ASHRAE Journal - May 2013 - 80

IAQ APPLICATIONS

A

B

Ward
Corridor

Courtyard

Figure 2: Combined wind- and buoyancy-driven natural ventilation in the courtyard type (inner corridor) hospital. A) Section
plan; B) floor plan.2

A

B

Figure 3: Wind-driven natural ventilation in the wind catcher type hospital. A) Section plan; B) floor plan.2
4. Wind catcher type (Figure 3). A wind catcher can capture the wind at the roof level and direct it down to the rest of
the building. Weatherproof louvers are installed to protect the
interior of the building, and volume control dampers are used
to moderate flow. Stale air is often extracted at the leeward side
of the wind catcher shaft. This device is often divided into four
quadrants that can run the full length of the patient’s body and
become air intakes or extractors depending on wind direction.
5. Atrium and chimney type (Figure 4). The existence of
an atrium or chimney may help enhance the natural ventilation potential. Based on the relative position between wards
and atrium/chimney, there is a side-atrium/chimney type and
a central atrium/chimney type. The outdoor air is sucked into
the wards through the windows, typically, because of the
combination of wind and buoyancy effects. After diluting
the contaminated air in the ward, the warmer and polluted
air converge in the atrium/chimney and discharge through
the termination device at the top of the atrium or chimney.
The efficacy of this type of design is generally improved by
varying the height of the chimney or atrium and the detailed
design of the termination device and, therefore, its ability
to create a negative (suction) pressure that is independent
80

ASHRAE Journal

of wind direction, and the indoor-outdoor temperature
difference.
WHO2 provides a comparison of the performance of different types of natural ventilation systems for hospital use in four
major climates conditions: hot and humid, hot and dry, moderate, and cold. For example, at this time the atrium/chimney type
design is not recommended for hot and humid or hot and dry
climates without further research and development. One limitation of natural ventilation is that it can depend too much on the
outdoor climate. For example, if the outdoor wind is too weak
or the outdoor temperature is too high, the driving forces will
be reduced. To overcome this, hybrid ventilation can be used.
A hybrid ventilation system includes a mechanical component,
i.e., a fan, to ensure that the minimum ventilation rate is met.
In a simple hybrid ventilation system, mechanical and natural
forces are combined in a two-mode system where the operating
mode varies according to the season and within individual days,
taking advantage of ambient conditions at any point of time.

Design Considerations

Allard4 presented a comprehensive design guideline. WHO2
gives a brief introduction to the topic. Design guides of natural
ashrae.org

May 2013



ASHRAE Journal - May 2013

Table of Contents for the Digital Edition of ASHRAE Journal - May 2013

ASHRAE Journal - May 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
VAV Reheat Versus Active Chilled Beams & DOAS
A Stable Whole Building Performance Method for Standard 90.1
Technology Award Case Studies:
PSU Design Build Project
Passive Cooling for School
Standing Columns
Building Sciences
InfoCenter
Refrigeration Applications
IAQ Applications
Engineer's Notebook
Products
Data Centers
Emerging Technologies
Classified Advertising
Advertisers Index
ASHRAE Journal - May 2013 - ASHRAE Journal - May 2013
ASHRAE Journal - May 2013 - Cover2
ASHRAE Journal - May 2013 - 1
ASHRAE Journal - May 2013 - 2
ASHRAE Journal - May 2013 - Contents
ASHRAE Journal - May 2013 - Commentary
ASHRAE Journal - May 2013 - 5
ASHRAE Journal - May 2013 - Industry News
ASHRAE Journal - May 2013 - 7
ASHRAE Journal - May 2013 - 8
ASHRAE Journal - May 2013 - 9
ASHRAE Journal - May 2013 - 10
ASHRAE Journal - May 2013 - 11
ASHRAE Journal - May 2013 - 12
ASHRAE Journal - May 2013 - 13
ASHRAE Journal - May 2013 - Letters
ASHRAE Journal - May 2013 - 15
ASHRAE Journal - May 2013 - Meetings and Shows
ASHRAE Journal - May 2013 - 17
ASHRAE Journal - May 2013 - VAV Reheat Versus Active Chilled Beams & DOAS
ASHRAE Journal - May 2013 - 19
ASHRAE Journal - May 2013 - 20
ASHRAE Journal - May 2013 - 21
ASHRAE Journal - May 2013 - 22
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ASHRAE Journal - May 2013 - 30
ASHRAE Journal - May 2013 - 31
ASHRAE Journal - May 2013 - 32
ASHRAE Journal - May 2013 - A Stable Whole Building Performance Method for Standard 90.1
ASHRAE Journal - May 2013 - 34
ASHRAE Journal - May 2013 - 35
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ASHRAE Journal - May 2013 - PSU Design Build Project
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ASHRAE Journal - May 2013 - Passive Cooling for School
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ASHRAE Journal - May 2013 - Building Sciences
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ASHRAE Journal - May 2013 - InfoCenter
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ASHRAE Journal - May 2013 - 73
ASHRAE Journal - May 2013 - 74
ASHRAE Journal - May 2013 - Refrigeration Applications
ASHRAE Journal - May 2013 - 76
ASHRAE Journal - May 2013 - 77
ASHRAE Journal - May 2013 - IAQ Applications
ASHRAE Journal - May 2013 - 79
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ASHRAE Journal - May 2013 - 81
ASHRAE Journal - May 2013 - 82
ASHRAE Journal - May 2013 - 83
ASHRAE Journal - May 2013 - Engineer's Notebook
ASHRAE Journal - May 2013 - 85
ASHRAE Journal - May 2013 - Products
ASHRAE Journal - May 2013 - 87
ASHRAE Journal - May 2013 - Data Centers
ASHRAE Journal - May 2013 - 89
ASHRAE Journal - May 2013 - 90
ASHRAE Journal - May 2013 - 91
ASHRAE Journal - May 2013 - Emerging Technologies
ASHRAE Journal - May 2013 - 93
ASHRAE Journal - May 2013 - 94
ASHRAE Journal - May 2013 - Classified Advertising
ASHRAE Journal - May 2013 - Advertisers Index
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