page_title: Leadership in Energy and Environmental Design
section_title: Energy performance research
hierarchical_section_title: Leadership in Energy and Environmental Design / LEED Performance / Energy performance research
context_page_description: Leadership in Energy and Environmental Design is a
  green building certification program used worldwide. Developed by the non-profit U.S. Green Building Council it includes a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighborhoods which aims to help building owners and operators be environmentally responsible and use resources efficiently.
context_section_description: In 2009 Newsham et al. analyzed a database of 100 LEED certified (v3 or earlier version) buildings.  In this study, each building was paired with a conventional "twin" building within the Commercial Building Energy Consumption Survey (CBECS) database according to building type and occupancy.  On average, LEED buildings consumed 18 to 39% less energy per floor area than their conventional "twin" buildings, although 28 to 35% of LEED-certified buildings used more energy than their "twin.”  The paper found no correlation between the number of energy points achieved or LEED certification level and measured building performance.
  In 2009 Scofield published an article in response to Newsham et al., analyzing the same database of LEED buildings and arriving at different conclusions.  In his analysis, Scofield criticized that Newsham et al.'s study only considered the energy per floor area instead of a total energy consumption. Scofield considered source energy (accounting for energy losses during generation and transmission) as well as site energy, and used area-weighted energy use intensities, or EUIs (energy per unit area per year), when comparing LEED and non-LEED buildings to account for the fact that larger buildings tend to have larger EUIs.  Scofield concluded that, collectively, the LEED-certified buildings showed no significant source energy consumption savings or greenhouse gas emission reductions when compared to non-LEED buildings, although they did consume 10-17% less site energy.
  Scofield in 2013 analyzed 21 LEED-certified buildings in New York City. He found that buildings that had achieved LEED Gold used, on average, 20% less source energy than did conventional buildings.  Buildings with LEED Silver or LEED Certified ratings actually used 11 to 15% more source energy, on average, than did their conventional counterparts.
  In 2014, Fuertes and Schiavon developed the first study that analyzes plug loads using LEED documented data from certified projects. The study compared plug load assumptions made by 92 energy modeling practitioners against ASHRAE and Title 24 requirements, as well as the evaluation of the plug loads calculation methodology used by 660 LEED-CI and 429 LEED-NC certified projects. In general, energy modelers considered the energy consumption of plug loads of equipment that are constantly running (such as refrigerators) as well as monitors and computers predictable. Overall the results suggested a disconnection between energy modelers assumptions and the actual performance of buildings. In conclusion, the study suggests LEED or ASHRAE to develop guidelines for plug loads calculations.
  Energy model might be a source of error during LEED design phase. Stoppel and Leite evaluated the predicted and actual energy consumption of two twin buildings using the energy model during the LEED design phase and the utility meter data after one year of occupancy. The study's results suggests that mechanical systems turnover and occupancy assumptions significantly differing from predicted to actual values.
  Most of the current available energy consumption analysis of LEED buildings focuses on LEED v3 (2009) or even earlier versions certified buildings instead of the newest LEED v4 (2014) certified buildings. According to Newsham et al., these analyses should be considered as preliminary and should be repeated with longer data history and larger sample buildings, including new LEED v4 certified buildings. Newsham et al. also pointed out that further work needs to be done to define green building rating schemes to ensure more consistent and substantial energy consumption reduction success at the individual building level in long term.
caption: The Empire State Building in New York City is one of the tallest and most well-known LEED-certified buildings, certified as an existing building[41]
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