Providence School Meets 40% Energy-Reduction Goal, Lowers HVAC First Cost

Posted 1 April, 2012 — Newsroom

Designing a new high school to be 40% more efficient than
ASHRAE 90.1-2001 energy requirements is a feat in itself. To
achieve this degree of efficiency on a very limited capital budget
while designing a state-of-the-art, energy-demanding technical
high school is an even greater feat.

This is exactly what the StudioJAED architectural and
engineering firm accomplished at the Providence Career and
Technical Academy in Providence, RI, to comply with the design
requirements of the Northeast Collaborative for High
Performance Schools.

PCTA opened its doors to its first class of students on Sept. 2,
2009, after 212,000 sq ft of new construction plus 72,000 sq ft of
renovation in the previously existing Hanley Classroom Building.
Now, one of New England’s premiere technical high schools,
PCTA features high-tech classrooms, equipment, labs, media centers, athletic facilities and other
amenities. The school offers nine vocational programs, including automotive technology, construction
technology, cosmetology, culinary arts and HVAC.

The school building was designed to satisfy the full requirements of NE-CHPS, whose mission is to
promote school environments that are not only energy and resource efficient, but also healthy,
comfortable and well lit. Oftentimes, highly efficient buildings mean premium costs. Because PCTA,
like many other schools, was no stranger to budget constraints, designers had to limit initial costs in
creative ways.

HVAC cost savings with energy recovery
A major design directive to save on construction costs led PCTA to install a dual-temperature, twopipe HVAC system. In contrast to the more common (and more expensive) four-pipe system where
heating and cooling are available at any time, two-pipe systems cannot engage cooling coils to reduce
humidity on cool, damp days while in the heating mode. The solution to this dilemma was to install
Airxchange energy-recovery wheels containing a silica-gel desiccant for moisture transfer. By rotating
between building exhaust and outdoor intake air streams, the wheels remove moisture from outdoor
air on damp days and reject it into the exhaust air stream to keep indoor relative humidity at a
comfortable level.

Engineer Brian Zigmond, a Principal of StudioJAED, stated, “Since the school utilizes a two-pipe
system, we needed a way to mitigate humidity issues typical to the area during ‘shoulder’ seasons.
Rejecting as much humidity as possible back to the outdoors with an energy-recovery wheel is the
most practical solution available. We’ve h ad success with implementing energy-recovery wheels in
new and existing schools. Given school budget constraints, installing energy-recovery wheels to save
on upfront and operating costs is a no-brainer.”

Reducing OA load and staying in the “comfort zone”
StudioJAED also realized during the planning phase that energy
recovery would have to be incorporated into the design of
PCTA’s HVAC system if the 40% energy-reduction goal were to
be achieved. The team chose to utilize a combination of airhandling units and standalone energy-recovery ventilators with
Airxchange energy-recovery wheels to provide outdoor air to
PCTA’s new and retrofitted classrooms, labs, auditorium and
media center. The Airxchange wheels help to condition 45,215
cfm of outdoor air by continuously recycling the heating or
cooling energy (depending on the season) from the exhaust air
stream. On peak design days, the energy-recovery wheels reduce
the outdoor air load by as much as 80%.

The ability of Airxchange wheels to save on energy is evident at
PCTA, especially during the heating season. In the first winter
operation, PCTA Facility Manager David Gaudet kept his eye on
the boilers to ensure they were able to handle the load. He was
surprised at how infrequently the boilers actually started up,
stating: “I kept waiting for the boilers to fire up on cold days. But
the energy-recovery wheels were able to heat the outdoor air enough to significantly reduce boiler
operation. The wheels keep the supply air in a nice comfortable zone where frequent additional
heating is not required.”

With rising fuel prices, the conditioning provided by the Airxchange wheels to reduce boiler operation
generates tremendous cost savings. PCTA HVAC Technician Brian Polak added that he was able to
shut down the entire boiler system for a few hours to perform emergency work during one of the
coldest days of the winter without the system being negatively affected.
The results speak for themselves

PCTA operates in the 43 kBtu/sq ft range, which is about 40% lower than the national average for all
high schools, not just technical schools. The improved efficiency yields huge savings on utility bills.
Through their reduction in outdoor air load, Airxchange energy-recovery wheels account for an
estimated $28,000 in annual utility savings.1 Because of PCTA’s Northeast location, the majority of
the savings are realized in ithe heating months, but because Airxchange wheels exchange moisture and
maintain superior IAQ, they benefit the school year-round.

For more information, visit www.airxchange.com.
1Estimate based on a 10-month, 10 hours/day and 5 days/week operating schedule using actual utility
costs of $0.17/kWh (electric) and $1.30/therm (gas).