Patterns of Use
Although climate-specific, resource-efficient house design strategies exist, per capita material use and energy consumption in the residential sector continue to increase. From 2000 to 2010, the U.S. population increased by 9.7%, while the number of housing units increased by 13.6% and urban land area increased by 15%.1 The following trends demonstrate usage patterns in the residential building sector.
Size and Occupancy
- Increased average area of a new U.S. single-family house:2,3,4
1950 983 ft2; 1970 1,500 ft2; 2000 2,265 ft2
2017 2,599 ft2, a 164% increase from 1950.
- Decreased average number of occupants per U.S. household:2,5
1950 3.37; 1970 3.14; 2015 2.62
2017 2.54, a 25% decrease from 1950.
- Increased average area per person in a new U.S. single-family house:2,3,5
1950 292 ft2; 1970 478 ft2; 2000 840 ft2
2017 1,023 ft2, a 250% increase from 1950.
- A majority of Americans live in single-family houses. In 2013, 64% of the 116 million U.S. households were single family.6
- In 1950, 9% of housing units were occupied by only one person.7 By 2017, this value had increased to 28%.5
Average Size of a New U.S. Single-Family House3,4
U.S. Single-Person Households5,7
- A 1998 study by the Center for Sustainable Systems of a single-family house in Michigan showed an annual energy consumption of 1.3 GJ/m2.9
- A study of 3 houses in Sweden built in the 1990s estimated annual energy consumption from 0.49–0.56 GJ/m2, less than half the energy consumed by the Michigan house.10
- Electricity consumption increased 13-fold from 1950 to 2017. In 2017, the residential sector used 1.38 trillion kWh of electricity, 37% of U.S. total electricity sales.11
- In 2017, the U.S. residential sector consumed 20 quadrillion Btu of primary energy, 20% of U.S. primary energy consumption.12
- Miscellaneous load per household doubled from 1976 to 2006.13 In 2017, miscellaneous loads consumed more electricity than any other residential end use (lighting, HVAC, water heating, and refrigeration), accounting for 39.7% of primary energy and 52.3% of a household’s electricity consumption.8,11
- Wasteful energy uses include heating and cooling of unoccupied homes and rooms, inefficient appliances, thermostat oversetting, and standby power loss. Together, these uses represent about 39% of residential primary energy use.14
- Home energy management systems display energy use via in-home monitor or mobile application and enable remote control of devices. Home energy management systems can reduce a house’s energy use by an estimated 4-7%.15
Average U.S. Residential Energy Consumption BY END USE, 20178
- The average U.S. single-family house built in 2000 required 19 tons of concrete, 13,837 board-feet of lumber, and 3,061 ft2 of insulation.16
- From 1975 to 2000, the consumption of clay for housing and construction more than tripled, due to its use in tiles and bathroom fixtures.17
- In 2012, around 24% of all wood products consumed in the U.S. were used for residential construction.18
- Approximately 10 million tons of waste was generated in the construction of new residential buildings in 2003—4.4 lbs per ft2.19
- U.S. average recycling rate of waste from construction and demolition (C&D) is 20-30%.20 Seattle recycled 57% of its C&D waste in 2015.21
Codes and Standards
- DOE Pacific Northwest National Laboratory estimated cumulative savings from the International Energy Conservation Code (IECC) for 42 states. From 2010-2016, the IECC saved 0.27 quadrillion Btu of primary energy, 1.4% of residential primary energy consumption in 2016.12 Cumulative energy savings generated $3.2 billion (2016 dollars) in cost savings and avoided 17.6 million metric tons of CO2.22
- For most building types, conventional energy efficiency technologies can achieve a 20% reduction in energy use relative to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) 90.1-2004 standard.23
- Florida’s 2007 energy code saved 13% relative to pre-2007 energy consumption through the reduction in heating, cooling and hot water demand. Efficiency gains were offset by increasing house sizes and plug loads.24
- The U.S. Green Buildings Council provides Leadership in Energy and Environmental Design (LEED) home rating system and certification.27
- Houses built to Energy Star program requirements are 15% more energy efficient than houses built to 2009 IECC or better.28
Residential Building Energy Code Status by State25,26
Life Cycle Impacts
- Between 1990 and 2005, total residential GHG emissions increased by 30%. In 2016, GHG emissions were reduced to 999.6 million metric tons, only 5% up from 1990 level.29
- In 1998, the Center for Sustainable Systems conducted an inventory of the life cycle energy consumption of a 2,450 square foot, single-family house built in Ann Arbor, Michigan.9
- Only 10% of the house’s life cycle energy consumption was attributed to construction and maintenance; 90% occurred during operation.9
- Energy efficiency measures reduced life-cycle energy consumption by 63%. Careful selection of materials reduced embodied energy by 4%.9
- Life cycle greenhouse gas emissions were reduced from 1,013 to 374 metric tons CO2-equivalent over the 50-year life of the house.9
- Top contributors to primary energy consumption were polyamide for carpet, concrete in foundation, asphalt roofing shingles, and PVC for siding, window frames, and pipes.9 Improved HVAC system and cellulose insulation were the most effective strategies to reduce energy costs.9
- Substituting recycled plastic/wood fiber shingles for asphalt shingle roofing reduced embodied energy by 98% over 50 years.9
- A 900-ft2 house in Davis, CA, modeled innovative design and technologies to reduce energy consumption. Measures such as LED lighting, efficient appliances, graywater heat recovery and a radiant heating and cooling system brought annual energy consumption to 5,854 kWh, 44% less than a standard house of the same size and location. Electricity generation from rooftop PV made the house energy net-positive.30
- Operating energy accounts for 80-90% of a building’s life cycle energy consumption and embodied energy accounts for 10-20%. As houses improve energy efficiency and reduce operating phase energy, embodied energy accounts for a larger fraction of life cycle energy. Design and materials selection are key ways to reduce embodied energy.31
Solutions and Sustainable Alternatives
Reduce Operational Demand
Energy and water consumption during the life of a building contribute more to its environmental impact than do building materials. The following suggestions can significantly reduce operational energy demand:
- Downsizing: build smaller to reduce embodied and operating energy.2 Tiny houses are designed for the efficient use of space.32
- Space heating and cooling make up 35% of residential energy consumption.8 Passive heating and cooling can reduce operating energy.9
- By adding ceiling fans, air conditioning can be comfortably set about 4oF higher.33
- Adequate insulation can reduce heating and cooling costs. R-value needs differ based on location, building design, and heating methods.34
- Water heating accounts for 14% of residential energy consumption.8 Save energy with a graywater heat recovery system.35
- Install low-flow water fixtures (less than 2.5 gallons-per-minute of flow) to save both water and energy.36
- Maximize natural lighting with south-facing windows. Properly shade windows to minimize summer heat gain.37
- Purchase energy efficient appliances and lighting. Appliances and lighting typically account for 25% of household energy costs.38
- Replace incandescent lamps and halogen lamps with compact fluorescent lamps or LEDs in order to reduce energy costs and GHG emissions.39
Select Durable and Renewable Materials
Durable building materials last longer and require fewer replacements than flimsier alternatives. Depending on the materials, building with more durables could lower longterm replacement costs and associated environmental burdens.
- Durables: cork or hardwood floors, standing-seam roofing.
- Renewables: cork, linoleum, wool carpet, certified wood and plywood, strawboard, cellulose insulation, straw-bale.
- U.S. Census Bureau (2012) United States Summary: 2010 Population and Housing United Counties. 2010 Census of Population and Housing.
- Wilson, A. and J. Boehland (2005) “Small is beautiful, U.S. house size, resource use, and the environment.” Journal of Industrial Ecology, 9(1-2): 277-287.
- National Association of Home Builders (2007) “Housing Facts, Figures and Trends and Single-Family Square Footage By Location.”
- U.S. Census Bureau (2018) 2018 Quarterly Starts and Completions by Purpose and Design.
- U.S. Census Bureau (2018) America’s Families and Living Arrangements: 2017.
- U.S. Census Bureau (2015) “American Housing Survey 2013.”
- U.S. Census Bureau (2004) “Historical Census of Housing Tables: Living Alone.”
- Energy Information Administration (EIA) (2018) Annual Energy Outlook 2018.
- Blanchard, S. and P. Reppe (1998) Life Cycle Analysis of a Residential Home in Michigan. CSS98-05.
- Adalberth, K. (1997) “Energy use during the life cycle of single-unit dwellings: examples.” Building and Environment, 32(4): 321-329.
- U.S. Department of Energy (DOE), EIA (2018) Use of electricity.
- U.S. DOE, EIA (2018) Monthly Energy Review April 2018.
- Roth, K., et al. (2008) “Small devices, big loads.” ASHRAE Journal, 50(6): 64-65.
- Meyers, R., et al. (2009) “Scoping the potential of monitoring and control technologies to reduce energy use in homes.” Energy and Buildings, 42(2010): 563-569.
- Thayer, D., et al. (2015) Characterization and Potential of Home Energy Management (HEM) Technology. Pacific Gas and Electric Company.
- U.S. Environmental Protection Agency (EPA) (2013) Analysis of the Life Cycle Impacts and Potential for Avoided Impacts Associated with Single-Family Homes.
- World Resources Institute (2008) Material Flows in the United States: A Physical Accounting of the U.S. Industrial Economy.
- APA-The Engineered Wood Association (2015) Wood Products and Other Building Materials Used in New Residential Construction in the United States.
- U.S. EPA (2009) Estimating 2003 Building-Related Construction and Demolition Materials Amounts.
- U.S. EPA (1998) Characterization of Building-Related Construction and Demolition Debris in the United States.
- Seattle Public Utilities (2016) 2015 recycling rate report.
- U.S. DOE, Pacific Northwest National Laboratory (PNNL) (2016) Impacts of model building energy codes.
- Kneifel, J. (2011) “Beyond the code: Energy, carbon, and cost savings using conventional Technologies.” Energy and Buildings, 43(2011): 951-959.
- Withers, C., and R. Vieira (2015) Why Doesn’t 25 Years of an Evolving Energy Code Make More of a Difference? Behavior, Energy, and Climate Change Conference.
- International Code Council (2017) International Code Adoptions.
- Building Codes Assistance Project (2017) Residential Code Status.
- U.S. Green Buildings Council (2017) “LEED v.4 Homes Design and Construction Guide.”
- Energy Star (2016) “Sponsoring an ENERGY STAR Residential Program.”
- U.S. EPA (2018) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2016.
- Payman, A., and F. Loge (2016) “Energy efficiency measures in affordable zero net energy housing: a case study of the UC Davis 2015 solar decathlon home.” Renewable Energy 101(2017): 1242-1255.
- Ramesh, T., et al. (2010) “Life cycle energy analysis of buildings: An overview.” Energy and Buildings, 42(2010): 1592-1600.
- Mitchell, R. (2014) “Tiny house living.”
- U.S. DOE, Energy Efficiency and Renewable Energy (EERE) (2001) Cooling Your Home with Fans and Ventilation.
- Federal Trade Commission (2009) “Home Insulation: It’s All About the R-Value.”
- U.S. DOE (2012) “Drain Water Heat Recovery.”
- U.S. DOE (2012) “Reduce Hot Water Use for Energy Savings.”
- U.S. DOE (2012) “Daylighting.”
- Energy Star (2013) “Where Does My Money Go?”
- Liu, L., et al. (2017) Replacement policy of residential lighting optimized for cost, energy, and greenhouse gas emissions. Environmental Research Letters. 12(11): 1-10.