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Tue 23 Feb 2010
Measures of Sustainability
Overview / Embodied Energy / Operating Energy / Exergy / Durability / Externalities / Ecological Footprint / Eco-Labeling / Life Cycle Assessment
Embodied energy in building materials has been studied for the past several decades by researchers interested in the relationship between building materials, construction processes, and their environmental impacts.
What is embodied energy?
There are two forms of embodied energy in buildings:
· Initial embodied energy; and
· Recurring embodied energy
The initial embodied energy in buildings represents the non-renewable energy consumed in the acquisition of raw materials, their processing, manufacturing, transportation to site, and construction. This initial embodied energy has two components:
Direct energy the energy used to transport building products to the site, and then to construct the building; and
Indirect energy the energy used to acquire, process, and manufacture the building materials, including any transportation related to these activities.
The recurring embodied energy in buildings represents the non-renewable energy consumed to maintain, repair, restore, refurbish or replace materials, components or systems during the life of the building.
As buildings become more energy-efficient, the ratio of embodied energy to lifetime consumption increases. Clearly, for buildings claiming to be “zero-energy” or “autonomous”, the energy used in construction and final disposal takes on a new significance.
How is it measured?
Typically, embodied energy is measured as a quantity of non-renewable energy per unit of building material, component or system. For example, it may be expressed as megaJoules (MJ) or gigaJoules (GJ) per unit of weight (kg or tonne) or area (square metre). The process of calculating embodied energy is complex and involves numerous sources of data. Refer to the Related Resources + References page for further information on embodied energy.
Implicit in the measure of embodied energy are the associated environmental implications of resource depletion, greenhouse gases, environmental degradation and reduction of biodiversity. As a rule of thumb, embodied energy is a reasonable indicator of the overall environmental impact of building materials, assemblies or systems. However, it must be carefully weighed against performance and durability since these may have a mitigating or compensatory effect on the initial environmental impacts associated with embodied energy.
How much embodied energy is typically found in buildings?
The amount of embodied energy in buildings varies considerably. Initial embodied energy consumption depends on the nature of the building, the materials used and the source of these materials (this is why data for a building material in one country may differ significantly from the same material manufactured in another country). The recurring embodied energy is related to the durability of the building materials, components and systems installed in the building, how well these are maintained, and the life of the building (the longer the building survives, the greater the expected recurring energy consumption).
Research carried out by Cole and Kernan(1) using a model based on Canadian construction of a generic 4 620 m2 (50,000 ft2) three-storey office building with underground parking, considered three different construction systems (wood, steel and concrete), and yielded the following results for average total initial embodied energy. (Note: Data were averaged for the three construction systems as the overall differences between the building types were not significant.
Breakdown of Initial Embodied Energy by Typical Office Building Components Averaged Over Wood, Steel and Concrete Structures [Cole and Kernan, 1996].
The building envelope, structure and services contribute fairly equally and account for about three-quarters of total initial embodied energy. The finishes, which represent only 13% of the embodied energy initially, typically account for the highest increase in recurring embodied energy. Embodied energy may not be significantly different between building systems (e.g., wood versus steel versus concrete), however, the environmental impacts associated with one material versus another can be dramatically different.(2)
It is interesting to consider the relationship between site work (6% of initial embodied energy) and services (24%). The reallocation of embodied energy, and hence project budget, from conventional services to the site management of stormwater, for example, may have a negligible effect on initial embodied energy, but the impact on recurring embodied energy may prove significant. Additional benefits downstream of the building at the community infrastructure level should also be considered. This points to one of the shortcomings of embodied energy analysis, which typically ends at the property line and is somewhat unwieldy in dealing with a broader context.
When recurring embodied energy in buildings is considered, yet more interesting relationships are revealed from the work of Cole and Kernan. First, to the credit of civil engineers, the structures of buildings normally do not expend recurring embodied energy, lasting the life of the building. By year 25, however, a typical office building will see an increase of almost 57% of its initial embodied energy due mostly to envelope, finishes and services. By year 50, recurring embodied energy will represent about 144% of the initial embodied energy, and it was projected that by year 100, this proportion would rise to almost 325%. This relationship is a direct result of what is referred to as differential durability, where the service lives of the various materials, components, and systems comprising the building differ dramatically. The current preoccupation with lower first costs in buildings reveals its disregard for sustainability when viewed from a building life cycle perspective.
Comparison of Initial to Recurring Embodied Energy for Wood Structure Building Over a 100-Year Lifespan [Cole and Kernan, 1996].
Is embodied energy a useful measure?
Embodied energy can be a very useful measure provided it is not viewed in absolute terms. The initial embodied energy of various materials, components and systems can vary between projects, depending on suppliers, construction methods, site location and the seasonality of the work (e.g., winter heating). The recurring embodied energy is difficult to estimate over the long term since the non-renewable energy contents of replacement materials, components or systems are difficult to predict. For example, how energy intensive will glass be 100 years from now? However, as buildings become more energy efficient and the amount of operating energy decreases, embodied energy becomes a more important consideration. There also exist strong correlations between embodied energy and environmental impacts. But it is widely acknowledged today that embodied energy represents one of many measures and should not be used as the sole basis of material, component or system selection.
1.Cole, R.J. and Kernan, P.C. (1996), Life-Cycle Energy Use in Office Buildings, Building and Environment, Vol. 31, No. 4, pp. 307-317.
2.Comparing the Environmental Effects of Building Systems, Wood the Renewable Resource Case Study No.4, Canadian Wood Council, Ottawa, 1997.
The next section deals with Operating Energy as a measure of sustainability.
Thu 24 Dec 2009
Whatcom county energy challenge executive summary.
This Index page has to do with the Architecture 2030 program.
By Nick Hartrich, Green Building and Smart Growth program manager for Sustainable Connections
The City of Bellingham – a community praised for its successes as a leader in sustainability was recently recognized as the No. 1 Smartest Small City in the Nation by the National Resources Defense Council for our achievements in green space, transportation, energy conservation, air quality and green building.
Meanwhile, the last two years of the Sustainable Connections’ Green Building & Smart Growth program has seen close to 3,000 participants attending a workshop, tour or conference dedicated to green building and innovative land use solutions. While these figures demonstrate a strong public interest and a growing national recognition as a leader in sustainability, there is a local perception that a lack of predictability in code interpretation is hindering the absorption of green building practices into the market.
These local effects mirror regional and national trends. Climate Solutions and Clean Edge Inc. recently identified green building design services as the one of the areas with the greatest potential for green job growth in the Pacific Northwest. However, they also identified outdated building codes and the absence of “a streamlined process for green building permitting and approval” as significant hindrances to the realization of the economic potential of this sector. In addition, McGraw-Hill and the National Association of Home Builders project that the market value of green building construction will increase to $60 billion by 2010. This is a significant increase in the market share and the No. 1 factor that they anticipate will contribute to this success is an unprecedented level of government initiatives.
A solution: FIVE/12
Sustainable Connections and the city of Bellingham have responded to the building community’s challenge and worked in partnership to develop the FIVE/12 Agenda, a program to reduce green building barriers by creating at least five tangible green building incentive success stories over 12 months in 2009.
As part of this process, the FIVE/12 Agenda documented Bellingham building professionals’ interest in green building incentives. Example incentives for green building include areas surrounding reduced permit time, tax/fee incentives, technical assistance, low impact development incentives, density bonuses, etc. The Agenda also evaluated current barriers to green building based on these individuals’ experiences with the City of Bellingham.
Several themes related to green building challenges consistently surfaced from the building community. They include the following observations:
- Green building’s integration into the market has been delayed by a lack of consistency in code interpretation.
- Incentive creation should take into account the possibility of “greenwashing” – the existence of projects which appear to be sustainable but are not.
- Future incentives and related legislation should be heavily publicized in order to increase their use.
The City’s efforts
City of Bellingham staff worked diligently to answer the call of the building community and integrated components of the FIVE/12 Agenda into their 2009 strategic plan. The five concepts the City will employ by end of 2009 include:
Developing a green permit review team
An interdepartmental team has been established to review BuiltGreen, LEED, and comparable “green” building designs and applications. A designated lead for the team serves as project manager for green building projects which will result in a more coordinated and efficient review.
Create a system for reducing permit review time
The dedicated green permit review team will review green building projects in an integrated, rather than linear process which yields greater efficiency and improved outcomes.
Identify, analyze, and make available to the public alternative methods for green construction
Alternative methods and materials for green construction will be developed into policy with the intent to streamline the allowance of these alternatives by avoiding repetitive interpretations, thereby providing greater predictability to the public. (Most recently, clear code interpretation guidelines were published for waterless urinals and solar photovoltaic installations).
Incorporate LEED for Neighborhood Development prerequisites and other sustainable frameworks into urban villages
Urban Villages comply with the essential components of LEED-ND, and a proposal is being made in the City’s comprehensive plan update to use LEED-ND as a tool to measure the long-term sustainability of proposed Urban Village master plans.
Analyze effectiveness of “Green Factor” program
The Green Factor is a scorecard for low impact development techniques and landscaping requirements that result in an increase in the quality and quantity of landscaping provided with new development.
As 2009 comes to a close, Sustainable Connections will be dedicated to supporting the City of Bellingham staff in implementing integration into their strategic plan and reporting success stories. The City’s recent hire of two new employees (Jim Tinner, City Building Official and Ted Carlson, Director of Public Works) have already shown strong interest and support for ideas brought about by the FIVE/12 Agenda. Both the City and Sustainable Connections will continue to develop strategies to build on these successes that drive momentum in a community that is supportive and responsive to green building. Keep an eye out for future accomplishments and achievements. The only question left is which ten incentives will there be for 2010?
Fri 18 Dec 2009
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