Which environmental factors influence Equilibrium Moisture Content in timber?

• A. Altitude and Temperature
• B. Humidity and Temperature
• C. Light and Humidity
• D. Pressure and Color

Answer: (B)

Equilibrium Moisture Content is the moisture level timber reaches when it is in balance with its surroundings. The factors that set that balance most directly are the ambient humidity and the air temperature. Relative humidity tells us how much water vapor is available to move into or out of the wood—higher humidity pushes EMC higher. Temperature matters because warm air can hold more moisture, so for the same humidity, the wood’s EMC tends to be higher at higher temperatures. The other listed factors don’t directly determine the moisture balance in the timber: light and humidity don’t alone define EMC, while altitude and pressure have only indirect or negligible direct effects. Understanding this helps predict how timber will swell or shrink with different environments and informs storage and construction decisions.