Airborne- When air molecules carry pathogens, allergens, or chemicals through the air, increasing exposure.

Airflow- A measurement of the total amount of air that can or is flowing through a respective HVAC system. This is usually measured in Cubic Feet per Minute (CFM).

Air Changes Per Hour (ACH)- The number of times per hour that an area or room is supplied with air through mechanical or other forms of ventilation. ACH acts as a measurement to gauge how effectively air is being exchanged. The formula to determine ACH is to multiply the CFM of air by 60 and divide that number by the total volume of air being exchanged. 

Air to Air- As pertains to HVAC, two end sources of air are involved. Outdoor air is drawn in by an ERV system’s intake fan as indoor air is driven out by a second fan. 

Allergen (or Antigen)- A substance that can cause a strong immune system response followed by allergic reactions. Continuous indoor air circulation and filters with an appropriate MERV rating reduce airborne allergens such as pollen, dander from animal skin, dust mites, and spores.

Annual Fuel Utilization Efficiency (AFUE)- A measure of how efficiently a gas furnace can convert fuel into energy. This ratio shows the percentage of heat produced for every dollar of fuel consumed. Subsequently, a higher percentage AFUE rating means that it is able to convert fuel into energy more efficiently.

Annual Operating Hours (AOH)- The amount of time that a specific HVAC product is estimated to be operated during the course of a year.

ASHRAE- The American Society of Heating, Refrigerating and Air Conditioning Engineers was founded in 1894 with the goal of “advancing human well-being through sustainable technology for the build environment”. Look to ASHRAE for ventilation standards. Their website is https://www.ashrae.org/.


Balanced Ventilation System- Balanced mechanical ventilation can be created using an ERV or HRV that introduces outdoor air and expels indoor air in equal amounts. In this manner, an indoor space does not suffer too much positive or negative air pressure.

Boiler- A canister which uses a pressurized process to burn fuel in order to create either steam or heat to raise the temperature of water.

British Thermal Unit (BTU)- A measurement of heat energy. More specifically, a BTU is the amount of heat needed to raise the temperature of one pound of water by one degree Fahrenheit. The more BTUs, the higher the heat energy power.

BTU/H- A measure of the rate at which a system either consumes or delivers heat energy over the course of an hour.


Carbon Dioxide- (CO2) a colorless and odorless gas produced through the byproduct of respiration or as a result of burning fossil fuels. Too much carbon dioxide (and other types of emissions) in the atmosphere contributes to the greenhouse effect, which results in our current climate crisis.

Carbon Footprint- the total amount of carbon dioxide (CO2) released into the atmosphere resulting from the energy usage behaviors of a specific individual, organization, or community. 

Carbon Neutrality (or Carbon Neutral)- This state of the atmosphere is reached when society’s emissions-releasing activities are offset or balanced by means of eliminating carbon dioxide emissions elsewhere.

Centrifugal Fan- A type of fan that moves air by pulling it into the blower and pushing it out at a 90-degree angle. The main components are the motor and the impeller, which draw air into the fan. A centrifugal fan is widely regarded as a blower or direct-driven blower.

Combined Energy Efficiency Ratio (CEER)- A measurement of how efficient an HVAC system is when the system is cooling a space or in standby mode. A CEER rating is generally used for window and room air conditioners. The higher a CEER rating is the more efficient the system.

Cubic Feet per Minute (CFM)- A measurement of how many cubic feet of air passes through a single point in one minute. CFM requirements vary by ASHRAE standards, however the higher the CFM number the more air that is passed through a system and distributed.


Damper- A movable plate in the ductwork which allows the redirection and regulation of airflow to various areas of the home. These are primarily seen in zoning systems. 

Department of Energy (D.O.E)- A cabinet-level government agency which oversees and monitors the United State’s consumption of energy and “addresses its energy, environmental and nuclear challenges through transformative science and technology solutions” (DOE, n.d.). Their website can be found at https://www.energy.gov/.

Design Conditions- Specified environmental conditions (i.e. temperature and relative humidity) for a project’s area or location. At BPE, we use Dry Bulb, Wet Bulb/Relative Humidity for design conditions to run schedules that help determine the effectiveness of our units. 

Direct Counterflow- BPE’s patented Energy Recovery Ventilator designs send incoming and outgoing air in opposite directions in a true, linear flow path. Extremely low static pressure is a byproduct of this design which means less airflow resistance.

Dedicated Outdoor Air System (DOAS)- A type of HVAC system that is mounted outside and used to bring fresh air into a building. A DOAS unit can be combined with other HVAC units or used by itself. Having a BPE ERV as the core of your DOAS delivers superior energy efficiency and thermal comfort. 

Dry Bulb Temperature (DB)- The temperature of air when measured with a thermometer and not affected by moisture or radiation. DB usually is universally regarded as the measurement of air temperature in the HVAC industry.

Ductwork- The use of ducts, tubing or other means to transfer air (stale outgoing and fresh incoming) to, from, and through HVAC systems to designated areas.


Energy Efficiency Ratio (EER)- A ratio which determines the efficiency of an air conditioner. The ratio is taken by dividing the cooling capacity by the electrical energy input. The higher the EER rating, the better.

Energy Recovery Ventilator (ERV)- A type of HVAC system that uses the exhausting air out of a building to precondition the air entering a building by either cooling or heating it. The ERV draws fresh outdoor air into the unit and filters it before distribution. A highly efficient ERV is able to effectively and efficiently transfer heat and moisture between incoming and outgoing airstreams. ERVs can be used as standalone units or become integral and in-line to other HVAC systems.

Energy Recovery Module (ERM)- The base ERV unit without fans and filters included (order separately according to need and choice). These galvanized steel units are specifically sized to handle commercial and industrial dedicated ventilation applications. The efficiency, depending on airflow, can be adjusted from 70% to 95% thermal efficiencies. The BPE-XE-MIR-2000 ERMs are stackable up to 20,000cfm.

ENERGY STAR®A joint program between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE) to promote energy efficiency efforts. Products and buildings can receive certifications and ENERGY STAR ratings by meeting specific standards set forth by the governing bodies.

Entering Air Temperature (EAT)- Refers to the temperature of the air as it enters into the module (in this case, the fresh air inlet of a BPE ERV).

Environmental Protection Agency (EPA)- An organization run by the United States government to protect human and environmental health. There are programs that promote energy efficiency, sustainability, and better qualities of air and water while preventing pollution. The EPA also oversees the ENERGY STAR® program. Their website is https://www.epa.gov/.


Fixed Plate Heat Exchanger- A type of energy recovery ventilator system that is an alternative to more conventional enthalpy wheel designs. The difference between the two designs rests with how fixed plate heat exchangers are often cost-effective as there are no moving parts to wear out. BPE’s energy recovery ventilators are all fixed plate heat exchangers.

Flow Geometry- In regards to BPE ERVs, this is the geometric path in which the air flows through from one end to another.

Fossil Fuels- A form of fuel created through natural processes such as the decomposition of organisms. Examples of fossil fuels include coal, petroleum, and natural gas. All forms of fossil fuels are considered non-renewable resources.


Gas Furnace- A home appliance that creates and circulates heat through the combustion of natural gas. 

Greenhouse Effect- This phenomenon involves the warming of Earth’s surface as well as its troposphere (lowest layer of the atmosphere) thanks to natural gasses such as carbon dioxide that trap the sun’s heat. This process helps keep our planet inhabitable. However, human activities that involve burning fossil fuels overload the process, sending too many emissions into the atmosphere to trap more and more heat. This causes the planet to heat up too much. This is why furthering clean energy practices and reducing the use of fossil fuels is imperative for normalizing our climate.

Greenhouse Gasses- Gasses such as carbon dioxide, methane, and nitrous oxide that contribute to the greenhouse effect.

Guide Vanes- Fixed grooves primarily built into ductwork to allow air to flow smoothly around corners and 90 degree turns. The vanes can reduce static buildup and pressure by over 1 in. wc. (inches of water column).


Heat Exchanger- A device that enables and allows for the transfer of heat between two entities. In regards to HVAC, energy recovery ventilation systems can act as heat exchangers which will transfer heat from one airstream to another.

Heat Pump- A form of HVAC system that acts as an air conditioner but also contains a reversing valve, allowing for the same unit to provide heating capabilities as well. For detailed Heat Pump terminology, please visit the glossary at Green Foot Energy Solutions.

Heating Seasonal Performance Factor (HSPF)- A calculation and metric used to measure the heating efficiency of heat pumps. The higher the rating, the better.

HEPA Filter- Abbreviation for a High Efficiency Particulate Absorption filter that can remove common particulates and particulate matter such as pollen, dust, and mold from the air. 

Horizontal Flow- The design of a unit that traditionally draws air into one side of the unit and disperses the air out of the other side and into the respective area.

Humidifier- A device or system that adds additional moisture into the interior air. 

Humidistat- A tool or device that monitors and manages the levels of humidity in a home or building.

Humidity- The measure of moisture in the air.

HVAC- The abbreviation for heating, ventilation, and air conditioning. These systems are installed and used to modify various aspects of air qualities to create a more comfortable indoor atmosphere.


Indoor Air Quality (IAQ)- The overall quality of air inside a building as it relates to the well-being of the occupants. Poor IAQ can lead to phenomena such as sick building syndrome and lowered productivity.

Indoor Environmental Quality (IEQ)- These are the all-encompassing aspects of the thermal comfort and well-being of occupants in a building. IEQ includes IAQ among other building aspects such as what the occupants see, hear, and feel.

Integral Filters- Filters that are directly built into the infrastructure of a product. An example of this is the Building Performing Equipment, Inc.® BPE-XE-MIR-200i which has integral Merv 8 filters.


Kilowatt (kW)- The measure of how much electric power a product consumes. There are 1,000 watts (W) in a kilowatt (kW).


Latent Effectiveness-  Latent heat, present in humidity, is created by increases and decreases in moisture. It is the energy needed to change the state of a substance such as liquid to gas or a gas to a liquid without changing the temperature. The latent effectiveness of an HVAC system is a measurement of its ability to remove moisture from the air. Complaints over humidity are actually dissatisfaction over the latent heat within it. Thermostat temperatures do not take this heat into account.

Leadership in Energy Environmental Design (LEED)- A global program based around the design, construction, and efficient operations of buildings. LEED Certifications are able to earn points based on different categories with four rating levels: Certified, Silver, Gold, and Platinum. More information on LEED can be found at https://www.usgbc.org/leed/why-leed.

Lineset- The conduit for refrigerants to be able to move between interior and exterior components.

Load Calculation– An analysis for determining the HVAC system needed for a building or the production capacity of an HVAC system for a specific building.

Louver- A type of grate or shutter that allows for the passage of air either into or exhausting out of a unit or space. The grate can have slants to allow air to pass through while keeping out sun and rain. Louvers can be fixed or capable of changing angles to allow less or more air into or out the system..


Manual D- The last step in the design process and layout of a new HVAC system is a Manual D. This is the selection, sizing, and installation of ductwork systems which carry air from the respective HVAC unit to the area where the air will be supplied. Having the proper ductwork sizing is important to keep static pressures low, CFM and airflow consistent, and for providing a comfortable atmosphere for the occupants.

Manual J-  An outline used to determine total heating and cooling a home needs for sustaining the thermal comfort of occupants. HVAC specialists are able to perform load calculations which include insulation and ventilation levels to understand the type of HVAC equipment needed.

Manual S- An analysis of how to select the proper equipment in regards to ventilation and air flows while considering sensible and latent heating capabilities with static pressures.

Manual T-  A Manual T references the actual HVAC system’s air distribution. This includes how to select the amount and location of the supply air coming into spaces and exhaust air leaving those same areas. Manual T is a critical component as it allows for an adequate airflow and even distribution of air throughout the home or building.

Makeup air- A method to bring in additional air/ replace the air that cannot be refiltered and recirculated. These types of processes are generally needed for exhaust fans such as range hoods and often seen in homes that have a tighter envelope and are more tightly sealed or passive house applications. 

MERV Rating- The Minimum Efficiency Reporting Value (MERV) dictates how well a filter removes particles from the air. Filtration is rated from 1 – 20. (See EPA’s rating list.) Best MERV ratings for home and office HVAC are MERV 8 – 13. Anything higher risks a drop in air pressure that can damage your system and raise energy bills. Hospital and manufacturing HVAC systems typically use higher MERV Ratings.

Microchannel- A coil specifically designed with smaller channels in the tubing to increase energy efficiency.


Net Metering- A service used by utility companies for customers who have installed solar panels on their homes. Customers who add to the grid through their solar panels can be “credited” and billed only for their net use.

Net-zero- The act of removing the same amount or more greenhouse gasses from the atmosphere that you create. Becoming net-zero focuses on using renewable resources to produce energy. 


Oil Furnace- A combustion heating system which uses oil for fuel.


Package Unit- An HVAC system or complete unit that includes all necessary equipment to heat or cool. In regards to BPE’s ERVs, our packaged units include all components for a single price point.

Passive House- A set of attributes, characteristics, and principles for building or renovating a home that is ecologically sound and super energy efficient while offering thermal comfort—all without a formal heating or cooling system. See the Passive House Institute’s passive house principles. 

Pathogen- An organism that can cause disease. Continuous indoor air circulation and filters reduce airborne pathogens such as viruses, bacteria, funghi, and parasites. 

Parts per Million (PPM)- A measurement of the concentration of a specific molecular makeup within a larger defined space or area.

Pilot Light- A small gas flame used to ignite the burner. These are often seen on gas stoves as well.


Radiant Floor- A type of flooring that circulates hot fluids through subfloor channels beneath the flooring panels to deliver heating that rises through the floors, increasing thermal comfort of occupants.

Refrigerant- The chemical used in an air conditioning system found within a coil that traps and moves heat throughout the system to cool the air.

Regenerative Condensate Return™(RCR)- BPE Regenerative Condensate® Return Technology recycles moisture to increase thermal effectiveness, making BPE ERVs over 90% sensible with 34% latent effectiveness, as tested by Edison Testing Laboratory. 

Relative Humidity– The amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the same temperature.

Renewable Energy- Energy derived from sources that are not able to be depleted. Examples include wind, solar, and hydro powers.

Retrofit- The addition of new technologies, products, or features to older existing technologies. An example of this is installing a Building Performing Equipment, Inc.® (BPE) Energy Recovery Ventilator in-line with an existing HVAC system.

Return Air- The temperature of the air that is being exhausted from a specific area and entering into the energy recovery ventilator to be exhausted out of the building.

Return On Investment (ROI)- As pertains to HVAC, the ROI is used to evaluate the efficiency of your investment. It is the ratio between net income and how much you invested in a piece of equipment. When does your ERV finish paying for itself?

Rooftop Unit (RTU)- An HVAC system that has all components of heating and cooling features integrated into one single unit. The integral unit often includes fans, coils and compressors to heat and cool the air at point of entry before distributing it throughout the building. RTUs are primarily seen in commercial applications.

Room Air Conditioner- A single-zone air conditioning unit that is very compact and used primarily for single rooms. Size and CFM levels may vary depending on each unit. Oftentimes, these units are installed through the window or a wall. 


Seasonal Energy Efficiency Ratio (SEER)- The measurement of how efficiently an air conditioner or other product operates over the duration of a cooling season. The SEER is found by taking the cooling output of an air conditioner and dividing its use in Watt-Hours. The higher the SEER, the more efficient the unit.

Sensible Effectiveness- The ability for heat to be transferred from the exhaust airstream to the supply airstream expressed as a percentage. The higher the percentage, the more efficiently the energy recovery ventilator is able to precondition the air before supplying the air to a specific area.

Sensible Recovery Efficiency (SRE)- This rating reports the amount of sensible energy recovered from exhausted air by the incoming air. The higher the measurement (in terms of percentage), the more efficient the product. The SRE and Total Recovery Efficiency (TRE) were formulated to place HRVs and ERVs on a level playing field by taking into account variables such as mass and flow imbalance, electric consumption (i.e. fans), as well as internal and external energy gains and losses. BPE has been utilizing this rating in their products for over twenty years.

Speed Controller- A device used to control the speed of a normally fixed speed fan. The speed controller will allow for changing the speed to varied levels. Also referred to as variable speed drives (VSDs) or adjustable speed drives (ASDs). See variable speed.

Split System- A type of HVAC system which has interior and exterior components connected to each other. There are various types of split systems, however all will have an outside component and an inside component. 

Static Pressure- The amount of resistance that air must overcome to reach the area where it must cool. Static pressure can be caused by a variety of factors including ductwork, the HVAC unit the air is passing through, etc. Measured in Inches of Water Column (in. wc.).

Supply Air Temperature– The temperature when the outdoor air has completely passed through the BPE energy recovery ventilator and is being distributed through the ductwork to respective areas. This temperature varies based on the outdoor air temperature and the returning air temperature.

Sustainability- The ability to use natural resources efficiently in a way that doesn’t jeopardize those resources for future generations. This includes focusing on resources that are easily renewed such as power from the sun and wind.


Thermal Efficiency- a measure of how much heat a system is able or capable of producing/generating from a specific amount of energy given to that system. 

Thermidistat- A device that not only monitors the temperature and humidity levels indoors but also adjusts the HVAC system to maintain a specific level. 

Thermostat- A device that is able to read the temperature of indoor air and adjust accordingly by turning on or off an HVAC system. 

Tonnage Avoidance- The ability to choose an HVAC system that has lower overall tonnage as a result of having a Building Performance Equipment, Inc.® ERV in-line to precondition the air traveling into the HVAC system.

Total Recovery Efficiency (TRE)- This rating reports total effectiveness of sensible and latent (enthalpy) energy recovered from exhausted air by the incoming air. The higher the measurement (in terms of percentage), the more efficient the product. The SRE and Total Recovery Efficiency (TRE) were formulated to place HRVs and ERVs on a level playing field by taking into account possible variables such as mass and flow imbalance, electric consumption (i.e. fans), as well as internal and external energy gains and losses. BPE has been utilizing this rating in their products for over twenty years.

Transition- A type of ductwork adapter piece that is used to move from one type of ductwork run to another. Transitions can also be used as the first piece of ductwork when leaving the HVAC unit. 


USGBC- The United States Green Building Council, a private nonprofit organization, is focused on promoting sustainable practices regarding the design, construction and operation of buildings. Their website is https://www.usgbc.org/


Vanes (Turning Vane) – Curved devices within ductwork that direct airflow around corners.

Variable Speed- Referred to as variable speed drives (VSDs) or adjustable speed drives (ASDs), these devices allow a user to adjust the speed of a fixed speed motor. The most common application of VSDs are for fixed speed motor fans. See speed controllers.


Water Column (Inches of)- A unit of measurement that measures static pressure expressed as inches of water column (i.e. WC or WG), usually through a nanometer. The measurement is used to determine the amount of resistance that air must overcome to reach the area where it must cool. One inch of water column equals about 1/28 psi (pound per square inch) of pressure.

Water Heater- A device that heats water for household use.

Wet Bulb Temperature (WB)- A measurement of the lowest temperature at which air is able to be cooled down through evaporative cooling at a constant pressure.


Zoning- The sectioning of a building into different zones allowing for custom heating or cooling zones to increase comfort and efficiency. The zoning of buildings is often-times done through the use of air dampers within ductwork.

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