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Need help figuring out the terminology most frequently used in the home performance industry?

Click here for a helpful website on key terms related to home energy efficiency from the NC Cooperative Extension’s Home Energy Management Program.


Absolute Energy Saving Target –  This target is set based on the energy consumption after the renovation and this needs to be below a certain threshold (i.e. reduction in energy consumed)

Air Changes –  Expression of the amount of air movement or air leakage into or out of a building in terms of the number of building volumes or room volumes exchanged

Air Conditioning System –  Assembly of equipment for air treatment to simultaneously control its temperature, humidity, cleanliness, and distribution to meet the requirements of a conditioned space

Air duct –  A hollow conduit or tube (square or round) that circulates air from a forced-air heating and/or cooling system to a room (supply duct) or returns air back to the main system from a room (return duct)

Air Infiltration –  the uncontrolled inward airflow through openings in the building envelope caused by the pressure effects of wind, the effect of differences in indoor and outdoor air density, or both (cfm) [m[sup]3[/sup]/s]

Air Leakage –  Uncontrolled or unwanted infiltration or exfiltration of air into or out of a building

Audit (energy audit) –  an assessment of a home’s energy use


Barriers –  An obstacle or impedement to the implementation of energy efficiency policies or energy efficiency into your home or lifestyle

Benchmarking –  Process of building energy performance measurement, consisting of assessing a building’s pattern of energy consumption (with an energy rating) then comparing it against its historical usage (also internal benchmarking) or to consumption patterns of similar buildings (also external benchmarking). Benchmarking can be used to compare performance over time, within and between peer groups, or to document top performers

Bioclimatic Design –  Bioclimatic design/architecture is designing a building that is in harmony with the natural features and resources surrounding the site, taking advantage of free available renewable resources, e.g., using sunlight through passive solar, and reducing the impact on energy demand for heating and cooling by appropriate orientation, lay out and compact shape of the building

Blower door –  A home performance test conducted by a contractor to evaluate a home’s air-tightness. During this test a powerful fan mounts into the frame of an exterior door and pulls air out of the house in order to lower the inside air pressure. While the fan operates, the contractor can determine the house’s air infiltration rate and better identify specific leaks around the house.

Building Energy Efficiency Codes –  Energy efficiency codes set minimum requirements for the energy-efficient design and construction/renovation of new and existing buildings

Building Envelope –  The integrated elements of a building which separate its interior from the outdoor environment


Calculation with Coupled Zones –  Multi-zone calculation (within residential area) with thermal coupling between zones, taking into account any heat transfer by thermal transmission and/or by ventilation and/or by air infiltration between zones

Carbon Dioxide –  Carbon dioxide (CO2) is a colorless, odorless and non-poisonous gas formed by combustion of carbon and in the respiration of living organisms and is considered a greenhouse gas. Emissions mean the release of greenhouse gases and/or their precursors into the atmosphere over a specified area and period of time

Caulk –  used for sealing cracks and gaps between two non-moving or stationary parts.

CDD –  Cooling Degree-Days are the number of degrees per day that the daily average temperature is above a given temperature (18°C or 65°F). This temperature is the point above which the consumer is assumed to use energy for space cooling. During the cooling season, warmer-than-normal temperatures tend to lead to increased electricity use, with increased demand for electricity often met by incremental use of oil products and natural gas

CFL –  compact fluorescent light bulb; it uses 65 percent less energy than a traditional incandescent bulb

Commercial Buildings –  A commercial building is a building that is used for commercial use. Types can include office buildings, warehouses, or retail

Conditioned Floor Area –  Space within a building provided with heated or cooled air, or both (or surfaces); and, where required, with humidification or dehumidification means, to maintain conditions for an acceptable thermal environment

Cost Effectiveness –  A measure or package of measures is cost-effective when the cost of implementation is lower than the value of the benefits that result, taken over the expected life of the measure

Cost Optimal Level –  The energy performance level which leads to the lowest cost during the estimated economic lifecycle

C-PACE –  An innovative program that is helping commercial, industrial and multi-family property owners access affordable, long-term financing for smart energy upgrades to their buildings

Crawlspace –  An area of limited height under a floor or roof that usually contains wiring and plumbing infrastructure


Deep Retrofit – Deep retrofit or Deep Energy Retrofit implies replacing existing systems in a building with similar ones that are of higher quality and performance, which leads to a better energy performance of an existing building. The primary energy consumption includes energy used for heating, cooling, ventilation, hot water, lighting, installed equipment and appliances. After the deep retrofit the buildings consume 50% less primary energy compared to the status of theexisting building/s the retrofit

Duct – A network of metal, fiberboard or flexible material throughout a space delivering air from the outdoor unit to indoors


Eco Innovation –  any form of innovation resulting in or aiming at significant and demonstrable progress towards the goal of sustainable development, through reducing impacts on the environment, enhancing resilience to environmental pressures, or achieving a more efficient and responsible use of natural resources

Electric grid – Network of shared electric power. Generators feed power into a regional grid; energy is drawn on an as needed basis. The electricity you receive is determined by a generator’s physical location.

Energy Certification of Buildings – A process, program or system to assess and identify a building’s energy performance and allow this information to be standardized, displayed and communicated to the real estate market

Energy Efficiency – The ratio between the energy services provided and the energy consumed. Something is more energy efficient if it delivers more services for the same energy input, or the same services for less energy input

ENERGY STAR – a joint EPA/DOE program that encourages energy conservation by improving the energy efficiency of a wide range of consumer and commercial products, enhancing energy efficiency in buildings, and promoting energy management planning for businesses and other organizations



Green Buildings – Green Buildings are those with increased energy efficiency, but at the same time reductions are made on water consumption, materials and assessment of the general impact on health and environment. Green buildings can include a long list of requirements including resources, indoor air quality and requirements that all products for the building must come from a local region

Greenhouse gas – Gases that trap heat in the atmosphere are often called greenhouse gases. Some, like carbon dioxide, occur naturally and are emitted through both natural processes and human activities, but other greenhouse gases (e.g. fluorinated gases) are created and emitted solely through human activities.


Heat Pumps – A machine, device or installation that transfers heat from natural surroundings such as air, water or ground to buildings or industrial applications by reversing the natural flow of heat such that it flows from a lower to a higher temperature. For reversible heat pumps, it may also move heat from the building to the natural surroundings

Holistic Approach – Combines integrated design with regulatory mechanisms, labeling schemes and financial incentives to reduce energy consumption in the buildings sector. The holistic approach means being flexible towards building design, adaptive to changing technologies and responsive to local environmental and socio-economic contexts

HVAC – Heating, ventilation and air conditioning system; The mechanical systems that provide thermal comfort and high air quality in an indoor space


Insulation – A material or substance used to prevent or slow down the passage of heat, electricity, or sound

Integrated Design – The process of reducing a building’s energy consumption through designing the interaction of all building components and systems including passive use of renewable energy and other natural sources. Integrated design requires more emphasis first on energy sufficiency measures then energy efficiency measures in the early planning phase than traditional design. The most advanced building codes are based on integrated building design

International Energy Conservation Code –  (IECC) is a building code created by the International Code Council in 2000. It is a model code adopted by many state and municipal governments in the United States for the establishment of minimum design and construction requirements for energy efficiency



kWh – A unit of energy used to measure electricity, measured as 1 kilowatt (1,000 watts) of power expended for 1 hour. One kWh is equivalent to 3,412 Btu’s


Life Cycle Assessment – A concept and a method to evaluate the environmental effects of a product holistically, by analyzing its entire life cycle. This includes identifying and quantifying energy and materials used and wastes released to the environment, assessing their environmental impact, and evaluating opportunities for improvement

Low Energy Building – Low energy building indicates a building that has a better energy performance than the standard alternative/energy efficiency requirements in building codes. Low-energy buildings typically use high levels of insulation, energy efficient windows, low levels of air infiltration and heat recovery ventilation to lower heating and cooling energy. They may also use passive solar building design techniques or active solar technologies. These homes may also use hot water heat recycling technologies to recover heat from showers and dishwashers

Low Energy Windows – A low energy window is a window that significantly reduces the amount of heat lost by heat transfer across a part of the building envelope by increasing the number of window panes separated by air or other gas filled space


Mitigation – In the context of climate change, a human intervention to reduce the sources or enhance the sinks of greenhouse gases. Examples include using fossil fuels more efficiently for industrial processes or electricity generation, switching to solar energy or wind power, improving the insulation of buildings, and expanding forests and other sinks to remove greater amounts of carbon dioxide from the atmosphere


Net Zero Energy Buildings – NZEB are buildings that over a year are neutral, meaning that they deliver as much energy to the supply grids as they use from the grids. Seen in these terms they do not need any fossil fuel for heating, cooling, lighting or other energy uses although they sometimes draw energy from the grid

Non-Residential Buildings – A building is regarded as a non-residential building when the minor part of the building (i.e. less than half of it’s gross floor area) is used for dwelling purposes. Non-residential buildings comprise: Industrial buildings; commercial buildings; educational buildings; health buildings; other buildings


On-bill financing –  On-bill financing allows the utility to incur the cost of the clean energy upgrade, which is then repaid on the utility bill. Provides property owners to pay for investments in clean energy upgrades through their utility

Overall Efficiency – Overall efficiency means the annual sum of electricity and mechanical energy production and useful heat output divided by the fuel input used for heat produced in a cogeneration process and gross electricity and mechanical energy production


Passive House –  A passive house is a building in which a comfortable indoor climate can be obtained without a traditional heating or cooling system. Compared to traditional building they use far less energy. For most countries these demands are 70–90 % reduced compared to the actual energy efficiency requirements for heating and cooling, but this depends on the actual energy standards

Pay As You Save (PAYs) –  A market-based system that enables utility customers to purchase and install cost-effective energy efficiency upgrades or distributed renewable energy assets through a voluntary tariff that assures immediate net savings to customers

Payback Time –  The length of time required to recover the cost of an investment

Peak Load –  The highest electrical demand within a particular period of time. Daily electric peaks on weekdays occur in late afternoon and early evening. Annual peaks occur on hot summer days

Performance Contracting –  Means of raising money for investments in energy efficiency that is based on future savings



Residential Buildings – A building should be regarded as a residential building when more than half of the floor area is used for dwelling purposes. Other buildings should be regarded as non-residential. Two types of residential buildings can be distinguished: 1.) Houses (ground-oriented residential buildings): comprising all types of houses (detached, semi-detached, terraced houses, houses built in a row, etc.) each dwelling of which has its own entrance directly from the ground surface; 2.) other residential buildings: comprising all residential buildings other than ground-oriented residential buildings as defined above

ROI (Return of Investment) –  Usually expressed as a percentage and is typically used for personal financial decisions, to compare a company’s profitability or to compare the efficiency of different investments. The return on investment formula is: ROI = (Net Profit / Cost of Investment) x 100


Smart Metering – Smart metering system means an electronic system that can measure energy consumption, providing more information than a conven­tional meter, and can transmit and receive data using a form of electronic communication

Solar Heat Gains – Heat provided by solar radiation entering, directly or indirectly (after absorption in building elements), into the building through windows, opaque walls and roofs, or passive solar devices such as sunspaces, transparent insulation and solar walls

Source Energy – Source energy is a measure that accounts for the energy consumed on site in addition to the energy consumed during generation and transmission in supplying the energy to your site




Ventilation – Process of supplying or removing air by natural or mechanical means to or from a space. Note- Such air is not required to have been conditioned

Ventilation Heat Recovery – Heat recovered from exhaust air to reduce the ventilation heat transfer

Ventilation Systems – The process of supplying air to or removing air from a space for the purpose of controlling air contaminant levels, humidity, or temperature within the space





Zero Energy Buildings – Zero Energy Buildings are buildings that do not use fossil fuels but only get all their required energy from solar energy and other renewable energy sources

Zero Energy Renovation – A deep renovation with large energy consumption reductions where the rest of the energy supplied as a renewable energy on site

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