ASHRAE Journal - May 2013 - 18

VAV Reheat Versus
Active Chilled Beams & DOAS
By Jeff Stein, P.E., Member ASHRAE; and Steven T. Taylor, P.E., Fellow ASHRAE

S

everal recent articles claim that dedicated outdoor air systems
(DOAS) plus active chilled beam (ACB) systems are superior to vari-

able air volume reheat (VAVR) systems on energy efficiency, first cost,
air quality, etc.1–4 The ASHRAE Golden Gate Chapter recently decided
to hold a head-to-head competition to put these claims to the test.

Three mechanical engineering ﬁrms
with ofﬁces in the Bay Area provided
a Design Development (DD) level design for a real ofﬁce building currently
in design, the UC Davis Medical Center Graduate Studies Building (GSB)
in Davis, Calif. One ﬁrm designed an
ACB+DOAS system, another ﬁrm designed a VAVR system, and the third
designed a hybrid combination of these
two systems. A fourth engineering ﬁrm
simulated each of the three designs using the EnergyPlus energy simulation
program. Finally, a major mechanical
contractor provided a detailed HVAC
18

ASHRAE Journal

construction cost estimate for each design.
The VAV reheat system had the lowest ﬁrst costs and the lowest energy
costs of the three systems. The analysis showed that many of the supposed
advantages of ACB+DOAS relative to
VAVR, such as improved indoor air
quality and a lower ﬂoor/ﬂoor height,
also turned out to be largely overstated.
Note that the results of this analysis are
only strictly applicable to these three
designs and this building and climate,
but the conclusions also may apply
more broadly.
ashrae.org

Genesis of Competition
The UC Davis Medical Center Graduate Studies Building (GSB) will be a
56,500 ft2 (5249 m2) ofﬁce building.
The space program is fairly evenly split
between private ofﬁces, open ofﬁces and
classroom/conference rooms. Chilled
water and hot water will be provided by
the campus central plant.
When UC Davis ﬁrst decided to
build the GSB, it started with a traditional plans/speciﬁcations approach
with Firm A as the engineer-of-record.
Firm A, which has designed more than
1 million ft2 (92 900 m2) of chilled
beam buildings, chose an ACB+DOAS
design. In early 2012, when the design
was in the design development (DD)
stage, the owner decided to switch
About the Authors
Jeff Stein, P.E., and Steven T. Taylor, P.E., are
principals of Taylor Engineering in Alameda, Calif.
Stein is a consultant to SSPC 90.1 and a member
of SPCs 155P and 195. Taylor is a member and
former chair of SSPC 90.1 and is vice chair of TC
4.3, Ventilation Requirements and Infiltration.

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
ASHRAE Journal - May 2013 - 23
ASHRAE Journal - May 2013 - 24
ASHRAE Journal - May 2013 - 25
ASHRAE Journal - May 2013 - 26
ASHRAE Journal - May 2013 - 27
ASHRAE Journal - May 2013 - 28
ASHRAE Journal - May 2013 - 29
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
ASHRAE Journal - May 2013 - 36
ASHRAE Journal - May 2013 - 37
ASHRAE Journal - May 2013 - 38
ASHRAE Journal - May 2013 - 39
ASHRAE Journal - May 2013 - 40
ASHRAE Journal - May 2013 - 41
ASHRAE Journal - May 2013 - 42
ASHRAE Journal - May 2013 - 43
ASHRAE Journal - May 2013 - 44
ASHRAE Journal - May 2013 - 45
ASHRAE Journal - May 2013 - PSU Design Build Project
ASHRAE Journal - May 2013 - 47
ASHRAE Journal - May 2013 - 48
ASHRAE Journal - May 2013 - 49
ASHRAE Journal - May 2013 - 50
ASHRAE Journal - May 2013 - 51
ASHRAE Journal - May 2013 - 52
ASHRAE Journal - May 2013 - 53
ASHRAE Journal - May 2013 - Passive Cooling for School
ASHRAE Journal - May 2013 - 55
ASHRAE Journal - May 2013 - 56
ASHRAE Journal - May 2013 - 57
ASHRAE Journal - May 2013 - 58
ASHRAE Journal - May 2013 - 59
ASHRAE Journal - May 2013 - 60
ASHRAE Journal - May 2013 - 61
ASHRAE Journal - May 2013 - Building Sciences
ASHRAE Journal - May 2013 - 63
ASHRAE Journal - May 2013 - 64
ASHRAE Journal - May 2013 - 65
ASHRAE Journal - May 2013 - 66
ASHRAE Journal - May 2013 - 67
ASHRAE Journal - May 2013 - 68
ASHRAE Journal - May 2013 - 69
ASHRAE Journal - May 2013 - InfoCenter
ASHRAE Journal - May 2013 - 71
ASHRAE Journal - May 2013 - 72
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
ASHRAE Journal - May 2013 - 80
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
ASHRAE Journal - May 2013 - Cover3
ASHRAE Journal - May 2013 - Cover4
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