Embodied energy is the amount of energy associated with extracting, processing, manufacturing, transporting, and assembling building materials. In historic buildings, this includes the expense and effort sued to fire bricks, cut and tool stone, transport and assemble the wood framing, and prepare and apply interior plaster, to name just a few. Buildings represent an enormous expenditure of energy. To demolish an historic building and replace it with a new energy efficient building would require decades to recover the embodied energy lost in the processes of demolition and construction.
An old growth window (left) has a longer life expectancy than most new vinyl windows (right). Vinyl windows expand and contract more than twice as much as wood and seven times more than glass. This often results in failed seals between the frame and glass, a significant performance reduction, and contributes to their shorter life expectancy of 25 years or less.
Life cycle assessments are a tool to analyze the environmental impacts of buildings. Assessments examine and determine the impacts of material and energy usage at each stage of a building, including materials extraction, construction, use, and disposal. When completing an assessment, the cost of construction as well as the costs and energy required to operate the building during its life are examined. The quality of materials used is one of the key considerations in a life cycle assessment. The materials in historic buildings are often able to last indefinitely with proper care. Many historic buildings in San Dimas have old-growth wood in their windows, framing and siding, and may also feature brick or stone foundations and walls. Because of their high quality, these materials can easily last another century. Modern materials like vinyl and new-growth wood often require replacement after just 10 to 20 years.
Historic buildings are often as energy efficient as new ones. The United States Energy Information Agency found that buildings older than 1920 have better energy efficiency than those built at any time until the past decade, when builders began a concerted effort to develop buildings with greater energy efficiency. Common historic features like tall ceilings that help to reduce heat in summertime and brick and plaster walls that insulate well, contribute to efficiency. Upgrades like the addition of attic insulation, and more efficient heating and cooling systems, can boost efficiency even further. Repairing and weather stripping historic wood windows are a powerful way to attain energy performance equal to new vinyl or aluminum windows and at a lower cost.
Construction and demolition material waste stream includes concrete, asphalt, soils, gypsum, wood, metals, brick, cardboard, plastic and composite materials. In California, construction debris accounts for 11.6 percent of annual landfill waste. Demolishing a single 2,000 square foot home results in an average of 230,000 pounds of waste. Demolishing sound historic buildings wastes existing materials and building efforts, and strains the limited capacity of landfills. The 2010 California Green Building Code (CALGREEN) requires at least a 50% reduction in construction waste sent to landfills for both residential and non-residential construction.