Les, RH levels in excess of 25% during periods where the outside temperature is 0 degrees F or less can deteriorate the building structure according to ASHRAE ( American Society of Heating, Refrigeration, and Air Conditioning Engineers). All the humidifier manufacturers recommend adhering to the following chart: Outdoor Temp Recommended Max. Degrees F Indoor Humidity % --------------------- ------------------------------- +20 35% +10 30% 0 25% -10 20% -20 15% A home air conditioning system will generally drop the RH level to 60%. I've not seen a situation yeilding less than 60% This leads to, 60% in the summer and 20% to 30% in the winter. If this 30 to 40% swing produces satisfactory results then stay with it. If not, and you want tighter humidity control, you may wish to install a Dampp-Chaser humidity control system. Bob Mair Dampp-Chaser Electronics
This PTG archive page provided courtesy of Moy Piano Service, LLC