Backdrafting

The occurrence of combustion gases from a gas appliance entering the living space instead of being drawn up the vent pipe and exiting a building. This may happen as a result of depressurization (for example when the furnace or exhaust fans are turned on).

Backflow preventer

An anti-siphoning device on a water pipe to prevent water/liquid (which might be contaminated) from backing up into the water system. For example, the end of a garden hose lying in a flower bed could become contaminated by pesticide and back into the fresh water supply, if no backflow preventer were installed. Frequently required by building codes.

Bakeout

The process by which a building is heated in an attempt to accelerate VOC emissions from furniture and materials.

Balance point

The outdoor temperature at which a building's heat loss to the environment is equal to internal heat gains from people, lights, and equipment. Surface load dominated buildings such as single family detached residences will have balance points in the 55-65 degree Fahrenheit range. Internally load dominated structures, like office buildings, may have balance points so low that the climate never overcomes their internal heat gain.

Ballast

A device used to provide the starting voltage or to stabilize the current in a circuit (as of a fluorescent lamp). May be magnetic or electronic.

BEES

Building for Environmental and Economic Sustainability: a free software tool implementing a rational, systematic technique for selecting cost-effective green building products. The technique is based on consensus standards and designed to be practical, flexible, and transparent.  BEES measures the environmental performance of building products using the environmental life-cycle assessment approach specified in the International Standards Organization (ISO) 14040 series of standards.

Benefit/cost analysis

An economic method for assessing the benefits and costs of achieving alternative health-based standards at given levels of health protection.

BIBS

Blown-in-Blanket System: blown-in-fiberglass insulation. This fluffy, white insulation will not settle in the bottom of the wall cavity, but remains where it is placed.  It is best applied in walls without voids (outlet and switch boxes).

Bicycle Storage

Covered and/or secured storage for building occupants commuting by bicycle. This amenity is considered a sustainable building technique in that it encourages human-powered transportation options. Some local governments offer subsidies or incentives to include bicycle storage in an existing or proposed building project.

Bioaccumulants

Substances that increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.

Bioconcentration

The accumulation of a chemical in tissues of a fish or other organism to levels greater than in the surrounding medium.

Biodegradable

Capable of decomposing under natural conditions.

Biodiesel

Biodiesel is a domestic, renewable fuel for diesel engines derived from natural oils like soybean oil, and which meets the specifications of ASTM D 6751. Biodiesel can be used in any concentration with petroleum based diesel fuel in existing diesel engines with little or no modification. Biodiesel is not the same thing as raw vegetable oil. It is produced by a chemical process which removes the glycerin from the oil. Biodiesel, as defined in D 6751, is registered with the US EPA as a fuel and a fuel additive under Section 211(b) of the Clean Air Act.

Biodiversity

The tendency in ecosystems, when undisturbed, to have a great variety of species forming a complex web of interactions. Human population pressure and resource consumption tend to reduce biodiversity to dangerously low levels; diverse communities are less subject to catastrophic disruption.

Biogas

Biogas is created when manure is placed in a machine called a "biodigester," designed to capture methane gas released by decomposing material such as cow manure.

Biological contamination

Contamination of a building environment caused by bacteria, molds and their spores, pollen, viruses, and other biological materials. It is often linked to poorly designed and maintained HVAC systems. People exposed to biologically contaminated environments may display allergic-type responses or physical symptoms such as coughing, muscle aches and respiratory congestion.

Biological wastewater management

Purifying wastewater in a natural or emulated wetland environment. Such systems are powered mainly by sunlight and achieve purification through the combined action of living food chains, many of which are microscopic.

Biomass

Plants and plant materials, trees, crop residues, wood and bark residues, and animal manure that can be converted to heat energy to produce electricity.

Biomass energy

The energy released from biomass when it is eaten, burned, or otherwise used as or converted into fuel.

Biome

Entire community of living organisms in a single major ecological area. There are six main biomes in the world: tundra, taiga (boreal forest); desert; tropical rainforest, savannah (grasslands); and marine.

Biomimicry (from bios, meaning life, and mimesis, meaning to imitate)

The art and science of studying and modeling nature, mimicking these designs and processes and then applying them to solve human problems. Examples include studying a leaf to invent a better solar cell, imitating the rotation of a sunflower for solar panels to track the sun and observing how water moves in whorls to design a ship’s propeller.

Biophilia

Edward O. Wilson introduced and popularized the hypothesis in his book entitled Biophilia describing "the connections that human beings subconsciously seek with the rest of life." The term literally means "love of life or living systems."

Bioremediation

The cleanup of a contaminated site using biological methods, i.e., bacteria, fungi, plants, etc. Organisms are used to either break down contaminants in soil or water, or accumulate the contaminants in their tissue for disposal. Many bioremediation techniques are substantially less costly than traditional remediation methods using heat, chemical or mechanical means.

Bioswale

A technology that uses plants and soil and/or compost to retain and cleanse runoff from a site, roadway, or other source. A vegetated depression in the soil.

Blackwater

Water from toilets, kitchen sink, or other dirty sources which may be contaminated with microorganisms or harmful bacteria.

Blower door

Diagnostic equipment consisting of a fan, removable panel and gauges, used to measure and locate air leaks and determine envelope tightness.

BMP

Best Management Practice: methods that have been determined to be the most effective, practical means of preventing or reducing pollution from non-point sources.

Borate

Borate is a mineral product derived from borax and is benign compared with most other wood treatments. Treatment of wood and insulation with borates to make it resistant to insects and fire.

Brownfield

Abandoned, idled, or under-used industrial and commercial facility/site where expansion or redevelopment is complicated by real or perceived environmental contamination.

Btu

British thermal unit: a measure of heat energy. Approximately the heat required to raise the temperature of a pound of water one degree. About equal to the energy released by the lighting of one match.

Building codes

Municipal ordinances that regulate the construction and occupancy of buildings for health and safety reasons.

Building ecology

Physical environment and systems found inside the building. Key issues include air quality, acoustics, and electromagnetic fields.

Building envelope

Building elements (e.g., walls, roofs, floors, windows, etc.) that enclose conditioned spaces and through which energy may be transferred to and from the exterior.

Built environment

All human-built structures (as opposed to the natural environment).

Building footprint

The area of a building formed by the perimeter of the foundation. Shrinking the footprint of a building allows for more open space and pervious surface on a site.

Building science

The body of knowledge focusing on the analysis and control of the physical phenomena affecting buildings, such as ventilation, construction techniques, materials, moisture, climate and temperature. This includes the analysis of building materials and envelope systems for optimizing building performance and understanding or preventing building failures.