Occupancy sensor

A monitoring device, commonly connected to a room’s lighting but also occasionally to heating or ventilation, that shuts down these services when the space is unoccupied, thus saving energy.

Off-gas

The emitting of fumes into the air. Most new paints, carpeting, and many other building materials typically offgas chemical compounds which are unpleasant to breathe and may be hazardous to occupant health. Also known as out-gas.

On-demand hot water

(See Tankless water heater).

On-site stormwater management

Building and landscape strategies to control and limit stormwater pollution and runoff. Usually an integrated package of strategies, elements can include vegetated roofs, compost-amended soils, pervious paving, tree planting, drainage swales, and more.

Operating costs

Costs directly related to the operation, maintenance, repair, and management of a property and the utilities that service it. Includes insurance, property taxes, utilities, maintenance, and management expenses.

Operations and maintenance manual (O&M manual)

Manual developed to assist building occupants in maintaining and operating a green building and its features. Many features’ effectiveness can be reduced or eliminated by the actions (or inaction) of occupants and maintenance crews. An operations manual usually includes product and system information and warranties, contact information, and other information required for effective operations and maintenance.

Organic compound

Vast array of substances typically characterized as principally carbon and hydrogen, but that may also contain oxygen, nitrogen and a variety of other elements as structural building blocks.

Organic matter

Materials of animal or vegetable origin.

Orientation

The relation of a building and its associated fenestration and interior surfaces to compass direction and, therefore, to the location of the sun. It is usually given in terms of angular degrees away from south, i.e., a wall facing due southeast has an orientation of 45 degrees east of south.