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HOME Ventilation
Guide
Many ERVs look and operate very similarly to HRVs. An ERV not only conducts
heat but also allows water vapor to pass from one air stream to the
other. In cold weather, moisture is transferred from the exhaust air stream to
the fresh air stream. In warm, humid summer weather, the ERV transfers
moisture from the fresh air stream into the exhaust air stream, which the air
conditioner has cooled. In both cases, this moderates the humidity from the
extreme levels found outdoors.
Selecting a model
There are many different models of HRVs and ERVs, each with its own advantages
and uses. To select the right model for your application, consult HVI’s Certified
Home Ventilating Products Directory, available at www.hvi.org, which
contains performance-testing reports for HVI-Certified HRVs and ERVs.
Airflow is an important consideration when selecting an HRV or ERV, as the
unit’s first function is ventilation. It is critical to select a unit suitable for use in
the climate in which it will be installed. In cold climates, the unit’s frost
protection must be sufficient
“RECIRCULATION”
IS NOT VENTILATION
Ventilation is one of the most
misunderstood parts of any central
heating and air-conditioning system.
Builders, contractors and
homeowners alike may believe that
the home’s ventilation needs are
being met by the central forced-air
system since it provides air
movement and distribution. The
American Society of Heating,
Refrigerating and Air-Conditioning
Engineers (ASHRAE) defines
ventilation for indoor air quality as,
“the process of supplying outdoor air
to or removing indoor air from a
dwelling by natural or mechanical
means.”
Traditional forced-air heating and
cooling systems do not ventilate;
they only recirculate the same air
through the dwelling over and over
again, controlling temperature but
doing little to improve air quality. A
large variety of excellent mechanical
ventilation solutions is available, from
single-point exhaust fans to
balanced supply and exhaust
systems with heat and energy
recovery. Installation of HVI-Certified
ventilation products will help to
ensure optimum indoor air quality.
to ensure that ventilation
will continue throughout the
winter.
Other factors to consider
include “sensible heat-recovery
efficiency,” controls, type of
defrost system and power consumption.
To determine the best choice
for your area, contact HVI
member companies, which
have many years of experience
with HRVs and ERVs.
Control options
The controls for continuous
ventilators range from simple
to complex. Controls are
available that permit variable
ventilation rates, automatic
high-speed operation (when
bathrooms are in use, for example),
automatic operation
to control excess humidity,
timed or proportional operation,
and even air-quality-sensing.
HVI member companies
can provide detailed information
to guide your selection
process. ■
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www.hvi.org