Saturday, December 12, 2009

Oh the Weather Outside is Frightful!

Oh the weather outside is frightful, and the furnace is so delightful. But since it dries out the air so, humidify, humidify, humidify! I took a few liberties with the popular holiday tune “Let It Snow” to point out how important humidification is to maintaining comfort. Being warm blooded, our bodies normally produce more heat than they need and then regulate our temperature using different cooling mechanisms. The primary cooling mechanism is evaporation of perspiration from our skin. Dry air makes us feel cooler because it accelerates the evaporation from our skin. Humid air makes us feel warmer because the evaporation process is slowed down. Heated air is drier because the air volume increases, creating more places for water molecules to fit. In the winter, the cold outside air simply cannot hold very much moisture because of its decreased volume. Take it in the house, heat it up, and it expands in volume and decreases in relative humidity. It still has the same amount of specific humidity in grains, but its relative humidity is much lower because it can now hold more water. Many people overheat their homes to compensate. Have you ever had a customer that wanted to maintain 78°F in the winter and 72°F in the summer? They are not batty, they are using temperature to compensate for poor humidity control. However, overheating only increases static electricity, dry mouth, chapped lips, and other humidity related discomfort. So it fixes one problem, feeling cold, and creates a whole bunch of other problems. Adding a humidifier to their system will make them more comfortable by addressing the real problem, humidity. It also can save money because they can maintain a lower thermostat setting and still feel comfortable. To read more about the effect of humidity on comfort, check out Unit 61 Fundamentals of Psychrometrics in Fundamentals of HVAC/R. To download an interactive pschrometric chart for free, go to

No comments:

Post a Comment