You may have noticed that your boilers and other heating equipment had to work a little overtime this year. As the data shows, May 2002 was an unusually cold month for much of the country.
In some cites, the resulting increase in heating and humidification energy costs were actually large enough to measure, which is unusual for May. Take Minneapolis for example, where the May heating degree days were close to 50% higher than normal. If 100,000 cfm of outside air was heated and humidified to maintain 70 degrees F and 30% rh space conditions and the fuel costs were $0.85/therm, the ventilation heating and humidification costs would have been $3,513 higher than normal.