ASHRAE Journal - June 2023 - 23

FIRST PLACE 2023 ASHRAE TECHNOLOGY AWARDS
basement spaces for operational back-of-house areas
and a guest gym; the lower two levels for public gathering,
dining and cooking; the upper 13 floors for guest
rooms; and the top level and roof for MEP infrastructure.
This project demonstrates that historic preservation
does not require sacrificing sustainability and
energy goals in an urban community.
Energy Efficiency
Hotels with food service operate with an average
energy use intensity (EUI) of 106 kBtu/ft2·yr,
(1204 MJ/m2·yr) according to the Architecture 2030's
Zero Tool. Per LEED v4, the ASHRAE/IES Standard
90.1-2010 baseline system was modeled at an EUI of
132 kBtu/ft2·yr (1499 MJ/m2·yr), while the proposed
system was modeled at an EUI of 74 kBtu/ft2·yr (840 MJ/
m2·yr). Based on one year of energy data, the Ingalls
Building is operating at an EUI of 66 kBtu/ft2·yr (750 MJ/
m2·yr), exceeding the energy model's expectations. The
reduction in EUI from 132 kBtu/ft2·year (1499 MJ/m2·yr)
to 66 kBtu/ft2·yr (750 MJ/m2·yr) saves the owner approximately
$116,000 in annual utility costs. See Table 1 for a
month-by-month breakdown of actual versus modeled
energy consumption.
Our team contributed 12 points to the LEED scorecard
by overcoming several constraints to achieve the drastic
energy reduction goals.
 The tight 5,000 ft2 (465 m2) urban site eliminated
the option for a geothermal wellfield.
 The west façade imposed a significant and unavoidable
solar heat gain with a window-to-wall ratio of 0.4.
 Historical criteria constraints prevented removing,
externally shading or significantly altering the glazing.
As a result, storm windows were incorporated, which
reduced the U-value of the windows from 1.0 to 0.5.
 A 3 in. (76 mm) layer of spray foam insulation was
added to the uninsulated concrete walls, increasing the
R-value from R-2 to R-22.
 High-efficiency water-source heat pumps (WSHP)
were chosen for space conditioning, with a cooling tower
and condensing boiler used for heat rejection or addition.
The guestroom WSHP temperature sensor uses
passive infrared occupant-sensing, setting back the temperature
when the room is vacant.
 Ventilation and exhaust are provided 24/7 as
CASE STUDY
required by the hotel standards via the roof-mounted
dedicated outdoor air unit (DOAS) with sensible and
latent energy recovery.
Indoor Air Quality and Thermal Comfort
The rooftop DOAS unit provides ventilation directly to
each space. The unit includes MERV 13 filters, providing
constant dehumidified 72°F (22°C) air, delivered 24/7.
The ventilation rate for each guestroom is 25% above
ASHRAE Standard 62.1-2016 requirements, maintaining
800 ppm of CO2 for occupants. Each guestroom includes
its own WSHP with full occupant control. In addition,
the lower-level public spaces include electric radiant
heating in custom-built windowsills to provide additional
comfort along the extensive, street-facing glazing
where historical limitations prevented the introduction
of the required airflow.
The high-rise design meant building pressurization
was especially important. To prevent winter infiltration
due to the stack effect and promote guest comfort, the
DOAS unit was designed to provide outdoor air 100%
above code to positively pressurize public spaces. And,
as a side effect, it maintains less than 800 ppm of CO2
when the space is fully occupied.
Innovation
An added egress stair, existing concrete columns, and
new MEP shafts meant the 3,000 ft2 (280 m2) floorplate
had to be carefully programmed to achieve the desired
guestroom count. This tight floorplate left no room for
floor-mounted mechanical equipment. The owner had
prior negative experiences with above-ceiling horizontal
WSHPs because the access was inadequate. The design
team worked with the owner to arrive at a solution that
mitigated concerns over maintenance while keeping the
floor plan compact.
Each guestroom entryway includes 8 ft (2.5 m) ceilings
to accommodate a vertical WSHP (not a typical
high-rise heat pump) in the space above because of a 14
ft (4 m) floor-to-floor story height. A single hinged 30
in. by 30 in. (762 mm by 762 mm) access panel is all that
is required to maintain the unit and its runout piping
accessories. The filtered return grille allows for a 2 in. (51
mm) pleated filter to be easily replaced from the floor
without requiring ceiling access.
Tyler Larkin, P.E., is a mechanical engineer, Tracy Steward is a partner/mechanical engineer and Thom Anderson, P.E., is a mechanical engineer at CMTA.
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ASHRAE Journal - June 2023

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