Introduction and Overview of LEED
In the 21st century, sustainable development, or maintaining the ability to provide for current needs without compromising the ability to meet future needs, is a primary concern (United Nations). In order to achieve sustainable development, the performance of the built environment must be dramatically improved through more effective energy use without compromising indoor air quality. One prominent effort to promote a high performance built environment is the Leadership in Energy and Environmental Design (LEED) green building accreditation system developed by the United States Green Building Council, USGBC. LEED is a comprehensive system of standards that seeks to promote “buildings and communities [that] will regenerate and sustain the health and vitality of all life within a generation” by defining the characteristics of a sustainable built site (USBGC). Under LEED, a recognized sustainable built site is awarded one of four levels of LEED accreditation: Certified, Silver, Gold, or Platinum.
This study will evaluate the effectiveness of the LEED standard as a vehicle for indicating high performance residential sites at universities. One LEED Silver accredited site and 14 non-accredited sites are evaluated in this study based on three metrics: utility costs per permanent occupant, land affected per permanent occupant, and greenhouse gas emissions per permanent occupant. As the findings will illustrate, lower utility costs and CO2 emissions of the LEED Silver accredited site serve as positive indicators regarding the effectiveness of the LEED rating system, while the land area impacted per permanent occupant by the LEED accredited site is not significantly better the than non-accredited sites. This shortcoming also provides lessons for sustainable building using the LEED system of standards.
Criticism: How effective are LEED Standards?
Since its introduction, some experts have questioned the effectiveness of the LEED system. Important criticism comes from Harvey Bryan, a professor at Arizona State University who was active in the development of ASHRAE 90.1 Appendix G, a universally accepted energy efficiency standard also used to assess projects for the LEED accreditation. Bryan notes that LEED assesses a built site’s performance through modeling the energy use of two structurally identical versions of the site in accordance with ASHRAE 90.1 Appendix G standard (2009, 175). The first version provides a baseline for site performance—if the site was constructed as a “typical” site of the same type. The second version models the site exactly as it will be built. The difference is used for awarding credits toward LEED recognition. According to Bryan, project teams sometimes choose to model an abnormally low performance site for the baseline, dramatically inflating the modeled performance of the project (LEED, 70). In one case, the Biodesign Institute, a LEED Gold accredited project at Arizona State University modeled 60% energy savings, but only realized 21% savings (LEED, 70).
Evaluation: Comparative Performance of LEED Accredited
Versus Non-LEED Accredited Residential Sites
To assess the effectiveness of the LEED system, the data from these 15 residential sites was compiled and evaluated.
|Site Name||Number of Occupants||Usable Square Feet|
|Thayer Hall(LEED Silver Accredited)||157||44630|
The 15 sites are assessed on three different metrics:
- Annual utility cost per permanent occupant
- Annual greenhouse gas emissions (GHG) per permanent occupant
- Annual land area affected per permanent occupant
Thayer Hall received LEED Sliver accreditation in 2011, so all measurement are based on averages from FY2012, FY2013, and FY2014.
To evaluate the performance of each site, utility usage and cost data were acquired using Interval Data Systems’ Energy Witness reporting tool. Unless noted otherwise, all years referenced in this study are Harvard fiscal years. Thayer Hall received its LEED Silver accreditation in July of calendar year 2011, so the data includes fiscal years after accreditation, FY2012, FY2013, and FY2014. The results are an average of FY2012, FY2013 and FY2014 usage and cost data. Averaging three years eliminates abnormalities caused by random short-term fluctuations in usage. The most resource intensive dorm amenities, laundry and irrigation are not distributed evenly among the 15 dorms. Therefore, to allow for a valid comparison, this difference was mitigated by assessing electricity and water consumption of sites with laundry facilities and sites without, then adjusting for usage based on population data and facility distribution. Water and sewage consumption values in this study exclude site irrigation. The GHG emission metric accounts for both utility consumption and the mix of fuels in production. Metrics are calculated on a per occupant basis to allow direct comparison between sites that would otherwise be impossible to compare because the 15 sites are of different sizes and house different numbers of occupants.
Metric: Annual Utility Cost
Annual utility costs provide insight into the economic validity of LEED. USGBC claims that sites with LEED accreditation have lower utility costs than equivalent non-LEED sites. If the LEED accreditation system is valid, then sites granted any level of accreditation should have substantially lower utility costs per occupant then sites without accreditation.
From FY2012-FY2014, LEED Silver accredited Thayer Hall was the third most efficient site, surpassed only by Straus Hall and Weld Hall. Thayer Hall operates at a cost of $95.66/occupant less than the average of the 14 other sites, a 16.3% advantage. Thayer has 157 occupants. In this instance, over $15,000 per year is saved by constructing to LEED’s standards. This demonstrates that LEED can make buildings more cost effective, as claimed.
Metric: Annual Greenhouse Gas Emissions
Site performance should also be evaluated based on GHG emissions because they provide more complete information about the performance of a site’s fuel mix than utility cost alone, considering that utility cost could be lower due to reliance on cheap, CO2 intensive fuels. The USGBC claims that LEED accredited buildings will emit less CO2 than equivalent sites without accreditation.
GHG emissions for all 15 sites in this study have three sources: electricity consumption from the New England electric grid (eGRID sub region NPCC New England), natural gas consumption, and steam consumption. All fuel emission factors are from the Energy Information Administration. GHG emissions from steam production are adjusted to account for secondary electricity production through Harvard’s district heating system. The results are as follows:
Thayer Hall emits 1,617 lbs CO2/year per occupant less than the average of the 14 other sites, an 18.1% difference. This indicates that LEED accredited residential sites emit significantly less greenhouse gases per occupant than sites without accreditation. This supports the conclusion that LEED is a valuable tool for certifying low CO2 residential sites in university environments. This is valuable since GHG emissions are understood to be disruptive to global climate systems and many universities face significant pressure from within and without to dramatically reduce their GHG emissions. This metric indicates that constructing built sites to comply with the LEED rating system is an effective strategy for universities to respond to the pressure to reduce GHG emissions.
Metric: Land Impact
Built sites also affect land use patterns through energy consumption, producing a “land footprint.” Some cheap and low CO2 energy sources, such as biomass or natural gasderived electricity, have huge land impacts (McDonald). This contributes to food shortages, biodiversity loss, and habitat destruction. As a result, a sustainable built site will optimize its energy mix to impact as small an area as possible while minimizing GHG emissions. In assessing land use, water and sewer usage are assumed to have a negligible impact on land use.
Thayer Hall’s land use per occupant is the 7th lowest out of the 15 sites assessed and only 1.6 % below the 14-site average. Therefore, the LEED Silver accredited Thayer Hall does not perform as favorably by this metric as it did with utility usage or greenhouse gas emissions. Thayer Hall’s poor performance is a direct result of the fact that electric power consumption is the most land intensive of all three energy utilities measured, accounting for an average of 65% of land impact across all 15 sites, but only 29.8% of energy consumption. Thayer Hall draws 40.1% of its total energy consumption in the form of electric power, which is more than any other site. Its reliance on electric power accounts for its high land area impacted, a direct consequence of the fact that Massachusetts derives 46% of electric power from land intensive natural gas (2014, 13).
Summary of Metrics and Conclusion
Unfortunately, limitations on available data limited the scope of this study to one LEED accredited site. Additionally, all of the sites studied are located in the city of Cambridge, MA, which has adopted local building energy codes that may be more or less stringent that those used in other localities. This suggests that further research is necessary before any broad conclusions can be made. However, utility costs, greenhouse gas emissions and land impact indicates that the LEED system provides advantageous standards for constructing sites with reduced utility costs and reduced GHG emissions. But the site land impact results suggest that LEED may not enhance site performance on significant metrics that fall outside of its immediate scope, such as land area impacted. Therefore, LEED is a useful tool for developing a sustainable built environment, but institutions that utilize the LEED system should do so with an actively clear vision regarding built site performance, as LEED is not inclusive of every relevant metric of a high performance built environment. As a result, the LEED system is still valuable, butthe construction of sustainable environments requires careful diligence in addition to using the LEED system.
Clifford Goertemiller is an undergraduate at Harvard.
 A note on transparency: All data used in this study is available on Harvard’s Energy Witness tool. http://www.energyandfacilities.harvard.edu/tools-resources
 The Harvard fiscal year runs from July 1st to June 30th
References of the Article here.