An externality is a consequence of an economic activity that affects other parties who are not directly involved in the activity. Externalities can be positive or negative, depending on whether they create benefits or costs for others. When a developer builds a new shopping center in a rural area, one externality might be an increase in traffic on adjacent roads. This is a negative externality because it imposes costs on other road users who are not part of thedevelopment project, such as increased travel time, fuel consumption, air pollution, noise pollution, and accident risk13. References: LEED v4 Green Associate Candidate Handbook1, Investopedia's Externality

A brownfield site is appropriate for development of LEED projects because it is a site that has been previously used for industrial or commercial purposes and may be contaminated by pollutants or hazardous substances. Developing a brownfield site can help reduce environmental impacts, such as soil erosion, habitat loss, and water consumption, by reusingexisting infrastructure and restoring degraded land. LEED projects can earn credits for developing on brownfield sites under the Sustainable Sites category. References: LEED v4 BD+C Reference Guide, Sustainable Sites, page 35; Best Management Practice #14: Alternative Water Sources1

Building-level energy metering is a prerequisite in LEED that requires the installation of energy meters to track the total energy usage of a building12. It helps to monitor and optimize the energy performance of the building and to report the data to USGBC3. Green metering, site evaluation data, and energy savings records are not terms used in LEED.

The methodology that is used to evaluate and study the economic performance of a building or system over its entire life is life cycle assessment (LCA). LCA is a technique that assesses the environmental aspects and potential impacts associated with a product, process, or service throughout its life cycle, from raw material extraction to end-of-life disposal or recycling7. LCA can also include an economic dimension by incorporating life cycle costing (LCC), whichestimates the total costs of ownership over the life cycle of a product or system8. By combining LCA and LCC, one can evaluate the environmental and economic performance of a building or system in a holistic way, taking into account both the initial investment costs and the long-term operational costs. This can help identify trade-offs and synergies between environmental and economic objectives, as well as opportunities for improving efficiency and reducing impacts9. References: Life-cycle assessment7; What is Life Cycle Assessment (LCA)?8; Life Cycle Costing in Construction Projects: A Case Study of a Municipal Building in Portugal9

ASHRAE developed the MERV scale, which rates air filter efficiency in capturing airborne particles. LEED references MERV ratings in Indoor Environmental Quality credits to ensure air quality.