User Guide

8
The Ductwork System
Fully insulated ducting with an integral vapour
barrier must be used on all runs passing
through unheated areas in order to avoid con-
densation problems and energy losses from the
air systems.
ATTENTION
!
A properly designed ducting system will allow the HRV to
operate at its maximum efficiency. (Air flow will be re-
stricted by undersized ducting, use of too many elbows,
tees, bends, etc.). Always try to keep duct runs as short
and straight as possible.
NOTE: Fully insulated ducting with an integral vapor
barrier must be used on all runs passing through unheat-
ed areas in order to avoid condensation problems and
energy losses from the air steams.
All joints must be airtight, sealed and impervious to
moisture. See specification sheets for each unit for exact
duct sizes and location.
To minimize pressure drop and noise, galvanized metal
ducts, properly sized, are recommended. Keep ducting
as short as possible and use a minimum of elbows and
tees.
Outside Weatherhoods
The weatherhoods must have built-in “bird” screen with
1/4 in (6.35 mm) minimum mesh to prevent birds and
rodents from entering into the ductwork. Do not use
smaller mesh as it will be very susceptible to plugging
up. Gravity dampers at the vents must not be used as
they will restrict air flow and often “seize up”. The pre-
ferred location of the outside weatherhoods is:
 no less than 10 ft. (3 m) apart from each other
 at least 18 in (46 cm) above snow line or ground
level
 away from sources of contaminants, such as auto-
mobile exhaust fumes, gas meters, garbage cans,
containers, etc.
 not exposed to prevailing winds
The outside perimeter of the weatherhood must be
caulked to prevent leakage into the building.
The design and size of the weatherhoods or louvers cho-
sen by the installer must allow for adequate free area.
Water and debris penetration of the system is minimized
when the airflow does not exceed 1000 FPM (5.08 m/s)
free area velocity.
Ducting from the Weatherhoods
Galvanized sheet metal ducting with sufficient cross sec-
tion with an integral single piece vapor barrier should be
used to connect the HRV to the weatherhoods. All duct-
ing must meet UL Class 1 requirements.
A minimum R value of insulation should be equal to 4
(RSI 0.75)
A good bead of high quality caulking (preferably acousti-
cal sealant) and taping with a high quality aluminum foil
tape is recommended to seal the duct to both the HRV
and the weatherhood.
Connecting sections and shorter runs may be flexible
ducting one size larger than the metal equivalent. Use
flexible duct connectors at the HRV to avoid noise trans-
mission.
All duct joints must be secured with screws, rivets or duct
sealant and sealed with aluminum duct tape to prevent
leakage.