New ZCB-Design v4 Addenda out 

CAGBC has released addenda to the Zero Carbon Building – Design Standard Version 4 to provide additional compliance options and clarify how several systems and project conditions are addressed. ZCB-Design helps guide the design of new buildings and major renovations of existing ones so they can achieve zero carbon operations. 

Read the updated ZCB-Design Standard V4

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The addenda updates include:   

New TEDI compliance path for combustion-based heating used for resiliency support

Project designs that incorporate combustion-based space or service water heating equipment for resiliency support solely outside the energy model conditions can use a new TEDI compliance path. Path 5: Combustion for Resiliency Support provides TEDI targets that are 50% more lenient than the default Path 2 targets. Additionally, resiliency support systems do not need to be addressed in Alternative Design Evaluations and Transition Plans, though they do impact eligibility for the Impact & Innovation strategies for 100% electrified heating. Note that any combustion-based space heating, including resiliency support systems and combustion-based air-handling or make-up air units, makes a project ineligible for TEDI compliance Path 1: No Combustion. 

Emergency backup generators exempted

Emergency backup generators are treated as power systems and not as space-heating or service-hot-water equipment, even when they power equipment serving those functions. Therefore, they do not need to be included in the onsite combustion limits, Alternative Design Evaluations and Transition Plans, or when assessing the Impact & Innovation strategies for 100% electrified heating. 

Critical service hot water systems may qualify for an exemption from the combustion limit

The exemption applies where the loss of hot water would compromise primary safety or vital processes. Additionally, equipment serving these critical needs does not need to be addressed in Alternative Design Evaluations and Transition Plans. The Impact & Innovation strategy for 100% electrified service hot water has also been expanded to include projects with critical service hot water needs. 

Specialized exhaust and heating systems can use a trade-off calculation to demonstrate equivalency to the onsite combustion limit for space heating

The trade-off calculation applies to air-handling and make-up air units serving spaces with specialized heating and ventilation requirements. The ZCB-Design v4 Energy Modelling Guidelines provide the trade-off methodology.  

Buildings on district energy systems (DES) have new compliance paths and modelling guidance

The ZCB-Design v4 Energy Modelling Guidelines provide new EUI compliance paths and explain how to model projects connected to a DES. Additionally, TEDI paths now clearly address DES projects and projects procuring eligible green heat for all space heating needs. A new Impact & Innovation strategy also recognizes projects that procure eligible green heat, with updates specifying clearer accounting and verification requirements for green heat programs.  

Projects in colder climate zones have clearer TEDI requirements

TEDI targets for climate zone 7B are differentiated from those for 7A. The ZCB-Design v4 Energy Modelling Guidelines also explain how to apply the Path 3: Adjusted TEDI target for climate zones 7A, 7B, and 8. 

Eligibility extended to certain Part 9 project

This recognizes the ZCB-Design v4 Part 9 Residential Pilot that was launched in June 2025. 

Reference for new heat wave weather files provided

NRC’s new weather files for long, intense, and severe future heat waves can provide critical new insights into resiliency.  

A complete list of changes is provided in appendices to the ZCB-Design v4 Standard and the ZCB-Design v4 Energy Modelling Guidelines, while the ZCB-Design v4 Workbook lists updates in the Version History tab. Note that updated emission factors and minor fixes have been made to the ZCB-Design v4 Workbook along with the enhancements and updates to reflect the addenda. 

ZCB-Design v3 projects should consult the ZCB Interpretations Database to determine how this ZCB-Design v4 addenda can apply to their project.