This is a legacy version of the WELL Building Standard. Please check the latest version here.


The following pages list the sources used statistics and other material in the descriptions for the concepts and the featuresin the WELL Building Standard TM.

Acute Exposure
Single exposure to an environmental condition (not lasting more than a day). Acute exposures contrast with chronic exposures, which are prolonged and repeated. Single exposures still have effects on health.
Allergic Reaction
An exaggerated or pathological reaction (sneezing, respiratory irritation, itching or skin rashes) to substances that are without comparable effect on the average individual.
Small thin-walled air-containing compartments of the lung that are typically arranged in saclike clusters that give the tissue a honeycomb appearance and expand its surface area for the purpose of air exchange.
Alzheimer’s Disease
A type of dementia marked by the loss of cognitive ability, affecting memory, thinking and behavior generally over a period of 10 to 15 years.
Ambient Lighting
Electric lighting fixtures on walls and ceilings that contribute to the ambient amount of light in a space. This excludes light from daylight, task lamps, and sources such as computer screens.
Chronic inflammatory disease of the airways. Asthma attacks are often triggered by exposure to allergens, and during an attack the airways spasm, alternatively swelling and narrowing, causing the individual to wheeze or gasp for air.
Building Envelope
The separation between the interior and the exterior environments of a building, restricting transfer of air, water, heat, light, noise and creatures.
Chronic Diseases
Any disease that is persistent or has long-lasting health effects.
Chronic Exposure
Repeated, continuous exposure to a substance or condition over an extended period from several years to a lifetime.
Circadian Rhythms
Internal clock that keeps the body's hormones and bodily processes on a roughly 24-hour cycle, even in continuous darkness.
Collaboration Zone
A physical area within a building that encourages group interplay and discussion though its strategic layout and design.
Cone Cells
Photosensitive cells in the eye used to differentiate colors and brightness in moderate and high levels of illumination.
A group of diseases that impact the metabolism due to insufficient insulin production (Type 1) and/or high insulin resistance (Type 2), and a leading cause of death. Results in poor blood sugar control, frequent urination, increased thirst, increased hunger and other symptoms.
Environmental Product Declaration (EPD)
Quantified environmental data for a product with pre-set categories of parameters based on the International Organization of Standards (ISO) 14040 series of standards, but not excluding additional environmental information.
An opening in a surface (as a wall or membrane).
Focus Zone
A physical area within a building that encourages concentration and attentiveness to a task among occupants though its strategic layout and design.
Free Address
Ability for occupants to be able to choose their own workspace within the office or workplace.
Any of a group of unicellular, multicellular or syncytial spore-producing organisms feeding on organic materials.
Glasswork, which must be carefully designed in order to avoid excessive glare and heat gain.
Health Product Declaration (HPD)
A standard format for reporting product content and associated health information for building products and materials.
Heart Disease
A class of disease that affects the heart, arteries, capillaries or veins.
Heating, Ventilating, and Air Conditioning System (HVAC)
Equipment, distribution systems and terminals that provide the processes of heating, ventilating or air conditioning.
High Efficiency Particulate Air (HEPA) Filter
Filter which removes 99.97% of all particles greater than 0.3 micrometers and satisfies standards of efficiency set by the Institute of Environmental Sciences and Technology.
High-touch Surfaces
Surfaces that are frequently touched by building users and occupants such as door knobs, hand rails and tables. See Table A1.
A state of having regulated responses to environmental conditions to retain stability.
Immune System
The integrated body system of organs, tissues, cells and cell products such as antibodies that differentiates self from non-self and neutralizes potentially harmful organisms or substances.
An inability to develop a normal immune response, usually as a result of disease, malnutrition or medical therapy that affects the immune system.
Localized protective reaction of tissue to irritation, injury or infection, characterized by pain, redness, swelling and sometimes loss of function.
Pertaining to products within and including the waterproofing membrane.
Intrinsically Photoreceptive Retinal Ganglion Cells (ipRGCs)
Relay environmental light levels to the suprachiasmatic nucleus through the retinohypothalamic tract. Most sensitive to blue light.
An organ that plays a vital role in a range of important metabolic processes including detoxification, protein synthesis and glycogen storage.
Main Air Duct
The duct or ducts connected directly to the air handling unit.
A condition that results from insufficient nutrient intake, excess nutrient intake or nutrient intake in the wrong proportions.
Any biochemical process that occurs within an organism that is necessary to sustain life.
Metabolic Syndrome
A cluster of medical conditions or risk factors that increase the chances of developing cardiovascular disease, diabetes fatty liver disease and several cancers.
Different spectral distributions of light which produce the same response on the cones and are therefore visually identical.
Particles between 1 and 100 nanometers in size.
Nap Pod
A personal dedicated resting space optimized to offer a short but regenerative sleep.
National Ventilation Procedure
ANSI/ASHRAE Standards 62.1 is the recognized standard for ventilation system design and acceptable procedure with regards to establishing an effective ventilation system.
Neurocognitive Diseases
Diseases of the brain and nervous system.
Newly Installed
Products or materials applied or installed within one year prior to the WELL Performance Verification are considered to be newly installed.
A medical condition in which the accumulation of excess adipose tissue poses an adverse effect on health.
Occupational Safety and Health Administration (OSHA)
Outlines current indoor air quality guidelines for the workplace.
Occupiable Space
An enclosed space intended primarily for human activities. Excludes storage rooms, equipment rooms and others that are occupied only occasionally and for short periods of time.
Party Wall
A wall separating spaces under different ownership or tenancy.
An infectious biological agent such as bacteria, virus and fungus that is capable of causing disease in its host.
Permanent movable items
Items that are permanently located on site, but not fixed or stationary, for example desk or desktop organizers.
Photocatalytic oxidation (PCO)
Achieved when you combine UV light rays with a TiO2-coated filter.
Project size
The gross square footage entered for the project should include the sum of the floor areas of the spaces within the building, including basements, mezzanine and intermediate-floored tiers, and penthouses with headroom height of 7.5 ft or greater. Measurements must be taken from the exterior faces of the exterior walls OR from the centerline of walls separating buildings. The gross square footage should exclude non-enclosed (or non-enclosable) roofed-over areas such as exterior covered walkways, porches, terraces or steps, roof overhands, and similar features. Excludes air shafts, pipe trenches, chimneys, and floor area dedicated to the parking and circulation of motor vehicles.
Public Health Goals (PHGs)
Unenforced regulations developed by California Office of Environmental Health Hazard Assessment. Similar in concept to the EPA's Maximum Contaminant Level Goal (MCLG).
The energy and particles which are released during the decomposition process of atomic nuclei is called radiation.
Regularly occupied
An area that has daily, continuous use, at minimum an hour per day, by one or more individuals.
Regularly Occupied Space
An area or areas where workers or other building occupants perform focused activities inside a building for an average of one hour a day or more.
Respiratory Failure
Inadequate gas exchange by the respiratory system, with the result that oxygen and/or carbon dioxide levels leaving the heart cannot be maintained within their normal ranges.
Light-sensitive membrane found at the back end of the eyeball that receives the image produced by the lens.
Rod Cells
Photosensitive cells in the eye used to discern peripheral vision in low levels of illumination.
Sharp Internal Angle
Angles or corners of less than 135 deg.
Sick Building Syndrome (SBS)
A set of symptoms, such as headache, fatigue, eye irritation and breathing difficulties, that typically affect workers in modern airtight office buildings, and that are believed to be caused by indoor pollutants and poor environmental control.
Sleep Hygiene
Personal habits and practices that help maximize sleep quality.
Teleconference Room
A teleconference room is a space within the office that is primarily used for audio or video conferencing.
A group of cells that perform a common and specified function. At an organizational level, tissues are between cells and organs.
Extent to which a substance is harmful to a living thing.
Any outdoor pathways designated for pedestrian or biker use.
Ultraviolet Germicidal Irradiation (UVGI)
A sterilization method that uses ultraviolet (UV) light to break down microorganisms by destroying their DNA. Often used in a variety of applications, such as food, air and water purification.
Universal Design (UD)
Designing objects and spaces with aesthetically pleasing while maximizing accessibility, usability and operability regardless of the user's age, ability and other factors.
View window
A view window is offset at least 25ft from the nearest obstruction
Act of spatial problem solving.
Weather Resistant Barrier (WRB)
A sheet, spray- or trowel-applied membrane or material layer that prevents the passage of liquid water even after long or continuous exposure to moisture.
An area where an individual performs daily work-related tasks. This could comprise of a traditional seated-height desk, standing-height desk, adjustable-height desk or other work surface that is appropriate for the type of work being performed.
Physical stimuli which have an impact on the body's circadian rhythm. Examples include light, temperature and eating or drinking behaviors.
2,4-Dichlorophenoxyacetic Acid (2,4-D)
A major herbicide that is very susceptible to running off or leaching into ground and surface water sources.
A potentially toxic and potentially cancer-causing substance that can be naturally present in uncooked, raw foods in very small amounts.
Substances consisting of very fine particles of a liquid or solid suspended in a gas. For example, mist which consists of very fine droplets of water in air.
Environmental substance that can produce an allergic reaction in the body but may not be intrinsically harmful. Common allergens include pollen, animal dander, house dust, feathers and various foods.
Proteins generally found in the blood that detect and rid the body of potentially damaging organisms, such as bacteria and viruses.
A naturally occurring metal found in ore deposits; the most common form of antimony is antimony trioxide, which is used as a flame retardant.
An element found in the earth’s crust that has applications in various industrial processes, however runoff from factories, agricultural practices and natural deposits can lead to high concentrations in water.
A naturally occurring mineral that was commonly used in insulation because of its chemical and flame resistance, tensile strength and sound absorption properties. It is now known to be a leading cause of mesothelioma and lung cancer.
Among the most widely used pesticides in the United States and among the most commonly detected pesticide in drinking water.
Widely used as a precursor to various materials such as detergents, dyes, pesticides, Styrofoam, nylon and other synthetic fibers.
Any of a group of organic compounds that includes sugars, starches, celluloses and gums and serves as a major energy source to support bodily functions and physical activity. Easily digestible carbohydrates found in white bread, pastries and soda may contribute to weight gain and promote diabetes and heart disease.
Carbon Monoxide
Colorless, odorless and highly poisonous gas formed by incomplete combustion. Replaces oxygen in hemoglobin, limiting blood's ability to deliver oxygen and can lead to death.
A compound that increases the risk of developing cancer.
A disinfectant formed when ammonia is added to chlorine and is commonly used as a secondary disinfectant in public water systems.
A highly irritating, greenish-yellow gaseous halogen, capable of combining with nearly all other elements, produced principally by electrolysis of sodium chloride and used widely to purify water, as a disinfectant and bleaching agent.
Coarse Particles
Particulate matter larger than 2.5 micrometers and smaller than 10 micrometers in diameter. Often found near roadways and dusty industries.
Metallic element that enters water sources through natural deposits, but contamination most commonly occurs through corrosion of copper or brass.
A hormone that plays a primary role in stress, during which it increases blood sugar, suppresses the immune system and aids in protein, fat and carbohydrate metabolism. Also undergoes diurnal variation, playing an important role in the sleep-wake cycle.
Decorative Glazing
Coating on window surfaces purely for aesthetic purposes with no other functionality.
A naturally occurring component of crude oil and a combustion byproduct.
Fine Particles
Particulate matter 2.5 micrometers in diameter or smaller. Can be directly emitted from combustion sources such as forest fires or can form when gases emitted from power plants, industries and automobiles react in the air. Also called PM₂.₅
Flame Retardants
Chemicals used in thermoplastics, thermosets, textiles and coatings that inhibit or resist the spread of fire. Some of these chemicals have been linked to cancer, delayed development, low IQ and thyroid disruption.
Food Additives
Substances typically added to processed foods to enhance or preserve flavor or appearance.
A colorless gas compound, HCHO. Used for manufacturing melamine and phenolic resins, fertilizers, dyes and embalming fluids as preservatives and disinfectants.
A simple sugar that is found naturally in small amounts in fruits and vegetables, but which occurs in extremely large quantities in many modern foods. High fructose intake has been implicated in liver disease, inflammation, metabolic syndrome, diabetes, heart disease and cancer.
Chemicals applied to crops or structures to reduce the harmful effects of mold, mushrooms and other fungi.
A simple sugar that occurs widely in most plant and animal tissue. It is the principal circulating sugar in the blood and the major energy source of the body. Once eaten, carbohydrates break down immediately into glucose. Elevated blood glucose levels are one of the distinguishing elements of diabetes.
A non-selective herbicide used in many pesticide formulations; exposure may result from its normal use due to spray drift, residues in food crops and from runoff into drinking water sources.
Haloacetic Acid
When chlorine and chloramine are added to water and react with other organic matter to produce haloacetic acids known as a disinfectant byproduct (DBP), these can damage internal organs and the nervous system in elevated concentrations and can lead to cancer.
A group of pesticides commonly used on farms and lawns to eliminate weeds from the fields.