Figure 2 gives the VLI and degree day annual summary for 2002. The total cooling ventilation load index (VLI) is the total cooling energy (sensible plus latent) in ton-hrs/cfm of outside air that was required to maintain a constant 55˚F. The heating VLI is the sensible heating energy in therms/cfm of outside air that was required to maintain the same setpoint. The humidification VLI represents the gallons of water/cfm of outside air required to maintain 30% rh at 70˚ space temperature. All reported VLI data is based on 24/7/365 operation and all degree day data is based on a space neutral temperature of 65˚.
If you recall from last month’s report on ASHRAE design conditions, the 2002 cooling season was a real test for air conditioning systems and the heating season proved to be a little milder than normal, essentially countrywide. As can be expected, the degree day data tells us a similar story. Cooling degree days were higher in 2002 than in 2001 (and higher than normal) and heating degree days were lower for most of the country.