Efficiency Ratings

The materials used to construct a structure, as well as the systems and appliances installed inside, can have a significant impact on how much energy it consumes over its lifetime. Efficiency ratings have been developed for numerous building components and energy systems to help buyers evaluate the potential impact of one to another.
There are currently a plethora of energy ratings available, which might be perplexing for the consumers who these ratings were designed to assist. We’ll try to clear up any misunderstandings by explaining each of the ranking systems stated below as simply as possible. A glossary of efficiency terms is also supplied.

Building Materials

The materials used to construct a structure can have a significant impact on its efficiency. Materials that allow a lot of heat to travel through them reduce the building’s overall efficiency. Materials that prevent significant heat transfer, on the other hand, can help assure improved efficiency. The U-value of a construction component (such as a window or wall system) refers to how well it transfers heat. The R-value of a substance (for example, glass, wood, or metal) refers to its ability to resist heat transmission.

Appliances And Equipment

When we talk about an appliance’s or energy system’s efficiency, we’re really talking about how much energy that system needs to do a specific amount of work. The less efficient a system is, the more energy it consumes per unit of output. For example, an air conditioner that uses 750 watts to give 6,000 Btu of cooling is less efficient than one that uses just 500 watts to provide the same amount of cooling. EER and SEER for most central air conditioners; COP for some heat pumps and chillers; HSPF for heat pumps in their heating modes; and AFUE for gas furnaces and boilers are the most prevalent energy system ratings.

Glossary Of Efficiency Terms

AFUE (annual fuel usage efficiency):

AFUE is a rating that determines how efficiently gas and other fossil-fuel-burning furnaces and boilers utilize their major fuel supply over the course of a heating season. It disregards the efficiency with which any system component, such as a furnace fan motor, consumes electricity. The average number of Btu worth of heating comfort provided by each Btu worth of gas (or other fossil fuel) consumed by the system is stated as a percentage. A gas furnace with an AFUE of 80%, for example, would provide 0.8 Btu of heat for every Btu of natural gas used.

Air Infiltration:

Unconditioned outdoor air is introduced into a mechanically heated and/or cooled building by air infiltration, which is usually inadvertent. Any opening in the home’s structure can allow air infiltration, including seams where walls meet other walls, window or door frames, or chimneys; holes where wires or pipes penetrate walls, floors, or ceilings/roofs; and between the loose-fitting meeting rails of double-hung windows or a door bottom and door threshold. It is one of the most common sources of unwelcome heat gain and loss, as well as personal discomfort in buildings.

The Btu (British thermal unit):

The Btu (British thermal unit): is a unit of heat energy measurement. One Btu of heat is required to raise the temperature of one pound of water by one degree Fahrenheit. Btu can be used to describe the cooling capacity of an air conditioner (i.e., the number of Btu of heat that the system can remove) or the heating capacity of a furnace (i.e., the number of Btu of heat that can be supplied by the system).


Caulk: is a material that is used to seal air infiltration points between two immovable objects, such as where external or interior wall surfaces meet window or door frames, and at siding corners. The majority of caulks come in tubes and are applied with a caulk “gun.”

Compact fluorescent lamps (CFLs):

Compact fluorescent lamps (CFLs): are light “bulbs” that employ fluorescent technology but are designed to work in many of the same settings as normal incandescent “A” bulbs. They feature a looped or swirled tube with a small diameter that is coupled to a screw-in base. CFLs produce light levels that are comparable to 20- to 150-watt incandescent bulbs while using 70% to 75% less energy.


Heat is transferred through solid items such as glass, drywall, brick, and other construction components by conduction. The larger the temperature difference between outside and inside, the faster conduction can take place and the more homes a structure can acquire or lose.


The transport of heat to or from a solid surface via a gas or liquid circulation is known as convection. Heat convection is created by air (gas) currents that move heat from your body, furniture, interior walls, and other warm things to windows, floors, ceilings, external walls, and other chilly surfaces, causing home heat loss and gain.


It is the practice of supplementing or replacing a building’s artificial lighting system with natural light from windows, skylights, and other openings. When used correctly, daylighting can help a facility save money on lighting. When used incorrectly, however, it can not only result in insufficient lighting but also increase the building’s cooling expenses by allowing significant levels of solar heat to enter the interior.

Dedicated fixture:

It is a lighting device created expressly for use with a specific type of lamp (bulb). Because of the expanding popularity of compact fluorescents, a growing number of fixtures, such as torchieres, table lamps, ceiling drums, and recessed canisters, have been developed specifically for use with CFLs.

EER (energy efficiency ratio):

The energy required by a cooling system to maintain indoor comfort at a certain external temperature – commonly 95°F – is measured by the EER (energy efficiency ratio). When it comes to window air conditioners and geothermal heat pumps, the term EER is most usually employed. EER is calculated by dividing the number of Btu per hour of cooling provided by the number of watts used to provide that amount of cooling at the stated external temperature.


Insulation is a material that prevents heat transfer through conduction and convection. Because they contain more “dead air” pockets, some materials are naturally greater insulators than others. The heat movement is slowed by these pockets of trapped gas. However, practically any commodity, including glass, cotton, paper, and plastic, can be used to generate insulation if handled appropriately.

Internal Heat Gain (IHG):

Internal Heat Gain (IHG): is the buildup of heat generated by a building’s energy systems and appliances, as well as its occupants. Internal heat gain can account for up to 20% of a home’s total summer cooling load, depending on the number of occupants and the kind and quantity of energy systems used during the day.

Kilowatt (kW):

Kilowatt (kW): 1000 watts.

Kilowatt-hour (kWh):

1000 watts for one hour – or any combination of energy multiplied by time that is equivalent to that rate of electrical consumption, such as one watt for 1000 hours, ten watts for 100 hours, or fifty watts for twenty hours. A 100-watt light bulb, for example, would use one kWh every two days if left on for five hours each day. The kilowatt-hour is the principal unit of measurement used by electric providers in the United States to bill their customers. Residential clients of CWLP pay an average of 5.5 to 6 cents per kWh used.


Low-e: is a term used to describe a material that reduces the amount of radiant heat that may be transmitted through glass or other translucent window coverings. Low-e (low-emissivity) coatings or films have the capacity to re-radiate a significant amount of heat back toward the source. Low-E windows can help minimize the amount of solar heat that enters a home in the summer and the amount of furnace-generated heat that escapes to the outdoors in the winter.


Lumen: is a measurement of the amount of light emitted by a light source. A lumen is a unit of measurement that is used to compare the brightness of various light sources.

Payback Period:

Payback Period: The time it takes to get a full return on investment is known as the payback period. For example, if a high-efficiency air conditioner costs $300 more to buy than a lower-efficiency model but saves you $100 a year in operating costs, the extra $300 investment will pay for itself in three years.


Radiation: is a heat transfer process in which heat is transferred from one surface to another via infrared radiation. Radiant heat warms the surfaces it comes into contact with without raising the temperature of the air it travels through. Infrared radiation is emitted by all heated bodies.

Return on investment (ROI):

Return on investment (ROI): The annual rate at which an investment earns money is known as the return on investment (ROI). The annual earnings are divided by the investment to arrive at this figure. For example, a bank savings account that pays $3 per year on a $100 investment has a return of 3% ($3 / $100). The return on an efficient project comes from money saved on your energy bills, not money paid to you.

Thermostat Setback

It is a deliberate effort to reduce building energy usage by manually or automatically adjusting thermostat settings based on the amount of cooling or heat required at any particular time of day or night.


The measurement of how easily heat may pass through glass, masonry, drywall, and other building materials is known as the U-value. R-values are the polar opposite of U-values, which are stated in decimals (e.g., U-0.166). The lower the U-value, the less efficient the construction material. The lower the U-value of a material, the higher the R-value.

Vapour Barrier

Vapour Barrier: is a substance that prevents moisture from passing through a wall or other building components. Water vapour in the air can settle and condense on colder building components like rafters, beams, and walls as it flows from a warmer to a cooler portion of the building, creating mildew, rust, and decay. Vapor barriers, which are impervious to water vapour movement, can help to mitigate this risk. Plastic is the most popular vapour barrier material, however other materials, such as oil paint, can also be used.


Watt is an electric power unit. Watts are the units of measurement for the amount of power consumed by electric appliances.


Watt-hour is a unit of electric energy that is equal to one watt utilized for one hour.


Weatherstripping is a product that is used to seal cracks in windows, doors, and other moveable building components that exist between two moving parts or one moving part and one stationary portion. Weatherstripping is used to increase the energy efficiency of a building by avoiding unintended ingress of unconditioned external air.

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