BRANCH OPINION

Re: Application of HVAC Systems in Apartments in Houses Ontario Building Code (OBC), Parts 9, 10 and 11

As a rule of thumb, Part 10 of the OBC is applicable to a Change of Use without proposed construction regardless of the age of the building.

Section 9.41 applies to a Change of Use where construction is proposed and the building is less than five years old.

Part 11 is applicable to a Change of Use where construction is proposed and the building has been in existence for at least five years.

QUESTIONS AND ANSWERS:

Q1.

Neither Section 9.41 nor Sentence 11.3.4.1.(7) reference Section 9.25 or Section 9.33. It is assumed therefore that neither thermal insulation nor a heating system is required for a second dwelling unit. Is this correct?

A1.

No, Section 9.41 and Sentence 11.3.4.1.(7) are only applicable when a Change of Use is being proposed to an existing occupancy or space. A dwelling unit must be heated and insulated according to the OBC at the time when it was built. Therefore, heating and insulation would be present within a dwelling unit before the application of Change of Use is proposed. If the existing space is unheated, it means the space is not finished and therefore would involve construction and the construction must comply with OBC provisions.

Q2.

If a second dwelling unit is created within a space presently heated by the existing dwelling system, may the system remain unchanged if it is a forced system?..... or hydronic system?

A2.

Yes, that assumption is correct. If construction does not involve the heating system, the existing heating system is acceptable

Q3.

Does a second dwelling unit require a separate and distinct heating system? If so, under which Code sentence?

A3.

No, if construction does not involve the heating system, OBC does not require any upgrading.

Q4.

Where a second dwelling unit is provided with a new separate heating system, what changes are required to an existing forced air system serving the existing dwelling to meet the OBC?

A4.

The OBC does not have any requirements that would apply in this case. However, it may be prudent to limit the circulation of the forced air system to the original dwelling.

Q5.

Both Section 9.41 and Sentence 11.3.4.1.(7) reference Section 9.32. Where the existing dwelling is served by a Code complying mechanical ventilation system, may it also serve the newly created dwelling or must the systems be separate?

A5.

If the building is less than five years old and construction is being proposed, the newly created dwelling unit must have its own separate mechanical ventilation system (see Section 9.41 of the OBC). Where the building is over five years, Part 11 would permit natural ventilation in lieu of mechanical ventilation.

Q6.

If the mechanical ventilation systems must be separate, may the dwelling types be different? (For example Type I within a Type II)

A6.

Yes, one assumes that this building is less than five years old and Type II refers to the existing dwelling. Therefore, the existing dwelling has been evaluated as a Type II building at the time of construction and has complied with all relevant Parts of the OBC. Since the new proposed unit is a Type I dwelling, the ventilation system within this unit will not affect the existing unit and can be classified as a Type I dwelling assuming a separate mechanical ventilation system has been provided. This will be no different than any multiple dwelling residential buildings.

Q7.

If the mechanical ventilation systems must be separate but the heating systems are not (question #3 above), must an existing forced air system be modified to eliminate all return inlets from the second dwelling unit?

A7.

This scenario will simply happen in buildings less than five years old or in special cases in buildings over five years. Each ventilation system will require circulation system and therefore if the existing forced air system is providing re- circulation for the ventilation systems, it will need evaluation and may require modification.

Q8.

If a second dwelling unit is proposed to be heated with electric baseboard heaters is a heat recovery ventilator required under Sentence 9.32.3.7.(3)?

A8.

Yes.

Q9.

If a house is less than five years old, should all the requirements of Part 9 be complied with for the new basement apartment. Is this statement correct?

A9.

Use the rule of thumb provided in the beginning of this opinion. If construction is not required, compliance with Part 10 of the OBC is sufficient. However if construction is proposed, construction must comply with Section 9.41 of the OBC, in addition to other Part 9 provisions with respect to the proposed construction.

Q10.

If the statement of Q9 is correct then Part 11 does not apply. Is this correct?

A10.

No, Part 11 does not apply to a house which is less than five years old. Other Parts of the OBC may still permit the designer to refer back to other regulations contained in Part 11 of the OBC.

Q11.

If an existing home is less than five years old a separate heating system must be provided for the new basement apartment. Is this correct?

A11.

If there is a proposed Change of Use to create two units. Then separate systems are required where the ventilation system is coupled with the force air system that serves both units.

Q12.

If, in an existing home less than five years old, is a separate ventilation system required?

A12.

No, unless a Change of Use has been proposed.

Q13.

Referring to Q12 above, can natural ventilation be employed or is a mechanical ventilation system mandatory?

A13.

According to Section 9.32 of the OBC, mechanical ventilation must be provided within each dwelling unit.