Energy Retrofit Glossary

Conversations with energy retrofit experts or contractors can be riddled with industry-specific terminology. Here are some definitions that will help you understand some terms that may come up over the course of a home energy retrofit project. If you don’t see a term listed here, use the form on our Contact page to submit it to be added to this glossary.

Use the below links to navigate through the glossary

  • AFUE – Annual Fuel Utilization Efficiency. 
    AFUE is a measure of the fuel efficiency of an oil or gas heating system. It considers normal operating losses such as start-up, standby, and cycling. The higher the AFUE rating, the more efficient the heating system is. 
  • AHRI – Air-Conditioning, Heating, and Refrigeration Institute. 
    AHRI is a trade association that uses third party testing and certifies the performance of different Heating, Ventilation, and Air Conditioning (HVAC) systems available in North America. 
  • Air-conditioner – An air conditioner evaporates a liquid refrigerant to absorb heat from your home. The system then compresses the refrigerant and condenses it from a vapour to a liquid, releasing the heat so that the cooled/liquid refrigerant can be expanded and sent back into the home, where it starts the cycle again. This is how a heat-pump works, but more efficiently and can work in reverse to heat your room or entire home. 
  • Argon – Argon is a gas used to fill the space between window glazing. 
    Argon has a lower heat conductivity than air and suppresses gas movement between the glazing. A window filled with Argon gas will reduce heat loss better than a window filled with regular air. 
  • Asbestos – A fibre commonly found in many building supplies, including insulation materials, such as vermiculite. 
    If asbestos is exposed the fibres can become airborne inside the home. Inhalation of asbestos fibres can lead to different forms of cancer and scarring of the lungs. Check Health Canada’s website for more information.  

  • Back-drafting – See combustion spillage.  
  • Backflow Valve – Also called a backwater valve, it is a device used to prevent outbound water in a home’s drain pipes from re-entering, or “backflowing”—into your home. The valve has a flap that allows water to leave but closes to prevent water and sewage from entering. When the valve is closed during heavy rain events, you should not use any plumbing fixtures (i.e., toilets, sinks, dishwashers, washing machines) because water will not drain and will back up into your home. 
  • Boiler – Boilers use gas or oil to provide space heating and hot water to your home. 
    Boilers typically distribute heat using water pipes and radiators or in-floor radiant heating, but hydronic forced-air duct systems do exist.  
  • BTU – British Thermal Unit. A Btu is a unit for heat. 
    It is used to measure the heat output of a heating system. One Btu is the amount of heat energy given off by a typical birthday candle. 


  • Chlorofluorocarbons(CFCs) – CFCs are ozone-depleting chemicals. 
    Older appliances that use refrigerant (freezer, refrigerator, heat pump, etc.) are common sources of CFCs and need to be recycled properly to prevent CFCs from being released into the atmosphere. Visit ENERGY STAR® Canada for more information. 
  • CFL – Compact Fluorescent Lamp (or Light). 
    CFL bulbs are rated to last up to 10 times longer and use around 70% less energy than regular incandescent bulbs. 
  • Combustion Spillage – Oil, wood, or gas burning appliances produce heat by burning fuel.
    Burning fuel produces combustion gases, which are normally vented to the outdoors through a chimney or vent pipe. Combustion spillage, also called back drafting, is the unwanted flow of combustion gases into the home. If carbon monoxide is drawn into the living space of a home, it can sicken or even kill the occupants. To learn more about combustion spillage, visit Natural Resources Canada’s website
  • Conduction – Conduction occurs when heat moves through a material or building assembly (e.g., a wall). For example, the heat from a cast iron frying pan is transferred to the handle and eventually to your hand. Insulation reduces heat loss due to conduction. 
  • Convection – Convection is the movement of heat through fluids such as water or air due to the temperature and density differences within the fluid. For example, warm air is lighter and will rise to the top while relatively cooler air will be heavier and fall to the bottom, creating a convection current. Drafts next to windows can be attributed to convection currents. 
  • COP – Coefficient of Performance. COP is one way of measuring of a heat pump’s efficiency. 
    The COP is determined by dividing the energy output of the heat pump by the electrical energy needed to run the heat pump at a specific temperature. The higher the COP, the more efficient the heat pump. 


  • Detached Home – A home where the walls and roofs are independent of any other building (i.e., not attached to any other building). 
  • Dehumidifier – Dehumidifiers regulate the humidity in a room by removing excess moisture from the air, thereby creating a living condition that is inhospitable to dust mites, mould and other allergenic organisms. 
  • Dehumidistat – A device that monitors and maintains a set or preferred relative humidity in the air. If humidity levels rise above the level that you’ve set, the dehumidistat will automatically turn on a device, such as a bathroom fan, to remove excess moisture from the home. Dehumidistats also work with a whole-house dehumidifier. 


  • EnerGuide – The official mark of the Government of Canada for its energy performance rating and labeling programs for housing and energy-using products. The EnerGuide label allows consumers to find the most efficient products and homes. 
  • EnerGuide Rating – The energy performance rating of a house, stated in gigajoules per year, is determined using standard operating conditions and calculated by subtracting the annual renewable energy contributions from the annual energy consumption. Homeowners will receive an EnerGuide Rating after completing an EnerGuide home evaluation. 
  • Energy Factor (EF) – An efficiency rating of gas- or oil-fired tank or tankless water heaters. It is calculated by dividing the energy supplied as hot water by the total amount of energy the water heater uses over a 24-hour period, taking into account standby loss, cycling and recovery efficiency. The higher the EF, the more efficient the water heater.  
  • ENERGY STAR® – ENERGY STAR is an international symbol for energy efficiency – a simple way for consumers to find products that are among the top energy performers on the market. ENERGY STAR qualified products help save energy and money and protect the environment. To qualify for the ENERGY STAR symbol, products must meet stringent specifications for energy consumption without sacrificing the features, versatility and quality expected of high-performing products. 
  • Existing Home – A house that is older than 6 months, based on the date of occupancy by the first homeowner. 
  • Exposed Floor – Exposed floors are floors that hang over an unheated space and are exposed to outdoor temperatures. For example, an overhanging floor such as that found under a bay window or the floor over a garage are defined as exposed floors. 


  • Fenestration – Refers to all types of windows and doors, and their components (sash, frame, and glazing). 
  • Flood Alarms – Also known as flood detectors, are electronic devices that detect the presence of water and set off an alarm when its sensors are triggered. Newer models have WiFi capabilities with smart home integration. Early detection of water leakage can help you quickly determine the cause and source of the leak and address it before flooding occurs. 
  • Furnace – A furnace uses ductwork and vents to distribute warm air throughout your house, and typically burns gas to generate the heat. Oil furnaces do exist but are very inefficient and highly polluting. 


  • Gigajoule (GJ) – A unit of energy. One GJ is equivalent to 278 kilowatt-hours (kWh) of electricity, 27 m3 of natural gas, 39 L of propane, and 26 L of residential fuel oil. The EnerGuide Rating for a house is expressed in Gigajoules per year. 
  • Glazing – The panes of glass incorporated into a window unit. Single-glazed refers to a single pane window double-glazed refers to two panes of glass; triple-glazed refers to three panes of glass. Glazing often has a low-e coating(s) to improve the energy performance of the window. 
  • Green Roof – Green roofs are living roofs. They support the growth of vegetation and consist of a waterproofing membrane, drainage layer, organic growing medium (soil), and vegetation. Green roofs capture stormwater and improve air quality. Green roofs can help insulate your home in the summer and help reduce the overall temperature in summer through evapotranspiration. 


  • House-as-a-System – House-as-a-system is a building science concept that defines the house as an energy system made up of interdependent components, each of which affect the performance of each other and the entire system. The House-as-a-system approach considers the intended or unintended effects that retrofitting one component can have on other components, in terms of energy performance, moisture levels and air quality. 
  • HRAI – The Heating, Refrigeration and Air Conditioning Institute of Canada. HRAI is a non-profit national trade association of manufacturers, wholesalers, and contractors to the heating, ventilation, air-conditioning, and refrigeration industries. It advocates a safe, responsible, and fair industry where systems are designed, installed, and serviced by qualified professionals. 
  • HSPF – Heating Seasonal Performance Factor. A measure of the total heat output in Btu of a heat pump over the entire heating season divided by the total energy in watt hours it uses during that time. The higher the HSPF rating, the more energy efficient the heat pump is for heating. 
  • HVAC – Heating, Ventilation, and Air Conditioning. Refers to the different mechanical systems, machines and technologies used to maintain indoor air quality and temperature, such as heat pumps, furnaces, boilers, and mechanical ventilators. 


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  • Kilowatt Hour (kWh) – a measurement of energy supplied by one kilowatt (kW) of power over a one-hour period. This unit is often used to measure the amount of electrical energy used by your home (see your electrical bill). 


  • LED – Light Emitting Diode. LED light bulbs are more efficient than incandescent light bulbs because they require less power (watts) to produce the same amount of brightness (lumen) as standard incandescent bulbs. They have a low power consumption, low heat generation, and a much longer lifespan when compared to incandescent and compact fluorescent bulbs. 
  • Low-E Coating – Low-Emissivity Coating. A thin coating on window glazing that reduces the amount of solar heat allowed through the window, while still allowing visible light to pass through. Low-E coatings increase a window’s insulation value and make it more energy efficient. 


  • Mobile Home – a movable dwelling unit designed and constructed to be transported by road on its own chassis to a site, and placed on a permanent foundation such as blocks, posts, or a pad. 


  • New Home – A house that is six months old or less, based on the date of occupancy by the first homeowner. 
  • NRCan – Natural Resources Canada. It is the Canadian government department responsible for natural resources, energy, and others. NRCan administers the EnerGuide Rating System through the Office of Energy Efficiency. 


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  • Photovoltaic (PV) – A photovoltaic cell is a device that generates electricity by converting light from the sun into electricity. Solar Panels are composed of photovoltaic cells that allow sunlight to energize electrons, which generates the flow of electricity. 


  • R-Value – Thermal Resistance Value. R-Value is the imperial system unit of measurement (ft2·°F·h/BTU) of a material’s thermal resistance (i.e., how good it is at resisting heat flow by conduction). The higher the resistance value, the slower the rate of heat transfer through the material. Insulation materials are measured in R-Value. To convert an R-Value to an RSI Value (metric system), divide the R-Value by 5.678. 
  • RSI-Value – RSI-Value is the metric system unit of measurement (m2·K/W) of a material’s thermal resistance. To convert an RSI-Value to an R-Value, multiply the RSI-Value by 5.678. 
  • Infra-red Radiation – IR Radiation occurs when heat transfers from a warm object to a relatively cooler object by giving off heat waves in all directions. For example, heat energy from the sun or a heat lamp is in the form of radiant energy. 
  • Radon – Is a colourless, odorless, radioactive gas that naturally occurs when uranium in soil and rock breaks down. It can seep into homes and cause an increased risk of developing lung cancer when inhaled. Read more about Radon on the Health Canada’s website
  • Relative Humidity – The amount of moisture in the air compared to the maximum amount of moisture that the air could retain at the same temperature. Relative humidity is measured as a percentage and depends on the current air temperature. Dehumidistats connected to a ventilation system can help to keep indoor humidity at a comfortable level. 
  • Row-house – A dwelling unit separated either by one vertical division wall, termed a “party wall,” from the adjacent dwelling unit (end unit); or by at least two party walls from the adjacent dwelling units (middle unit). Townhouses are a type of row-house. 


  • SEER – Seasonal Energy Efficiency Ratio. SEER measures the cooling efficiency of an air conditioner or heat pump over the entire cooling season. It is determined by dividing the total cooling provided (in Btu) over the cooling season by the total electricity used during that time (in Wh). 
  • Semi-detachedHome – A set of two dwelling units separated from each other by one vertical division called a “party wall.” 
  • Solar Heat Gain Coefficient (SHGC) – Measures the fraction of solar energy transmitted through windows. SHGC is measured on a scale of 0 to 1, with 1 being 100% transmission. Values typically range from 0.25 to 0.80. The lower the SHGC, the less solar heat will be transmitted through the window. Homes looking to take advantage of passive solar heating often put windows with a high SHGC value on the south-facing side to maximize energy gains but should keep in mind that too much solar heat gain can lead to overheating in the summer. Homeowners should consult with their contractor to ensure they are getting the right windows for their home and not assume that one type of window is good for all locations in your home. 
  • Steady-State Efficiency – The maximum efficiency of a heating system after it has been running long enough to reach its peak operating temperature. It is expressed as a percentage. 
  • Sump Pump – A sump pump is a small pump that is installed at the lowest part of your basement or crawlspace (the “sump) and prevents flooding. The sump pump detects water in the sump and moves it away from your home through a network of pipes that is dug into the floor of the basement. There are two types of primary sump pumps available: submersible and pedestal pumps. Submersible pumps have the motor placed underwater in your sump basin, while pedestal pumps are positioned with the pump motor out of the water, above your sump basin. Submersible sump pumps are the quietest, most powerful and effective type of sump pump. They also allow for an airtight lid that will stop debris from falling into the pit and prevent moisture and odorous air from being released into your home. 


  • Tankless Water Heater – Tankless water heaters heat water as it flows through the unit from the intake pipe to your faucets, using an electric element or gas burner. They provide endless hot water, and the heat-on-demand feature means you only pay to heat water as you use it, instead of paying to keep a tank of water heated 24 hours a day, 365 days a year. Heating water accounts for about 20% of an average home’s energy expenses. 


  • UFFI – Urea-Formaldehyde Foam Insulation. A formaldehyde-based urea-foam insulation commonly used in homes in the 1970’s. This type of insulation has been prohibited since 1980 as it is known to release formaldehyde gas during and after installation. 
  • U-Factor – A measure of the rate of conductive heat transfer through the window. The lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating value. The U-factor is the inverse of the R-Value. 
  • U-Value – An alternative term for U-factor (See U-Factor). 
  • USI – U-factor Standard International, it is the metric U-factor value (see U-Factor). The metric U-factor can be calculated from an imperial U-factor by multiplying by 5.678. 


  • Vermiculite – A form of insulation used up until about 1990. Some vermiculite insulation may contain asbestos fibres that can pose health risks when disturbed. Read more about the health risks of vermiculite and asbestos on Health Canada’s website
  • Visible Transmittance (VT) – Measures the amount of light the window lets through. VT is measured on a scale of 0 to 1, with values generally ranging from 0.20 to 0.80. The higher the VT, the lighter that you see. 


  • Watt – A measurement of power. 
  • Window Well – Window wells are depressions in the ground around below-ground windows. 
    They should have proper drainage and be cleaned regularly to prevent water accumulation.  
  • Window Well Cover – Window-well covers are plastic or metal products that surround a basement window to create a gap between the window and the ground. They still allow some sunlight through but block excess rain and water from flooding the window. Window-well covers can help prevent debris accumulation inside the well and reduce overflowing in slow-draining wells.