UFC 3-400-02
28 FEBRUARY 2003
2-2.6.1
Weather Region. Eleven weather regions have been developed by the
Department of Energy. They are defined by the range of cooling-degree days and
heating-degree days based on 65 F. ASHRAE/IESNA Standard 90.1 of 2001 uses
annual HDD65 (Heating Degree Days based on 65 F) and CDD50 (Cooling Degree
Days based on 50 F) to select the appropriate Building Envelope Requirements table
for energy conservation design. Refer to paragraph 2-10 for further explanation of this
data.
2-2.6.2
Ventilation Cooling Load Index. The Ventilation Cooling Load Index
(VCLI) is a two-part index that defines the total annual cooling load for ventilation air by
calculating sensible heat load separately from the latent heat load (moisture). The
results are expressed in ton-hours per cubic feet per minute per year of latent and
sensible load. Values for sensible heat load are calculated by comparing the outdoor
temperature to indoor conditions (75 F and 60% relative humidity [RH]), and
calculating how much energy is required to bring the outdoor air to the indoor
temperature. The latent load is calculated similarly. Separate calculations are made for
each hour of the year and then summed to form the annual VCLI.
2-2.6.3
Average Annual Freeze-Thaw Cycles. This value is the average number
of times per year that the air temperature first drops below freezing and then rises
above freezing, regardless of the duration of either the freezing or thawing. The
number of cycles is summed per year and averaged over the entire POR. Days with
high temperatures or low temperatures at 0 C (32 F) are not counted for a freeze-
thaw cycle. A cycle is counted only when the temperature drops below freezing (-0.5 C
[31 F] or colder) or goes above freezing (0.5 C [33 F] or warmer).
2-2.6.4
Other Values. The following values are derived from sources other than
the AFCCC. Engineers and architects should review the publications listed below and
contact the organizations for current values, including background information and
complete guidelines for use of these data elements.
2-2.6.4.1
The National Ground W ater Educational Foundation
601 Dempsey Road
W esterville OH 43081-8978
(800) 551-7379
NOTE: Average groundwater temperature parallels long-term average air temperature,
because soil at a depth of 15 meters (50 feet) does not undergo significant temperature
change over the course of a year. Soil temperature at 15 meters stays slightly warmer
than average annual air temperature by approximately 1.4 C (2.5 F).
2-2.6.4.2
Rain Rate
International Plumbing Code
BOCA International
4051 W est Flossmoor Road
Country Club Hills IL 60478
(708) 799-2300
7
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