Buildings and Cities
Heat always moves from warmer areas to cooler areas, until a temperature equilibrium is reached. This heat flow presents a central challenge when keeping buildings within a desirable range of 67 to 78 degrees Fahrenheit. To close the gap on unwanted heat gain or loss and maintain comfortable room temperature, we use more energy. Air infiltration accounts for 25 to 60 percent of energy used to heat and cool a home—energy that is simply wasted.
By better insulating a building envelope, heat exchange can be reduced, energy saved, and emissions avoided. What makes insulation effective is its capacity for thermal resistance, measured as R-value—the higher the better. Ideally, a building’s thermal layer should cover all sides—bottom floor, exterior walls, and roof—and be continuous. Sealing gaps and cracks is also critical to a more effective building envelope.
Insulation is one of the most practical and cost-effective ways to make buildings more energy efficient—both in new construction and through retrofitting older buildings that often are not well encased. At relatively low cost, insulation results in lower utility bills, while keeping out moisture and improving air quality.
air infiltration…energy…wasted: St. John, Kathryn. “Building Green with Energy-Efficient Materials: Insulation.” U.S. Green Building Council. September 7, 2016.
range of insulating materials: Schiavoni, S., F. Bianchi, and F. Asdrubali. “Insulation Materials for the Building Sector: A Review and Comparative Analysis.” Renewable and Sustainable Energy Reviews 62 (2016): 988-1011.
waste feathers from poultry operations: Hickey, Shane. “The Innovators: Greener Home Insulation to Feather Your Nest.” The Guardian. April 10, 2016.
Passivhaus…saving energy: Trubiano, Franca. “Energy-Free Architectural Design: The Case of Passivhaus and Double-Skin Facades.” In Design and Construction of High Performance Homes, 37-54. New York: Routledge, 2013; James, Mary, and James Bill. Passive House in Different Climates: The Path to Net Zero. New York: Routledge, 2016.
Project Drawdown defines insulation as: the use of improved materials in building envelopes that resist heat flow and regulate indoor temperatures. This solution replaces the conventional practice of using older insulation materials that provide less thermal resistance.
Insulating the wall and roof surface area of buildings is one of the most accessible and effective ways to reduce heating and cooling energy use—and, therefore, greenhouse gas emissions—in the built environment. Increasing insulation of older buildings through retrofit and increasing the average R-value of new building stock costs more than current normal practices, but has a significant return on investment from lower operating costs due to reductions in heating and cooling costs.
To determine the emissions reduction potential of global adoption of building insulation in climate appropriate regions, the global stock of buildings was first analyzed to determine a total addressable market of building surface area appropriate for insulation. The energy savings were then calculated from a Reference Scenario of increased insulation adoption, based on 2015 retrofit rates of 1.4 percent. Last, those savings were compared to further reductions from scenarios of increased retrofit rates, the difference in energy savings was converted into carbon dioxide-equivalent emissions, the costs of increased retrofitting were calculated, then all resulting values were added to develop the global results.
Total Addressable Market 
A bottom-up approach was used to develop the total addressable market for insulation, by analyzing global building stock in 10-degree latitude slices and by estimating the average size of the buildings and their total surface area based on population, household size, building size, commercial building size, number of floors, and other assumptions calibrated by a literature review. Calculations for heat flow were developed that are sensitive to the average temperature gradient in the environment over time and position. The actual temperatures of the Earth over 12 months were modeled, taking latitude and daily and seasonal variations into account. All of these calculations were achieved as a function of latitude using published regression models. This allowed for temperature gradients for heating and cooling to be estimated using assumed comfortable indoor temperatures (high and low). While the temperatures are not necessarily accurate at any given location, they are accurate for the world as a whole; this helps to ensure that the model and its calibrated parameters can be understood. Heating and cooling energy use was determined per square meter of building surface area, and a retrofit rate was applied.
Current adoption  of insulation corresponds to a fixed retrofit rate of 1.4 percent.
Adoption Scenarios 
Impacts of increased adoption of insulation from 2020-2050 were generated based on three growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.
- Plausible Scenario: For this scenario, a retrofit rate of 2.1 percent was applied with a medium level of insulation, resulting in global increased insulation levels 31 percent greater than the Reference Scenario.
- Drawdown Scenario: This scenario assumes increased policy adoption of the Passive House Standard for insulation and a 3.55 percent retrofit rate, resulting in global increased insulation levels 75 percent greater than the Reference Scenario.
- Optimum Scenario: This scenario assumes a radical rate of adoption of the Passive House Standard with a 5 percent retrofit rate, resulting in global increased insulation levels 86 percent greater than the Reference Scenario.
Emissions assumptions were based on a combination of emissions factors related to heating fuel and grid electricity factors for cooling energy.
Financial variables were collected and assessed for the costs of a variety of materials, including cellulose sprays, windows and doors with seals for particular climates, silica aerogels, rigid floor panels, vacuum-insulated panels, mechanical ventilation heat recovery, and ventilation controls. An archetypal schedule of materials was assumed for each scenario. For example, the materials selected for the Reference Scenario would have a first cost of US$72.31 per square meter of insulation, and the Plausible Scenario would be US$76.59.  Operational savings were derived by multiplying the reduced heating and cooling use by the average costs for the type of heating or cooling that would have been delivered.
For integrating Drawdown solutions in the Building and Cities Sector, insulation was the first solution to be considered because of the low cost, likely adoption, and significant mitigation impact of bolstering the building envelope. All other building envelope and building solutions impacting heating and cooling use are impacted by insulation at the point of integration.
The Plausible Scenario results show a mitigation impact of 8.27 gigatons of carbon dioxide-equivalent emissions over the period 2020-2050. The increased adoption of the Passive House Standard in the Drawdown Scenario results in a mitigation impact of 14.6 gigatons of emissions, and the Optimum Scenario mitigates 16.90 gigatons.
There is little peer-reviewed literature assessing the potential global increased adoption of insulation, so the results developed require a significant number of assumptions and reasoned extrapolations of the data that does exist. Temperature variation and human comfort levels in buildings can significantly affect the adoption of insulation. Because of rising outside temperatures, Anthropogenic Global Warming is expected to decrease average energy used for heating buildings worldwide, but is also expected to drive more electricity use for cooling. These effects were not considered for the model prognostications.
 For more on the Total Addressable Market for the Buildings and Cities Sector, click the Sector Summary: Buildings and Cities link below.
 Current adoption is defined as the amount of functional demand supplied by the solution in the base year of study. This study uses 2014 as the base year due to the availability of global adoption data for all Project Drawdown solutions evaluated.
 To learn more about Project Drawdown’s three growth scenarios, click the Scenarios link below. For information on Buildings and Cities Sector-specific scenarios, click the Sector Summary: Buildings and Cities link.
 All monetary values are presented in US2014$.
 For more on Project Drawdown’s Buildings and Cities Sector integration model, click the Sector Summary: Buildings and Cities link below.