Energy Efficiency: The Ultimate Glossary


Air Barrier

Air barriers are barriers that separate the inside space from the outside. Generally, air barriers are the ceilings, walls and floors.

Air Duct

Air Duct improve energy efficiency

An air duct is a round or square tube that circulates air from a heating and cooling system around a room (a supply duct) or returns air from the room to the heating and cooling system (a return duct).

Air Leakage

Air leakage is outside air that enters a house through cracks or openings. This is different from ventilation, which is controlled fresh air entering a home to reduce moisture and odour.

Avoided Cost

Avoided cost is the value of gas or electricity that would need to be used in the absence of energy efficiency measures.


Baseline Data

Baseline data is a measurement of the efficiency of a building taken before interventions begin to increase the energy efficiency.

Blower Door Test

A blower door test determines the energy efficiency of a building

A blower door test is a test done to measure the airtightness of a building and locate air leakage. During the test, an expert mounts a powerful fan to the frame of an exterior door. The fan blows air in and out of the building, changing the air pressure and forcing air through any gaps. Based on the air pressure and openings, technicians determine the airtightness of a building and areas that need to be sealed.

The Home Winterproofing program, which we deliver on behalf of Enbridge Gas, can include a free blower door test to determine a home’s airtightness. 

Building Envelope

A building envelope is all the components of a building that separates the indoors from the outdoors—for instance, exterior walls, foundations, roofs, windows and doors.


Carbon Dioxide

Carbon dioxide is an odourless, colourless, non-poisonous gas made up of carbon and two oxygen atoms. This gas is a by-product of fossil fuel combustion and causes global warming by trapping heat in the atmosphere.


Diagnostic Test

A diagnostic test measures the energy efficiency of a building using specialized testing equipment, such as a blower door test. Diagnostic tests are usually done before and after the installation of energy efficiency upgrades to measure the difference.


Energy Assessment

An energy assessment is a study done to determine where, why and how energy is used in a home. Also, an energy assessment identifies opportunities to improve the energy efficiency of a home.

Our Home Insulation and Retrofit Services team can complete an energy assessment of your home to determine its efficiency. Visit our website to receive a free quote today.

Energy Advisor

An energy auditor evaluates a home's energy efficiency

An energy advisor is a professional who conducts energy evaluations on homes to determine their efficiency.

Energy Conservation

Any action or behaviour that results in less energy—for example, turning off lights when leaving a room or doing laundry at a lower temperature.

Energy Efficiency

Using technology that requires less energy to perform the same task—for instance, switching to LED bulbs, which use significantly less energy than incandescent bulbs.

Energy Star

An internationally recognized energy efficiency standard. Products and homes that are certified as Energy Star meet the highest standard of energy efficiency.


Greenhouse Gas

Greenhouse gases trap the sun’s heat in the earth’s atmosphere, warming the planet. This process is known as the greenhouse effect, and common greenhouse gases include carbon dioxide and methane.


Heating, Ventilation and Air Conditioning System (HVAC)

HVAC system

A heating, ventilation and air-conditioning system is a system that provides heating and cooling for residential and commercial buildings.



Insulation is material that traps warmth inside a building when it’s cold outside and decreases the amount of heat entering the building when it is warm.

To learn more, read our detailed guide to insulation.



A kilowatt is a unit of power used to quantify the rate of energy transfer. A kilowatt is equivalent to one thousand watts.


A kilowatt-hour (kWh) is a unit of measure of energy, typically applied to electricity. A kilowatt-hour is equal to the energy used at a rate of 1000 watts over an hour.


Light-Emitting Diode

LED lightbulb improve energy efficiency

A light-emitting diode (LED) bulb is a highly efficient lightbulb. They are more energy-efficient and cost-effective than other types of bulbs.

To learn more, read our guide to LED lightbulbs.


Natural Gas

Natural gas occurs naturally in underground deposits. It is made primarily of methane and other hydrocarbons and is fuel for electricity generation and space heating.



Retrofitting is the process of adding new technology to an existing building to make it more energy-efficient. For more information, read our guide to retrofitting a building to be more energy efficient.


Smart Thermostat

Smart thermostats improve energy efficiency

A smart thermostat is a thermostat that you can control remotely through internet-connected devices such as phones, tablets, and smart speakers. Smart thermostats allow you to schedule and modify the temperature of your home remotely.

To learn more, read our detailed article on smart thermostats.



Weatherization involves upgrading a home to make it more air-tight by sealing air gaps and adding insulation.



Weatherstripping is an energy efficiency measure where air leaks around doors and windows are sealed using foam or an adhesive.