Hi all, happy holidays. I have just finished drying my first load of lumber (4/4 black walnut). My little kiln seemed to do a nice job. Now I have a few hundred board feet 7% lumber and am concerned about bringing it out into the 60%humidity (18% moisture content) ambient environment.
Should care be taken when reintroducing dry lumber back into a "normal" atmosphere?
And is kiln drying to 6-7% necessary or is air drying to 18% (seems that's where we are in the Great Lakes region) okay?
HI Don, the space is an airplane hangar. So it is semi heated, I have a weather station installed and believe the data it is reporting. I only have it heated to 50 F and the humidity will vary, it's been in the 60% range as of late.
at 50F and 60% RH the EMC is about 11 so the lumber will gradually try to come into equilibrium at that MC. If you downpile it and wrap it well, you will slow the process down. If there is a sunny or warm side of the hanger, put the lumber there. If you wrap it, I doubt you would see more than 1% per month increase in the winter.
The outside humidity in the Lake States, not really close to the water of one of the Great Lakes is 65% RH average which is 12% MC in lumber, so we call it 12% EMC conditions of the air. Your data of 18% is not correct.
It would be unusual to find a Ludington that is heated slightly at 60% RH. Heat quickly lowers the RH. For example, heating foggy, 100% RH air by 25 degrees F results in 30% RH. This is why storage facilities are really good if heated 20 to 25 F above the morning low temperature. The EMC will be around 7% EMC.
A kiln can dry to whatever MC you want. Most wood for interior use is dried to 6.0 to 7.5% MC in a kiln as this is the MC that wood will have in use inside a home or office.
if you only heat the hanger to keep things from freezing, you might add a humidistat to also run the heat when the humidity is over 35-40%. The humidity drops as the temperature goes up. So lets say it is 50F and 60%, the humidistat would bring on the heat until the temp was about 65F. Then the EMC would be fine. You need to pay attention in the summer so it doesn't get too hot. This is not a great idea if you have people working in there regularly because the changes in temp will drive them nuts.
The pin meter is giving you poor readings. Not sure why. Who is the manufacturer? If Delmhorst, it should have an internal calibration check or send it back to NJ for a quick inspection. Do you get a reading even when the pins are inserted? Was the wood you tested treated wood? Can you test some wood in your home like the bottom of a table...about 7% MC?
I think the moisture meter is fairly accurate. It's made by General. I primarily heat my house with wood so I pump humidity in as best I can. RH in the house reads 49%% right now. I have pinned wood in the house in the past and I recall it read about 12%. For now I think I'll pull the load out of the kiln, stack it, cover it and keep an eye open for a better storage option - or get it on Craigslist and sell it.
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