Glossary

Please note, websites listed were last accessed September 25, 2025.  Some of the links below may require subscriptions to access content.

Active design: An approach to the development of buildings, streets, and neighborhoods that uses architecture and urban planning to make daily physical activity and healthy foods more accessible and inviting.

Adapted plant species: A non-native plant species that performs similarly to a native species in a particular region, state, ecosystem, and habitat, and that 1) can survive temperature or other weather extremes in the microclimate; 2) requires little irrigation or fertilization, once established; 3) is resistant to local pests and diseases; and 4) does not displace other plants, as invasives do.

Adaptive reuse: When an existing building is being renovated to accommodate a new use, e.g., rehabilitating an old school for use as housing.

Air barrier: Air barriers are systems of materials designed and constructed to control airflow between a conditioned space and an unconditioned space. The air barrier system is the primary air enclosure boundary that separates indoor (conditioned) air and outdoor (unconditioned) air. In multi-unit  construction, like townhomes and apartments, the air barrier system also separates the conditioned air between any given dwelling unit and adjacent units. www.buildingscience.com/documents/digests/bsd-104-understanding-air-barriers

Albedo: The fraction of light that a surface reflects. See also Solar Reflectance Index.

ARCSA: The American Rainwater Catchment Systems Association, a membership-based organization advocating for and supporting advancements in rainwater catchment and use. https://arcsainternational.org/

ASHRAE: An international society of heating, refrigerating, and air-conditioning professionals that sets standards relating to heating, cooling, and ventilation. (Formerly the American Society of Heating, Refrigerating and Air-Conditioning Engineers.) www.ashrae.org/

ASHRAE Standard 62.1 — Ventilation and Acceptable Indoor Air Quality and 62.2 — Ventilation and Acceptable Indoor Air Quality in Residential Buildings: The recognized standards in the U.S. for ventilation system design and acceptable indoor air quality. www.ashrae.org/technical-resources/bookstore/standards-62-1-62-2

ASHRAE Standard 90.1 — Energy Standard for Sites and Buildings Except Low-Rise Residential Buildings: Provides the minimum requirements for energy-efficient design of most buildings, including both passive systems like exterior walls and windows and active systems like HVAC systems. Also provides, in Appendix G, broadly accepted requirements for requirements for whole-building energy modeling.

Automatic Load Management System (ALMS): A system designed to manage load across one or more electric vehicle chargers to share electrical capacity and/or automatically manage power at each connection point. See also electric vehicle supply equipment. https://sbcc.wa.gov/sites/default/files/2021-08/Load%20Management%20System_Examples.pdf

Base flood elevation (BFE): The height floodwaters are predicted to reach during a 100-year flood event, commonly used while evaluating flood risk.

Berm: A sloped wall or embankment, typically constructed of earth, hay bales, or timber framing, used to prevent the flow of material into or out of an area.

Biophilic design: Architectural design that reconnects people with nature. It has been credited with reducing stress, improving cognition, and supporting health and well-being in other ways. www.terrapinbrightgreen.com/reports/14-patterns/, https://living-future.org.au/biophilic-design/

Bioswale: Vegetated, shallow depressions in the landscape engineered to capture, treat, and infiltrate stormwater to reduce runoff. Compared with conventional swales, bioswales are intentionally designed with enhanced soil and plants to maximize treatment. https://nacto.org/publication/urban-street-design-guide/street-design-elements/stormwater-management/bioswales/

Blue roof: A non-vegetated stormwater detention system that is installed over a sealed roof membrane. It typically uses check dams, trays, or modified roof drains to capture and temporarily detain stormwater before it reaches downspouts. https://water.phila.gov/gsi/tools/blue-roof/

Blue-green roof: A roof system with a separate layer beneath the vegetated layer that contains structural voids that provide temporary detention capacity in addition to the retention capacity of the vegetated layer. Best suited for flat or low-sloped roofs. www.sciencedirect.com/science/article/pii/S0301479721018120

Bollards: A series of vertical posts or barriers that guide traffic and/or protect pedestrian areas. www.wbdg.org/resources/bollard-non-crash-and-non-attack-resistant-models

Building enclosure: The building enclosure is made up of the roof, foundation, and exterior wall assemblies, that separate the indoors from the outdoors, providing protection against weather, pests, noise, and other elements that impact comfort and energy efficiency. www.wbdg.org/resources/residential-building-enclosure

Building Performance Institute (BPI): A national standard developer and credentialing organization for residential energy auditing and upgrade work and provides training through affiliate organizations as well as other related programs. www.bpi.org/, https://bpi.org/about-us/

Carbon: See Emissions.

CFM (cubic feet per minute): A standard unit of measurement for airflow through HVAC systems. It indicates how many cubic feet of air are passing through a fixed point per minute and is used to test air tightness.

Charrette: An intensive work session in which various stakeholders and experts come together before schematic design to articulate project goals and begin integrating green principles into design while setting the project up for success during construction and operation. In addition to housing professionals, a charrette may include funders, policymakers, health practitioners, and community stakeholders.

CO (carbon monoxide): A colorless, odorless and tasteless gas that greatly affects indoor air quality. Because it is impossible to see, taste, or smell the toxic fumes, CO can kill you before you are aware that it is in your home. At lower levels of exposure, CO causes mild effects that are often mistaken for the flu. These symptoms include headaches, dizziness, disorientation, nausea, and fatigue. www.epa.gov/co-pollution

CO2 or CO2e: See Emissions

Colonias community: Any identifiable community in the U.S.–Mexico border regions of Arizona, California, New Mexico and Texas that is determined to be a colonia on the basis of objective criteria, including lack of a potable water supply, inadequate sewage systems, and a shortage of decent, safe and sanitary housing. The border region means the area within 150 miles of the U.S.–Mexico border, excluding Metropolitan Statistical Areas with populations exceeding one million (according to the National Affordable Housing Act of 1990, Section 916).

Common area: An area available for use by more than one person, including rental or sales offices, entrances, hallways, laundry rooms, shared activity or leisure rooms, and spaces for providing resident services.

CSA (Community-supported agriculture): A community of individuals who pledge support to a farm operation so that the farmland becomes the community’s farm, with the growers and consumers providing mutual support and sharing the risks and benefits of food production. Typically, members of the farm or garden pledge in advance to cover the anticipated costs of the farm operation and the farmer’s salary. In return, they receive shares in the farm’s bounty throughout the growing season. Members also share the risks of farming, including poor harvests due to unfavorable weather or pests. www.nal.usda.gov/farms-and-agricultural-production-systems/community-supported-agriculture

Community solar: A solar-powered electrical system that, through a voluntary program, provides power and/or financial benefit to, or is owned by, multiple community members. www.nrel.gov/docs/fy11osti/49930.pdf

Compost blanket: A layer of loosely applied compost or composted material that is placed on the soil in disturbed areas to control erosion and retain sediment resulting from sheet-flow runoff.

Critical root zone (CRZ): The critical root zone, or CRZ, is defined as the area of soil where roots required for future tree health and survival are located. This area can also be defined as a circle with a minimum radius of 1 foot for every 1 inch of trunk diameter at 4.5 inches above ground.

Dead leg: A length of pipe leading to an outlet which has been removed, is rarely used, or is entirely unused. Dead legs do not have regular water flow, increasing the opportunity for bacterial growth in the system.

Dedicated bike lane: A dedicated travel area exclusively for bicyclists that is located on or directly adjacent to the roadway. https://ddot.dc.gov/sites/default/files/dc/sites/ddot/DDOT%20Bicycle%20Facility%20Design%20Guide%20-%20Version%202%20%28Final%29.pdf

Defensible space: In the context of wildfire adaptation, defensible space is a buffer between a structure and the surrounding area that acts as a barrier to slow or halt fire progress. www.fire.ca.gov/dspace

Design flood elevation (DFE): The minimum elevation to which a structure must be elevated or floodproofed, as set and regulated by local authorities. www.reducefloodrisk.org/glossary/design-flood-elevation-dfe/

Detention basin: An artificial pond or structure designed to capture and hold stormwater runoff with an engineered discharge structure that controls the elevation and rate of release. A dry detention system does not permanently maintain a permanent pool of water and provides treatment via infiltration. A wet detention system is designed to retain a permanent pool of water and has specific vegetated zones designed to provide treatment through nutrient uptake.

Dial-a-ride program: A program that provides an on-demand ride service, requiring passengers to call ahead to reserve a ride. These programs may be privately or publicly operated and usually provide connections between different transportation systems and/or employment centers.

Diameter at breast height (DBH): Diameter of a tree taken at 4.5 feet (or 1.37 meters) above ground level. Common measure of tree girth used for tree preservation during construction projects.

Distribution uniformity: A measure of the evenness of irrigation water coverage over a defined area.

Drying potential: The extent to which a material or building assembly permits evaporation of moisture. www.greenbuildingadvisor.com/article/understanding-drying-potential

Dwelling unit: A single unit providing complete, independent living facilities for one or more people, including permanent provisions for living, sleeping, eating, cooking, and sanitation. From Addendum J to ASHRAE 62.2-2010, found online at: www.ashrae.org/standards-research--technology/standards-addenda

ECM (electronically commutated motor): Also known as brushless DC motors, ECMs are synchronous motors that are powered by a DC electric source via an integrated inverter/switching power supply that produces an AC electric signal. Used, for example, in HVAC equipment that uses electricity efficiently, particularly at lower speeds.

Ecologically sensitive: Describes a natural area with significant ecological value that is vulnerable and could be easily harmed by human activities or environmental disturbances.

Ecosystem services: The direct and indirect economic, social, and environmental benefits that ecosystems provide to humans. www.climatehubs.usda.gov/ecosystem-services

Electrical vehicle service equipment (EVSE): A system that transfers power to an electric vehicle. EVSE must include an energized conductor as well as charging equipment — either a connector and plug (i.e., charging cord) or apparatus for wireless (e.g., inductive) charging — to provide power directly to a vehicle. EVSE may also optionally include load management, scheduling, adapters, and other features to facilitate on-site electric vehicle charging.

Embodied carbon or Embodied emissions: The greenhouse gas emissions arising from the manufacture, transportation, installation, maintenance, and disposal of building and infrastructure materials. https://carbonleadershipforum.org/embodied-carbon-101-v2/

Emissions: For indoor emissions, see VOCs. The release of heat-trapping gases into Earth’s atmosphere, contributing to global warming and climate change. Primarily used to describe atmospheric pollution caused by human activities, particularly combustion of fossil fuels. The following terms are commonly used as synonyms: carbon, carbon footprint, carbon dioxide, carbon dioxide equivalent, greenhouse gas emissions, GHG emissions, fossil fuel emissions, global warming potential, climate change potential. “Carbon” is often used as an abbreviation to refer to global warming potential. See also Life-cycle emissions, Embodied carbon, Operating carbon, and scope 1, scope 2, and scope 3 greenhouse gas emissions.

Emissions intensity: Emissions per square foot per year at a property. Can be used before design to set a carbon target, during design to compare performance scenarios, and during operation to measure carbon performance.

Employer vanpool: A program in which 5 to 15 people over the age of 16 ride together to and from work. The vanpool may be public or private but must carry all passengers more than half the distance to work to qualify. Vanpools may be employer-operated, sponsored by transit agencies, or administered by third-party operators.

ENERGY STAR: A set of voluntary certification and labeling programs designed to incentivize energy efficiency in buildings. Introduced by the U.S. Environmental Protection Agency in 1992, ENERGY STAR includes labels for appliances and equipment, newly constructed single- and multifamily homes, and existing multifamily and commercial buildings. www.energystar.gov

Energy use intensity (EUI): Energy use per square foot per year at a property. Used before design to set an energy target, during design to compare performance scenarios, and during operation to measure energy performance.

Engineered wood products: Wood building materials manufactured by gluing particles, fibers, or veneers to increase strength. For the purposes of Criterion 6.4 Advanced Material Selection, Green Communities considers prefabricated and precut wood products to be engineered wood products. https://iwpllc.com/products/engineered-wood-products/

Entryway: Threshold separating the indoor space from the outdoor space.

Environmental product declaration (EPD): An independently verified and publicly registered document that discloses standardized data representing the estimated environmental impacts of products at different stages in their life cycles. The standardized format and other controls enable practitioners to compare the estimated environmental impacts of multiple products in the same product category. EPDs are frequently used to compare embodied emissions of different products. See also Embodied carbon.

Environmental site assessment: An investigation of the site’s conditions, often performed before acquisition of a property to satisfy the due-diligence requirements of a property transaction.

Energy Rating Index (ERI): A rating that compares the energy performance of an actual home with the energy performance of a reference home of the same geometry built to the requirements of the 2006 International Energy Conservation Code. The lower the number, the better the energy performance. An ERI of 100 means no difference in energy between the actual home and the reference home. An ERI of 0 means no net purchased energy annually. The rules for rating homes and reporting their scores are established in ANSI/RESNET/ICC 301 — Standard for the Calculation and Labeling of the Energy Performance of Dwelling and Sleeping Units Using an Energy Rating Index. One example of an ERI Is RESNET’s proprietary HERS Index.

Erosion blankets or Geotextile mats: Porous fabrics used on a construction or building site for a variety of purposes, including separators, reinforcement, filtration and drainage, and erosion control.

Erosion control plan (ECP): A plan detailing the devices and conservation measures used to minimize erosion caused by stormwater runoff and to prevent sediment pollution from entering waterways. https://doee.dc.gov/esc

Fenestrated panel: Screen or panel with openings (perforations) used to reduce wind exposure. The perforations allow some wind to pass through, reducing overall wind load and mitigating wind impact.

Filter sock: A mesh tube filled with composted material that is placed perpendicular to sheet-flow stormwater runoff to control erosion and retain sediment in disturbed areas.

Formaldehyde: A chemical used widely by industry to manufacture building materials and numerous household products. Formaldehyde is also a by-product of combustion and certain other natural processes and thus may be present in substantial concentrations both indoors and outdoors. Health effects include eye, nose, and throat irritation; wheezing and coughing; fatigue; skin rash; and severe allergic reactions. High levels of exposure may cause some types of cancer. www.epa.gov/formaldehyde

Freeboard: The additional height above base flood elevation (BFE) protecting a building from flooding, usually 1 to 3 feet for critical facilities. www.reducefloodrisk.org/glossary/freeboard/

Furnishing zone: A section of sidewalk located adjacent to a curb that serves as a buffer, typically 3 to 5 feet wide, between pedestrians and the roadway. So called because it often includes seating or other amenities. Furnishing zones enhance pedestrian safety and provide space for sidewalk elements to maintain a clear path of travel. www.nycstreetdesign.info/furniture/furnishing-zone

Global warming potential (GWP): The capacity of a gas to trap heat in Earth’s atmosphere. GWP is a way to compare the climate impact of different substances, with carbon dioxide as the benchmark with a GWP of 1. A higher GWP means a gas can trap more heat, worsening global warming. Although established for comparing greenhouse gases, GWP can apply by extension to any activity, process, or physical object, and it is one of the impact categories in an environmental product declaration (EPD). In that context, it is roughly equivalent to embodied carbon. GWP is expressed as carbon dioxide equivalent, or CO2e.

Green infrastructure (GI): A landscape feature designed to mimic nature and capture rainwater where it falls instead of allowing it to run off the site as stormwater. GI reduces and treats stormwater at its source while also providing multiple community benefits, such as reducing localized flooding and improving community quality of life and resilience. www.epa.gov/G3/why-you-should-consider-green-stormwater-infrastructure-your-community

Green roof: A vegetated rooftop system (extensive or intensive) consisting of barriers to prevent water or root damage to the structure, a drainage layer to aid in water drainage, a growing medium, and a vegetative layer. Green roofs reduce roof surface and adjacent air temperatures, helping moderate the heat-island effect; filter rainwater and reduce runoff; absorb pollutants and carbon dioxide; provide natural habitat; and can serve as recreational green space. www.epa.gov/soakuptherain/soak-rain-green-roofs and www.epa.gov/heatislands/using-green-roofs-reduce-heat-islands

Greywater: Wastewater produced from baths and showers, clothes washers, and lavatory sinks. Greywater gets its name from its cloudy appearance and from its status as being neither fresh (as in potable water) nor heavily contaminated (as in blackwater from toilet waste). (Source: U.S. Environmental Protection Agency)

Health Product Declaration (HPD): a document that provides standardized information about the contents of building products and their potential health impacts.

Hydrozone: The landscaping practice of grouping together plants with similar water requirements, with the goal of conserving water.

Hygrothermal: The dynamic and interrelated movement of heat and moisture. Requires awareness and attention in the context of green building because energy-efficient design impacts moisture dynamics, including condensation potential and drying potential inside the building enclosure. www.designingbuildings.co.uk/wiki/Hygrothermal

ICC (International Code Council): Produces model building codes, including the International Building Code (IBC) and the International Residential Code (IRC).

IECC (International Energy Conservation Code): A model building energy code created by the ICC to set a minimum standard for energy efficiency; updated on a three-year schedule. www.iccsafe.org/

iHPWH (integrated heat pump water heaters): Integrated heat-pump water heaters (iHPWHs) are the most commonly used heat-pump technology for domestic water heating. iHPWHs have their heat-pump compressor and heat exchangers attached directly to the water heater’s storage tank. www.energystar.gov/partner-resources/residential_new/educational_resources/sup_program_guidance/heat_pump_water_heater_guide#:~:text=*%20Integrated%20Heat%20Pump%20Water%20Heaters,propane%2C%20or%20kerosene%20water%20heaters.

Immediate impact measures: In the context of Zero Over Time planning, immediate impact measures are building strategies identified to achieve early, meaningful reductions in carbon emissions while maintaining flexibility for future renovations within the project plan to achieve net-zero emissions in 20 years or less.

Impact Insulation Class: Impact Insulation Class (IIC) is an acoustical rating used to quantify impact sound absorption and vibration isolation in floor and ceiling assemblies. Assemblies with acoustical underlayments have a higher IIC rating because they block more impact sound. https://acousticalsolutions.com/what-is-iic-impact-insulation-class/?srsltid=AfmBOor7q_PQKL9sIois4xuZlJ2cVwvff5Wz_pj9gQMkNDSh0IJZgv6yInfill

Infill site: A site with 75% of its perimeter bordering existing development or roads and with access to existing infrastructure.

Integrated water factor (IWF): An efficiency metric used for clothes washers, IWF is the quotient of the total weighted per-cycle water consumption divided by the capacity of the clothes washer. Lower numbers indicate more efficient use of water.

Integrative design: A design approach that brings together at an early stage in project planning all the members of the building stakeholder community, including residents or potential residents, and the design and construction team (including green building consultants such as the green rater, energy experts, and others) to look at the project objectives, building materials, systems, and assemblies from many different perspectives. This approach is an alternative to the typical planning and design process of relying on the expertise of specialists who work in their respective specialties somewhat isolated from each other. www.enterprisecommunity.org/solutions-and-innovation/green-communities/tools-and-services/charrette-toolkit

Invasive species: A species that is non-native (or alien) to the ecosystem under consideration and whose introduction causes or is likely to cause economic or environmental harm or harm to human health. www.fs.usda.gov/wildflowers/invasives/index.shtml

JA8 bulbs: High-efficiency light bulbs certified to meet California’s Title 24 Building Energy Efficiency Standards, Joint Appendix 8. www.energy.ca.gov/sites/default/files/2022-08/CEC-400-2022-010-AP.pdf

LED (light-emitting diode): Energy-efficient lighting products that produce less initial heat per lumen, consume less energy, and last longer than conventional incandescent and fluorescent lights.

Life-cycle emissions: The sum of the operating emissions and embodied emissions of a building.

Lighting power density (LPD): An indicator of energy efficiency for a space’s lighting scheme. Measured in watts of lighting per square foot of room floor area (W/sf).

Local food system: The geographic context in which food is produced, marketed, and consumed, including intermediate supply-chain steps taking food from farm to table. https://localfood.ces.ncsu.edu/about-localfood/more-about-local-food/

Low-Impact development (LID): A stormwater management approach and set of practices that can reduce runoff and pollutants by managing runoff as close to the source as possible. LID includes both overall site design approaches and individual small-scale stormwater management practices that promote the use of natural systems for infiltration of rainwater. www.epa.gov/sites/default/files/2015-09/documents/bbfs2terms.pdf

Luminaire: A complete lighting unit consisting of a lamp or lamps together with the parts designed to distribute the light, to position and protect the lamps and ballast (where applicable), and to connect the lamps to the power supply.

Manual D Residential Duct Design: Standard developed by the Air Conditioning Contractors of America (ACCA) for designing residential duct systems. www.acca.org/store#/productDetail/71E94104-BC20-E511-80F8-FC15B428DD54/

Manual J Residential Load Calculation: Standard developed by ACCA for determining heating and cooling loads of residential structures. www.acca.org/store#/productDetail/DB68FDFC-BB20-E511-80F5-C4346BAC9A78

Manual LLH Low Load Homes: Standard developed by ACCA that uses Manuals J, S, D, T, and others as a baseline and identifies equipment options and approaches to address low cooling and/or heating loads. www.acca.org/standards/

Manual S Residential Equipment Selection: Manual prepared by ACCA on selecting residential heating and cooling equipment to match the heating and cooling loads of residential structures. www.acca.org/technical-manual/manual-s/

MERV: Minimum Efficiency Reporting Values (MERVs) report an air filter’s ability to capture larger particles between 0.3 and 10 microns (µm). www.epa.gov/indoor-air-quality-iaq/what-merv-rating

Micromobility: Small, low-speed vehicles intended for personal use. https://highways.dot.gov/safety/pedestrian-bicyclist/safety-tools/pg-25-transit-and-micromobility

Moderate rehabilitation: Refer to the definition in Appendix A of this manual.

Modular construction: The fabrication of building components in an off-site facility, which are then transported and put together on-site. www.wbdg.org/resources/site-and-modular-construction-explained

Mudflat: An unvegetated area of land consisting of mud, sand, or gravel deposited by oceans, seas, or tributaries when the tide comes in, and exposed when the tide lowers.

Native plant: Plant species that occurs naturally, without direct or indirect human actions, in a particular region, state, ecosystem, and habitat. www.audubon.org/content/why-native-plants-matter

On-site renewable energy: Any renewable energy collected and generated within the site boundary that is used for building energy; includes any excess renewable energy exported outside the site boundary. The renewable energy certificates (RECs) associated with the renewable energy must be retained or retired by the building owner or lessee to count as on-site renewable energy for the purposes of the Green Communities Criteria. www.energy.gov/sites/prod/files/2015/09/f26/bto_common_definition_zero_energy_buildings_093015.pdf

Open space: Undeveloped land that is permanently set aside for public use. Open space may be used as community open space or preserved as green space, and includes parcels in conservation easement or land trust, park or recreation areas, and community gardens.

Operating carbon or Operating emissions: Commonly refers to the global warming potential attributed to the operation and use of a building. https://buildinginnovationhub.org/resource/get-started/understanding-building-emissions/

Particulate matter: A mixture of solid particles and liquid droplets found in the air, including those so small that they can be inhaled. www.epa.gov/pm-pollution/particulate-matter-pm-basics

Permeable paving: A porous cover system that encourages groundwater recharge and infiltration. “Permeable” and “pervious” are often used interchangeably to describe these systems. www.epa.gov/green-infrastructure

PFAS (per- and polyfluoroalkyl substances): A group of manufactured chemicals, widely used as water- and stain-repelling ingredients, that break down slowly and can build up in people, animals, and the environment over time. PFAS are commonly referred to as “forever chemicals.” www.epa.gov/pfas/our-current-understanding-human-health-and-environmental-risks-pfas

Photosensor: A light-sensitive device that detects ambient light and controls exterior fixtures accordingly.

Photovoltaics (PV): Composite materials that convert sunlight directly into electrical power.

PNA (physical needs assessment): A comprehensive evaluation of a property’s current physical condition, repair needs, and long-term capital requirements. https://files.hudexchange.info/course-content/pha-occupancy-webinar-series-physical-needs-assessment/PHA-Occupancy-Webinar-Physical-Needs-Assessment-Handout.pdf

PSH (permanent supportive housing): See Supportive housing dwelling units.

Public–private regional transportation: Arrangement in which a private company offers public transit services, with a regular schedule and permanent stops, through a public funding stream.

Purple roof: Roof system with a friction-based fabric layer integrated with a vegetated layer; the fabric layer provides detention capacity in addition to the retention capacity of the vegetated layer. It can be installed on flat or sloped roofs. www.hydrotechusa.com/sites/default/files/press/CAM%20Magazine%20-May%20-2023.pdf

Qualified energy rater: Trained and certified professional who evaluates a building’s features to identify opportunities for enhanced performance. www.energystar.gov/partner-resources/residential_new/working/energy_rating_cos

Radon: The second leading cause of lung cancer in the United States, according to the EPA. Radon is a colorless, odorless, and tasteless radioactive gas that is naturally occurring in soil and rocks and can circulate undetected in a home’s indoor air. Tests are inexpensive, and simple mitigation strategies can protect residents from exposure to this major carcinogen. www.epa.gov/radon

Rainwater: In the context of stormwater management and water reuse, rainwater generally refers to precipitation that falls on roof surfaces and is thereby less contaminated than rainfall that has come into contact with ground surfaces.

Recapitalization: A process whereby the type, amount, income, return, or priority of a loan, ownership interest, or other securities of a property are adjusted, restructured, or replaced. https://files.hudexchange.info/course-content/hud-multifamily-affordable-housing-preservation-clinics/Preservation-Clinic-Glossary-of-Multifamily-Affordable-Housing-Preservation-Terms.pdf

Recessed light fixture (recessed can): A luminaire that is installed into an opening in the ceiling or wall.

Renewable energy: According to the U.S. Energy Information Administration glossary, these energy resources are naturally replenishing but flow–limited, meaning they are virtually inexhaustible in duration but limited in the amount of energy that is available per unit of time. Renewable energy resources include biomass, hydro, geothermal, solar, wind, ocean thermal, wave action, and tidal action. www.energy.gov/sites/prod/files/2015/09/f26/bto_common_definition_zero_energy_buildings_093015.pdf

Renewable energy certificates (RECs): A REC represents and conveys the environmental, social, and other nonpower qualities of one megawatt-hour of renewable electricity generation and can be sold separately from the underlying physical electricity associated with a renewable-based generation source. www.energy.gov/sites/prod/files/2015/09/f26/bto_common_definition_zero_energy_buildings_093015.pdf

Resilience: The capacity to adapt to changing conditions and to maintain or regain functionality and vitality in the face of stress or disturbance. Relative to climate change, resilience involves adaptation to the wide range of regional and localized impacts that are expected with a warming planet: more intense storms, greater precipitation, coastal and valley flooding, longer and more severe droughts in some areas, wildfires, melting permafrost, warmer temperatures, and power outages. May be used to describe a community of people, a physical property, or both. www.resilientdesign.org/resilient-design/

Resilient flooring: An organic floor-surfacing material made in sheet or tile form or formed in place as a seamless material of which the wearing surface is non-textile. These products are characterized by having some elasticity (when compared with hard-surface flooring, like wood or stone) and are typically able to recover from strain or deformation caused by compressive stress. Includes linoleum, cork, rubber, and polymeric products. https://rfci.com/about-the-industry/

RESNET (Residential Energy Services Network): An ENERGY STAR Home Certification Organization (HCO), RESNET is a national nonprofit membership corporation that is also a recognized standard-making body for national energy-efficiency rating and certification programs. www.resnet.us

Retention basin: An artificial pond or structure designed to capture, retain, and treat stormwater runoff. Retention basins are designed to permanently hold water without an engineered surface discharge structure and provide treatment via nutrient uptake from planted vegetation.

Rock filter or Filter berm: A permanent or temporary stone structure installed to serve as a sediment-filtering device in drainage ways. Allows a pool to form in an excavated or natural depression, where sediment can settle. The pool is then dewatered through the gravel rock dam. http://water.epa.gov/polwaste/npdes/swbmp/Construction-Site-Stormwater-Run-Off-Control.cfm

Rural: Refer to the definition in Appendix A of this manual.

Scope 1 greenhouse gas emissions: Emissions from sources controlled directly by the building owner or operator, such as those from on-site fossil fuel combustion when heating water or cooking on a gas range. www.epa.gov/climateleadership/scopes-1-2-and-3-emissions-inventorying-and-guidance

Scope 2 greenhouse gas emissions: Emissions associated with purchased energy and thus controlled indirectly by the building owner or operator, such as electricity purchased from the grid or heating purchased from a district energy system. www.epa.gov/climateleadership/scopes-1-2-and-3-emissions-inventorying-and-guidance

Scope 3 greenhouse gas emissions: Emissions associated with the value chains of products and services, such as the embodied carbon of building materials purchased by an owner or developer, or the emissions from a general contractor’s equipment during building construction on behalf of the owner or developer. www.epa.gov/climateleadership/scopes-1-2-and-3-emissions-inventorying-and-guidance

Seasonal wetlands: Areas of land that are inundated by water for variable periods from winter to spring, when water is plentiful, but may be completely dry for most of the summer and fall.

Sight triangle: The area of visibility required on a corner to allow for the safe operation of vehicles, trains, pedestrians, and cyclists in the proximity of intersecting streets, rail lines, sidewalks, and bicycle paths. https://store.transportation.org/Item/CollectionDetail?ID=180&AspxAutoDetectCookieSupport=1

Silt fencing: A temporary fabric barrier surrounding a site to control stormwater runoff.

Silt sacks: Tube-shaped erosion-control devices.

Site energy: Energy consumed by buildings on the property, as measured at the site boundary. Comprises energy delivered to the property (e.g., gas, electricity, district heat) and energy that is both generated and used on the property — but does not include energy that is generated on the site and then exported to the grid. Aside from energy generated and consumed on the property, site energy is reflected in utility bills for operating HVAC, domestic hot water, lighting, plug loads, process loads, and all other end uses in buildings. Site energy does not account for losses occurring when energy is generated or transported. See Source energy.

Slab: One type of foundation, with many variations (monolithic slabs, floating slabs, rat slabs, in conjunction with a basement, etc.), that may be above, at, or below grade. Wood frame crawl foundations are an alternative to slabs.

Social isolation: Social isolation is when a person does not have relationships or contact with others and has little- to-no social support. www.cdc.gov/social-connectedness/risk-factors/index.html

Solar hot water system: Captures, converts, and transfers heat from direct and indirect sunlight to heat an auxiliary water tank and provide hot water for a building’s occupants.

Solar reflectance index (SRI): A measure of a material’s ability to reflect sunlight (including the visible, infrared, and ultraviolet wavelengths) on a scale of 0 to 1. A SRI value of 0.0 indicates that the surface absorbs all solar radiation, and a 1.0 solar reflectance value represents total reflectivity.

Sound transmission class: Sound transmission class (STC) ratings are a single-number metric which describes how much sound is blocked from going through a product. This rating is helpful in attempting to reduce the amount of noise leaving a room. www.acousticalsurfaces.com/blog/acoustics-education/sound-transmission-class-stc-rating/

Source energy: Site energy plus the energy lost or consumed beyond the site boundary in the extraction, processing, and transport of primary fuels such as coal, oil, and natural gas; energy losses in thermal combustion in power generation plants; and energy losses in transmission and distribution to the building site. www.energy.gov/sites/prod/files/2015/09/f26/bto_common_definition_zero_energy_buildings_093015.pdf

Static service pressure: The pipeline or municipal water supply pressure when water is not flowing.

Stormwater: Excess rainwater or melted snow that runs off streets and rooftops, and over land, rather than soaking into the ground at the point of origin.

Stormwater pollution prevention plan (SWPPP): A site-specific written document required by the EPA’s National Pollutant Discharge Elimination System (NPDES) program. The SWPPP identifies potential sources of pollution and describes how a project will prevent pollution runoff during the construction process. See also Erosion control plan.

Straw bale: A bound block of straw and organic material used as an erosion control measure. Straw bales can also be used a bio-based insulation and/or structural material in low-rise construction.

Substantial rehabilitation: Refer to the definition in Appendix A of this manual.

Supportive housing dwelling units: Permanent housing with attached intensive services targeted to populations that have special needs, including people who are currently or formerly homeless; those with serious, chronic mental health issues; people in various stages of recovery from substance abuse; people with HIV/AIDS, or physical or developmental disabilities; the formerly incarcerated; the frail elderly; homeless or emancipated youth; victims of domestic violence; and other groups that would not be able to live independently and maintain housing without intensive support. Permanent supportive housing is commonly abbreviated as PSH.

Swale: A shallow, grass-covered channel that helps slow stormwater runoff and facilitate infiltration — relying, in contrast with a Bioswale, on natural conditions for basic conveyance and infiltration rather than intentional engineering.

Tenant-in-place rehabilitation: Occurs when planned construction activity will take place during daytime hours, requiring tenants to leave their homes for several hours on one day or for several days, but allowing tenants to return to a safe and functional dwelling unit every night with a working bathroom, working kitchen, and space conditioning, as applicable.

Thermal pollution: The release of excess heat or cold into the environment, commonly from construction or industrial processes.

Tiers: Earthen embankments that reduce erosion by slowing, collecting, and redistributing surface runoff to stable outlets that increase the distance of overland runoff flow.

Title 24: The building energy-performance standards for the state of California. www.energy.ca.gov/title24/

Transit ride: An opportunity to take a transportation line or route from a permanent, scheduled stop along a defined route of one form of public transportation (bus, rail, or ferry).

Universal design: The design of products and environments to be usable by all people, to the greatest extent possible, without the need for adaptation or specialized design. The principles of universal design are 1) equitable use, 2) flexibility in use, 3) simple and intuitive use, 4) perceptible information, 5) tolerance for error, 6) low physical effort, and 7) size and space for approach and use. https://disabilityandmultimodality.wordpress.ncsu.edu/universal-design-ud/

Usable roof space: The total usable roof space is calculated as the horizontally projected gross roof area less the area covered by skylights, occupied roof decks, rooftop equipment, vegetated roof areas, and mandatory access or setback areas required by the International Fire Code (IFC).

Vapor profile: Vapor profile is an assessment of the vapor permeabilities of each component in a building assembly (a wall, ceiling, or roof). This assessment determines the assembly’s drying potential and its drying direction. The vapor profile shows whether the building assembly protects itself from getting wet and how it dries when it gets wet.

Vapor retarder: The International Residential Code (IRC) defines vapor retarders as Class I, II, or III based on how permeable they are to water vapor: The lower the permeability, the less water vapor will pass through the vapor retarder.

Vehicle-share program: A private system in which a company or a group of individuals share vehicles on a reservation basis and pay for use based on time or mileage. To qualify under Criterion 2.6 Transit, Mobility, and Walkability, a vehicle-share program must have an established formal agreement among participants.

Ventilation: The process of supplying outdoor air to, or removing air from, an interior space by natural or mechanical means. Such air may or may not have been conditioned.

Virtual power purchase agreement (VPPA): A financial structure allowing a buyer to fund development of new clean-energy capacity by purchasing the RECs for a new energy project. A VPPA differs from a physical PPA because the buyer continues to procure retail energy directly from the local grid through a utility. The buyer owns the environmental attributes of the clean energy by virtue of owning the RECs, while the owner of the energy project sells the energy itself on the open market. https://rmi.org/insight/virtual-power-purchase-agreement/VOCs (volatile organic compounds): A large group of carbon-based chemicals that easily evaporate (or “off-gas”) at room temperature, causing indoor emissions that can continue for extended periods of time after building materials have been installed. Exposure to certain VOCs in our homes can harm our health, depending on how much we breathe in and how often. www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality

Walk distance: The distance a pedestrian must travel between origins and destinations without obstruction, in a safe and comfortable environment on a continuous network of sidewalks, all-weather-surface footpaths, crosswalks, or equivalent pedestrian travel areas. Any crossing of a street with speeds at or greater than 30 miles per hour requires controlled crossing (e.g., a stop sign or stop light).

Weather-based irrigation controller (WBIC): An automated device that uses current weather data to operate an irrigation system based on local weather, landscape conditions, and plant watering needs rather than on a preset, fixed schedule. www.epa.gov/sites/production/files/2017-01/documents/ws-products-minireport-irrigation-controllers.pdf

Weekend service: When a public transit service (bus, rail, or ferry) is available to riders on Saturday and Sunday. Employer-assisted vanpools and dial-a-ride programs are examples of qualifying weekend service for Criterion 2.6 Transit, Mobility, and Walkability.

Well-being: The presence of positive emotions and moods (e.g., contentment, happiness), the absence of negative emotions (e.g., depression, anxiety), satisfaction with life, fulfillment, and positive functioning. While “health” primarily means the absence of sickness, well-being can be described as judging life positively and feeling good.

Wildland-urban interface (WUI): The line, area, or zone where structures and other components of human development meet or intermingle with undeveloped wildland or vegetative fuels. www.usfa.fema.gov/wui/what-is-the-wui/