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Credit: Emmanuel Dunand

Buildings and Cities


A receptionist sits behind the information booth during the $530 million retrofitting of the Empire State Building, originally constructed in 1931. The retrofit to the Art Deco icon saw the replacement of all 6,500 windows and all heating, cooling, and lighting systems—an energy reduction of 38 percent.

Worldwide, buildings account for 32 percent of energy use and 19 percent of energy-related greenhouse emissions. They pull from the electric grid or natural gas lines to heat, cool, and light the spaces within them and to power appliances and machinery. As much as 80 percent of the energy consumed is wasted—lights and electronics are left on unnecessarily and gaps in the building’s envelope allow air to seep in and out, for example.

Much of the attention paid to green buildings is in new construction, but retrofitting brings energy efficiency to the existing built environment. The world has 1.6 trillion square feet of building stock, 99 percent of which is not green. Retrofitting addresses how heat and cold are escaping or entering the building, the systems that cool or warm inhabitants, and how spaces are illuminated. It ultimately improves the experience of being inside the building.

Retrofitting is a well-understood practice, and good building performance data is making it increasingly effective. The payback on retrofits, depending on the building, is five to seven years on average. A recent retrofit of New York’s iconic Empire State Building will cut energy use by 40 percent and avert 105,000 tons of greenhouse gas emissions.


“world’s tallest building”: Tauranac, John. The Empire State Building: The Making of a Landmark. Ithaca and London: Cornell University Press, 2014.

buildings…energy use and…emissions: Lucon, O., D. Ürge-Vorsatz, A. Zain Ahmed, H. Akbari, P. Bertoldi, L. F. Cabeza, N. Eyre et al. “Buildings.” In Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge, UK, and New York: Cambridge University Press, 2015.

[U.S.] buildings’ energy consumption: U.S. Department of Energy. “Buildings Share of U.S. Primary Energy Consumption (Percent).” Buildings Energy Data Book.

80 percent of…energy…wasted: Next 10. Untapped Potential of Commercial Buildings—Energy Use and Emissions. San Francisco: Next 10, 2010.

critical to modify existing buildings: Al-Kodmany, Kheir. “Green Retrofitting Skyscrapers: A Review.” Buildings 4, no. 4 (2014): 683-710; Preservation Green Lab. The Greenest building: Quantifying the Environmental Value of Building Reuse. Washington, D.C.: National Trust for Historic Preservation, 2011.

buildings in the United States; commercial: Nemtzow, David. “140 Million Places to Save Energy.” September 1, 2016; U.S. Energy Information Administration (EIA). 2012 Commercial Buildings Energy Consumption Survey.

[longevity] of the existing building stock: Ma, Zhenjun, Paul Cooper, Daniel Daly, and Laia Ledo. “Existing Building Retrofits: Methodology and State-of-the-Art.” Energy and Buildings 55 (2012): 889-902; Campbell, Iain, and Koben Calhoun. “Old Buildings Are U.S. Cities’ Biggest Sustainability Challenge.” Harvard Business Review. January 21, 2016.

Empire State Building…energy [use]: Malkin, Anthony E. “Four Reasons Why the Empire State Building Retrofit Model Works.” The Clinton Foundation. August 12, 2014.

retrofit…[reduce] usage by 40 percent: Harrington, Eric and Cara Carmichael. Project Case Study: Empire State Building. Rocky Mountain Institute, 2009.

energy costs and…emissions [avoided]: Navaro, Mireya. “Empire State Building Plans Environmental Retrofit.” New York Times. April 6, 2009.

windows…rebuilt on-site: Lehner, Peter. “Empire State Building Cuts Energy Waste, Becomes Unexpected Model of Efficiency.” Natural Resources Defense Council. October 26, 2012.

buildings over 500,000 square feet: EIA, Commercial Buildings.

commercial buildings…[rate] upgraded: Olgyay, Victor, and Cherlyn Seruto. “Whole-Building Retrofits: A Gateway to Climate Stabilization.” ASHRAE Transactions 116, no. 2 (2010).

[returns on] retrofitting [U.S.] buildings: Fulton, Mark, ed. United States Building Energy Efficiency Retrofits: Market Sizing and Financing Models. New York: The Rockefeller Foundation and Deutsche Bank Climate Change Advisors, 2012.

1.6 trillion square feet of building stock: Navigant Research. Global Building Stock Database. Boulder: Navigant Research, 2015.

Rocky Mountain Institute…strategy in Chicago: Campbell and Calhoun, “Old Buildings.”

view all book references

Technical Summary


Project Drawdown defines retrofitting as: the renovation of building components (including building envelope, appliances, and controls) to include high-efficiency solutions. This replaces the conventional practice of retrofitting buildings with conventional solutions. 

Building retrofits can be undertaken in a myriad of ways, initiated by either the building owner or manager, the tenant, or an external party, and with a suite of different financing models. The most suitable measures can also vary considerably depending on the climate and the building location, shape, and form. Most building retrofits focus on either passive design measures such as improving the building envelope (e.g. installing better insulation and double-pane window glazing), or active design measures to improve the efficiency of lighting, HVAC (heating, ventilation, and air conditioning), water heating, and plug loads.


Retrofitting encompasses several solutions in the Buildings and Cities Sector that have been modeled individually by Project Drawdown. Building retrofits can involve installing better insulation, energy-efficient glazing, more efficient lighting, improved HVAC, and efficient water heating. Since these solutions were modeled separately, retrofitting was not modeled in order to avoid double-counting. Modeling retrofitting was also impractical, since building retrofits vary greatly depending on the size of the building, its location, the climate where the building is located, and other factors.


The emissions and financial impacts of retrofitting are included in individual solutions in order to avoid double counting. For more information, see the Sector Summary: Buildings and Cities link below.


While many initiatives focus on new buildings, in most countries the majority of the buildings that will make up the urban environment by the year 2030 already exist. Improving building energy efficiency is one of the most cost-effective and fastest ways to reduce electricity demand and associated fuel imports, while indirectly slashing carbon emissions as well as improving local air quality and public health. Energy-efficient buildings are also believed to be healthier buildings, resulting in lower health-related absenteeism or productivity drops. Retrofitting buildings is increasingly used for public relations and brand management, contributing to a company’s ‘social license to operate’, while the green credentials can often also be used to satisfy reporting, procurement, or investment requirements. A retrofitted building is therefore less likely to lose value and be subject to functional obsolescence. For all these reasons, retrofitting for the world’s existing commercial, industrial and residential buildings is compelling.

Often, building the case for retrofitting also means proving the value of investing in energy savings beyond the simple ‘energy cost savings’ story. To do so, it is helpful to tap into what really motivates key decision-makers and show them how energy efficiency can contribute to those goals. The rise of better financing and contracting models that mitigate or eliminate the risk and burden of high upfront cost and somewhat uncertain operational cost savings, as well as schemes that provide incentives to utilities to help their customers save rather than consume more energy, are also increasingly important drivers for greater uptake of building energy-efficiency retrofitting. In addition, a number of global trends are likely to drive interest in retrofitting. For example, new building risks have emerged, such as increased volatility of fuel prices for electricity generation and energy insecurity from dependencies on scarce fossil resources and the locations from which these are sourced.

Full models and technical reports coming in late 2017.

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