Habitat

The environment in which an organism or biological population usually lives or grows.

Halogen

A type of incandescent lamp with higher energy-efficiency than standard incandescents.

HCFC’s

Hydrogen chlorofluorocarbons: considered to be a contributor to ozone layer destruction. 1/20th as potent as CFC’s.

HDPE

High Density Polythene: a kind of plastic used in the manufacturing of bottles, plastic bags and other products. It produces toxic fumes when burned and is often recycled. It is resistant to chemicals and UV light.

Heat Exchanger

Device for exchanging heat present in wastewater or stale air to preheat incoming water or air. See Heat Recovery Ventilator for more information on air-to-air heat exchangers.

Heat island effect

The rise in ambient temperature that occurs over large paved areas. Strategic placement of trees can reduce this effect and reduce energy consumption for cooling by 15-30%.

Heat pump

A mechanical device used for heating and cooling which operates by pumping heat from a cooler to a warmer location. Heat pumps can draw heat from a number of sources, i.e. air water or earth and are classified as either air-source or water source units.

Heavy Metals

Metallic elements with high atomic weights; (e.g., mercury, chromium, cadmium, arsenic, and lead); can damage living things at low concentrations and tend to accumulate in the food chain.

HEPA

High Efficiency Particulate Air: encompasses specifications and testing requirements set for air filters by the U.S. Department of Energy. HEPA filters can remove at least 99.97% of airborne particles 0.3 micrometres (µm) in diameter. Particles of this size are the most difficult to filter and are thus considered the most penetrating particle size (MPPS).

HID

High Intensity Discharge: a generic term for mercury vapor, metal halide, and high-pressure sodium lamps and fixtures.

High efficiency

General term for technologies and processes that require less energy, water, or other inputs to operate. A goal in sustainable building is to achieve high efficiency in resource use when compared to conventional practice. Setting specific targets in efficiency for systems (e.g., using only EPA Energy Star certified equipment, furnaces with an AFUE rating above 90%, etc.) and designs (e.g., watts per square foot targets for lighting) help put this general goal of efficiency into practice.

Highest and best use

The conventional definition is the property use that, at a given time, is deemed likely to produce the greatest net return in the foreseeable future, whether or not such use is the current use of the property. Green development defines it as not just in terms of maximum return on investment, but also as that use which best reflects long-term social, cultural and financial values held by a community.

High-heeled truss

Roof truss design that allows space for insulation near the eaves. Conventional truss design limits the amount of insulation that can be applied in this area.

High-mass construction

Passive building strategy of constructing buildings of massive, heat-retaining materials (such as masonry or adobe) to moderate diurnal temperature swings, especially in arid climates (See Thermal storage capacity).

High performance glazing

Generic term for glazing materials with increased thermal efficiency.

High performance workspace

A workspace that is business-efficient, environmentally friendly to construct, healthy for occupants, and safer and less costly to operate.

Historic preservation

The identification, protection, and enhancement of historic resources. This includes preservation (focusing on the importance of changes and alterations to the structure over the years, which is accomplished by retaining all of the historic fabric through conservation, maintenance and repair); rehabilitation (also known as adaptive use, or using an old building for a new function, emphasizes the retention and repair of the historic integrity of a building, while allowing certain liberties to be taken in the process for the retrofit); restoration (retaining materials and features specific to the most significant time in a property's history, including the removal of any materials or features that are not indicative of that time period), and reconstruction (an authentic reproduction of a structure that no longer exists).

Hogged fuel (hog fuel)

A specific grade of ground up wood and bark. It varies in size but is generally between ½" and 6" screen size. In the Pacific Northwest, hog fuel from C&D recycling facilities is generally used to fuel boilers for the wood and paper processing or other industries.

Horizontal axis clothes washer

A washing machine designed to clean without an agitator. It uses much less water than vertical-axis models, reduces wear and tear on clothes, and result in drier clothes.

Hot roof

A hot roof may be a flat, cathedral, gable, or shed roof with no natural ventilation in the roof cavity. In a commercial roof, rigid insulation may be placed on the top of the decking. In a residence, the rafters may be packed with insulation, leaving no air space for natural ventilation of the cavity. Roofing applied over a hot roof needs to be able to withstand the roof’s higher temperatures. Potential issues can include condensation, leaks, and attic mold.

HRV

Heat recovery ventilator: exhaust fans that warm the incoming air with the heat from the outgoing air, recovering about 50-70% of the energy. In hot climates, or warm weather, the function is reversed so that the cooler inside air passes by the incoming hot air and reduces its temperature. Also called air-to-air heat exchangers. (See ERV).

HSPF

Heating Seasonal Performance Factor: the total seasonal heating output of a heat pump, in Btu, divided by the total electric energy input during the same period, in watt-hours

using a defined test methodology.

Human comfort zone

A band of dry bulb temperatures from 67.5 degrees Fahrenheit to about 78 degrees Fahrenheit and 20% to 80% relative humidity. Within that zone on the Psychrometric Chart, all weather conditions which occur are said to be conducive to thermal comfort, assuming occupants are in full shade, lightly clothed and only moderately active. All climate data that are plotted at lower dry bulb temperatures (to the left of the comfort zone) are indicative of time when solar radiation (passive heating) could be utilized to restore comfort. All hours above 67.5 F require shading (see Psychrometric chart).

Humidistat

Device for measuring relative humidity.

HVAC

Heating, Ventilation and Air Conditioning (Cooling): general term for the heating, ventilation and air conditioning system in a building. System efficiency and design impact the overall energy performance of a home and its indoor environmental quality.

Hybrid vehicle

This vehicle uses a gasoline engine to drive an electric generator and use the electric generator and/or storage batteries to power electric motors that drive the vehicle’s wheels.

Hydrogen

A nonmetallic element that is the simplest, lightest and most abundant of the elements; it is normally a colorless, odorless, flammable gas.

Hydronic heating

A space heating system that uses water circulated through a radiant floor or baseboard system or a convection or fan coil system.