ASHRAE Journal - August 2021 - 72

ASHRAE TECHNOLOGY AWARD CASE STUDIES
strategies were analyzed to balance cost and effi cient
design:
* Whole building variable air volume (VAV) systems;
and
* Decoupled variable refrigerant fl ow (VRF) indoor
units with a dedicated outdoor air system.
As the design progressed, the gas-phase air scrubber
unit was evaluated for improved IAQ as well as energy
use and cost savings. Additional energy conservation
measures included in the model comparisons are:
* Decoupled VRF indoor units with a DOAS (without
gas-phase air cleaning); and
* Decoupled VRF indoor units with a DOAS (with gasphase
air cleaning).
Energy modeling confi rmed the decoupled VRF system
design with the DOAS and gas-phase air cleaning is the
most effi cient design in terms of energy and cost savings
for the building.
The VRF system, designed in compliance with ASHRAE
Standards 15-2010 and 34-2010, provides energy savings
in several ways:
* With dedicated units in each space, individual zone
control of heating and cooling eliminates reheating that
would be required in a VAV system and reduces fan pressure
drop resulting in minimized fan energy consumption.
*
The system is capable of simultaneous heating and
cooling with heat recovery. The heat rejection from the
cooling mode in some spaces is used for the heating in
other spaces, which reduces condenser fan energy and
heating energy.
* VRF has higher cooling and heating effi ciency by
using inverter compressors.
Indoor Air Quality/Thermal Comfort
VRF units directly serve individual spaces, allowing
localized controllability of actual heating and cooling
needs, rather than overcooling or overheating that
occurs when multiple spaces are controlled by a single
thermostat. Providing ventilation directly to the space
allows VRF indoor units to cycle based on heating and
cooling loads, rather than running continuously, to provide
minimum ventilation. This results in more thermally
satisfi ed occupants. A post-occupancy thermal
comfort survey was performed to confi rm compliance
with Standard 55-2010 and identify areas of concern.
The gas-phase air scrubber system includes CO2,
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ASHRAE JOURNAL ashrae.org A U G U S T 2 0 2 1
formaldehyde and volatile organic compound (VOC) sorbents
housed in cartridges; heating element for regeneration;
two small fans for regeneration and sorption; and
sensors measuring temperature, relative humidity, CO2
and VOCs in return, supply, treated and regenerated air.
The system interprets the output of these sensors using
control algorithms to actively and automatically manage
the outdoor air, HVAC load and IAQ. During normal
operation, a fraction of the return airstream is directed
through the sorbent cartridges to remove contaminants.
Contaminant concentrations stay well below Standard
62.1-2010 VRP design concentrations even during
events, resulting in enhanced air quality (Figure 1).
During the regeneration cycle, the smart scrubber system
is temporarily decoupled from the building as warm
air is blown over the cartridges to release adsorbed contaminants,
which are in turn exhausted into the ambient
air via the building's exhaust systems.
Innovation
VRF offers a unique solution for preserving the aesthetic
and architectural integrity of this historic building. The
Railroad Depot lacked space for conventional ductwork
due to the height of the original glazing and ceilings. And,
the wood roof framing and beams complicated coordination
with the existing structure. VRF minimized the size of
ductwork (limited to ventilation and exhaust air) and the
size of penetrations through the existing internal masonry
walls. The weight of piping and ceiling cassettes had marginal
impact on the existing wood structure.
Cost Effectiveness
The energy conservation measures reduced the peak
cooling load by about 21%, while achieving a 44.97%
annual energy-cost savings over the Standard 90.1-2010
Appendix G baseline. This savings resulted in a payback
period of less fi ve years for the smart air scrubbers.
Environmental Impact
The 11 ton (39 kW) reduction in peak cooling load
equates to less refrigerant charge, which means less
potential for emissions that contribute to ozone depletion
and global warming. The high performance architectural,
lighting and HVAC systems achieve 231 MWh
of annual electricity savings, or a CO2e reduction of
216,521 lb. The utility donated solar trees reduce the
electricity consumption by another 8,049 kWh.
2021
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ASHRAE Journal - August 2021

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