This Task Group continues the work of the previous Task Group (TG) on Overheating with a new Chairperson and some new members including, for example the former Chair of the Standing committee on Housing and Small Buildings and the former chair of this TG as well as a representative from HVAC Designers of Canada. The mandate for the next few meetings of the Task Group is the review of the comments from the ad-hoc public review in February 2025 and providing its recommendations to the National Model Code Committee on Climate Change Adaptation to which the TG now reports.

TG members reviewed the comments categorized into common subject areas and agreed to possible committee actions confirming that:

• the design of a cooling system needs to be done to CSA F280, but code users can use good engineering practice tools (other methods) to verify whether cooling is required in the first place and that good engineering practice can also be used to calculate the effect of natural ventilation or shading devices to lower cooling loads.
• the code change will not satisfy extreme heat events; rather the changes are a stop gap measure that help to reduce the negative health effects in new housing in the event of future unknown heat events, and because the current climatic data in the code only allow using a basic method using trigger temperatures and design temperatures.
• the TG responded to public review comments for multiple temperatures that it chose a single interior safe temperature (of 26°C ) for all spaces in a home because that is the common HVAC design practice and because spaces like basements, service spaces or conditioned crawl spaces rarely need cooling as they tend to be cooler by nature.
• NRC research on the health impact of relative humidity - in response to a TG  action item - will be presented so that the TG can review the need to regulate humidity control if that is what the research suggests.

Up to this point, the TG has not revised any code language in the proposed change.

For more information, please contact Frank Lohmann.