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Guideline E.4: Atmospheric Protection

Intent

To encourage the investigation and evaluation of refrigerants to reduce environmental impacts harmful to the atmosphere. Energy conservation should be achieved with the lowest reasonable environmental impacts.

Recommended Performance Criteria

Guidelines apply to all projects designated New Buildings and are recommended for Major Renovations.

There are no required levels for atmospheric pollution from refrigerants at this time except for CFC reduction, which is required in the MN State Building Code. Meet the following criteria refrigerants:

Achieve an Atmospheric Lifetime (AtL) < 33. Atmospheric Lifetime is a measure of the average persistence of the refrigerant if released. A longer lifetime has worse environmental effects.
Achieve an Ozone Depletion Potential (ODP) < 0.034. Ozone Depletion Potential is a normalized indicator based on the ability of a refrigerant to destroy atmospheric ozone, where CFC-11 = 1.00. A higher ODP has worse environmental effects.
Achieve a Global Warming Potential (GWP) < 3500. Global Warming Potential is an indicator of the potency of the refrigerant to warm the planet by action as a greenhouse gas. A higher GWP has worse environmental effects.
Design, maintain, and operate the mechanical equipment to reduce refrigerant leakage over the life of the building.

Meeting the Guidelines

Refrigerant Climate Data[1]

[1] James M. Calm, “Refrigerant Data Summary,” Engineered Systems Magazine November 2001.

Refrigerant	Atmospheric Lifetime in Years	Ozone Depletion Potential	Global Warming Potential
HFC-152a	1.4	0	120
HCFC-123	1.4	0.012	120
HCFC-21	2	0.01	210
HFC-32	5	0	550
HCFC-124	6.1	0.026	620
HFC-245fa	7.2	0	950
HFC-134a	13.8	0	1300
HCFC-22	11.9	0.034	1700
HFC-125	29	0	3400
HFC-227ea	33	0	3500

CFCs generally have high Ozone Depletion Potential and Global Warming Potential with long Atmospheric Lifetimes. CFCs are therefore not allowed by these guidelines and prohibited by MN state law. Halons have a higher Ozone Depletion Potential though a lower Global Warming Potential but a much longer Atmospheric Lifetime. Halons should be avoided if possible. HCFCs such as R-123, which other guides put in the same class as Halons, can have an Ozone Depletion Potential, a Global Warming Potential and an Atmospheric Lifetime two orders of magnitude less than CFCs and Halons. HFCs offer near zero Ozone Depletion Potential, but some have high Global Warming Potential. For example, R-134 has an Ozone Depletion Potential of 0.0 but a Global Warming Potential and an Atmospheric Lifetime approximately ten times greater than R-123, an HCFC alternative. Substituting an HFC, which tends to be less energy efficient than an HCFC, may result in the use of more energy, resulting in a further increase in global warming.

Implementation in the Design Process:

In Predesign and early design determine onsite fire suppression requirements. Plan and organize building to minimize the need for the use of Halon fire suppression systems

Using the tables above and other information as may be available at the time of design, identify candidate refrigerants that have a low Global Warming Potential, short Atmospheric Lifetime, and a low Ozone Depletion Potential.

Use one of the weighted evaluation metrics provided to evaluate the refrigerants, and prioritize the list in the order given. Evaluate the economic and community impacts of the prioritized list and adjust priorities pursuant to the analysis.

In construction documents based on this analysis, develop specifications based on adjusted priorities. Verify shop drawings to assure compliance.