20-0409 Zero Carbon - Existing Combustion Systems in Existing Buildings

The purpose of this post is to clarify the conditions for the use of combustion in existing building projects pursuing Zero Carbon certification, in reference to the statement: “any fuel type used by existing projects is acceptable, including natural gas.” 


Projects pursuing Zero Carbon may utilize combustion-based systems if they existed in the building. However, project teams may not install new combustion-based equipment in Zero Carbon projects where they previously did not exist.

Project teams that are making renovations to an existing building or an interior tenant space are encouraged to convert existing combustion-based equipment to electrical whenever possible. However, projects may directly replace or upgrade combustion-based components if a conversion to electric based systems would require a significant increase in project scope. Examples of a significant scope increase include expansion of the base building footprint or mechanical spaces to accommodate larger equipment (i.e. outside of an interior renovation scope) or an upgrade to the electrical service capacity of the base building that would otherwise not be necessary to service the project space. Note that any replacement or upgrades to combustion-based equipment may not result in higher fuel consumption; the intent should be to increase efficiency and otherwise minimize combustion-based fuel use.

Project teams that replace or upgrade combustion-based equipment should provide additional documentation to describe their investigation of electrical-based alternatives and clearly outline the project scope boundaries that inhibit their use.

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