MIL-HDBK-1011/2
3.2.2.2
Considerations for Zoned Buildings. To determine the potential for
a zoned building, examine the programmed uses of the building. Uses requiring
differing environmental conditions suggest a zoned building system.
3.2.2.3
Considerations for Seasonably Variable Buildings. To determine the
acceptability of designing a seasonally variable building, determine the
number and months when natural ventilation and mechanical systems should be
used by completing the Design Method contained in Appendix B.
3.2.2.4
Computer Applications. Review the cooling strategies and design
features that could be applicable for different parts of the building and for
different times of the year to determine whether combinations of natural
ventilation and HVAC systems will work more efficiently than natural
ventilation or HVAC alone. For simple buildings, this may not require
detailed analysis. In more complex cases, where computer simulation is
desirable, the computer program needs to have multizoned or attached-sunspace
capabilities in order to simulate a zoned building configuration. Use the
concepts in Sections 2 and 3 and the building features in Section 4 for
natural ventilation as applicable.
3.2.2.5
Seasonal Adjustments. The naturally ventilated part(s) of the
building may require seasonal adjustment in some climates to extend the period
of its use. Examples of this seasonal adjustment include screened porches
which are enclosed with glass "storm windows" to become useful as sun spaces
during the winter. Movable insulation panels may also be used either
seasonally or on a night-day cycle to maintain habitability.
3.2.3
Special Considerations
3.2.3.1
Mechanical Systems Integration. In zoned or combination buildings,
the connection between the zones must be carefully detailed so that neither
side creates a negative thermal impact on the effectiveness of the other side.
The naturally ventilated portion of the building should be separated from the
mechanically-cooled portion by insulated partitions (a minimum of R-6
insulation for walls, single glazing for windows between zones). Exfiltration
from the mechanically cooled zone should not exceed 1 air change per hour
during the period when mechanical cooling is in operation.
3.2.3.2
Heat Loss through Glazed Areas. During the heating season, glazed
areas are the most vulnerable component of the building envelope to unwanted
heat loss by radiation and convection. Movable insulation can substantially
reduce both heat loss through glazed components at night and undesirable solar
heat admission during the day.
3.2.4
Analysis and Testing Procedure. In complex or important buildings,
computer simulation may be necessary or desirable. The computer program must
have multizoned or attached sunspace capabilities in order to simulate a zoned
building configuration.
A single-zone model cannot provide a useful analysis of building
energy use, or of the hourly thermal conditions expected in the various zones.
At a minimum, hourly runs should be done for peak four-day periods in each
season. The naturally ventilated zone(s) of the building may be evaluated
using any of the techniques outlined in para. 3.1.5.
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