Green Building Terms Glossary

Alternative fuel vehicle

Vehicles that utilize fuel other than gasoline or diesel fuels. Vehicles may be electric, LPG, natural gas, bio-diesel or a hybrid of these fuels.


Abandoned, idle or underused industrial or commercial buildings where expansion or development is complicated by real or perceived environmental contamination.

Certified Wood

See FSC-certified wood

Conditioned Space

The part of a building where temperatures are controlled through heating or cooling.

Cool Roof

Specialized roofing materials designed to reflect the heat of the sun away from the building, thus reducing the cooling load and associated air conditi Dual flush toilet — These toilets have two different settings, usually 0.8 gallons for liquid removal and 1.6 gallons for full flush solid removal. On the average they use about 2,500 gallons per year, compared to a 1.6 single flush that uses about 4,500 gallons per year.

Energy Star

Introduced in 1992 by the U.S. Environmental Protection Agency (EPA) as a voluntary labeling program to identify and promote energy-efficient products to help reduce greenhouse emissions. Originally designed for computers and monitors, it has now expanded to include office products, major appliances, lighting, home electronics and more. New expanded programs now also include complete buildings such as homes, commercial and industrial buildings.

Engineered lumber

Designed to reduce the amount of material needed for framing a building. By designing away from full dimension sawn lumber, fewer large-growth trees need to be cut, and smaller dimension lumber can be assembled in various configurations to span long distances with equal or superior strength. Trusses have always been a good example of engineered lumber by using smaller dimension lumber and distributing forces more efficiently; the materials needed are a fraction of that required to span the same distances with sawn lumber.

Engineered studs

A little different from engineered lumber, usually smaller diameter stock is shredded and reassembled by forming them into nominal-sized framing materials. The material is combined with a binder and compressed into large billets that are then cut to dimensional size. Similar products have been around for many years in the form of oriented strand board (OSB) and other laminated wood beam products. An advantage of engineered studs is that they are dimensionally stable and less susceptible to warping. These studs are considerably heavier than sawn wood, cost about twice as much and may be subject to water damage.

Finger-jointed studs

Often the lumber being cut today is a shadow of the old-growth lumber of yesterday in quality, density and overall suitability for construction. However, by conserving the shorter sections of lumber and removing the undesirable wane and knots, these sections can be fitted with special splicing techniques to form longer and more dimensionally stable lumber. The application is usually limited to vertical installation because of this splicing technique.

Flow reducer

A device attached either just downstream from the water shutoff valve to a building or at the outlet of a fixture designed to reduce or limit the amount of water flow in relation to the delivery pressure from the street. Flow reducers can cut the flow of water dramatically, saving thousands of gallons each year in a dwelling or even more in larger buildings. Flow reducers are never installed on automatic fire extinguishing systems for obvious reasons.

FSC-certified wood

The Forest Stewardship Council is a non-profit organization that certifies various forests around the world exhibiting good sustainability and management practices based on a specific management criteria. The wood from these forests is often quickly renewable using hybrid timber and advanced forestry methods. Other forests are simply carefully managed by limiting the impact on both the environment and the people and demonstrating a social benefit in the process.

Granny flat

Another name for an accessory dwelling unit. Granny flats are usually attached to the main dwelling unit, but may also be detached. City regulations limit the number and size of these units.


Waste water from lavatories, showers, baths and sinks only. This water can be stored in special equipment and may then be used to water lawns, gardens or other relatively benign non-potable uses such as groundwater recharge. Water from toilets is called black water; it must be properly drained to the sewer or septic system.

Green power

Generally this is the production of electricity from environmentally friendly sources such as photovoltaic, geothermal, hydroelectric, biomass, hydrogen fuel cells, ocean energy and wind power. As with all forms of electricity generation, there are significant costs involved and in some cases undesirable byproducts such as vane noise, unsightly appearance or diversion of wild waterways. While large-scale versions of these methods are not practical within an urban environment, many homes and businesses are taking advantage of solar systems that not only make electricity but also heat water and interior environments. In the future if clean-fusion-process electrical production can be developed, the use of fossil fuel generation can be greatly reduced or eliminated. Another advantage of green power is the reduction of carbon dioxide generation.

Green roof

A growing roof system using a specialized undercarriage for the waterproof membrane and excess water removal. Various types of vegetation in a special growing medium help to replace displaced vegetation in the building footprint as well as greatly reduce the heat-island effect of a roof, especially in hot climates. Depending on the species of plants chosen, significant increases in watering requirements may be required. On the other hand, on large walkable roofs, pleasing garden atmospheres can be created, and watering requirements can be reduced by the installation of stormwater-recovery systems. Green roofs can also regulate the flow of excessive stormwater by metering the release of the water from the roof area.

Heat-island effect

As cities replace natural landscaping with streets, buildings and other infrastructure, the average ambient temperatures within these areas begin to rise, as much as 10 degrees F higher than in less developed rural areas. This increases the need for cooling energy; can exacerbate pollution problems; and may contribute to the problem of global warming. Heat islands can be effectively reduced by shading streets with trees and improving the urban forest overall. Ironically, heat islands can be beneficial in cold climates in the winter by reducing heating demands; however, the overall effect is much more on the negative side.


The acronym for heating, ventilation and air conditioning.

Hydronic radiant heating

A system of heating a building by using a central boiler or hot water heater to distribute heat through a system of tubes just under the flooring surface. A single heater may be zoned to provide independent heat to different parts of a building as needed. The heating system is efficient and provides a comfortable conditioned room.


Indoor air quality. As buildings become tighter, indoor air quality suffers unless specific measures are taken to improve the exchange of fresh air without sacrificing heating/cooling economy.


The entrance of exterior unconditioned air through various means into a building. Under the older codes, a dwelling generally had the equivalent of a 4-foot-diameter hole in infiltration leakage. While newer buildings greatly improve this leakage, other problems such as poor indoor air quality and transpiration of moisture to internal stud bays now occurs and must be remedied with such items as air-to-air exchangers and specialized waterproofing techniques.

Insulated concrete form (ICF)

Expanded polystyrene foam (EPS), high-density polyethylene (HDPE), polyvinyl chloride (PVC) or polycarbonate (PC) is cast or injection-molded in various panel shapes and become the permanent forming method for reinforced concrete walls. These highly insulated forms have various thermal resistance values (R-values) ranging from about R-22 up to about R-40. In hot or cold climates, these forms can significantly reduce heating and cooling loads. The panels are usually pre-engineered and produce a fire resistive barrier up to 4-hour rated.

Light pollution

Light pollution comes from many sources, but generally from unshielded lighting that allows light on a site to escape. Shielding cannot effectively reduce some lighting, such as parking-lot or street lights that reflect off structures and bounce light away from the site. However, simple hooding of the "naked" light source directing the light to the ground or limiting its outward influence can significantly reduce light pollution.

MDF — medium density fiberboard

An engineered panel product that can be used for such things as cabinets and wall panels, while other MDF products can be shaped into moldings, ceiling tiles, flooring, interior doors and a variety of other uses. Exterior grades of MDF can be made into garage doors, sheds and other outdoor applications. A middle grade called "moisture resistant MDF" can be used externally but must be protected from water intrusion by sheltering.

OSB — oriented strand board.

A manufactured wood structural panel generally cut to the size of standard plywood sheets and in various thicknesses. It is made by chipping very specific species of wood from smaller growth trees and "orienting" the grain of these chips into a pattern that provides optimum strength in the panel. The chips are then saturated with glue and pressed into production sizes.

Ozone depletion

Destruction of the earth's ozone layer by the photolytic breakdown of chlorine and/or bromine containing compounds (chlorofluorocarbons or CFCs) which catalytically decompose ozone molecules. Commonly used as refrigerants, CFCs have been found to damage the stratospheric ozone layer, creating holes and allowing harmful ultraviolet radiation to leak through.

Permeable paving

Pavement that allows the passage of water into the ground. There is a variety of permeable pavement method, including spaced pavers with soil infills and newer specialized asphalt and concrete applications that actually allow rainwater to pass through the surface and help to keep the water table from being depleted.

Photovoltaic panel

Either roof- or ground-mounted to collect solar energy and, through the use of special solar voltaic cells, convert the energy to direct current electricity. A special controller converts this electricity to alternating current, making it usable in most residential and commercial applications. Electricity made in this fashion can be stored in batteries for later use; consumed as it is made to help offset the overall electrical use of a building; or placed into the commercial electrical grid for use in other locations. These panels only work when there is light, but surprisingly produce electricity even on cloudy days.

Pressed earthen block

Like adobe, pressed (or compressed) earthen block is made from a mixture of soil and aggregate with no chemical additives. Often machine manufactured at the construction site. Because there is relatively no quality-control routine compared with other types of manufactured block, its use may be limited, especially in high seismic zones. Careful engineering will be required to use this material in structural applications.

Usually a foil-faced plywood, manufactured with proprietary methods and used as the roof sheathing under the roofing material itself. The reflective surface of the material actually reflects heat away from the roof back through the shingles without significantly increasing the thermal load on the material (usually only 2 to 5 degrees). Other methods are rolled materials that are applied after the regular plywood or OSB sheathing. Both materials can reduce attic and subsequent living area cooling loads significantly. Some manufacturers claim up to 97 percent effectiveness.

Rammed earth

A soil-cement mixture that is rammed into forms to created walls that are generally 18 to 24 inches thick. The screened soil is usually engineered to assure the correct clay-to-sand ratio and is mixed with about 3 percent cement; sprinkled with water to provide cohesion; and compacted in 5- or 6-inch lifts to a relative density of around 120 to 130 pounds per cubic foot. Often concrete tie beams are incorporated to help stabilize the lateral strength of the material. The material is relatively labor-intensive and the cost of a rammed earth house can be significant.

Reclaimed lumber

Lumber reclaimed by "deconstruction" of a building or structure. This lumber can be used for non-structural applications such as paneling and flooring and, if re-graded, can be used in structural applications. Major advantages include usually higher quality surface characteristics (it often came from tight-grained old-growth lumber), less cost than new lumber and reduction in landfill wastes (although it can easily be mulched). Major disadvantages are that it is fairly labor-intensive to clean up and, after many years of drying, is often very hard to nail. It may need to be predrilled, increasing installation cost.

Recycled-content aggregate

Crushed and reused concrete salvaged from demolition projects. Some can be introduced as a percentage of the aggregate in new concrete, while some can be used for roadbed underlayment. The actual use of the product is limited to imagination and the structural requirements of the project. Use of the material also reduces the amount of new aggregate that must be mined from quarries and the associated environmental concerns associated with the operation.

Recycled-content material

Products manufactured using post-consumer materials such as plastic, fiber, wood and glass. Deconstruction of various structures can also produce a variety of "raw" materials to create new products from — everything from tiles to carpeting to composite flooring materials and beyond. Recycled-content materials help to reduce the need for new raw materials and the accumulation and manufacturing processes involved.

Recycled-content steel studs

Most new light-gauge metal studs are manufactured from a combination of new and recycled steel. About 66 percent of the total make-up is recycled content. Considering that the production of new steel is one of the highest embodied energy manufacturing processes, the use of recycled steel not only redirects a virtually ever-reusable resource, but can reduce significantly the impact on other environmental concerns. The use of light-gauge metal studs on interior infill and demising walls lessens the amount of wood studs needed for construction. However, more specialized skills are needed to install the material properly.

Roofing materials, safe and durable

This can have a variety of definitions depending on one's point of view, but essentially these are roofing systems designed to last a significantly longer time to delay having to remove them and sending them to the landfill. Modern fiberglass roofing materials now carry warranties between 20 and 40 years. Of course slate, concrete and fired clay tiles can last significantly longer. Additionally, a safe roof generally refers to a fire-safe roof.


The energy efficiency at which air conditioners produce cooling. SEER, which stands for seasonal energy efficiency ratio, is the amount of cooling produced (BTU) divided by the amount of electricity (watts) used. The higher the SEER, the greater the efficiency.

Solar water heating

Generally this is a method of heating domestic water by allowing ground- or rooftop-mounted panels to collect solar rays as the water flows slowly through a series of small tubes. The heat transfer is then stored either in a potable drinking-water vessel (your water heater) or introduced into a closed-loop transport system to provide environmental space heating.

Straw bale

This is a methodology developed to use special tightly bound straw bales as either bearing or infill walls in a variety of structures including homes. The straw bale system was an offshoot of the Nebraska straw house, where their construction more than 100 years ago solved the basic problem of no lumber. The bales provide a substantial increase in insulation value, but their installation can be rather labor-intensive.

Structural bamboo

Bamboo as a construction material has many uses. Because the material is very hard, it has recently found a niche as flooring material. However, the material is also very strong and with new methods of handling the material, structural uses of bamboo are finding their way into the construction industry. They can be derived into trusses, supporting poles and simple beams. However most building departments are not familiar with the capacity of the material, and builders will have to supply significant engineering and detailing to satisfy plan check requirements.

Sustainable deck materials

Most of us are familiar with the wooden deck. However, new materials on the market are making a dramatic impact in the form of recycled content decking and railing systems. Usually manufactured with recycled plastics, wood chips and binders, the materials hold up well to hostile environments and generally outlast even naturally durable woods such as redwood and cedar. The intent is to select materials that are sustainable or easily replaced with limited effect on the ecology. Similar to wood, these new materials are easily worked but are considerably more expensive. The trade-off is the longevity of the material. While there are variations to the support structure under these materials, treated wood is still the primary structural system.

Tankless water heater

Most of us have a 30- or 40-gallon storage water heater in our houses. Even when you are not home or sleeping, that water heater is diligent in keeping your hot water ready at all times. Modern advances in storage tank water heaters reduces the number of times it must fire to maintain temperature, but the basic operation remains the same. Tankless water heaters are designed to wait until you actually need the hot water and on demand to fire up and raise the water temperature very quickly to operating level. The definition instantaneous is often used for these heaters and generally by the time the water clears the heat exchanger inside, it's ready for use. Additionally, these water heaters take up less space than a storage tank type. The amount of fuel needed to reach temperature quickly usually exceeds most storage types, but it reaches temperature in a lot less time and a lot less often.

Thermal Bridging

The process in which a material with poor insulation quality allows heat to pass through a material with greater insulation quality.

Title 24

Title 24 is contained in the California Code of Regulations (CCR) and is the embodiment of most of the construction and energy conservation requirements for the state. All cities and counties are mandated to enforce the requirements of Title 24.

Treated wood
  • CCA (chromated copper arsenate) — As the name implies, the chemicals used to treat wood to prevent attacks by wood-destroying organisms, such as boring insects, fungi and dry rot, contains arsenic, a rather nasty poison. Since December 31, 2003, the distribution of CCA has been severely limited and is generally not available to the average homeowner anymore. It still can be manufactured for very specific commercial applications, such as underwater saltwater pilings and cross member materials, but not for the decking, above-water bracing or railings.
  • ACQ (alkaline copper quaternary, or Quat) — This method of treatment uses copper as the primary active ingredient. While the material is effective for direct contact and above-ground protection, it is highly corrosive to fasteners and fittings, and special precautions must be taken in their selection (usually hot-dipped galvanized or stainless steel fasteners) and the handling of the material.
  • CA (copper azole) — Like ACQ, the primary active ingredient is copper. While not quite as corrosive as ACQ, the material does have a tendency to migrate into the soil. Again special care in selection of fasteners and handling is required.
  • DOT (disodium octaborate tetrahydrate) — DOT or simply borate- or boron-preserved wood is the least corrosive of the treatments. The material is intended for interior or protected use only and must be protected from direct water exposure, which can leach the material out of the wood. Protected in dry conditions, the borates will migrate into the wood even deeper than the initial pressure injection application over time. The material is very effective against many wood pests, including the voracious Formosan termite.
TXV (Also TEV) Thermostatic expansion valve

A TXV installed on an air conditioning system can dramatically improve the efficiency of the unit. When cooling demand is high, the valve opens up and lets more coolant pass through the indoor coils. When demand is low, the valve closes to reduce the refrigerant flow. AC units not equipped with TXVs have either a fixed orifice or capillary tube system.

Volatile organic compound (VOC)

Many of the products that we buy are made with materials that off-gas VOCs, usually in the form of formaldehyde gas, a by-product of hydrocarbon-based materials. Building materials such as particle board, plywood, adhesives, paints, varnishes, carpet, drapes and furniture are often made with formaldehyde products. Other sources include some you may not think of: tobacco, burning gas, perfume, cleaning agents, hairspray and even copy and printing machines. Degrees of exposure to VOCs can cause everything from mild symptoms such as irritated eyes, ears and throat to more severe reactions such as wheezing and lung, memory and anxiety problems. By using low-VOC products, exposures are reduced and indoor air quality is improved.

Whole-house fan

Essentially a large fan that draws hot air out of a building and replaces it with cooler exterior air, as opposed to attic fans that only remove the hot air from the attic. Compared with an air conditioner, which can draw up to 6,000 watts, whole-house fans use about the same amount of electricity as a couple of light bulbs, or around 120 watts for smaller units up to about 700 watts for larger units. New homes of especially tight construction may need to have barometric vents installed a distance away from the exhaust intake to prevent negative pressure problems in the house, which could have an adverse effect on fuel-burning appliances. (Simply opening a couple of screened windows can also equalize the pressure.) It is important to prevent creating negative pressure around fuel-burning appliances in the house and starving them for combustion air as the fire can actually leave the firebox looking for oxygen. A good whole-house fan can reduce the interior temperature of a house by 10 to 15 degrees within about 20 minutes, as well as create a "sensible" feeling that the moving air is cooler. The exhaust intake is usually located in the highly heated attic air space, and many homes use a gravity damper system in the ceiling that opens automatically as the systems operates and then seals closed upon shut-down.

Zero water urinal

This wall-mounted urinal uses virtually no running water, with the exception of an occasion servicing to clean the unit. The units rely on simple physics: Urine has a specific gravity that is greater than a special sealing liquid. Several inches of the liquid are used to create a trap seal allowing the urine to flow into the system. The super slick surfaces do not allow material to remain behind and thus reduces odor and maintenance. The obvious advantage is a significant reduction in water usage over long periods of time. A disadvantage to steel plumbing is a build-up of salts on the pipe interiors, increasing corrosion. Careful maintenance schedules must be followed to keep systems working properly.