GREEN Vocabulary

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Speak to Manufacturers, Suppliers, Installers, Architects, and Builders from a position of knowledge – at least basic knowledge. We have organized this glossary by category and alphabetically within each one to make it quick and easy for you to get the information.

This Glossary Includes Six Major Categories:

General ‘Eco-Language’
Heating & Air Conditioning (HVAC)
Water Heating

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General ‘Eco-Language’
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Energy Star
ENERGY STAR is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy helping us all save money and protect the environment through energy efficient products and practices. Results are already adding up. Americans, with the help of ENERGY STAR, saved enough energy in 2006 alone to avoid greenhouse gas emissions equivalent to those from 25 million cars — all while saving $14 billion on their utility bills.

FSC-certified wood. A key component of green building is using sustainable wood. Quickly renewable woods like bamboo are inherently sustainable. In selecting other types of hardwoods, it’s important that the wood be grown and harvested in a sustainable manner. The Forest Stewardship Council (FSC) maintains standards and certifies woods for sustainability.

Geothermal. Geothermal power uses heat from the earth to generate electricity. This is a clean, renewable power source. Geothermal energy is harnessed with a Ground Source Heat Pump (GSHP) to tap the stored energy beneath the planet’s surface. These pumps can be used to provide heating, cooling, and hot water for residential and commercial buildings.

LEED. LEED is an abbreviation for Leadership in Energy and Environmental Design. The LEED rating system was designed by the U.S. Green Building Council and is the standard for the design, construction, and operation of green buildings. LEED started in the commercial building sector, and a rating system for residential construction is in the works with a pilot program in 2007. Architects and builders often refer to themselves as LEED AP; the AP stands for Accredited Professional. This means they have passed the LEED exam and are well-versed in the program’s standards.

Native landscaping. Selecting plants indigenous to your area means they’re better adapted to the local climate, use appropriate amounts of water, resist local pests, and provide food for area wildlife.

Runoff. The waste water that flows from our gardens, lawns, driveways, and streets into our sewer systems carries various pollutants, including fertilizers and pesticides from our yards. The water eventually travels into rivers and oceans where they degrade water quality for humans and animals. To reduce runoff, home owners can make sure they don’t over-water their lawns or accidentally water their sidewalks and driveways. Permeable stone pavers in driveways also help curb runoff.

Solar PV/ Solar Water Heaters. Solar PV stands for Solar Photovoltaic, which are the panels used to create electricity. PV cells are comprised of semi-conductors, most often made of silicon, which convert sun power into electricity. These are different from (and more expensive than) solar water-heating systems. A solar water-heating system is fairly simple with the solar panels typically installed on a roof. The sun then heats the panels; the solar collectors heat a fluid in pipes held in the interior of the panel boxes, and the fluid is transported into the house where it heats water in a storage tank.

Sustainable/Sustainability. Sustainability refers to meeting present needs without compromising the ability of future generations to meet their needs. This involves using, re-using, and conserving natural resources to do the least harm to the natural environment. It’s now used almost interchangeably with “green” and “eco-friendly.”

Solar Heat Gain Coefficient (SHGC) A measure of how effective a window or door is at keeping out solar heat. It is calculated by taking the amount of solar heat that enters a room through a window or door (center glass), divided by the amount that is actually contacting the exterior of the unit. The lower the value, the better the unit keeps out solar heat.

VOC. An abbreviation for Volatile Organic Compounds, VOCs are emitted as gases from various solids and liquids like wall paint, furniture, and household cleaning supplies. Many chemicals are harmful to human health; some are carcinogenic. But no- or low-VOC products now available represent good non-toxic replacements.


Heating & Air Conditioning (HVAC)

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ACH stands for Air Changes per Hour. It is the number of times in one hour that the air in your house is completely replaced with outside air.

The AFUE, or Annualized Fuel Utilization Efficiency, is the ratio of the total useful heat your gas furnace delivers to your house to the heat value of the fuel it consumes.

Btu, short for British Thermal Unit is a unit of heat energy. One Btu is the amount of heat needed to raise the temperature of one pound of water 1°F. To get a rough idea of how much heat energy this is, the heat given off by burning one wooden kitchen match is approximately one Btu.

The transfer of heat through a solid material.

The transfer of heat by air flow.

Coefficient of Performance, COP, is the ratio of energy input to heating capacity. This is the instantaneous measurement of the heating performance of your heat pump. It is comparable to knowing how many miles per gallon of gasoline your car gets when it is going full speed. You can find the COP on the nameplate of your heat pump.

Energy Efficiency Ratio, EER, is the instantaneous measurement of the cooling efficiency of your air conditioner or heat pump. The higher the EER for your air conditioner or heat pump, the more efficient it is.

Heat Pump
A heat pump is basically an air conditioner with a reversible valve that allows it to operate in reverse, removing heat from your house and shunting it outdoors in the summer, and removing heat from outdoor air and shunting it into your house in the winter. Because heat pumps do not actually create heat—they just move it from one place to another—heat pumps are more efficient than other forms of heating.

The Heating Seasonal Performance Factor, HSPF, is an efficiency rating for heat pumps. It is a measure of the average number of Btu of heat delivered for every Watt-hour of electricity used by the heat pump over the heating season. It takes into account variations due to weather conditions over a season. HSPF is comparable to knowing how many miles per gallon of gasoline your car got, averged over the entire year.

Programmable Thermostat
A thermostat with the ability to record different temperature settings for different times for your heating and/or cooling equipment. Programmable thermostats can be electronic, or mechanical.

The transfer of heat directly from one surface to another (with out the intermediate air acting as a transfer mechanism).

The Seasonal Energy Efficiency Ratio, SEER, measures the average cooling efficiency, over the entire cooling season for your air conditioner or heat pump.

System Capacity
System capacity is a measurement of the total amount of heat or cooling your furnace, heat pump or air conditioner can produce in one hour. This amount is reported in Btu/hr on the nameplate of your equipment.


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Cellulose insulation is made from wastepaper, such as used newspaper and boxes. It is shredded into small particles, and chemicals providing resistance to fire and insects are added. Cellulose insulation is dusty and brown, with flat particles, on which you can frequently find legible print.

Fiberglass is the most familiar type of insulation. It is spun from molten glass, and is pure white in its virgin state. Additives and binders often color the fiberglass, with pink and yellow being the most common. Fiberglass comes in rolls, batts and as loose insulation which is blown into place.

Insulation is a substance that resists the transfer of heat, generally by incorporating small pockets of air. Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness and density.

Radiant barrier
Radiant barriers are thin sheets of highly reflective material, like aluminum, which reduce heat transfer from thermal radiation across the air space between the roof and the attic floor. Radiant barrier do nothing to prevent heat transfer by conduction or convection.

Rigid Boards
Rigid boards are fibrous materials or plastic foams pressed or extruded into board-like forms. These provide thermal and acoustical insulation, strength with low weight, and coverage with few heat loss paths.

Dirty grey, although the color can range through green and brown as well. Rockwool looks like old wool with dark flecks, and you can often find what looks like sand or small pebbles underneath the insulation. Rockwool is spun, like fiberglass, from the slag from refining metals. The debris that settles underneath the insulation is remnants of the slag, and condensed droplets of metal.

R-value is a measurement of heat resistance. It is the inverse of the U-value, so the higher the R-value the better the insulation resists heat transfer. Many factors can affect the R-value of insulation, including the type of insulation, and the age of the insulation.

U-Value is a measurement of heat flow. The lower the U-value the more slowly the material transfers heat in and out of your home.

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Color Rendition or CRI
The CRI rates the ability of the bulb to render an object's true color when compared to sunlight. Look for lamps with a CRI of 80 or higher.

Color Temperature or CCT
The CCT refers to the color objects emit when heated to a certain temperature on the absolute temperature scale (Kelvin). The lower numbers correspond to reddish color and the higher to blue-white color. For color similar to incandescent lighting look for CCTs around 2700.

Compact Fluorescent Lamps
These fluorescent lamps are small, and are designed to fit in regular lamp sockets. They do require a special fixture. The electronic ballast-based fluorescents are more efficient, and produce better light than the older magnetic ballast models.

The physical item referred to as a "lamp," i.e., "table lamp" or "floor lamp," is called the fixture by the lighting industry.

Fluorescent lamp
Fluorescent lamps are up to five times more efficient than incandescent lamps, and last up to twenty times longer. They require a special fixture. Electronic ballast fluorescents are a new efficient improvement over the traditional magnetic ballast fluorescents. Fluorescent lamps are available as straight tubes, U-shaped tubes, circular tubes and compact fluorescent lamps.

Incandescent lamp
The most common source of light, glass bulbs with a filament inside. Approximately ninety percent of the energy consumed by an incandescent lamp is given off as heat rather than light.

The lighting industry uses the term lamp to refer to the source of light, the light bulb itself, not the fixture where the light bulb is located.

A lumen is the total amount of light emitted from a source. Lumens are typically used to rate the output of lamps.


Water Heating
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Energy Factor
The efficiency of storage water heaters is indicated by its Energy Factor (EF), which is based on an average hot water consumption of 64 gallons/day. The higher the EF, the more efficient the water heater.

First-hour rating
The ability of a water heater to meet peak-hour demands. It measures how much hot water the heater will deliver during a busy hour. The first-hour rating accounts for the effects of tank size, and how quickly cold water is heated.

Peak-hour demand
The maximum water usage, in gallons/hour, during the time of day when your family is likely to use the greatest amount of hot water.

Recovery efficiency
How efficiently heat from the heat source is transferred to the water. The hot water tank, the recovery efficiency for a fuel-fired water heater must be 1 or less (it represents the fraction of energy in the fuel that actually makes it into the hot water). A reasonable value to use for recovery efficiency is 0.76. If you want the exact value for your model, you might have success looking at the GAMA web site (this is the water heater trade organization). Go to and click on water heaters. You can enter your exact manufacturer and model number and find out the exact specifications for that unit. Note that they provide recovery efficiency as %, but you need to divide by 100 to get a value between 0 and 1 to input to HES.

Standby losses
Storage water heaters constantly loose heat by conduction through the walls of the tank, and through the first few feet of water pipes. To reduce standby losses, insulate the tank, the first two feet of the cold water inlet pipe, and the first three feet of the hot water outlet pipe.

Storage capacity
The gallons of hot water a storage water heater can hold in the storage tank.

Water Heater Temperature
Water heaters have a thermostat which controls the temperature of the water. Many people have their water heater thermostat set at 140°F, but if you lower the temperature of your water heater to 120°F (about midway between the "Low" and "Medium" settings) you will save money and the environment.

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Condensation is the buildup of water droplets on a cold window pane. This can occur on the inside of single pane windows, and in between the panes of multiple pane windows. Condensation on single pane windows can damage windowsill and wall surfaces if extensive. Condensation between the panes of multiple pane windows indicates a problem with the seal between the panes.

Frame material
Wood, vinyl or fiberglass frames conduct less heat than aluminum frames, increasing window efficiency.

Gas fill
An inert gas such as argon is used instead of air between the window panes. Inert gases have a much better insulation value than air.

Low-E glazing
A special window coating that helps prevent the warmth inside your house from escaping through the glass in the winter (pyrolitic). A variation (solar control) is designed to block heat from the summer sun. Low-E coating can reduce energy use by up to 35 percent.

Multiple layers of glazing
Each layer of additional glazing improves the efficiency of a window, as dead air between panes prevents conduction of heat. Proper spacing of panes prevents convection loops from occurring between the window panes, further reducing heat loss.

R-value is a measurement of heat resistance. It is the inverse of the U-value, so the higher the R-value the better the window resists heat transfer.

Thermal break
A material that doesn't transmit heat well, such as plastic, sandwiched inside the metal parts of the frame. This reduces the heat being transferred through the frame. Thermal breaks can be used in the spacer between panes of glass in multi-pane windows as well as in the main body of the frame.

Tinted glazing
Tinted glass and tinted window films reduce the amount of the sun's heat entering the building. The shading coefficient (SC) of a window is the amount by which the window reduces heat gain. The lower the shading coefficient, the less solar heat is admitted. New glazings reduce the heat gained by your house without reducing visibility as much as older tinted glass and films. Visible light transmittance (VLT) is the measure of the amount of light that comes through the window. Select a window with a VLT of 0.60 or higher.

U-Value is a measurement of heat flow. The lower the U-value, the more slowly the window transfers heat in and out of your home.

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