A New Embodied Carbon Calculation Tool for Passive House

The Passive House Network is out to change that with its PHribbon software. Used along with the Passive House Planning Package (PHPP) tool, PHribbon incorporates the cradle-to-grave carbon impacts of materials in U.S. buildings, providing opportunities to lower a building’s overall carbon footprint.

According to the Passive House Network, the PHN PHribbon is a collaboration between Building Transparency and The Passive House Network. This collaboration gives PHribbon access to Building Transparency’s EC3 database of third-party-verified environmental product declarations (EPDs) and the embodied carbon data therein (EC3 was a BuildingGreen Top 10 product for 2021).

These EPD data include manufacturing (found in section A1­­­–A3), construction (A4­–A5), operations (B1­­–B5), and end of life (C1­­–C4); but PHribbon also incorporates data from the PHPP tool, as well as data from the U.S. Environmental Protection Agency for power supply (used for operational carbon) and end-of-life. End users can input transportation data, estimated lifespan of materials, and more.

Data generated by PHribbon are displayed on a spreadsheet that shows which materials contain the most embodied carbon (in red) and those with less (in green). Passive House designers get a quick snapshot of materials or systems with the highest impacts and can substitute lower-embodied-carbon options accordingly. PHribbon also generates graphs—one showing embodied carbon in CO₂ equivalent (CO₂e) and one showing cumulative operational and embodied emissions over time. The latter is important since some materials have higher embodied carbon during manufacturing but “pay it back” through lower operating emissions.

PHN acknowledges that the data inputs for PHribbon are not always perfect. It can be challenging to determine carbon impacts, such as when FSC wood is used (FSC can have a lower carbon impact due to forestry practices). Also, embodied carbon values can be incomplete; industry-standard assumptions may be used; and European data may be used when U.S. data aren’t available. But PHN also states the software will be updated to keep pace with the latest data. In the end, PHribbon provides a robust tool for quickly determining the carbon impacts of materials and systems throughout a building’s complete life cycle.