modelers only considered the energy consumption of predictable plug loads, such as refrigerators, computers and monitors. Overall the results suggested a disconnection between assumptions in the models and the actual performance of buildings. Energy modeling might be a source of error during the LEED design phase. Engineers Christopher Stoppel and Fernanda 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 suggest that mechanical systems turnover and occupancy assumptions significantly differ from predicted to actual values. Most of the current analysis of LEED buildings focuses on LEED v3 (2009) or earlier versions rather than LEED v4 (2014) certification. According to Newsham et al., these analyses should be considered as preliminary and should be repeated with longer data history and larger building samples, including new LEED v4 certified buildings. Newsham et al. also noted that further work needs to be done to define green-building rating schemes to ensure more consistent and substantial long-term reduction of energy consumption at the individual building level. IEQ performance research The Centers for Disease Control and Prevention (CDC) defines indoor environmental quality (IEQ) as "the quality of a building's environment in relation to the health and wellbeing of those who occupy space within it." The USGBC includes the following considerations for attaining IEQ credits: indoor air quality, the level of volatile organic compounds (VOC), lighting, thermal comfort, and daylighting and views. In consideration of a building's indoor environmental quality, published studies have also included factors such as: acoustics, building cleanliness and maintenance, colors and textures, workstation size, ceiling height, window access and shading, surface finishes, furniture adaptability and comfort. In 2013, a paper published by Schiavon and architectural physicist Sergio Altamonte studied occupant IEQ satisfaction in LEED and non-LEED buildings. Using occupant surveys from the Center for the Built Environment at Berkeley database, 65 LEED-certified and 79 non-LEED buildings were analyzed for 15 IEQ-related factors. These factors include the ease of interaction, building cleanliness, the comfort of furnishing, the amount of light, building maintenance, colors and textures, workplace cleanliness, the amount of space, furniture adjustability, visual comfort, air quality, visual privacy, noise, temperature, and sound privacy. The results showed occupants tend to be slightly more satisfied in LEED buildings for the air quality and slightly more dissatisfied with the amount of light.