Equilibrium Moisture Content of Wood
The moisture content wood drifts toward at a given air temperature and relative humidity, from the USDA Forest Products Lab (Hailwood-Horrobin) sorption equation - the reference a restoration drying setup moves a material toward. The exact value varies by species; the IICRC S500 dry standard and the dry, unaffected reference reading govern when a material is 'dry.'
Formula and source
EMC% = (1800/W)[Kh/(1-Kh) + (K1 K h + 2 K1 K2 K^2 h^2)/(1 + K1 K h + K1 K2 K^2 h^2)], h = RH/100, with W, K, K1, K2 temperature polynomials in degrees F (USDA FPL / Hailwood-Horrobin).
USDA Forest Products Laboratory Wood Handbook (Hailwood-Horrobin sorption equation) by name; the four temperature polynomials are bundled, no edition cycle.
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