Embodied Energy

1.0 Introduction


Embodied energy is an abstract way to measure the environmental impact of a product, material, system,
or service. Embodied energy does not have one set definition because it's definition depends upon the extent of its parameters.[1] In Construction, it is thought of as the total energy that goes into the construction of the building. It generally includes extraction, processing, manufacturing, delivery, and disposal, of the materials used. Some parameters may only include the energy used in a few of the above steps.

Embodied energy does not assess the entire energy associated with the life of a building because it does not include the energy that goes into operation.[2] The energy that goes into operation is known as operational energy. Together embodied energy and operational energy are know as life cycle assessment (LCA).

The point of the life cycle assessment process is to learn about the environmental costs associated with a building project.[3] Embodied energy is a very important consideration for engineers because is can account for 20 to 100 percent of the total energy use for a building. In a world that is trying to create a completely sustainable building, embodied energy is very significant. The figure below shows energy use for a building with a one hundred year life.
 Figure 1: Embodied energy over the life of a product
Figure 1: Embodied energy over the life of a product











2.0 History


Embodied energy finds its roots in environmental study; in the life cycle assessment process. In 1969, Coca-Cola
Figure 2: Life Cycle Assessment
Figure 2: Life Cycle Assessment
was the first large company to look at the environmental impacts of their products. Coca-Cola's research dealt with bottle materials and their impacts. In the decades following the study, Coca-Cola and several other companies began developing programs to remove harmful products or to recycle harmful products. At that time, companies only considered pieces of a product's life. As a result, environmental improvement didn't really happen. Improvement in one area led to greater issues in other areas.[4]

In the 1980s, the life cycle assessment method was introduced as a more holistic way to look at the environmental impacts of products. However, the term was not coined until 1990. It was at that time that the International Organization for standardization(ISO) began to push for standardization of the method. This was achieved in 1997. Standardization meant that a set of guidelines was created to guide engineers through the assessment process. In 2002, the method began to spread globally. Today, the method is very effective. It has expanded out of the product and system development industry into the construction industry.[5]

At first, engineers believed that the embodied energy was relatively insignificant compared to the operational energy. Significant research was done and advances were made in lowering operational energy costs. However, engineers have since learned that embodied energy can be very significant. For example, in residential construction, the embodied energy of a home can be comparable to 15 years of operational energy. As a result of the studies, embodied energy has become a highly researched sustainability topic today. [6]

3.0 Measuring Embodied Energy


Operational energy can be easily measured. It includes energy used for appliances, lighting, heating and cooling, and so on. Monetary costs can be directly associated with energy usage. It is not so with embodied energy. Embodied energy is hard to measure. As was mentioned above, it depends upon strict parameters. To account for this fact, several variations for analysis exist. Each variation defines parameters differently. It is important to recognize that clearly defined definitions and parameters are the keys to successful measurement of embodied energy. It is also important to recognize that different methods cannot be compared because parameters are not the same.[7]

3.1 Cradle to Grave

The cradle to grave approach evaluates energy used during the entire life of the building. It includes energy used in extraction, processing, manufacturing, transportation, construction, maintenance, and disposal. The cradle to grave approach is the most accurate and comprehensive method for determining embodied energy. It is also the most complex and time consuming method.[8] The figure below shows a cradle to grave cycle for wood along with the chosen boundaries.
Figure 3: Cradle to grave example for wood products
Figure 3: Cradle to grave example for wood products

3.2 Cradle to Cradle

The cradle to cradle approach is exactly the same as the cradle to grave approach with the exception of one difference. The cradle to cradle approach incorporates the recycling of disposed materials. It makes sense then that the cradle to cradle approach would have a lower embodied energy provided that the same materials are used. This method is ideal if recyclable materials can be used without additional energy costs for production.[9]

3.3 Cradle to Site

The cradle to site approach evaluates energy used during extraction, processing, manufacturing, and transportation. It essentially accounts for the energy required to deliver building materials to the work site. This approach would be used as a quick estimate for project mangers and engineers. It does not include energy for construction, maintenance or disposal. Even though these three steps are not included, this method is still very helpful because most embodied energy costs take place during the extraction, processing and manufacturing.[10]

3.4 Cradle to Gate

The cradle to gate approach evaluates energy used for extraction, processing, and manufacturing. It is thought of as the energy to get the building materials to the factory gate. This method is best used by manufactures as they seek to streamline production methods and reduce energy costs. It is also the most simplistic of the methods. It ignores transportation, construction, maintenance, and disposal.[11] The diagram below shows and example of cradle to gate for a product.
Figure 4: Production of Accoya-Cradle to Gate
Figure 4: Production of Accoya-Cradle to Gate

3.5 Further Considerations

Even when the major variations above are used correctly, a wide scope of the analysis can still cause calculations to be difficult. Refer to the diagram above for an example. Petrol is used for forestry operations. It is used to harvest wood. A person doing the embodied energy calculations for this product would possible consider: the energy used to drive employees the work, the energy used to feed the employees, the energy used to produce the tools used in the forestry operations, and the energy used to build the factory that produced the tools used for the forestry operations. As is apparent, it would be very difficult to incorporate any of these considerations into the embodied energy assessment. To define boundaries for assessment engineers either use the Gross Energy Requirement(GER) method or the Process Energy Requirement(PER) method.[12]

3.5.1 Gross Energy Requirement

This method is an attempt to thoroughly determine the embodied energy for the building. It sets very loose boundaries. It takes into account all of the considerations above and many more. The process is done by gathering many data points and imputing them into one of many computer softwares that will run the analysis. In practice, this method is very difficult and impractical.[13]

3.5.2 Process Energy Requirement

This method is a simplified attempt to determine embodied energy. Its sets tight boundaries and makes several assumptions. The numerical value is within 50 to 80 percent of the gross energy requirement. Even with the narrower boundaries, the process is still very difficult.[14]

3.6 Calculations and Material Choice

Once boundaries are established, the actually calculations for embodied energy of materials can be completed. Calculations can be completed by computer software or hand drawn with numerous modeling equations. The numerical value for a given material can differ by a factor of 10 depending on boundaries. That being said, it is useless to compare materials which were evaluated with different boundaries. The only way to look at embodied energy and make sustainability choices is by measuring all materials with the same boundaries. Below is a chart that has a set of values for one specific calculation.[15] The units in the figure are non-renewable energy/unit weight.[16]

Figure 5: A graph showing the different amounts of embodied energy for different materials.
Figure 5: A graph showing the different amounts of embodied energy for different materials.

4.0 Relevance in Construction

Embodied energy is very applicable to the construction industry. In today's society there is a huge push for sustainability. According to the Environmental Resource Guide, 30 percent of the energy consumed in the United States goes to construction and maintenance of building. As a result, engineers are constantly looking for cheaper ways to build sustainable homes. While this method is complex and often does not yield accurate results, it is commonly used during the design process. Even general conclusions can allow engineers to compare materials and make sustainable decisions. This method helps engineers to identify materials that meet structural, architectural, economical, and environmental, and social standards.[17]

5.0 Recent Research

Much of the research being conducted today revolves around the idea of standardization. While the life cycle assessment process has a general set of standards, the embodied energy parameters and calculations are still far from standardized. As was mentioned earlier, it is relatively impossible to arrive at accurate repeatable values.The method could become far more useful and efficient if this research is completed. A standard set of values could be established for various materials. This would allow engineers to very efficiently design green buildings. Below is a link detailing some work that is being done in this area.[18]

http://www.sciencedirect.com/science/article/pii/S0378778810000472

6.0 Case Study

The APS Environmental Showcase Home in Arizona is an example of a building that successfully incorporates embodied energy principles. The home was designed to display many sustainability techniques and technologies. The home is 2,600 square feet. It operates on 60 percent less energy and water. 90 percent of it materials are recyclable. All of its materials were chosen because they have most efficient embodied energy values. The environmental load is 23% percent below average for Arizona.[19] The links below provides more details.
.
http://www.smartcommunities.ncat.org/success/APS_showcase_homes.shtml

http://www.scotzimmermanphotography.com/images/APS-3.jpg

7.0 Links and Videos

For more information on Life Cycle Assessment:












  1. ^ Institute of Civil Engineers. (2014). "Embodied energy and Carbon." Ice Energy.
    <http://www.ice.org.uk/topics/energy/Briefing-Sheets/Embodied-Energy-and-Carbon>(Nov 29, 2014)
  2. ^ Branz Ltd. (2014). "Embodied Energy." Level.org.
    <http://www.level.org.nz/material-use/embodied-energy/>(Nov 29,2014)
  3. ^ Haynes, Richard. (2010). "Embodied Energy Calculations within Life Cycle Analysis for Residential Buildings." Etoolglobal.com
    <http://www.etoolglobal.com/wp-content/uploads/2012/10/Embodied-Energy-Paper-Richard-Haynes.pdf> (Nov 29, 2014)
  4. ^ PE-International. (2013). "A brief history of Life Cycle Assessment(LCA)." pe-international.com
    <http://www.pe-international.com/america/company/newsroom/news-detail/article/a-brief-history-of-life-cycle-assessment-lca/>(Nov 28 2014)
  5. ^ PE-International. (2013). "A brief history of Life Cycle Assessment(LCA)." pe-international.com
    <http://www.pe-international.com/america/company/newsroom/news-detail/article/a-brief-history-of-life-cycle-assessment-lca/>(Nov 28 2014)
  6. ^ Designing Buildings Ltd. (2014). "Embodied Energy in Construction." DesigningBuildings.co.uk
    <http://www.designingbuildings.co.uk/wiki/Embodied_energy_in_construction>(28 November 2014)
  7. ^ Haynes, Richard. (2010). "Embodied Energy Calculations within Life Cycle Analysis for Residential Buildings." Etoolglobal.com
    <http://www.etoolglobal.com/wp-content/uploads/2012/10/Embodied-Energy-Paper-Richard-Haynes.pdf> (Nov 29, 2014)
  8. ^ Institute of Civil Engineers. (2014). "Embodied energy and Carbon." Ice Energy.
    <http://www.ice.org.uk/topics/energy/Briefing-Sheets/Embodied-Energy-and-Carbon>(Nov 29, 2014)
  9. ^ Ecomii LLC. (2014). "Cradle to Cradle." ecomii.com
    <http://www.ecomii.com/ecopedia/cradle-to-cradle> (Nov 20 2014)
  10. ^ Institute of Civil Engineers. (2014). "Embodied energy and Carbon." Ice Energy.
    <http://www.ice.org.uk/topics/energy/Briefing-Sheets/Embodied-Energy-and-Carbon>(Nov 29, 2014)
  11. ^ Institute of Civil Engineers. (2014). "Embodied energy and Carbon." Ice Energy,
    <http://www.ice.org.uk/topics/energy/Briefing-Sheets/Embodied-Energy-and-Carbon>(Nov 29, 2014)
  12. ^ Milne, Goeff. (2013). "Embodied Energy." yourhome.gov,
    <http://www.yourhome.gov.au/materials/embodied-energy > (Nov 30, 2014)
  13. ^ Milne, Goeff. (2013). "Embodied Energy." yourhome.gov,
    <http://www.yourhome.gov.au/materials/embodied-energy > (Nov 30, 2014)
  14. ^ Milne, Goeff. (2013). "Embodied Energy." yourhome.gov,
    <http://www.yourhome.gov.au/materials/embodied-energy > (Nov 30, 2014)
  15. ^ Milne, Goeff. (2013). "Embodied Energy." yourhome.gov,
    <http://www.yourhome.gov.au/materials/embodied-energy > (Nov 30, 2014)
  16. ^ Branz Ltd, (2014). "Embodied Energy." Level.org.
    <http://www.level.org.nz/material-use/embodied-energy/>(Nov 29,2014)
  17. ^ Mumma, Tracy. (1995). "Reducing the Embodied energy of Buildings." homeenergy.org,
    <http://www.homeenergy.org/show/article/id/1105> (Nov 30, 2014)
  18. ^ Dixit, Manish Kumar. (2010). "Identification of Parameters for embodied energy measurement: a literature review." sciencedirect.com
    <http://www.sciencedirect.com/science/article/pii/S0378778810000472
  19. ^ Nowak, Mark. (1998). "APS Environmental Showcase Home." Smart Communities Network,
    <http://www.smartcommunities.ncat.org/success/APS_showcase_homes.shtml> (Nov 30 2014)