MIL-HDBK-1011/2
APPENDIX B (continued)
Any cooling strategy involving large openings in the building
envelope will not be appropriate during months when appreciable heating is
required unless the openings can be closed to thermal and infiltrative losses.
For one possible method, refer to para. 3.2 in the main text.
5.3
Using Thermal Mass for Heating. The natural cooling strategy using
thermal mass might also act to reduce auxiliary heating requirements if the
heat losses occur during the daily minimum temperatures, and are relieved the
same day by a substantial temperature rise.
STEP 6:
DETERMINING THE MONTHLY FEASIBILITY OF A COOLING STRATEGY
6.1
Feasibility of Natural Cooling.
The cooling strategy shall be
evaluated as follows:
a) If the chosen natural cooling strategy is applicable for four
months or more (i.e., heating and air conditioning are required for less than
8 months), then the strategy is effective and must be used in the building
design.
b) If the most suitable strategy is natural ventilation, then go
to STEP 7 (section 8) to determine whether ceiling fans are required.
c) If the number of months when air conditioning and heating are
required is greater than 8, then the natural cooling strategy may be used
seasonally or zonally to reduce loads on the required mechanical systems. In
this case, para. 3.2 and Section 4 of this handbook may be used in conjunction
with MIL-HDBK-1190 and DM 3.03 for design recommendations and specifications.
A life-cycle cost analysis can be used to determine whether the natural
cooling strategy will be cost effective and should be used.
STEP 7:
DETERMINING NEED FOR CEILING OR WHOLE-HOUSE FANS
Procedure. It may be necessary to include back-up ventilation
7.1
using a ceiling or whole-house fan to ensure comfort when wind-driven
ventilation is inadequate. Ceiling fans can increase the interior ventilation
caused by wind through the windows. If the window sizing (refer to Appendix
C, Section 1) provides a ventilation rate of 98 fpm (0.5 m/sec) during periods
when 197 fpm (1 m/sec) is required, ceiling fans can be used to provide the
additional ventilation required for comfort.
Fans are required in all major occupied spaces of naturally
ventilated buildings when comfort cannot be achieved by natural ventilation
alone. The requirement is determined by the following procedure:
a) If an SMOS summary is available, use Part E "Percentage
Frequency of Air Temperature versus Wind Directions" for the two hottest
months of the year as determined in STEP 3. If the total percent time that is
calm and above 81deg.F (deg.C)*** is greater than 10 percent for either month,
then
fans must be installed.
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