Product Evaluation & Testing
Central exhaust ventilation systems are one of the biggest drivers of energy and
indoor air quality performance in multifamily buildings. Despite the critical nature
of these systems, the vast majority do not work as designed in either existing
buildings or new construction. As a rule, upper floor apartments (closer to the
fan) are over-ventilated, lower floor apartments are under-ventilated and poorly
sealed ventilation ductwork can result in roof fans exhausting as much air from
building cavities as they draw from the bathrooms and kitchens that actually
require ventilation! With funding from the New York Energy Research and
Development Authority, SWA is halfway through a project to demonstrate a fix for
these systems that incorporates the Carrier AEROSEAL process to seal ventilation
shafts and the American ALDES’ Constant Air Regulator Dampers (CAR) to
balance exhaust ventilation flows from floor to floor.
AEROSEAL works by sealing holes from the inside with
a polymer based sealing agent that is injected into
duct systems after exhaust grilles at each floor are
removed and duct openings are temporarily blocked
with friction fit foam blocks. The sealing agent does
not coat the ducts, remains rubbery over time and
can seal holes up to 3/8”. CAR dampers are used to
regulate airflow at each exhaust grille location. A
silicon bladder mechanism expands as the pressure
drop across the damper increases, which results in a
constant airflow rate over a wide range of conditions.
With existing buildings CAR dampers can be installed immediately after AEROSEALING, minimizing
apartment access requirements.
To date, SWA has worked closely with Dunn Development,
Phipps Houses and the Women’s Housing and
Economic Development Corporation to evaluate the
costs and benefits of this approach in four NYC buildings
(three existing, one new construction). As a result of our
work with these early adopter building owners, SWA has
developed and fine tuned a strategy to coordinate and
implement AEROSEALING and CAR dampers to
improve the energy and indoor air quality performance
of multifamily buildings.
Results indicate that the AEROSEALING can reduce
ventilation shaft leakage by 90%
and that CAR dampers can be
used to “dial in” exhaust airflows
at each floor to precisely meet
code requirements. Moreover,
the two technologies complement
each other since sealing
duct leaks increases suction at
the bottom of the shafts, allowing
CAR dampers to better regulate
airflow. SWA is still quantifying the
energy savings benefits associated
with shaft duct sealing and eliminating over-ventilation; however initial
results indicate that simple paybacks of well under five years can be expected.
While the economic benefits may be attractive to building owners, residents also benefit from a ventilation system that actually works.
Improving the built environment through research, sustainable design and technology. © 2008 Steven Winter Associates, Inc.