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Building Science

153 Green Building Acronyms and Initials

If you're bewildered by the jargon, here's a list to help you decipher all those abbreviations

Acronyms and initials are part of the jargon of every field. Here's a list of 153 green building abbreviations.
Image Credit: tikitoy998 from - Creative Commons license

Acronyms and initials (let’s call that AI,† for short, not to be confused with the other AI, which stands for artificial intelligence, or AIA, which stands for American Institute of Architects) are part of the jargon of every field. Our field, whether you call it building science, green building, home performance, or something else, is no exception. So, a few years ago I started putting together a list that I now include in the manuals that we give out in our training classes.

I’m up to 153 total lines in my list, which our students find helpful in sorting out all the jargon that’s new to them. When you first come into this field and start getting the barrage of ACH50, HVAC, COP, HDD, WRB, and more thrown at you, it’s good to have somewhere you can look these things up.

Also, if two AI have the same definition, I included them on the same line. For example, SHR and SHF both refer to the same quantity, even though one uses the word fraction and the other ratio.


GBA Glossary

When a single AI has two different definitions, however, I put them on separate lines. The only one I have like that right now is CO, which could stand for carbon monoxide or certificate of occupancy.

Anyway, I’m sure you’re dying to find out what RTFM stands for, so let’s get on with it. Below is a table of my 153 acronyms and initials. If you want to download the list, see the link below the table.

Acronym What it stands for
AAC autoclaved aerated concrete
ABAA Air Barrier Association of America
ACCA Air Conditioning Contractors of America
ACH50 air changes per hour at 50 Pascals
ACHnat air changes per hour natural
ACI Affordable Comfort Inc.
ADA another damn acronym (although this would really be initials)
ADA Americans with Disabilities Act
ADC Air Distribution Council
AFUE annualized fuel utilization efficiency
AGW above-grade wall
AHJ authority having jurisdiction
AHRI Air Conditioning, Heating, and Refrigeration Institute
AHU air handler unit
ANSI American National Standards Institute
APHN American Passive House Network
ASHP air-source heat pump
ASHRAE Amer. Soc. of Heating, Refrigerating, and Air-conditioning Engineers
ASTM American Society for Testing and Materials
BA Building America
BAS building airflow standard
BCAP Building Codes Assistance Project
BOP Builder Option Package
BPI Building Performance Institute
BS building science
BSC Building Science Corporation
BTL building tightness limit
BTU British Thermal Unit
CAZ combustion appliance zone
CCF hundred cubic feet
CDD cooling degree days
CFA conditioned floor area
CFL compact fluorescent lamp
cfm cubic feet per minute
cfm50 cubic feet per minute at 50 Pascals
CHP combined heat & power
CO carbon monoxide
CO certificate of occupancy
CO2 carbon dioxide
COP coefficient of performance
CYA cover your ass
CZ climate zone
DIY do it yourself
DOE Department of Energy
ECM electronically commutated motor
EEM energy efficient mortgage
EER energy efficiency ratio
EF energy factor
EFL Environments for Living
EIA Energy Information Administration
EIM Energy Improvement Mortgage
ELA envelope/enclosure leakage area
ELR Envelope/Enclosure Leakage Ratio
EPA Environmental Protection Agency
EPS expanded polystyrene
EqLA equivalent leakage area
ERV energy (or enthalpy) recovery ventilator
ES / ESTAR Energy Star
ES V3 Energy Star version 3
FHA U.S. Federal Housing Authority
FLA four letter acronym or five letter acronym
FROG finished room over garage
GBA Green Building Advisor
GC general contractor
GSHP ground-source heat pump
GWP global warming potential
HDD heating degree days
HEPA high efficiency particulate air
HERS Home Energy Rating System
HOT2000 A type of Canadian energy modeling software
HP home performance
HPwES Home Performance with Energy Star
HRV heat recovery ventilator
HSPF heating season performance factor
HUD U.S. Department of Housing and Urban Development
HVAC Heating, Ventilating, & Air Conditioning
IAQ indoor air quality
ICAT insulation contact, air tight (designation for recessed can lights)
ICC International Code Council
ICF insulated concrete form
IEA International Energy Agency
IECC International Energy Conservation Code
IEQ indoor environmental quality
IR infrared
IRC International Residential Code
IREC Interstate Renewable Energy Council
iwc inches of water column (pressure unit)
iwg inches of water gauge (pressure unit, same as iwc)
KISS keep it simple, stupid
LBL Lawrence Berkeley Laboratory (old name, still used by some)
LBNL Lawrence Berkeley National Laboratory
LCA life cycle analysis
LED light emitting diode
LEED Leadership in Energy & Environmental Design
LEED AP LEED Accredited Professional
MEC Model Energy Code
MERV Minimum Efficiency Reporting Value
NAHB National Association of Home Builders
NAPHN North American Passive House Network (a.k.a. APHN)
NASEO National Association of State Energy Offices
NATE North American Technician Excellence
NCI National Comfort Institute (not to be confused with Comfort Institute)
NIST National Institute of Standards and Technology
NPP neutral pressure plane
NPV net present value
NREL National Renewable Energy Laboratory
NZE Net Zero Energy
OCEAN Online Code Environment and Advocacy Network
OEM original equipment manufacturer
ORNL Oak Ridge National Laboratory
OSB oriented strand board
OVE Optimal Value Engineering (includes advanced framing)
PDW pre-drywall
PHAUS Passive House Alliance U.S.
PHIUS Passive House Institute U.S.
PM project manager
PPE personal protective equipment
PSC permanent split capacitor
PTAC packaged terminal air conditioner
PTHP packaged terminal heat pump
PV photovoltaic
PV present value
QA quality assurance
QAD Quality Assurance Designee
RECS Residential Energy Consumption Survey
RESNET Residential Energy Services Network
RH relative humidity
RTFM read the friendly manual
SDO Standards Development Organization (ANSI designation)
SEER seasonal energy efficiency ratio
SFBE square footage of building enclosure
SHF or SHR sensible heat fraction (or ratio)
SHGC solar heat gain coefficient
SIP structural insulated panel
SIPA Structural Insulated Panel Association
SIR savings investment ratio
SMACNA Sheet Metal and Air Conditioning Contractors’ National Association
SPF spray polyurethane foam
SPFA Spray Polyurethane Foam Association
SWAG scientific wild-ass guess
TESP total external static pressure
TLA three letter acronym
TXV or TEV thermal expansion valve
USGBC U.S. Green Building Council
VOC volatile organic compound
VRF variable refrigerant flow
VRV variable refrigerant volume
WRB water-resistive barrier (not weather-resistant barrier)
wrt with respect to
WUFI Wärme-und Feuchtetransport instationär
XPS extruded polystyrene
ZEB zero energy building (should be ‘net’ zero)
ZPD zone pressure diagnostics

Sorry. No definitions for the AI above. The purpose of this list is just to help people decode the letters when they hear or read them. Some of these terms are defined in the GBA glossary.

Get the full list

If you’d like the list of what is currently 153 acronyms and initials in both pdf and MS Excel formats, go here: Get the List!.

I hope you find it useful. If you’re relatively new to the field, this list can be quite handy. If you’ve been in the field for a while, you probably know all or most of what’s here, but maybe you have some others that you think I should add. Let me know.

Allison Bailes of Decatur, Georgia, is a speaker, writer, energy consultant, RESNET-certified trainer, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.


† AI isn’t an acronym because if you tried to say it, someone might dial 911. To be an acronym, it’d have to make a nice word-like sound. Something like IMP (Insulation Manufacturers and Partners) or LUST (leaking underground storage tank), for example. (Only one of those is something I made up, btw.) AI isn’t an abbreviation either, which is usually a shortened version of a single word. And don’t get me started on contractions! No, AI is a set of initials, which is usually the word people should use when they call something an acronym.


  1. user-1135248 | | #1

    double jeopardy
    The amusing thing is that some mechanism of GBA tries to identify
    glossary terms in posted text and insert some form of the
    definition in a way that isn't clear to me, perhaps it's
    supposed to be a mouse-over that expands a pop-up or the like.
    Reading GBA with a text-only or bare-bones browser as I usually
    do, things get confusing because that text simply shows up inline
    right after the term in question without even any separation
    added. It's theoretically smart enough to do that only on the
    first instance per post of the term and not all of them, but
    makes for amusing reading sometimes.

    Now imagine what happens when I read this article!

    I see similar glossary mechanisms on other forums, but the terms
    are simply highlighted clickable links that readers can *optionally*
    follow if they want a definition. Hopefully the coming website
    revamp can also present glossary references in a slightly less
    stuffed-down-your-throat fashion, which will also cause slightly
    less text to be sent out per page anyway.


  2. GBA Editor
    Martin Holladay | | #2

    Response to Hobbit
    Thanks for letting us know about one more glitch in the design of our GBA website. I really appreciate the feedback. I have added your suggestion to a long list of hoped-for improvements to the GBA web site, and I will be sharing the list with our technical team.

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