MIL-HDBK-1011/2
1.2
Purpose. When natural ventilation can supplant some or all of a
building's mechanical cooling requirements, two types of cost savings may
result:
a) The energy costs of operating the air conditioning system.
b) The first cost of unnecessary mechanical equipment. As a
result, the Navy is requiring that the potential for natural ventilation be
examined in the design of all applicable projects in tradewind and tropical
regions.
1.3
Objective. This handbook provides state-of-the-art information on
natural ventilation, and a manual procedure for the design of ventilated
buildings. Its use will facilitate the design of buildings that save energy
by substituting natural ventilation for mechanical cooling. Although "natural
ventilation" strictly refers to ventilation induced by external wind or
interior thermal buoyancy, the meaning usually includes ventilation from
low-powered equipment such as whole-house fans and ceiling fans.
1.3.1
Naturally Ventilated Buildings and Climate. The external climate
(temperature, radiation, humidity, and wind) determines the heating and
cooling requirements of the building. Since the building envelope acts as a
mediator between the external and internal environment, its design and
composition affect the interior conditions of the building, its energy
consumption and life-cycle cost. The design of naturally ventilated buildings
attempts to adjust to the regional and site-specific sun and wind patterns on
a daily and annual basis to maximize occupant comfort at minimum energy cost.
1.3.2
Consideration of Natural Ventilation in the Design Process.
Because building site has a strong influence on how well natural ventilation
will function, it is important that such ventilation be a primary design
parameter from the very beginning of the design process. The siting of the
building will influence the ease or difficulty with which solar shading may be
achieved, how much insulation is required, etc. Ventilation should also be
considered throughout the design of the building. This handbook provides
guidelines and suggested practices at both of these scales.
1.4
Primary Criteria. This handbook provides a procedure to evaluate
the success or failure of a building design by examining the expected
percentage of time that human thermal comfort will be achieved. The choice of
building cooling strategy (i.e. natural ventilation, evaporative cooling,
thermal mass, nocturnal ventilation, or mechanical air conditioning) is
determined from the climate data for the site and an evaluation of what
strategies work in different climates. Methods are given for determining and
achieving the interior ventilation rates required for comfort. When wind or
buoyancy-driven ventilation alone cannot provide adequate interior windspeeds
for comfort, mechanical fan backup systems shall be used.
Because naturally ventilated buildings respond to the site
conditions and microclimate, there is no one set of specific criteria
applicable to every naturally ventilated building. However, general building
design criteria are included whenever possible. A description of the "optimal
configuration" for achieving continuous natural ventilation is presented in
para. 3.1.4.
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