March 14, 2024

Cutting Carbon: Resources for Preservationists

The building sector is the biggest source of carbon emissions causing global warming. Reducing and eventually eliminating these emissions is a realistic goal that requires swift action. Below are resources for preservationists who want to become more involved in fighting climate change by reducing emissions from older and historic buildings.

Confused about terms? We've developed a glossary of terms to orient you to the words of climate work.

View of a digger at the National Trust Historic Site Brucemore as it prepares to install Geothermal systems.

photo by: Brucemore

View of National Trust Historic Site Brucemore during the installation of geothermal systems.

Climate Change in Two Numbers

Although climate change is extremely complex, two numbers capture the challenge we face and our progress toward meeting that challenge.

Global Average Temperature (since the pre-industrial era): The International Panel on Climate Change (IPCC), which publishes regular reports on the science of climate change, estimates that global average temperatures have risen 1.1°C above pre-industrial levels. The IPCC’s Special Report on Global Warming of 1.5°C explains the importance of limiting global warming to no more than 1.5°C to avoid risking catastrophic effects.

Human Generated (CO2) Emissions Worldwide: These emissions are the cause of rising temperatures and must ultimately decrease to zero. For 2023, global CO2 emissions totaled 36.8 billion tons, which is a slight increase from 2022. Several organizations track global CO2 emissions and estimate how much remains in our “carbon budget” if we hope to keep global temperature increases below 1.5°C. At current emission rates, we will exceed our carbon budget within a decade. Reducing annual C02 emissions sooner rather than later will stretch our carbon budget over more years, buying additional time to achieve the transition to a zero emissions future.

Data About Buildings and Climate Change

The challenge of reducing the impacts of climate change can seem overwhelming. Understanding the connections between buildings and carbon emissions helps clarify the opportunity for preservationists to make an impact:

  • Worldwide, the construction and operation of buildings is responsible for 37 percent of all human-generated carbon emissions — more than the amount contributed by sectors such as transportation or industry. The Global Alliance for Buildings and Construction (Global ABC) compiles annual data on carbon emissions from building construction and operations.
  • In the United States the Energy Information Administration tracks energy use and other data for commercial and residential structures. This data shows that building operations are responsible for 31 percent of total carbon emissions nationally.

Decarbonizing Buildings

Building decarbonization eliminates carbon emissions from the construction and operation of buildings. The Department of Energy is developing a National Definition of a Zero Emissions Building that will inform future programs, policies, and incentives. There are two types of carbon emissions from buildings.

Operational carbon emissions result from building occupancy and use (heating, cooling, lighting, equipment, etc.). Strategies to reduce operational carbon emissions include adding insulation, converting to all-electric HVAC systems, and connecting to renewable energy sources.

View of the Voltaic panels being installed on the San Miguel Chapel in August 2023.

photo by: Jake Barrow

View of Solar Panels on San Miguel Chapel, in Santa Fe, New Mexico.

  • Eliminating fossil fuel use in buildings is part of the effort to electrify everything in our economy and communities. For older and historic buildings, this means replacing old furnaces, boilers, water heaters, and stoves that burn gas or oil. Electric heat pumps (either air-sourced or ground-sourced) are more efficient than traditional heating and cooling systems.
  • The Inflation Reduction Act offers incentives for property owners seeking to insulate, electrify, and add renewable energy equipment to their buildings.

Embodied carbon emissions occur when the materials needed to construct and rehabilitate buildings are harvested, mined, manufactured, transported, and assembled.

Communicating Preservation’s Role in Decarbonization

Preservationists can effectively make the point that conserving, reusing, and retrofitting older and historic buildings can help address the urgent need to reduce CO2 emissions from the building sector. Reusing existing buildings rather than replacing them avoids the carbon emissions that occur during new construction.

  • Research conducted by the National Trust’s Preservation Green Lab found that it can take between 10 and 80 years to overcome the carbon debt that is incurred when an existing structure is replaced, even if the new building is highly energy efficient.
  • Architect Larry Strain’s influential white paper, The Time Value of Carbon, explains why building reuse is a particularly effective way to reduce CO2 emissions quickly to help keep global warming under 1.5°C.

Making Older Buildings More Energy Efficient

By reducing the need for power generation, energy conservation is a key decarbonization strategy. Since the 1970s, preservationists have sought to strengthen the connections between historic buildings and energy efficiency.

PastForward 2024

PastForward 2024

PastForward 2024 will kick off a celebration of the 75th anniversary of the National Trust and the evolving practice of preservation in one of the country’s most historic cities: New Orleans.

  • Improving Energy Efficiency in Historic Buildings was one of the first Preservation Briefs published by the National Park Service and continues to provide good advice for how to insulate older buildings, improve the performance of historic windows and doors, add efficient new systems, and build on passive energy features. Other NPS publications provide additional guidance on sustainability and historic buildings.
  • A report from the National Trust’s Preservation Green Lab compares the energy savings and financial costs of a range of options to improve the performance of historic windows.

Measuring Energy Use and Carbon Emissions

As building decarbonization accelerates, the ability to predict and track the energy and carbon impacts of the decisions we make about buildings will become increasingly important.

  • Calculating the embodied carbon impacts of building construction and material use is more complex than simply looking at utility bills. The Carbon Leadership Forum maintains a compendium of tools to measure embodied carbon in building materials and construction.
  • A particularly useful tool for preservationists, architects, developers, and others considering whether to retrofit or replace older buildings is the “Carbon Avoided Retrofit Estimator” or CARE Tool.

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Jim Lindberg

Jim Lindberg is senior policy director at the National Trust for Historic Preservation. He has more than 30 years of experience in preservation, planning, and sustainable development.

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