Fresh Air Intake In Forced Air System

Existing forced air system duct leakage to outside will be less than 10% of the air handler flow when measured at 25 pascals with reference to outside

Any portion of the return located inside a combustion appliance zone will be sealed

Install intake to pull air from the outdoors, which does not include unconditioned spaces such as attics and crawl spaces that are ventilated with the outdoors

Install intake:

A minimum of 6" from grade;

A minimum of 10' from contaminant sources or exhaust outlets;

Above local snow or flood line;

A minimum of 18" above an asphalt based roof;

Never on a flat roof

Intake fitting will be labeled "ventilation air intake"

Install corrosion resistant screen, louver, or grille material over exterior intake with a hole size of no less than 1/4" and no greater than 1/2" in any direction

Install a motorized damper or equivalent between the intake fitting and the return side duct connection

Damper will be open only when the air handler fan is operating

Provide air flow by sequenced or scheduled operation of the damper or equivalent technology

Control system must operate both the air handler and the motorized damper or be interlocked to prevent damper operation when air handler is not on

Install all electrical wiring according to manufacturer specifications and applicable code

All mechanically-supplied outdoor air must pass through a filter before combining with conditioned air

Filtration must meet a minimum efficiency of MERV 8

Filter or air cleaning systems that intentionally produce ozone are not allowed

Install filtration in a readily accessible location for service

Filter opening must allow filter to be fully removed and inserted without bending or damaging the filter

Filter access panel must include gasket or comparable sealing mechanism and fit snugly against exposed edge of filter when closed

Filter plenum must be airtight and mechanically fastened to adjoining ductwork

Ensure motorized dampers and service disconnect switches are accessible for maintenance according to NEC, or applicable building code

Install all ducting in accordance with SWS detail for "Ventilation Ducts"

If fire dampers are required in the fresh air supply duct, install them according to applicable building code

Fire dampers must be accessible for inspection and/or testing

Sealing activities must not interfere with the operation of fire dampers, balancing dampers, or backdraft dampers

Adjust fan speed, dampers, and registers until design specifications are met