UFC 3-400-02
28 FEBRUARY 2003
2-11
DATA SET PAGE 14: VENTILATION AND INFILTRATION LOADS. Figure
2-14 is an example of Data Set Page 14. Data Set Page 14 consists of a graph and
table that display the independent loads imposed by heating, cooling, humidifying, and
dehumidifying outside air as it is brought into a building. The calculation assumes that
air inside the building is maintained at conditions between 68 F (20 C)/30% RH and
75 F (24 C)/60% RH. For the purposes of these calculations, when the outside air is
within that range of temperature and moisture, any incoming air is assumed not to
impose any load.
These values are calculated with the methodology used to calculate the annual
VCLI on Data Set Page One, except that values on this page are computed by month
and the result is displayed as British thermal units per cubic foot per minute (Btu/cfm)
rather than as ton-hours per CFM per year. The heating and humidifying loads are
shown as negative values. Cooling and dehumidifying loads are displayed as positive
values.
2-11.1
Suggestions for Use. Bringing fresh ventilation air into a building or
allowing air to infiltrate into buildings through cracks imposes heating, cooling,
dehumidification, and humidification loads on the mechanical system. The information
on this data set page helps the architect, engineers, and operating personnel
understand the nature and magnitude of those loads on an annual basis. It also shows
how the loads vary from month to month throughout the year.
2-11.2
Comments. These calculations are based on the load created when 1
cubic foot of outside air is brought into the building each minute. The results of the
calculation include the moisture load or deficit, and the sensible heat load or deficit
created by that cubic foot of air during each month of the year. Note that most months
have both a load and a deficit for temperature and moisture. The monthly deficit and
load do not "cancel" from the perspective of the mechanical system, because
temperature and moisture loads will often occur at different times of the day.
NOTE: The values displayed here assume that the inside air is maintained between
68 F/30% RH and 75 F/ 60% RH. If the inside conditions are held in a different range
of temperature or moisture, the loads will be different. For example, in calculating loads
for humidity-controlled but unheated storage, the loads vary according to the change in
both temperature and humidity, since the inside temperature varies but the inside
humidity is held constant. For estimating loads in that or similar applications, the
engineer may obtain better results by using the average maximum weekly humidity data
shown on Data Set Pages 11 and 12 (Figures 2-11 and 2-12).
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