Glossary

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R-Value
Measure of the resistance of a material to heat flow. The higher the number, the greater the resistance to heat flow.

Radiant Barrier
A material that reflects radiant heat, typically a foil-faced or foil-like material used in roof systems. Used properly in some climates, it can reduce cooling requirements but has no positive effect on heating requirements.

Radon
A radioactive gas that occurs naturally, but when trapped in buildings can cause health problems such as lung cancer.

Rainwater Harvesting/Catchment
A method of collecting rain and snow melt in a cistern for reuse.

Raised Floor
In underfloor air distribution systems, a platform structure typically consisting of concrete-filled steel floor panels supported on pedestals 8 to 18 inches above the concrete structural floor slab. Each panel can be independently removed for access to the underfloor plenum containing the air delivery system, electrical cables, and other services.

Rapidly Renewable
Materials that are not depleted when used. These materials are typically harvested from fast growing sources and do not require unnecessary chemical support. Examples include bamboo, flax, wheat, wool and certain types of wood.

Recharge Area
An area where rainfall can infiltrate into an aquifer.

Recirculated Air
Return air that is diverted from the exhaust route, mixed with incoming outside air, conditioned, and delivered to the conditioned space. Recycling the air circulating through an HVAC system reduces energy requirements.

Reclamation
Restoration of materials found in the waste stream to a beneficial use that may be other than the original use.

Recommissioning
Also called Tuning, a re-calibration of a facility's operating systems.

Recyclable
Commonly referred to as the ability of a product or material to be recovered from, or otherwise diverted from, the solid waste stream for the purposes of recycling. FTC guidelines indicate that a product may not be advertised as "recyclable" unless a viable, active reclamation system exists, that is available to a majority of end users, and collects and processes the product for recycling.

Recycled Content
Materials that have been recovered or otherwise diverted from the solid waste stream, either during the manufacturing process (pre-consumer), or after consumer use (post-consumer). Pre-consumer material does not include materials normally reused by industry within the original manufacturing process.

Recycling
Process by which materials that would otherwise become solid waste are collected, separated or processed and returned to the economic mainstream to be reused in the form of raw materials or finished goods.

Refrigerant
A liquid capable of vaporizing at a low temperature and used in AC systems.

Relative Humidity
Ratio of the amount of water vapor in air at a specific temperature to the maximum capacity of the air at that temperature.

Remanufacturing
A recycling concept by which an existing product has its useful life extended through a secondary manufacturing or refurbishing process such as remanufactured systems furniture.

Remediation
Efforts to counteract some or all of the effects of pollution after it has been released into an environment.

Renewable Energy
An energy source that, from an Earth perspective, is continually replenished.

Renewable Resources
A resource that can be replenished at a rate equal to or greater than its rate of depletion; i.e., solar, wind, geothermal and biomass resources.

Requirements and Submittals
LEED Green Building Rating System component that specifies the criteria to satisfy the prerequisites or credit, the total number of points available, and the documentation required for the LEED application.

Resource Conservation
Practices that protect, preserve or renew natural resources in a manner that will ensure their highest economic or social benefits.

Resource Efficiency
A practice in which the primary consideration of material use begins with the concept of "Reduce - Reuse - Recycle - Repair" stated in descending order of priority.

Respirable
Particles or aerosols capable of being inhaled into the deep lung, < 3 microns in diameter.

Respirable Suspended Particles (RSP)
Inhalable particulate matter in the air.

Retro-commissioning
Commissioning performed on a facility that has been in service but not previously commissioned.

Reuse
Using a product or component of municipal solid waste in its original form more than once.

Reused Components
Structural or finish materials removed from old buildings and reused in new or remodeled buildings.

Reversible Disassembly
Reverse manufacturing, in which the removal of screws, clips, and other fasteners permits refurbishment and reuse of some or all of the components and modules of a product.

RH
See "Relative Humidity."

Risk
A measure of the probability of an adverse effect on a population under a well-defined exposure scenario.

Risk Assessment
An evaluation of potential consequences to humans, wildlife, or the environment caused by a process, product, or activity, and including both the likelihood and the effects of an event.

Risk Factor
Characteristics (i.e., race, sex, age, obesity) or variables (i.e., smoking, occupational exposure level) associated with increased probability of a toxic effect.