Blackwater is wastewater that contains fecal matter and pathogens, such as from toilets. Greywater is wastewater that is less contaminated, such as from showers, sinks, and washing machines1. However, the classification of kitchen sink wastewater may vary depending on local codes and regulations. Some states and authorities consider kitchen sink wastewater as blackwater because it may contain food waste and germs123. Others consider it as greywater if it meets certain quality standards and is used for beneficial purposes, such as irrigation or toilet flushing45. A CIR (Credit Interpretation Request) is a process to seek clarification on a specific credit or prerequisite in a LEED rating system, but it does not change the definition of blackwater or greywater.
Greywater Reuse | WaterSense | US EPA4
Greywater - California Department of Water Resources5
What Is Greywater? What Is Blackwater? | HomeServe USA1
Grey Water / Reclaimed Water | University of Maryland Extension2
What is meant by the terms Gray water and black water3
Credit Interpretation Requests (CIRs) | U.S. Green Building Council

Designers and builders can construct a green building that uses significantly less water than a conventional building by incorporating native plant landscapes. Native plant landscapes are plants that are adapted to the local climate and soil conditions, and require little or no irrigation, fertilization, or pesticides. They also provide habitat for wildlife, reduce stormwater runoff, and enhance the aesthetic value of the site. The LEED Green Associate Candidate Handbook states that one of the intents of the Sustainable Sites category is to
"conserve water by using native or adapted plants" [1, p. 13]. References: [LEED Green Associate Candidate Handbook], [Native Plants | U.S. Environmental Protection Agency]

Acomposting toileteliminates water use by not requiring any water for flushing, unlike traditional or low-flow fixtures:
"Composting toilets... operate without water use, thus eliminating indoor water demand for flushing." WaterSense toilets and low-flow lavatories reduce water use but do not eliminate it.

A high-efficiency HVAC (Heating, Ventilation, and Air Conditioning) system can directly reduce a building's greenhouse gas emissions by using less energy than a standard system. Since most energy production involves the burning of fossil fuels, which releases greenhouse gases, using less energy results in fewer emissions. References: LEED Green Associate Candidate Handbook, U.S. Green Building Council resources

Life-cycle costing (LCC) is a method of estimating the total cost of owning and operating an asset over its entire life span. LCC considers all costs associated with the acquisition, installation, operation, maintenance, and disposal of the asset12. LCC can help businesses make better decisions about purchasing, budgeting, pricing, and investing in assets2.
LCC does not quantify environmental impacts such as acidification, eutrophication, or global warming. These impacts are measured by life-cycle assessment (LCA), which is a method of evaluating the environmental effects of a product or service throughout its life cycle. LCA considers the inputs and outputs of materials, energy, and emissions at each stage of the product or service life cycle34. LCA can help businesses identify opportunities to reduce their environmental footprint, improve their sustainability performance, and comply with environmental regulations4.
However, LCC and LCA are often used together to compare different alternatives based on both economic and environmental criteria. For example, a business may use LCC to estimate the energy costs of different lighting options, and LCA to estimate the greenhouse gas emissions of each option. By combining LCC and LCA results, the business can select the option that minimizes both costs and emissions.