Nu-Air ES Series - Ducting to The Outside

Nu-Air Ventilation Systems Inc. - HRV Operating &Installation Manual
Rev October 10, 2010 - 9 -
3.3. Ducting to The Outside
Between the weather hoods and the HRV you must use fully insulated ducting with an integrated
vapour barrier. Insulated ducting with an integrated vapour barrier must also be used on all runs
passing through unheated areas. This will help avoid condensation problems and energy losses.
The minimum RSI value of insulation should equal that of the local building codes.
3.3.1. Weather Hood Installation
1. Insulated flex duct slides over the
galvanized sleeve of the weather hood.
2. Use sheathing tape (red) to join the inner
duct to the hood's sleeve.
3. Tape the vapour barrier to back of the hood
without compressing the insulation. Caulk
or foam seal around the collars and hoods to
eliminate air and water leaks.
4. Locate the hoods for easy access to the bird
screen for cleaning purposes.
5. Be sure to use exterior sealant along the top
and side edges of the hoods, tooling the
sealant to ensure a good seal.
Make the insulated duct that connects the weather hoods to the HRV as short as possible to minimize
airflow restrictions. Avoid sharp bends and stretch out the inner lining of the flex duct as much as
possible to reduce static pressure and maximize airflow. For runs over 12’, increasing flex diameter 1”
to next size up will reduce pressure drop in the duct.
3.3.1.1. Locating the Weather Hoods
There should be a minimum of 6’ (feet) of separation between the fresh air and exhaust hoods. Supply
hoods should be a minimum of 18” (inches) above the ground level. Exhaust hoods should be at least 4
“(inches) above the ground level. Holes through the wall should be 1” larger than the collar on the
hood. Fresh air hoods must be 3’ away from any other appliance exhaust vent or furnace vent.
In addition ASHRAE Standard 62-99 recommends the following. Ventilation systems should be
designed to prevent the reintroduction of exhaust contaminants, condensation or freeze-ups and growth
of microorganisms. Make-up air inlets and exhaust air outlets shall be located to avoid contamination of
the makeup air. Contaminants from sources such as cooling towers, sanitary vents, vehicular exhaust,
and street traffic should be avoided.