Achieving Zero: How to Reach Zero Net Carbon, and Beyond

The global population is growing at a staggering rate, requiring an equally staggering amount of new construction worldwide. Most of the growth is occurring in cities, which are responsible for more than 66% of total global energy consumption and more than 70% of energy-related CO₂ emissions—and counting. The steps that architects, developers, planners, and the construction industry take in the next few years will determine whether the international community can meet demand for growth and still achieve the targets set out in the Paris Agreement to reduce global greenhouse gas emissions and limit warming to 1.5 C above preindustrial levels. Architecture 2030’s Achieving Zero framework provides a unified vision for building sector policies that drive climate action.

Rapid urbanization presents an extraordinary opportunity. Cities generate over 80% of global gross domestic product, serving as hubs of economic growth and innovation. Municipal governments have demonstrated the ability to act more rapidly than national governments in confronting environmental issues, embracing resilience strategies in the face of a changing climate, and working with communities to increase equity and protect those who are at the greatest risk.

Achieving Zero focuses on cities and subnational governments because of their direct impact on emissions and their position as leaders in climate action. By applying the Achieving Zero framework—through building codes, zoning, and other measures—mayors, city councils, and other leaders can phase out greenhouse gas emissions in their jurisdictions by 2040. Achieving Zero offers strategies in three key areas:

1. Energy upgrades for existing buildings, tailored differently for large and small buildings, and mandated to coincide with market-driven points of intervention such as changes in ownership and occupancy.
2. Zero-net-carbon operations for new construction, with no on-site fossil fuel use. To that end, Architecture 2030 developed the ZERO Code, which is currently available and detailed below.
3. Building with low to zero embodied carbon, or carbon sequestering materials, and consideration of embodied carbon at all levels of design and planning, including infrastructure and building reuse, site selection and landscape, and interior fittings and finishes.

Attaining zero emissions from the existing building stock will require new policies that accelerate the rate of energy upgrades by leveraging building intervention points.

Building energy upgrades include:

• Improvements in the energy efficiency of building operations
• A shift to electric or district heating systems powered by carbon-free renewable energy sources
• The generation or procurement of carbon-free renewable energy

Building intervention points include:

• Point of lease
• Point of sale
• Major renovations
• Systems, materials, and equipment replacements
• Capital improvement cycles
• Zoning or use changes
• Life-safety and resiliency upgrades (as for seismic, flooding, fire prevention, and power disruption)

Policies that align upgrades with market-driven intervention points will help mitigate the cost barriers and disruption associated with building renovation work. Such policies will also expand the market for building renovations, building systems and equipment, and carbon-free renewable energy, which in turn will create new local jobs, market growth, and tax revenue.

The Achieving Zero framework is tailored to two broad categories—big buildings such as multifamily residential, commercial, and institutional, and small buildings such as single-family residential and retail—recognizing that the timing, requirements, and implementation are different for these two categories.

Big buildings, such as high-rises and large offices and apartments, in a downtown core make up only 2%–5% of the total number of buildings in most cities, but they account for about half of total building emissions. Big buildings are sold infrequently, and are renovated periodically during capital improvement cycles. Decarbonization policies for big buildings should be applied consistently and over a suitable period of time, so that the market learns to act accordingly.

Small buildings, meanwhile, make up the vast majority of buildings in the city by number, and altogether account for the other half of total building emissions. Small buildings are sold more frequently, and don’t have traditional capital improvement cycles—instead, renovations typically occur after the failure of equipment, upon change of occupancy, or at the point of rental or sale. Decarbonization policies applied to small buildings should be equitable, simple, and prescriptive, in order to make implementation and compliance easy.

Decarbonization policies for big and small buildings are most efficient when they account for the differences between the two categories. Policies that reflect the timing and financial concerns of building owners and occupants are not only easier to pass into legislation, they are easier to implement, enforce, and build upon.

By 2060, the world is projected to add 2.5 trillion square feet of buildings—an area equal to the entire current global building stock. This is the equivalent of adding a new New York City to the planet every 34 days for the next 40 years. While improvements in the energy efficiency of buildings and growth in the generating capacity of renewable energy have both helped, it has not been nearly enough to offset the increase in emissions from new construction.

Only by eliminating CO₂ emissions completely from new building operations will we begin to reduce building sector emissions overall. Achieving zero-net emissions from new construction will require the complete elimination of fossil fuel consumption, such as natural gas for space and water heating or kitchen use. Instead, buildings must draw their power solely from carbon-free, renewable sources located either on- or off-site.

New construction must also rely on energy-efficient systems to ensure that total building energy use is minimal, enabling the carbon-free, renewable energy sources to easily meet demand.

Architecture 2030’s ZERO Code, a national and international commercial building energy standard for new building design and construction, integrates cost-effective energy efficiency standards with on-site and off-site renewable energy, resulting in zero-net-carbon buildings. The code applies to all new buildings and major renovations and includes guidelines for its incorporation. The code includes prescriptive and performance paths for building energy efficiency compliance, based on current standards that are widely used by municipalities and building professionals worldwide.

How Zero Code Works
After designing a building that meets an energy efficiency code standard such as ASHRAE 90.1 or the International Energy Efficiency code, which include …

• Efficient building envelope
• Daylighting
• Passive heating
• Cooling
• Ventilation
• Efficient systems
• Equipment
• Controls

Then meet the building’s main energy needs with on-site renewable energy …
And/or with off-site renewable energy from …

• Wind
• Solar
• Hydro
• Other non-CO₂-emitting sources

Managing embodied carbon begins with understanding the critical choices in the early phases of construction and development, as well as their impacts downstream: the choice to adapt and reuse an existing building, rather than raze it and erect a new structure; choices around location, size, and site design that require more or less material and infrastructure; and choices in the design of the building, ranging from material selection to designing for later adaptive reuse or for deconstruction and material reuse or recycling.

The embodied carbon of materials for the structures, enclosures, and construction of buildings represents 11% of total annual global greenhouse gas emissions. When interior walls, finishes, and fixtures; equipment; mechanical, plumbing, and electrical systems; and site infrastructure are taken into account, the percentage of global greenhouse gas emissions from embodied carbon is even greater.

Educating policymakers about building and infrastructure design and material specifications can help support them in the development of realistic, market-sensitive policies for low-carbon to carbon positive buildings. Policies that change the way architects and developers choose and use building materials can help manufacturing and industry to shift away from products and processes with heavy emissions. Architecture 2030 created the Carbon Smart Materials Palette as a resource for architects, engineers, and builders to identify high-impact building materials and the attributes that contribute to their carbon footprint, as well as provide strategies for reducing their emissions.

Cities can leverage their legal, regulatory, and financial powers to tackle embodied carbon through zoning and land use policies, administrative and financial incentives, and mandates for infrastructure, buildings, and products. Architecture 2030 is now in the process of developing a policy toolkit that will guide cities in implementing policies to reduce building sector embodied carbon through these mechanisms.

To maintain even a 67% chance of limiting warming to 1.5 C above preindustrial levels, humanity has to limit its total emissions to a “carbon budget” of about 340 gigatons of CO₂ starting in 2020. The numbers may be abstract, but the implications are firm: a 65% reduction in greenhouse gas emissions by 2030, and full decarbonization by 2040. In the face of these urgent demands, it is crucial that a comprehensive and unified framework of decarbonization policies reaches all segments of the building sector.

Even moderate change in the building sector can create powerful ripples that can become waves. Widespread electrification of existing buildings (eliminating natural gas) in tandem with grid decarbonization will remove operational emissions of existing buildings from the equation; zero-net-carbon new construction, with its demand for carbon-free renewable energy, will create a steady and predictable market for renewables and support the necessary advances in renewable energy storage and other technologies. A paradigm shift in building design and material selection will push manufacturing industries to catch up and reduce the embodied carbon of their products. Policies that reduce embodied carbon at the level of the neighborhood, city, and region have the potential to reshape patterns of consumption and waste. Such policies are being developed, adopted, and implemented in many cities across the world.

Active participation of the design, planning, and construction community in the creation and implementation of these policies can help ensure their success. The transformation of cities from contributors to greenhouse gas emissions and climate change to sites of carbon sequestration and hubs of activity for circular economies has the power to transform the world.

Project Team: Vincent Martinez, Erin McDade, Lindsay Rasmussen, Natasha Balwit, and Charles Eley