Lee, the purpose of Energy & Atmosphere (EA) Prerequisite 1, Fundamental Refrigerant Management, is to reduce stratospheric ozone depletion. Refrigerants have varying applications, lifetimes, ozone-depleting potentials (ODPs), and global-warming potentials (GWPs). Ideally, the project will choose and schedule equipment that utilizes refrigerants with the most minimal environmental impact possible.

Refrigerants and the Clean Air Act

The Environmental Protection Agency (EPA) has created the Significant New Alternatives Policy (SNAP) Program under section 612 of the Clean Air Act Amendments. This program evaluates potential alternatives to ozone-depleting substances and compiled into a list of acceptable and unacceptable substitutes, available for viewing here.

GWP: R-134a vs. R-410a

Of course for many projects, the choice between R-134a and R-410a is a recurring issue. When a project is pursuing the U.S. Green Building Council’s Leadership in Energy and Environmental Design (LEED) rating system certification, I believe it’s important to perform preliminary calculations to determine what refrigerants have the least environmental impact overall. These calculations should be performed ideally during the design development phase of the project, after preliminary load calculations have been completed (but before final energy modeling, if your project is pursuing that approach to EA Credit 1, Optimize Energy Performance).

As you mentioned, R-134a, otherwise referred to the in the LEED reference guide as HFC-134a (a common replacement for CFC-12 or HCFC-22) has an ODP of 0 and a GWP of 1,320. R-410a, referred to as HFC-410A also has an ODP of 0, but has a GWP of 1,890.

LEED and Refrigerants

EA Credit 4, Enhanced Refrigerant Management, sets out to reduce ozone depletion and support early compliance with the Montreal Protocol while minimizing direct contributions to climate change. Option 1 for compliance is to not use refrigerants, but unless your project utilizes district utilities in the form of chilled water, hot water or steam – that would be tricky.

So we’re left with Option 2, ‘select refrigerants and HVAC&R [systems] that minimize or eliminate the emission of compounds that contribute to ozone depletion and global climate change. Base building HVAC&R equipment must comply with the following formula… LCGWP + LCODP x 105 ≤ 100. Where LCGWP (Lifecycle Direct Global Warming Potential) = [GWPr x (Lr x Life + Mr) x Rc]/Life and LCODP (Lifecycle Ozone Depletion Potential) = [ODPr x (Lr x Life + Mr) x Rc]/Life. (More information on calculations and abbreviation definitions are available in the LEED Green Building Design and Construction Reference Guide.

By far the easiest way to perform these calculations is to utilize the official LEED EAc4 template, which can be downloaded from LEED Online after your project is registered. If, however your project is not registered and you’d like to get an idea of how your calculation will work out, several manufacturers provide Excel sheets to help you with the calculations. McQuay has a very detailed (and recently updated) calculator.

But to actually answer your question, I’ll have to make some assumptions. So let’s say that the project is trying to decide between the two refrigerants above for a 200 ton centrifugal chiller with refrigerant charge of 400 lbs. For R-134a, this equates to a LCODP of 0.00 and LCGWP of 64.28, while for R-410a, the calculation yields a LCODP of 0.00 again and LCGWP of 92.13. Obviously this calculation will change as more equipment is added and with actual manufacturer product data. But the two resources I mentioned above should be enough to get your preliminary questions answered.

Hope this helps!

Related Advice:

• LEED EQ Prerequisite 3: Fundamendal Refrigerant Management



• Refrigerant Management: What's are the Differences Between LEED EAp3 and LEED EAc4?



• LEED NC EA Credit 4: Enhanced Refrigerant Management