News Brief

With Early-Phase Carbon Tool, Designers Learn What Works

ZeroGuide, a free whole-life-emissions tool from NBBJ, is about education as much as it is about modeling. It’s also a gateway to more refined approaches.

screen shot of data output from a software tool, headed “baseline operational energy and carbon use.” various graphics compare baseline and design performance, show breakdowns by space type within the building, and rank the project as good, better, best

This ZeroGuide summary page for a mixed-use building displays total operational emissions and savings, and ranks the building’s performance as “better."

Image: NBBJ
It started as a way to strengthen carbon literacy among designers at NBBJ Design. Four years later, ZeroGuide has been released to the public for free with a dual mission: to support early design decisions for projects and to influence future projects.

Several widely respected data sources—including Cambium and PVWatts from the National Renewable Energy Lab, Architecture 2030’s Zero Tool, Carbon Positive Design’s Pathfinder, and the EC3 product-category baselines—underlie the tool, allowing for robust comparisons of design options. But just as importantly, ZeroGuide’s instant feedback “build[s] designers’ intuitions” to inform future decision-making, according to Margaret Montgomery, FAIA, principal and sustainability leader at the firm.

ZeroGuide’s workflow begins with basic information, including any building certifications the project team may be pursuing. It proceeds to whole-life embodied carbon selections, addressing structure, envelope, landscaping and other site features, parking footprint, HVAC replacements, and interior fit-out cycles over time.

Each section of ZeroGuide “ends with a summary page with total emissions and savings,” explained Pragya Gupta, firmwide design computation team leader and design performance analyst. Data are expressed in accessible terms, like acres of forest cut down or preserved. Each summary also designates solutions as good, better, or best. And each one links to outside resources, prompting users to “go deeper into performance” with more refined tools, Gupta said.

After embodied carbon, users move through a variety of inputs about operational carbon.

The first operational decision is whether to electrify. Subsequent questions include details about energy use intensity, onsite and offsite renewables, and other goals. ZeroGuide also uniquely targets transportation energy, asking about things like location and commuting.

Even the carbon experts who helped develop the tool have learned from it, noted Peter Alspach, P.E., principal and director of design performance. For example, “all the information we’ve found says that building height has a significant impact on embodied carbon,” he said. (It’s worth noting that those impacts might be even larger when properly estimating construction emissions, which are currently excluded or underestimated across the industry and in most modeling software.)

Alspach also learned how big a difference the user experience can make.

That aspect of the project “was really, really eye-opening for me,” he told BuildingGreen, joking that he personally would have just made a spreadsheet. “I’m an engineer, and that’s where my nerdy brain goes,” he said. But sending designers on what Alspach called a “guided journey” is pivotal to the tool’s effectiveness.

Asked how ZeroGuide fits into the whole ecosystem of early design tools, Alspach again emphasized education.

“We’re more of a guided, early-use, carbon-literacy tool,” he said, while others, like EPIC and CARE, are “for a more advanced user who wants to play with more buttons than we allow them to play with.”

More on carbon modeling

The Missing Embodied Carbon Link: Construction

Raze or Retrofit? CARE Tool Has the Answer

Free Tool Estimates Embodied and Operational Carbon

Investors Will Use EPIC Tool to Decarbonize Existing Assets

Webinar: LEED and Life-Cycle Assessment in Buildings

For more information:

NBBJ Design

Published August 7, 2023

Melton, P. (2023, July 27). With Early-Phase Carbon Tool, Designers Learn What Works. Retrieved from

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