Be an Informed LEED-er

Requirements To Consider When Preparing to LEED® Certify An Existing Building

The U.S. Green Building Council® (USGBC®) LEED for Existing Buildings Operations and Maintenance® is a program designed to recognize and rank buildings that have already been constructed that make great strides towards becoming environmentally friendly. For many buildings, this program begins where LEED for New Construction® ends, but the USGBC® also uses this program to recognize existing buildings that have not already been certified under the LEED for New Construction® program.

This article examines the prerequisites in LEED for Existing Buildings Operations and Maintenance® that have the potential to have large costs associated with them. The ultimate goal of this article is to assist with determining an accurate cost baseline for making buildings as environmentally friendly as possible.

Water Efficiency Prerequisite 1: Minimum Indoor Plumbing Fixture & Fitting Efficiency*

Prerequisite Summary: Establish a calculated Baseline, and a calculated fixture water usage, using LEED® guidelines (this can be determined through a calculation template that can be downloaded from the USGBC® website). Reduce calculated building fixture water usage to within 120% of this calculated Baseline (if the building fixtures were installed in or after 1993) or 160% of this calculated baseline (if the building fixtures were installed before 1993).

Consider: LEED® uses the International Plumbing Code® 2006 Edition to calculate the usage baseline. This prerequisite does not require that all of a building’s fixture water usage ratings must meet code, or be within 120% (or 160%) of it; the fixture usage rates are weighted, based on a usage profile defined by all the different groups of people using a building (such as visitors, students, residents, full-time employees, etc) that have access to each of these fixtures. Thus, a fixture that is installed in a publicly accessible location in a building with a high number of daily visitors will count more than the exact same fixture installed in a private office bathroom in the same building.

For many buildings (particularly buildings built after 1993), meeting this prerequisite may be as simple as installing new faucet aerators to meet the 0.5 gallon-per-minute (gpm) water flow rate required by code. Other, older buildings might require the installation of new low-flow flushometers for flush valve water closets or urinals. Unfortunately, most of the pre-1993 buildings face a much tougher road to fulfilling this requirement in the form of having to install all-new water closets and urinals. Most of the older 3.0 gallons-per-flush (gpf) water closets are not compatible with low-flow flushometers, and thus both the porcelain and the flushometer must be replaced in order to meet the requirements for this prerequisite. Special considerations must be taken for wall-hung fixtures, since replacement fixtures that are compatible with the existing bracket and connection locations must be selected if piping modifications and wall reconstruction are to be avoided. The total cost for this operation can run into the tens of thousands of dollars very quickly. The good news is that in many cases buildings that replace the older 3.0 or 3.5 gpf fixtures with the newer low-flow fixtures are likely to achieve payback from water savings in less than 10 years (this will depend entirely on fixture usage volume).

The Conclusion: When considering whether to try to get a building LEED® certified, it must be considered beforehand whether all-new bathroom fixtures must be installed before the building can qualify to begin earning points, and, if so, if the project budget can afford it. At an average installed rate of anywhere from $600 to $1000 per water closet or urinal (including labor), this prerequisite has the potential to eat up the entire budget for a LEED® project on its own. Payback periods should also be taken into consideration, and can soften the impact of a high-cost installation.

Energy & Atmosphere Prerequisite 2: Minimum Energy Efficiency Performance*

 Prerequisite Summary: The building must achieve either a 69 ENERGY STAR® rating, or have an Energy Usage Index (EUI) 19% lower than the average building of its type (the ENERGY STAR® rating for any building is based on that building’s EUI).

Consider: The true focus of this credit is on reducing the building’s Greenhouse Gas Emissions (GHG). LEED® considers conventional or “high-impact” electricity (non-renewable fuel source or high-impact hydroelectric) to be the most polluting energy on the market. This causes a building that receives 100% of its power from conventionally-generated electricity to have a much harder time satisfying this prerequisite than one with alternatively fueled space heating, water heating, etc. Table 1 below demonstrates the EUI advantage of using alternative fuels by comparing the EUIs of two buildings, one powered by conventional electricity alone, the other powered by a combination of conventional electricity and natural gas.

 Table 1Table 1: Energy Usage Index Comparisons









It is obvious that a building using alternative low-emissions fuel for at least part of its processes has a significant advantage over a building using conventional electricity. If the total energy usage in a building is difficult to reduce (because of process equipment required, etc.), some ways to reduce GHG emissions and improve a building’s EUI are as follows:

  1. Swap out electric-powered appliances/equipment for their natural gas (or other alternative low-emissions fuel) counterparts; e.g., swap electric water heaters for gas water heaters, electric strip-heaters for natural gas or propane furnaces, etc. Depending on what you replace, this can be quite expensive, and one must also consider the ongoing costs of the alternative fuel desired, when compared to those of electricity. Check to make sure your building has a natural gas service line installed, as well. Installing a new gas service line can be very expensive.
  2. Install on-site renewable power generation (solar, wind, etc.). All power that is generated on-site via renewable sources is not counted in the building’s total energy usage profile. This option also has the benefit of earning extra credits under Energy & Atmosphere Credit 4. Something to consider, however, is that (with government tax credits and grants) this option only sees payback after about 25 years at the time of this writing (this calculation is based on a municipal electricity cost rate of $0.16 per kWh). Most of the larger building are able to purchase electricity at a much lower rate (average rate is $0.08 per kWh for the buildings audited by Mullinax Solutions), and thus will see even longer payback periods of 45 years or more. Payback from the installation of on-site renewable power generation is essentially non-existent, in almost every case Mullinax Solutions has examined.
  3. Install energy meters on all process equipment. LEED® does not require process energy (computers, data centers, large kitchen equipment, etc.) to be included in energy usage index calculations; thus, all energy used to power process equipment may be subtracted from the total building power. Depending how much of a building’s total energy usage is due to process equipment, the project might be able to meet this prerequisite by using this method alone. This is typically the least expensive option, and is typically the easiest to implement as well.

The Conclusion: This credit has the potential to be the least, or most, expensive of all the prerequisites, depending on what needs to be upgraded or changed. Also, keep in mind that ENERGY STAR® uses a 1-year benchmark to give a rating, so once new energy-saving procedures have been implemented, it will take one full year for the savings to be fully reflected in the ENERGY STAR® rating or EUI. This will cause the project to be delayed for a minimum of one year.

Energy & Atmosphere Prerequisite 3: Fundamental Refrigerant Management*

Prerequisite Summary: Ensure that all HVAC equipment in the building contains no chlorofluorocarbon (CFC) refrigerants.

Consider: Newer buildings should have no problem with this prerequisite, since CFCs have not been in production for some time now, but older buildings (particularly those with chilled water systems) may have an older chiller that uses CFC-11 or CFC-114. Older restaurants may also have some issues, since many models of older walk-in coolers make use of CFC-12. Although some HVAC equipment may be able to be converted to use the more environmentally friendly hydro-chlorofluorocarbon (HCFC) refrigerants, many cannot be converted, and would have to be replaced before the building would be eligible to receive LEED® certification. The required modifications to equipment can range from relatively inexpensive and simple (such as installing a new thermal expansion valve, discharging old refrigerant, and recharging with an approved alternative refrigerant) to expensive and possibly very complex (such as purchasing a new walk-in cooler, or installing a new chiller).

The Conclusion: The nameplates and tags on all refrigeration equipment should be examined to determine what kind of refrigerant it uses. This will assist in determining what (if any) equipment needs to be retrofitted or replaced. Equipment manufacturers will be able to assist with supplying retrofit kits for equipment that can be modified to accept HCFC refrigerants. Lists of the various CFC refrigerants that have been banned can be found on the EPA® website at

Indoor Environmental Quality Prerequisite 1: Minimum Indoor Air Quality Performance*

Prerequisite Summary: Meet the outside air supply requirements set forth in ASHRAE® 62.1-2007.

Consider: In order to increase the maximum outside air supply capacity of a typical unit, it must be equipped with enthalpy wheels, reheat systems, etc. Such a system is commonly known as an Energy Recovery Ventilator (ERV), and is usually capable of properly conditioning anywhere from 55%-100% outside air by total volume. 

The Conclusion: Unfortunately, installing a brand new ERV can be quite expensive, so it must be carefully examined whether a building meets (or can be easily configured to meet) ASHRAE® outside air requirements with its existing equipment and system configuration. If the system does not meet ASHRAE® requirements with its existing equipment or system configuration, the best-case scenario would consist of a simple rebalance of the airflow distribution and unit settings by a certified test and balance technician in order to supply the proper amount of outside air to each zone. The worst-case scenario would require installation of a new HVAC unit (or even possibly a redesign of the HVAC system) before the building could submitted for LEED® certification. While LEED® does provide an alternative for buildings that cannot provide the amount of outside air required by ASHRAE® 62.1-2007 with their current equipment, the alternative requirement (10 CFM per occupant at all times) can be just as difficult to achieve. This is particularly true for equipment serving areas (such as office buildings) where ASHRAE® outside air supply rates for occupants are significantly lower than 10 CFM per occupant.

An alternative approach to this prerequisite might be to first set the outside airflows to satisfy the ASHRAE® space-only requirements (not including occupant outside air supply rates), and then install CO2 sensors to monitor the ambient air conditions and modulate the outside air supply to satisfy the occupants with outside air on an on-demand basis (a Credit Interpretation Request may need to be submitted to LEED® to obtain approval for this approach). This approach will require that a digital control system be installed, and thus would be most suitable for buildings with an existing Building Automation System (BAS); installing and programming a new BAS for an average building can be very costly. In all cases, proper thought must be put into how this prerequisite will be met, because it has the potential to cost the project a significant portion of its budget. 

Concluding Remarks:

Mullinax Solutions strongly believes in the principles of LEED®. Every building is unique in its purpose, design, and construction, and will need to be evaluated independently of all other buildings. Many buildings will meet the prerequisites examined in this article with no additional work necessary, while others will need modifications that will require anything from simple and inexpensive modifications to complex and costly replacements. One thing, however, is for certain: following these guidelines to environmentally responsible leadership, the people of our nation will become less energy-dependent, will learn to be better stewards of our valuable natural resources, and they will begin to secure a cleaner and healthier environment for our future generations.

Author: Miles D. Johnson, LEED® G.A., Mechanical Designer & LEED® Consultant


LEED® and the USGBC® logo are registered trademarks of the U.S. Green Building Council, and are used by permission.

*All prerequisites and credits mentioned in this article have been developed by the U.S. Green Building Council (USGBC), and remain the sole property of the USGBC and its affiliated


The US Green Building Council.

The US Green Building Council. Various. Web, October 14, 2009.

The US Green Building Council. LEED Reference Guide for Green Building Operations and Maintenance. 2009 Edition.The US Green Building Council: 2009. Print. 

The Environmental Protection Agency (EPA).

The United States Federal Government

August 28, 2009. Web, October 14, 2009.

The WEBstraunt Store.

The WEBstraunt Store Food Service & Supply Company

October 14, 2009. Web, October 14, 2009.


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