Date of Publication: September 18, 2025 [2022.15.V-01.C]
Subject: Minimum Effective R-Value & CI 2024 OBC UPDATE
2024 Ontario Building Code [O.Reg 163/24 Amended to 5/25] Reference(s):
OBC Sentence 12.2.1.2.(3)
Summary of Changes: No changes.
Incoming Request:
Does the Minimum Effective R negate the requirement for Continuous Insulation (CI)? Or is CI always required. The issue relates to a garage being converted to a living space.
Executive Summary:
Any assembly meeting the Minimum Effective R-Value is acceptable whether or not it has Continuous Insulation.
Discussion & Considerations:
Sentence 3.1.1.1.(13) of SB-12 clearly states that “Where a compliance package …specifies a nominal RSI value, an effective RSI value and U-Value for a component…and the component conforms to one of the thermal values, the component need not conform to the other thermal values…”. Stated more simply, if one of the values is met, the assembly is compliant. Therefore, if the Minimum Effective R-value is being met without the use of a continuous insulation layer, this is acceptable.
Additionally, compliance with one of the values for one building envelope element does not require the meeting of the same value for other building envelope elements. This means that you can use a nominal R-value for the roof and use an effective R-value for an exposed floor.
Risk/Benefit Analysis:
There are no risks for this matter.
Final Recommendation:
A continuous insulation layer is not required for an assembly meeting the minimum effective R-value or the maximum U-value.
Recommendation to Ministry of Municipal Affairs and Housing:
None at this time.
Referenced Documents:
- OBC Sentence 12.2.1.2.(3)
- SB-12 Sentence 3.1.1.1.(13)
Disclaimer:
This guidance document is intended to assist building officials by gathering relevant information to interpret the OBC Act and the prescriptive requirements of the Ontario Building Code, and is intended to be a best practice aid for building officials.
The views expressed within this guidance document should not be considered as the official interpretation of legislated requirements based on the Ontario Building Code, as the final responsibility for interpretation rests with the local Authority Having Jurisdiction.
The views of this advisory committee should not be construed as legal advice.