been mid 90s with high humidity most of the day.
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Re: Proper Humidity for Storage
« Reply #13 on: August 16, 2019, 07:57:11 AM »
The inside could get hot and dry this afternoon (it is hot and humid in the Athens, GA area too this week), which is good.  Maybe at 5AM, it will be cool and humid, but on the average, it will be just what the wood needs for storage.

Again, it is not designed as a kiln, so the wood must be dry before it goes into the trailer.
Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more

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Re: Proper Humidity for Storage
« Reply #14 on: August 20, 2019, 09:00:06 PM »
I am thinking I am going to rent a storage unit to store my dried lumber it, at least until I can find a more permanent solution.  Would it be better to rent an air conditioned unit (they say they keep it around 70 degrees), or a unit with no A/C which will get very hot at least this time of year.
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Offline doc henderson

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Re: Proper Humidity for Storage
« Reply #15 on: August 20, 2019, 09:16:12 PM »
an air conditioner and a dehumidifier are very similar, but the ac puts the hot air outside.  if the wood will end up in a home at 70į the it will be perfect with ac.  if the building can flux with the outdoors, then you may gain humidity and eventually be the same as air drying outside.  i vote ac, or cheap dehumidifier.  most storage units are not well sealed and you may gain water.
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Re: Proper Humidity for Storage
« Reply #16 on: August 20, 2019, 10:41:17 PM »
The most important feature is the humidity, not the temperature.  30% RH is for 6% MC lumber.  50% RH is for 9% MC.
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Re: Proper Humidity for Storage
« Reply #17 on: August 20, 2019, 10:48:51 PM »
Air conditioned generally is pretty dry, I would just stick with that.  You can very easily determine the relative humidity and temperature of the storage unit, and then look up the EMC value from the web.  Then you will know for sure.  Itís always good to have ready access to an EMC chart for determining the EMC value from actual ambient condions.  

I keep a chart in all my kilns for quick reference and also in the showroom for people who ask ďMy home thermostat says its 70 F and 50% humidity, what is the moisture content of the wood in my house?Ē

I have a copy of the chart on my webpage, about 3/4ís down the page 

https://www.hobbyhardwoodalabama.com/info-and-tips.html
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Re: Proper Humidity for Storage
« Reply #18 on: August 21, 2019, 07:00:57 AM »
your website is a great resource and i added it to my favorites.  thanks @YellowHammer 
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Re: Proper Humidity for Storage
« Reply #19 on: August 21, 2019, 11:34:56 AM »
STORAGE OPTIONS
To reduce the chance of moisture change for most of the lumber in a stack, remove the stickers promptly.  Now, with no air flow to the interior pieces, only the ends, the edge pieces and the top and bottom pieces will change MC over a month of storage at the wrong EMC.  Using a little plastic wrap can even protect the ends, edges, top and bottom.

Any storage facility must be extremely clean with no wood dust.  This will virtually eliminate any risk of bugs.  Also, never store any of your lumber close to (in the same room) "foreign" wood...that is, wood that you didnít dry, especially wood from outside North America and also bamboo...to prevent insect infestations.

Three storage options are:
1.  Of all the options for storage, the easiest for a bundle is to wrap the bundle, all six surfaces, with plastic film and tape the joints.  Now, it is impossible for any moisture to get in or out, so this stack can sit anywhere or even on a truck with no MC changes for a year or more...until the film cracks or is torn.  This technique will even work when the bundles are on a truck in any weather.

2.  When the individual pieces need access, wrapping the bundle is awkward.  So, consider making a small room perhaps with plastic sheets for walls, inside a larger room and then use an electric, household dehumidifier to control the EMC.  In some cases, an entire large room has a dehumidifier to control the RH...it takes a larger DH unit (more electricity) to control a larger space.  Note that dehumidifiers do have room temperature limits for proper operation.

3.  Another option is to take a used trailer from an 18-wheeler, patch any leaks and then paint it a dark color.  Align it running east to west.  Now, when the sun shines, the solar heat will heat the roof and south side, thereby heating the inside slightly.  (Maybe there is financial assistance for using solar energy.). When air is heated, the RH drops.  A small fan is needed to stir the air inside.  A small heater can be added with the heater regulated with a humidistat, turning on when the humidity is too high.  Generally, the trailer will need to be about 25 F hotter than the morning's low temperature.  To work better, the floor and north walls can be insulated.


Gene - Author of articles in Sawmill & Woodlot and books: Drying Hardwood Lumber; VA Tech Solar Kiln; Sawing Edging & Trimming Hardwood Lumber. And more


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