Retrocommissioning is a process applied to existing buildings to ensure that they continue to perform optimally for the current use. This process involves checking systems to see if they function as intended, making necessary repairs or improvements, and ensuring that building staff are trained in the operation and maintenance of systems. References: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources

According to the LEED v4 Glossary of Terms1, a site that has been graded is commonly defined as previously developed, which means "land that has been altered by paving, construction, and/or land use that would typically have required regulatory permitting to have been initiated (alterations may exist now or in the past)"1. A greenfield is "a site not previously developed or graded that could support open space, habitat, or agriculture"1. A brownfield is "a property, the expansion, redevelopment, or reuse of which may be complicated by the presence or potential presence of a hazardous substance, pollutant, or contaminant"1. A previously undeveloped site is "a site that has never been built on or graded for development"2.

Building and material reuse contribute to the sustainability goals of a project by reducing the use of raw materials, which can save energy, water, and natural resources, as well as reduce greenhouse gas emissions, waste generation, and environmental impacts. By reusing existing buildings or materials, project teams can avoid the extraction, processing, transportation, and disposal of new materials, which can have significant environmental and social costs. LEED v4.1 recognizes and rewards multiple strategies for building and material reuse in the Building-Life Cycle Impact Reduction credit1.

LEED certification is awarded based on the number of points a project earns across several categories of green building performance. The range of points required to maintain Gold level of LEED certification is 60-
79, out of a possible 110 points. The other levels of LEED certification are: Certified (40-49 points), Silver (50-59points), and Platinum (80 or more points)13. References: LEED v4 Green Associate Candidate Handbook1, LEED v4 BD+C Reference Guide3

Chlorofluorocarbons (CFCs) are the class of refrigerants that contribute the most to ozone depletion potential (ODP). Ozone depletion potential is a measure of how much a substance can damage the ozone layer in the stratosphere, which protects life on Earth from harmful ultraviolet radiation. CFCs are synthetic chemicals that contain chlorine, fluorine, and carbon atoms. They were widely used as refrigerants, aerosol propellants, solvents, and foam blowing agents until they were phased out by the Montreal Protocol due to their high ODP. The LEED Green Associate Candidate Handbook states that one of the strategies for achieving energy and atmosphere efficiency is to "eliminate chlorofluorocarbons (CFCs) in new building HVAC&R systems"
[1, p. 15]. References: LEED Green Associate Candidate Handbook, [Ozone Depletion Potential | U.S.
Environmental Protection Agency]