MIL-HDBK-1191
8.9.3
Control Precision. Temperature controllers shall maintain space
temperature within +/- 1.1 oC (2 oF) of design setpoint, as provided for
the individual spaces at Appendix A. The summer and winter design
setpoints normally differ. For some spaces, a temperature range is given
as the summer, or winter, interior design condition in lieu of a specific
temperature setpoint. The HVAC system for such spaces shall be designed
with the capability, under design conditions, to maintain any selected
temperature within that range.
8.9.4
Humidity Control.
8.9.4.1
Humidity controls shall be provided as necessary to meet the
requirements given for individual spaces at Appendix A. Humidity controls
for Critical and Sensitive areas shall be provided on a room basis.
Humidity controls for all other spaces may be provided on a zone or system
basis as determined to be sufficient to maintain the required conditions.
Note that for spaces for which precise relative humidity requirements are
not stated, humidity controls may be required to maintain an envelope of
30% to 60% RH during normally occupied hours; for such spaces, designers
shall determine the likely interior RH, based upon outside air conditions
and interior latent loads. Humidifiers are problematic from a maintenance
standpoint, and should not be utilized except when analysis indicates that
RH will drop below 30% for significant amounts of time.
8.9.4.2
Humidifying Equipment. Air handling system humidification shall
be achieved utilizing direct steam injection, with a steam source in
accordance with 8.10.1. Designers are responsible to designate the
location of steam injectors relative to ductwork and air handling unit
components, and so design them as to minimize concerns with moisture
collection in/on the downstream elements. Provide a minimum of 3 M (10 ft)
of straight ductwork, with no takeoffs, reducers, duct lining, or other
components, immediately downstream of the injection location; If this
separation space is not available, the design engineer shall provide a
detailed design, considering duct dimensions, airflow velocity and
psychrometric condition, and number and location of injection orifices,
with necessary instructions to the construction contractor, to maximize the
probability of moisture reevaporation before impact with downstream
elements.
8.9.4.3
Trim Humidification for Critical Spaces. For a minimum
distance of 2M downstream of trim humidifiers serving critical spaces,
ductwork shall be constructed of stainless steel or aluminum. In addition,
the humidifier shall be separated a minimum 4.5 M upstream from high
efficiency final filtration; when this separation cannot practicably be
achieved, a detailed design for the humidifier shall be provided as
addressed at 8.9.4.2.
8.9.5
Digital Electronic Controls. HVAC control systems shall be of
the digital electronic type, utilizing either a direct digital control
(DDC) or the Corps of Engineers Single Loop Control System (SLC), according
to the direction of the Using Agency for the particular project. When a
Using Agency determines that communication between a facility's DDC system
and a remote Energy Management and Control System (EMCS) is required to
facilitate maintenance, the design shall assure that the DDC system is
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