Common acronyms and definitions

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Categories: Beginners Guide

The building science and home performance industry is full of confusing acronyms. These acronyms are used a lot in articles, blog posts. social media posts, webinars, conference sessions, etc. To help you, we have compiled a list of some of the more popular acronyms you’re likely to hear or read.

ABAA – Air Barrier Association of America
The Air Barrier Association of America (ABAA) was incorporated in Massachusetts in 2001 and consists of stakeholders in the building enclosure industry. Stakeholders include manufacturers, suppliers, distributors, architects, engineers, contractors, researchers, testing & audit agencies, consultants and building owners. (Source:

ACI – Affordable Comfort Inc. (now known as the Home Performance Coalition)
The Home Performance Coalition creates energy-efficient, healthy, sustainable homes through education, training, advocacy and outreach. (Source:

ACCA – Air Conditioning Contractors of America
ACCA is a non-profit association whose membership includes more than 60,000 professionals and 4,000 businesses in the indoor environment and energy services community. ACCA works together to promote professional contracting, energy efficiency, and healthy, comfortable indoor environments. (Source:

ACH – Air Changes per Hour
Air Changes per Hour (ACH) is how many times all of the air in the structure is replaced by outside air per hour. For example, 5 ACH means all of the air in the structure is being replaced by outside air five times in one hour.

ACH50 – Air Changes per Hour at 50 Pascals
ACH50 is the number of times the total volume of air in a home or building is exchanged with outside air under typical pressurization or depressurization with a blower door.

ASHRAE – American Society of Heating Refrigerating and Air Conditioning Engineers
ASHRAE is a global society advancing human well-being through sustainable technology for the built environment. ASHRAE and its members focus on building systems, energy efficiency, indoor air quality, refrigeration and sustainability within the industry. (Source:

ASTM International – American Society for Testing and Materials
ASTM International, formerly known as the American Society for Testing and Materials (ASTM), is a globally recognized leader in the development and delivery of international voluntary consensus standards. Today, some 12,000 ASTM standards are used around the world to improve product quality, enhance safety, facilitate market access and trade, and build consumer confidence. (Source:

BPI – Building Performance Institute
BPI develops standards for energy efficiency retrofit work using an open, transparent, consensus-based process built on sound building science. From these standards, we develop professional certifications for individuals, companywide credentials for BPI GoldStar Contractors, home energy rating systems and quality assurance services that help raise the bar in home performance contracting. (Source:

BS – Building Science
Building science is the collection of scientific knowledge and experience that focuses on the analysis and control of the physical phenomena affecting buildings and architecture. It traditionally includes the detailed analysis of building materials, building envelope, heating, ventilation and air conditioning systems, natural and electrical lighting, acoustic, indoor air quality, passive strategies, fire protection, and renewable energies in buildings. (Source:

CAZ – Combustion Appliance Zone
Room and enclosed air volume that contains a combustion appliance. This may include, but is not limited to, a mechanical room, mechanical closet, or main body of the house. (Source:

CFM – Cubic Feet per Minute
A unit of measure for airflow velocity past a certain point or through a certain structure.

DOE – Department of Energy
Governmental department whose mission is to advance energy technology and promote related innovation in the United States. (Source:

EPA – Environmental Protection Agency
The United States Environmental Protection Agency (EPA or sometimes USEPA) is an agency of the U.S. federal government which was created for the purpose of protecting human health and the environment by writing and enforcing regulations based on laws passed by Congress. (Source:

ERI – Energy Rating Index
The Energy Rating Index performance path gives builders another option for complying with the 2015 International Energy Conservation Code (IECC). Homes are given a numerical score from 0 (which is the equivalent to a net zero home) to 100 (which is equivalent to a home built to the 2006 IECC standards).

HERS – Home Energy Rating System
The Home Energy Rating System (HERS) Index is the industry standard by which a home’s energy efficiency is measured. It’s also the nationally recognized system for inspecting and calculating a home’s energy performance. (Source:

HPC – Home Performance Coalition (Formerly ACI)
The Home Performance Coalition creates energy-efficient, healthy, sustainable homes through education, training, advocacy and outreach. (Source:

HRV – Heat Recovery Ventilator
Heat recovery ventilation, also known as HRV or mechanical ventilation heat recovery (MVHR), is an energy recovery ventilation system using equipment known as a heat recovery ventilator, heat exchanger, air exchanger or air-to-air heat exchanger. This equipment employs a cross-flow or counter-flow heat exchanger (countercurrent heat exchange) between the inbound and outbound air flow. Generally used in cold climates, HRVs remove heat from stale air as it is being exhausted from a building, moving that heat to incoming fresh air. This saves energy by raising the baseline heat level of incoming air before it enters the home or building.

HVAC – Heating, Ventilating and Air Conditioning
HVAC (heating, ventilating, and air conditioning; also heating, ventilation, and air conditioning) is the technology of indoor and vehicular environmental comfort. (Source:

IAQ – Indoor Air Quality
Indoor air quality (IAQ) is a term which refers to the air quality within and around buildings and structures, especially as it relates to the health and comfort of building occupants. (Source:

ICC – International Code Council
ICC is dedicated to developing model codes and standards used in the design, build and compliance process to construct safe, sustainable, affordable and resilient structures. (Source:

IECC – International Energy Conservation Code
The 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 states and municipal governments in the United States for the establishment of minimum design and construction requirements for energy efficiency. (Source:

IRC – International Residential Code
The International Residential Code (IRC) is a comprehensive, stand-alone residential code that creates minimum regulations for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences. (Source:

LEED – Leadership in Energy and Environmental Design
Leadership in Energy and Environmental Design (LEED) is a set of rating systems for the design, construction, operation, and maintenance of green buildings, homes, and neighborhoods. (Source:

NIST – National Institute of Standards and Technology
NIST is the federal technology agency that works with industry to develop and apply technology, measurements, and standards. (Source:

OCEAN – Online code Environment and Advocacy Network
OCEAN is an interactive resource designed to share experiences, best practices, educational resources, and news about building energy codes. (Source:

PHIUS – Passive House Institute US
Passive House Institute US (PHIUS) is a 501(c)3 organization committed to making high-performance passive building principles the mainstream best building practice, and the mainstream market energy performance standard. (Source:

RED – Residential Energy Dynamics
RED is a software company specializing in building diagnostic procedures and calculations in North America. They also offer building diagnostic training. (Source:

RESNET – Residential Energy Services Network
The Residential Energy Services Network or RESNET is a not-for-profit, membership corporation that is governed by a board of 20 (who are elected by membership). RESNET is a recognized national standards-making body for building energy efficiency rating and certification systems in the United States. (Source:

SEER – Seasonal Energy Efficiency Ratio
The Seasonal Energy Efficiency Ratio (SEER) measures air conditioning and heat pump cooling efficiency, which is calculated by the cooling output for a typical cooling season divided by the total electric energy input during the same time frame. A higher SEER rating means greater energy efficiency. (Source:

TEC – The Energy Conservatory
TEC is the world’s leading manufacturer of air tightness testing tools, including the Minneapolis Blower Door™ and the Minneapolis Duct Blaster®.

ZPD – Zone Pressure Diagnostics
The process of measuring and using intermediate/transition compartment/zone and blower door pressures and flows to evaluate the relative leakage between the inside of a building and intermediate zones, and between the intermediate zones and the outside of the building for the purpose of determining which boundary/barrier to use as the air barrier. (Source:

Print sources:
Green Building: Principles and Practices in Residential Construction. Kruger, Abe, and Carl Seville. Delmar Cengage Learning (New York, 2013).

Residential Energy: Cost Savings and Comfort for Existing Buildings. Krigger, John, and Chris Dorsi. Saturn Resource Management (Montana, 2004).