The principal ventilation system circulates air throughout the house for the purpose of maintaining acceptable indoor air quality. Each ventilation system has three main components:
- indoor air exhaust
- outdoor air supply
- distribution of air The principal ventilation fan extracts indoor air. Its operation is linked with a means of introducing and distributing outdoor air to the dwelling unit at approximately the same rate at which the indoor air is exhausted, except as permitted by Article 9.32.3.6. The principal ventilation fan must be capable of drawing air from throughout the dwelling unit and exhausting it to the outdoors. Though actual usage will be determined by the occupants, the fan must be capable of continuous operation.
Unfortunately, there is no standard method of testing and designating fans for continuous use. Therefore, such a designation is not a mandatory requirement. See Sentence 9.32.3.3.(4)) Supplemental exhaust fans, such as kitchen cooktop hoods and bathroom fans, provide more ventilation at point of source when needed. (See Article 9.32.3.7. and Note A-9.32.3.7.) Outdoor air is brought into a house either through a supply duct in the exterior wall or, in exhaust-only systems, by leaks through the building envelope. (See also Note A-9.32.3.6.) There are two approaches to ensuring air is distributed to all parts of the house:
- in forced air heating systems, the furnace circulation fan moves the air through heating distribution ducts, (See Note A-9.32.3.4.)
- in non-forced air heating systems, a supply fan circulates air through dedicated ventilation distribution ducts. (See Note A-9.32.3.5.) Figures A-9.32.3.3.-A to A-9.32.3.3.-F and A-9.32.3.6. show possible configurations of principal ventilation systems.
However, even within these prescriptive solutions, a significant degree of flexibility is available. The configurations illustrated should therefore not be regarded as the only configurations acceptable under Sentence 9.32.3.1.(2).
Possible Configuration of a Mechanical Ventilation System Coupled With a Forced Air Heating System
Notes to Figure A-9.32.3.3.-A:
(1) The outdoor air supply duct shall be connected not less than 3 m upstream of the plenum connection to the furnace.
Possible Configuration of a Mechanical Ventilation System Using a Heat Recovery Ventilator Coupled With a Forced Air Heating System
Notes to Figure A-9.32.3.3.-B:
(1) The outdoor air supply duct shall be connected not less than 3 m upstream of the plenum connection to the furnace.
(2) The HRV supply inlet and exhaust outlet shall be separated by a distance of not less than 900 mm.
Possible Configuration of a Mechanical Ventilation System Not Coupled With a Forced Air Heating System Note to Figure A-9.32.3.3.-C:
(1) The outdoor air supply duct shall be connected not less than 3 m upstream of the plenum connection to the furnace.
Possible Configuration of a Mechanical Ventilation System Using a Heat Recovery Ventilator not Coupled With a Forced Air Heating System Note to Figure A-9.32.3.3.-D:
(1) The HRV supply inlet and exhaust outlet shall be separated by a distance of not less than 900 mm.
Ventilation System Coupled With a Forced Air Heating System and Using a Dual-Capacity Principal Ventilation Fan to Eliminate the Need for Supplemental Fans
Notes to Figure A-9.32.3.3.-E:
(1) The make-up air fan operates when the PVF operates at 2.5 times the required capacity.
(2) The outdoor air supply duct shall be connected not less than 3 m upstream of the plenum connection to the furnace.
Ventilation System Coupled With a Forced Air Heating System and Using a Heat Recovery Ventilator as the Principal Ventilation Fan to Eliminate the Need for Supplemental Fans
Notes to Figure A-9.32.3.3.-F:
(1) The outdoor air supply duct shall be connected not less than 3 m upstream of the plenum connection to the furnace.
(2) The HRV supply inlet and exhaust outlet shall be separated by a distance of not less than 900 mm.