summer & EMC- wood moisture

[Curt Harms]

I was doing some poking around looking for a dewpoint calculator and found this cute little utility (http://www.dpcalc.org/). What was interesting is that it computes EMC. I'm not an expert in this stuff but I think this is right. Take a summer day when the average temperature is 75 degrees and the relative humidity is 60%. Under those conditions the dew point is 60 and the EMC is 10.9%. This means (to me at least) that lumber stored in these conditions will have a moisture content of 10.9% once it's in these conditions for a period of time. If the lumber is 12-14% it's not dry so leave it alone or plan for some shrinkage. If it's 8%, it's gonna swell some depending on species. Seems like this might be handy info for those of us that use air dried wood, or wood that has been stored in non environmentally controlled spaces.

On a side note for me at least, dew points above 70 are miserable. The actual air temperature can be in the low or mid 80's but if the dew point is above 70, I look forward to cooler dryer days. Temperatures in the mid 80's but dew points in the 50's is JUST FINE. I recognize that those of you in fire prone areas in the west might beg to differ.

Curt

[Nate Carey]

Curt, my July 14th post in reference to moisture content in wood...


A "tool" that every woodworker should own is a book titled Understanding Wood by R. Bruce Hoadley (I am privileged to have had Dr. Hoadley as a professor at UMASS Amherst 40 years ago).

Moisture content of wood is an oft mentioned topic by my fellow Creekers; and I fear misunderstood by most.

Beg, borrow, or buy Dr. Hoadley's book and read it cover to cover. Pay special attention to Chapter #6 - "Wood and Water". Become thoroughly familiar with Chapter #6; then and only then can you talk about moisture content in wood with confidence and conviction.

Those of you who have been in the business all your "working life" are exempt from the reading assignment.

...thanks for the "Dew Point Calculator"