3.4
Weather Hoods
Locating the Weather Hoods (Commercial Installations)
Designers should try to locate the hoods in such a way that there is easy access for cleaning purposes.
The H/ERV should be located close to the outside wall(s) containing the hoods, the resulting short duct
lines will minimize airflow losses.
There should be maximum separation between the fresh air and exhaust hoods. Supply hoods should be a
minimum of 36” (inches) above the ground level. Exhaust hoods should be at least 12" (inches) above the
ground level. Fresh air hoods must be min. 10’ 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 re-entrainment 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.
Locating the Weather Hoods (Residential Installations)
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.
NOTE: Refer to local code requirements.
Summary of Contents for NU0103
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