The Valley Hi-North Laguna library in Sacramento, California uses several passive and efficient design strategies to achieve a 36.9% reduction in energy use compared to code and LEED Gold certification. These strategies include daylight harvesting through a sloped roof and north-facing windows, rainwater collection, displacement ventilation, thermal mass to pre-cool interior surfaces at night, and efficient lighting. Monitoring has found that actual electricity use matches predictions, though natural gas use exceeds simulations, which designers continue to investigate.

1. 48 ASHRAE Journal ashrae.org S e p t e m b e r 2 0 1 1
ASHRAE’s BEST
Valley Hi-North Laguna library uses passive cooling, daylight harvesting, rainwater catchment and
efficient lighting systems to achieve the City of Sacramento’s goal that all of its libraries should be
green buildings. Completed in 2009, the LEED Gold building reduces energy consumption by a predicted
36.9% below ASHRAE/IESNA Standard 90.1-2004 and saves $18,200 in energy costs annually.
The Sacramento, Calif., building is ori-
ented 10° clockwise off the east-west axis.
Thisisadesignconsiderationtoself-shade
the north façade of the primary reading
room, the largest space in the project with
40% of the total floor area. Self-shading
allows the primary reading room to
maximize glazing for daylight harvesting
withouttheneedforcostlyshadingdevices
during the summer’s early evenings. The
reading room also uses a sloped roof and
ceiling with large, north-facing windows
to provide ample, diffuse daylight.
The slope of the roof and higher north-
facing windows is a classic method for
daylight harvesting, allowing for primar-
ily diffuse daylight to penetrate more
deeply into the space than would have
been possible with a flat roof and lower
window head height.
The roof also is pitched to collect
rainwater; the gutter being created by the
intersection of the slope of the clerestory
and the reading room roof, catching the
rainwater as it flows from either side.
The integration of all these features in a
single roofing system provided cost sav-
ings and multi-functional use from the
building’s architectural system. Skylights
complemented the design to the south of
the building, providing additional diffuse
overhead daylight in the reading rooms to
the south. Roofing consists of a cool roof
coating with high reflectivity.
HVAC innovations included the use of
a displacement ventilation system, with-
out the requirement for a raised floor, to
maximize thermal mass directly in the
space. The condenser of the main air
handler is evaporatively cooled, and the
smaller air handler serving the community
room has a heat recovery wheel due to its
library sets exampleBy Jeffrey Blaevoet, P.E., Member ASHRAE; and Chien Si Harriman
About the Authors
Jeffrey Blaevoet, P.E., LEED AP, is a principal and
Chien Si Harriman is senior building performance
engineer at Guttmann & Blaevoet Consulting Engi-
neers in San Francisco.
HONORABLE MENTION: INSTITUTIONAL BUILDINGS, NEW
CourtesyNoll&TamArchitects
Intense Southern Sunlight is Filtered Through Deep Sunscreens
Skylights Allow Limited Direct Sunlight that is Refracted Through Chain Drape
Sunlight Reflects Off Light Colored “Cool Roof” to Interior White Ceiling Lighting Central Spine
Northern Diffused Light Fills the Main Reading Room
Building Integrated PV Laminated to Standing Seam Metal Roof
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5
1 2 3
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5
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6
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Low Velocity Cool Air Enters Low and is Pulled Across the Room
Thermal Mass Walls Give Back “Coolth” or Warmth Depending on Season
Hot Interior Air Naturally Ventilates Out Top of Tower
Rainwater is Funneled with “V” Shaped Roofs to Bioswales in the Landscape
6
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9
Figure 1: Integration of sustainable features provides cost savings and multi-functional use from the building’s architectural system.
This article was published in ASHRAE Journal, September 2011. Copyright 2011 American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc. Posted at www.ashrae.org. This article may not be copied and/or distributed electronically or in paper form without permission
of ASHRAE. For more information about ASHRAE Journal, visit www.ashrae.org.

2. CourtesyNoll&TamArchitects
September 2011 ASHRAE Journal 49
technology award case studies
high ventilation load. A 95% condensing
boiler to serve reheat coils also increases
overallefficiency.Asolarhotwatersystem
preheats the building’s domestic hot water.
Thermal mass conditioning is a major
innovation feature of this project.Thermal
mass was emphasized on this project due
to local climatic conditions, and, with the
future in mind, given California utilities’
push to use building mass subcooling as a
means to reduce peak demand on the elec-
tricity grid. Designers endeavored to turn
heavy interior mass into a positive feature
of the project, as a way to complement the
heavy mass of the book stacks, thereby in-
creasing the overall interior thermal mass
of the project.A unique concrete sandwich
wall system and exposed concrete floors
were designed to express the mass to the
building interior and its occupants, un-
obstructed by any architectural features.
The intent of the HVAC designers was
to consistently subcool the mass during
evenings of the cooling season, to take
advantage of Sacramento’s delta breeze,
which regularly can cause diurnal swings
in outdoor temperature of 30°F (17°C),
with nighttime lows regularly reaching
the mid-fifties to low-sixties during the
summer. Currently, this night-flush of the
thermal mass is driven by the building’s
supply fans and exhausted by a small fan
in a single thermal chimney to assist the
air out of the stack in the evenings.
This charged thermal mass can be used
incombinationwithamixed-modevariable
air volume (VAV) displacement system to
provideadditionalcomfortatelevatedsup-
ply air temperatures from the air handler.
The thermal mass complements displace-
ment/mixed mode by depressing the mean
radiant temperature in the space due to the
cold surfaces in the space. This allows the
facilitiesoperationsstafftotestadjustments
tothespacethermostatsetpointhigherthan
normal, which can further extend the per-
formance of the displacement ventilation
system in mixed mode with no impact on
perceived thermal comfort.
The lighting design used efficient lamp-
ing averaging 0.87W/ft2 (0.08W/m2).The
Standard 90.1-2004 building area method
is 1.3 W/ft2 (0.12 W/m2). Lighting loads
were minimized by selections of high ef-
ficacy lighting fixtures to provide most of
the ambient illumination. Lower wattage
lamps and fewer total fixtures were needed
by using only T8, high color temperature,
high CRI lamps selected over lower color
temperatures.Theyprovideaperceptionof
brighterspaceswithlowertotalpowerused.
Occupancysensorsturnofflightingwhen
areas are not in use. Dual-level switching
was used in all spaces over 250 ft2 (23 m2)
allowing lighting levels to be reduced by
50% in a pattern that allows full function
ofspaceswithreducedpowerconsumption.
Lighting installed within 15 linear ft (4.5
linear m) of effective translucent surfaces
Building at a Glance
Name: Valley Hi-North Laguna
Library
Location: Sacramento, Calif.
Owner: City of Sacramento
Principal Use: Library
Includes: Teen room, food
court, study rooms, learning
center, computer lab and
classroom
Employees/Occupants: 9/250
Gross Square Footage: 20,300
Substantial Completion: 2009
Figure 2: Interior mass/summer night flush (top). Interior mass/summer daytime
cooling (bottom).
Interior Thermal
Mass Dissipates
the Day’s Warmth
Hot Air Released
Through Top of Tower
Cold Air Brought in to Cool
Interior Thermal Mass
Interior Thermal Mass
Radiates Cooling
Superinsulated Building
Envelope and Sun
Shading Protect
from Heat
Evaporative Cooling
Used During Peak
Temperature

3. 50 ASHRAE Journal ashrae.org S e p t e m b e r 2 0 1 1
(windows and skylights) have separate switching
fromtherestoftheinteriorspacesallowinglighting
to be controlled off when it is not needed. Outdoor
lightingusedhighefficacyfixtureswithlow-cutoff,
allowing the energy to be reduced by nearly 50%
below the ASHRAE minimum levels.
So far, the metered electricity (Figure 3) is in
line or exceeds expectations, although the natural
gas metered (Figure 4) consumption exceeds the
simulated consumption. A search for reasons for
the anomaly in December is still ongoing as the
building continues to be monitored.
Indoor Air Quality
ASHRAE Standard 62.1 and ASHRAE Stan-
dard 55 were considered essential in the design
process. The design used Standard 62.1-2004’s
Ventilation Rate Procedure to determine the
outdoor ventilation rates of each air handler.The
intent of Standard 62.1-2004 was more difficult
to meet in heating mode, because of the heated
air being delivered at the floor and returned at the
ceiling level where displacement is being used
and the use of 90°F (32°C) supply air from the
overhead VAV system, respectively.
Since the use of displacement ventilation was
a key energy efficiency feature of the project,
it did not make economic sense to provide two
return paths (ceiling and floor) to increase the
ventilation effectiveness of the system, and
super insulation of the windows and skylights
was not cost effective to reduce the winter sup-
ply air temperature; CO2 sensors were added to
the central air handlers to allow the outside air
dampers to turn down below the target calcu-
lated in the Ventilation Rate Procedure. In an
effort to overcome the ventilation effectiveness
penalty, this proved to be a wise choice given the
variability in occupancy in the library and first
costs, thereby saving energy despite the poor
wintertime ventilation effectiveness.
One space where special attention was given to ventilation
effectiveness was the main reading room, where the displace-
ment supply air temperature was not raised significantly in the
winter time, but instead the envelope loads were handled by
a perimeter finned tube convector, allowing the supply air to
remain slightly cooler than the space temperature.
The heating and cooling system was designed to maintain
75°F (24°C) in the summer and 70°F (21°C) in the winter
time, consistent with common procedures for an air-condi-
tioned design and meeting the requirements of ASHRAE
Standard 55. Improving and extending the comfort range by
night flushing the building to store “coolth” in the wall and
*DOE-2 is known as incapable of modeling radiant heat transfer between surfaces, and it is unable to always model thermal mass accurately without adjustments
to the custom weighting factors. Other load calculators also tend to deemphasize the role of radiant heat exchange.
floor slabs, and depressing the mean radiant temperature
has been initially an untested experiment. To understand
the transient behavior of the concrete during the flush
cycle, the team looked for software that extended beyond
DOE-2 or load calculators.* EnergyPlus has been devel-
oped with this transient behavior in mind. The design team
ultimately chose to use a similar well-validated tool with
a European background because of its calculation engine,
user interface, and ability to model PPD and PMV based
on Fanger’s comfort models. The simulations were used to
test a variety of conditions, wall thicknesses, and nighttime
flush control strategies
Figure 3: Simulated vs. metered electricity consumption.
Figure 4: Simulated vs. metered natural gas consumption.
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
0
kWh
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
Simulated Proposed Design
Metered Data
900
800
700
600
500
400
300
200
100
0
Therms
Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec.
Simulated Proposed Design
Metered Data
Metered data unavailable for July.
Metered data unavailable for September.

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52 ASHRAE Journal S e p t e m b e r 2 0 1 1
Innovation
Several key innovative features have been mentioned, includ-
ing the use of a fairly conventional packaged direct expansion
(DX) VAV air handler with a displacement system. This in-
novation allows the project to achieve high levels of efficiency
through innovative air delivery that extends economizer hours
and lowers pressure drop. The evaporatively cooled condenser
provides additional cooling savings.Thermal mass has also been
explained, and the exploration into alternative software choices,
with a validation of the modeling results, is forthcoming.A solar
hot water system preheats domestic hot water.
Operations and Maintenance
The evaporative condenser unit used a chemical free water
treatment system that requires very low maintenance, and also
reduces blow down of water. The building maintenance sys-
tem installed enabled the city to monitor the system remotely
through a wide area network (WAN).A separate dedicated unit
is used for the community room for stand-alone, after-hours
operation.
Cost Effectiveness
The incremental capital cost of the energy efficiency mea-
sures was approximately $306,400 and the associated annual
energy savings is $18,200. The total replacement cost every 20
years of the incremental systems is approximately $34,300.The
simple payback for the building systems is 17 years.
Environmental Impact
The air handlers have been specified with R-410A, which is
not a CFC and is non-ozone depleting. Compared to the Stan-
dard 90.1-2004, Appendix G baseline building, the project is
expected to save approximately 147,120 kWh/year of electric-
ity and 1,730 therms of natural gas, avoiding 127,400 lbs CO2
equivalent emissions annually.
Further Study of Thermal Mass Effects
To better understand the thermal mass effects on comfort,
controls and energy use, Guttmann & Blaevoet Consulting
Engineers helped establish a collaborative team consisting of
the Sacramento Municipal Utilities District (SMUD), the City
of Sacramento, the UC Berkeley Center for the Built Environ-
ment (CBE), Lawrence Berkeley National Labs (LBNL) and
Johnson Controls (JCI). The study commenced in June 2011
and will be completed in July 2013.
The purpose of the study is to create a greater understanding
of how building technologies can be analyzed and deployed
to achieve demand response control algorithms in an existing
building, which also has a substantial amount of interior thermal
mass. This understanding will be found by experimenting with
demand response control algorithms, monitoring the result-
ing energy consumption and levels of comfort achieved, and
maintaining digital records of the achieved results, some of
which will be available for publication to the general public.
Interior view showing custom displacement diffuser (bottom left).
PhotobyDavidWakely
High mass/multi-function construction.
PhotobyDavidWakely