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BRANCH OPINION

It has come to the attention of the Housing Development and Buildings Branch that there is some misunderstanding as to when the requirements for a carbon monoxide detector and a heat recovery ventilator are required when a solid fuel-fired appliance is installed. It is hoped that this explanation will clarify any misconceptions that may exist.

The necessity to provide a heat recovery ventilator as part of a mechanical ventilation system and the provision of a carbon monoxide detector are requirements for a system designed in conformance with Subsection 9.32.3 where a solid fuel-burning appliance is installed in the dwelling unit.

The ventilation system designer may however, choose to use Part 6 for the design of the ventilation system. If this is the case we recommend that the CSA-F326 Standard be used as the design standard.

There is no requirement within Part 6 to provide a heat recovery ventilator or a carbon monoxide detector as part of the ventilation system whether or not a solid fuel-burning appliance is installed. The design of the ventilation system may include a heat recovery ventilator however.

The design criteria of the CSA-F326 standard permits systems provided that if:

1. The system is designed so that when appropriate ventilating devices are operating, the dwelling unit will not depressurize to more than 5 Pa.

2. The system is installed and a pressure test is performed with the appropriate ventilating devices operating. If more than 5 Pa negative pressure is recorded, fresh air intakes must be provided.

In order to determine which requirements can be applied when a solid fuel-burning appliance is installed certain facts must be known about the age of the building and the type of ventilation system that was required at the time the building permit was issued.

With regard to the applicable provisions of the Ontario Building Code when a solid fuel-burning appliance is installed, it is a Housing Development and Buildings Branch opinion that:

1. Prior to October 1, 1990 there were no requirements in Part 9 with regard to a mechanical ventilation system and therefore if a dwelling unit was constructed in accordance with the OBC prior to October 1, 1990, there are no applicable requirements with regard to mechanical ventilation and therefore there are no provisions in the OBC other than those which would apply to the installation of the solid fuel-burning appliance. There would be no requirement for a heat recovery ventilator, a carbon monoxide detector or alternatively a pressure test of the dwelling.

2. On October 1, 1990 the provision for a mechanical ventilation system was included in Part 9. The system consisted of exhaust fans and the installation of a fresh air intake when there were fuel-burning appliances installed which would back draft if excessive negative pressure was present. The designer was also given the option of designing the ventilation system in accordance with Part 6.

   Therefore, if the dwelling unit was constructed in accordance with the OBC between October 1, 1990 and June 30, 1993 and no fresh air intakes were provided there are two choices available;

   1. install a fresh air intake of an appropriate size to prevent excessive depressurization, or

   2. perform a pressure test, the results of which indicate that there is sufficient air leakage through the envelope to prevent excessive depressurization.

3. On July 1, 1993 Section 9.32 was extensively revised to include the mechanical ventilation system presently required. Subsection 9.32.3. contains the option of designing the system in accordance with Part 6.

   Therefore, if the dwelling unit was constructed in accordance with the OBC after July 1, 1993 there are also two choices available;

   1. perform a pressure test in accordance with CSA-F326 and if not more than 5 Pa depressurization is found the installation would be permitted, or

   2. provide a heat recovery ventilator and a carbon monoxide detector in accordance with the appropriate requirements of Section 9.32.

Should you require further information or clarification please contact Walter Burningham at (416) 585-6654

April 24, 1995