Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).
This certification is applied to products with 95 percent of the ingredients derived from natural sources (for instance, plants, milk, honey, beeswax, minerals); synthetic ingredients are allowed only when no viable natural alternative exists. Regardless of source, the ingredients must not pose any potential human health problem, and companies can't process natural ingredients in any way that could significantly alter their purity.
Ventilation design that uses existing air currents on a site and natural convection to move and distribute air through a structure or space. Strategies include placement and operability of windows and doors, thermal chimneys, landscape berms to direct airflow on a site, and operable skylights.
A metering and billing arrangement that allows on-site generators to send excess electricity flows to the regional power grid. These electricity flows offset a portion of the electricity flows drawn from the grid.
The characteristic of requiring no additional energy input from outside sources.
The process of removing hot air from a building during the cool evening hours, to cool elements with thermal mass within the building and flush stale air.
A powerful greenhouse gas with a global warming potential of 296 times that of carbon dioxide (CO2). Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production and biomass burning.
A resource that cannot be replaced in the environment (e.g., fossil fuels) because it forms at a rate far slower than its consumption.
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