Air Changes Per Hour (ACH)
Air changes per hour is the measure, or rate, of air volume added or removed from a space (such as a house or a room). To derive ACH, you must divide by the volume of the space. The rate is a measure of how many times in that specific space is replaces.
Azimuth (Roof Azimuth)
The azimuth is the roof array's east-west orientation in degrees. In most solar PV energy calculator tools, an azimuth value of zero is facing the equator in the northern hemisphere. A positive 90 degrees is facing due west and a negative 90 degrees is facing due east. Each roof has an azimuth angle and a tilt angle.
After a home energy audit is performed, the auditor meets with the individuals who commissioned the audit to go over the audit findings. The comprehensive audit report lists the findings and provides prioritized recommendations for improving the energy efficiency and comfort of the home
Blower Door Test
A blower door test is performed to determine the air flow leakage of a building. The testing unit is a special powerful fan that is mounted into the frame of an exterior door. All windows and doors are closed. The furnace is turned off. The fan pulls air out of the house, lowering the air pressure. This creates negative pressure in the house. The greater outside air pressure will then flows in the home through all unsealed cracks and openings. Using an infrared camera, one can visualize where this air is leaking. Visit https://green-home-consulting.com/blower-door-test/ to learn more.
Building science focuses on the analysis and control of the physical phenomena affecting buildings. It covers things such as building materials; the building envelope; heating, ventilation and air conditioning systems; indoor air quality; passive energy-saving strategies; fire protection; and renewable energies in buildings.
British Thermal Unit (BTU)
This is a measurement of the heat required to raise the temperature of a pound of water 1°F. BTUs are commonly used to define the size or load of furnaces, boilers and water heaters.
Combustion Appliance Zone (CAZ) Testing
Combustion Appliance Zone (CAZ) testing is performed to ensure that existing home conditions, as well as air sealing and insulation improvements, do not result in unhealthy or hazardous conditions in the home. Both physical inspection and the use of pressure testing devices, gas detectors and carbon monoxide testing equipment, are used. The goal of the test is to learn whether open combustion appliances (i.e., in the mechanical room, furnace, boiler, water heater and elsewhere) are not leaking carbon monoxide and other dangerous gases into your home. Testing is the only way to ensure that the air quality in the home is safe. To learn more, visit
Condensation results when vapor is changed into liquid due to a loss of heat. The dew point is the temperature at which condensation begins. The exact point depends on the air pressure. If the temperature goes below the dew point, liquid water will start to condense on solid services. An example of this is early-morning dew on the grass.
Convective looping is a term to describe the transfer of heat by the circulation, or movement, of currents of the heated air with colder air.
When the heated air in your home comes in contact with cooler air from the windows, the warmer air moves up (because heat rises) and cooler air sinks down.
This process is repeated as heat continues to be added to the room. The loop of air constantly moving in front of your windows makes them feel drafty. It forms a continuous drafty convective loop.
Energy Recovery Ventilator (ERV)
This device, working in conjunction with your furnace, reduces the costs of heating ventilated air in the winter by transferring heat from the warm inside air being exhausted to the fresh (but cold) supply air. An ERV system provides controlled heat and moisture while minimizing energy loss.
A heat bridge can also be called a thermal bridge, cold bridge, or thermal bypass. It is an area or component of an object which has higher thermal conductivity than its surrounding materials. This creates a path of least resistance for heat transfer or cold transfer. A thermal bridge causes an overall reduction in thermal resistance of the object. The term is used in reference to a building's thermal envelope; thermal bridges result in heat transfer into or out of conditioned (heated or cooled) space.
The rate at which heat moves from an area of higher temperature to an area of lower temperatures. Heat flow is generally used to quantify the rate of total heat gain or heat loss of a system.
Heat Recovery Ventilator (HRV)
This device, working in conjunction with your furnace, provides a controlled way to ventilate your home while minimizing energy loss. It can reduce the costs of heating ventilated air in the winter by transferring heat from the warm inside exhaust air to the fresh (but cold) outside supply air. The main difference between an HRV and an ERV is that the HRV transfers heat while an ERV transfers both heat and moisture. Learn more about ventilation systems here: https://www.energy.gov/energysaver/weatherize/ventilation/whole-house-ventilation
Home Energy Audit (Home Energy Assessment)
A home energy audit is an assessment to determine if, and where, your home is wasting energy. The audit provides recommendations on what you can do to save energy as well as improve the comfort, efficiency, and safety of your home. When performed by an independent and unbiased auditor, you can learn where your home improvement dollars would be best spent. To learn more, visit https://green-home-consulting.com/home-energy-audit/
Ice dams result from the ice build-up of melting snow on the colder eaves and gutters of sloped roofs. Ice damming occurs when heat escapes from the home into the attic and is not exhausted properly. The warm air settles at the attic roof peak, thawing the snow. The water then drips toward the eave and gutter. That’s where the temperature is still freezing. Over the course of a few days, ice damming and large icicles start to form. Large icicles are typically the result of ice damming.
This is both a concept, as well as an approach, to home energy. It considers how improvements throughout your homework together to yield the most cost-effective results.
Infrared Scan - Infrared Imaging
Also called a thermographic scan, this test utilizes a specialized camera to capture heat differences in a home. An auditor can detect otherwise hidden places where the home leaks heat; holds moisture; has problematic hidden electrical systems; insulation; and can sometimes uncover pest problems. A blower door test is used to exaggerate air leakage points to guide improvement efforts. To learn more, visit
International Code Council - ICC
The International Code Council, with more than 64,000 members, develops codes and standards used in the design, build and compliance of building structures. The codes are used in most US communities and many global markets. Visit https://www.iccsafe.org/about/who-we-are/ to learn more.
International Energy Conservation Code® - IECC
According to the International Code Council, these codes are address the “design of energy-efficient building envelopes and installation of energy-efficient mechanical, lighting and power systems through requirements emphasizing performance.” The goal is “optimal utilization of fossil fuel and nondepletable resources” in our communities. There are a separate set of codes for commercial buildings and low-rise residential buildings. “Each set of provisions, IECC-Commercial Provisions and IECC-Residential Provisions, is separately applied to buildings within their respective scopes” Learn more at https://www.iccsafe.org/products-and-services/i-codes/2018-i-codes/iecc/.
Kilowatt-hour - kWh
The kilowatt-hour is an energy billing term used to describe one unit of electric energy delivered to consumers by electric utilities. A Kilowatt-hour is a unit of energy equal to 3600 kilojoules (3.6 megajoules). The kilowatt-hour is referred to as kW⋅h, kW h but is most commonly written as kWh..
Loose fill insulation
Unlike more traditional rolls of insulation, this type of insulation is granular, nodular, fibrous, powdery, or of similar form that is installed in your attic. It is either blown, poured or placed by hand in spaces that require insulation. Insulation is measured by its R-Value.
Net Metering - Net Energy Metering - NEM
Net Metering is an electricity-billing mechanism (a meter) that allows consumers who generate some, or all, their own electricity to use that electricity anytime, rather than only when it is generated. This is important with renewable energy sources such as solar. Net metering allows consumers to use solar power generated during the day at night. Annual net metering rolls over a net kilowatt-hour (kWh) credit,. This allows solar power generated in the summer, for example to be used in the winter.
A NetZero home is one that is so energy efficient that all, or most, of the annual energy consumption is offset with renewable energy. This is considered a high-performance home.
Photovoltaic cells convert sunlight directly into electricity. Often called PV, Photovoltaics is the process by which light (photons) is converted to electricity (voltage). A Photovoltaic System, is also called a Solar Power or Solar Energy System. The photovoltaic system is comprised of several components. PV systems include solar panels that absorb and convert sunlight into electricity; a solar inverter that converts the output from direct to alternating current; and mounting, cabling, and other electrical accessories. All these components are arranged in a particular fashion to produce electricity. It is an alternative to the traditional electricity purchased from a utility company.
A post-project “test-out, is performed after home energy projects are completed. The blower door test, used with infrared imaging, helps determine a home’s air leakage. The Combustion Appliance Zone test (CAZ) verifies that proper ventilation and open combustions appliances (furnaces, hot water heaters, boilers) are operating safely. Green Home Consulting is certified by the Building Performance Institute (BPI) to perform all pre- and post-tests.
Insulation is measured by its R-value. This is a number that describes the effectiveness of the insulation. It is a measure of how well the insulation per unit of exposed area resists the conductive flow of heat. The higher the R-value, the higher the resistance.
Solar Energy System
A Solar Energy System (also known as a Solar Power System, Photovoltaic System or PV System)is a system designed to supply usable solar energy by means of photovoltaics. (See definition above.). The system is comprised of several components. This includes solar panels that absorb and convert sunlight into electricity; a solar inverter that converts the output from direct to alternating current; and mounting, cabling, and other electrical accessories. All these components are arranged in a particular fashion to produce electricity. It is an alternative to the traditional electricity that is purchased from a utility company.
Test In – Test Out (Before-and-After Testing)
Two tests, a pre-project “test-in” and a post project “test-out”, are performed before and after any home energy projects are completed. The blower door test, used with infrared imaging, helps determine the home’s air leakage. The Combustion Appliance Zone test (CAZ) verifies that proper ventilation and open combustions appliances (furnaces, hot water heaters, boilers) are operating safely. Once home energy improvements such as air sealing, insulation, windows, and other improvements) are completed, the post test, or “test-out” is conducted. Post-testing is the only way to ensure that the air quality in your home is safe for you and your family. Use a certified professional to perform all pre- and post- tests.
**Theoretically, achieving the passive house standard is not too expensive as many relatively inexpensive insulation materials are available on the market. However, it is important to use proper materials for each part of the building and also to install them consistently, avoiding "heatbridges".**
Thermography is a technique that used specialized imaging equipment (an infrared camera) to detect and measure variations in heat emitted by a building or structure. The data is transformed into visible images that are recorded photographically and used to help determine air leakage as well as hot and cold spots in the home.
Xcel Energy Trade Partner (Excel Trade Partner)
Xcel Energy, a Colorado utility, partners with vendors and contractors to help implement their programs. Xcel provides resources and updates information to help businesses work with customers, providing rebates, training and other resources. It’s an advantage to work with trade partners because the vendors and contractors have access to the latest information, updates and have the proper certifications. Only approved contractors are listed on the Xcel website. Some rebates are only available when working with Xcel’s trade partners.