Summary and critique of "LEED" Building Design & Construction Reference Guide, v4

Jonathan Ochshorn

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Following is my summary and critique of the USGBC's LEED Building Design & Construction Reference Guide, v4. Commentary on the Reference Guide can be found in these red boxes, sometimes within each of the chapter links immediately above, but also in my summary and critique of the prior versions: Version 2.2 NC and Version 3.0.

3. Water Efficiency (WE)

Overview

WE Prerequisite 1: Outdoor water use reduction

Intent: Use less "outdoor" water (benefits on both ends — less strain on local supply, plus less impact on local wastewater systems).

Requirements: There are two options for compliance. In the latter case, nonvegetated surfaces are not counted in landscape area calculations. Vegetated play fields and food gardens may or may not be included.

Option 1. No irrigation required (Note: Satisfying this option gets you 2 points for a later credit option). Actually, two years of irrigation is permitted in order to get the vegetation started.

Option 2. Reduced irrigation: Using smart species selection and advanced irrigation technology, show that outside water use is reduced 30% from the "baseline," at least during the "peak watering month." Calculations are based on the Environmental Protection Agency (EPA) WaterSense Water Budget Tool.

WE Prerequisite 2: Indoor water use reduction

Intent: Use less "indoor" water (benefits on both ends — less strain on local supply, plus less impact on local wastewater systems).

Requirements: Indoor water use must be reduced from "baseline" values for building water as well as for appliance and "process" water use.

A. Building Water Use: For toilets, public and private lavatory faucets, kitchen faucets, and showerheads (as applicable to the project scope), reduce aggregate water consumption by 20% from the baseline. All newly installed toilets, urinals, private lavatory faucets, and showerheads that are eligible for labeling must be WaterSense labeled (or a local equivalent for projects outside the U.S.). The baseline is defined as follows, in terms of the quantity of water per unit of time (or per flush):

Plumbing elementBaseline value
Toilet1.6 gallon per flush (gpf)
Urinal1.0 gallon per flush (gpf)
Public lav faucet0.5 gallon per minute (gpm) at a pressure of 60 psi
Private lav faucet2.2 gpm at 60 psi
Kitchen faucet2.2 gpm at 60 psi
Showerhead2.5 gpm at 80 psi

B. Other water use (appliances and process water): Other water use indoors must be regulated as follows:

Appliances

ApplianceRequired rating or specification
Clothes washer (residential)ENERGY STAR or equivalent
Clothes washer (commercial)CEE Tier 3A
Dishwasher (residential)ENERGY STAR or equivalent
Prerinse spray valves1.3 gpm or less
Ice machineENERGY STAR or equivalent, plus air- or closed loop cooling

Process water standards

ProcessRequired rating or specification
Heat rejection and coolingNo "once-through" cooling with potable water for any item that rejects heat
Cooling towers and evaporative condensersMust have makeup water meters, along with a few other things specified in LEED Table 3

In order to verify that water consumption has been reduced by 20%, it is necessary to multiply the anticipated water use for each fixture type by the number of anticipated users — this is done for the actual proposed fixtures and for the baseline fixtures. LEED provides guidelines for estimating the number of times per day (or the duration per use) that a fixture is typically used.

Not everyone likes low-flow fixtures. See Rand Paul's asinine comments about freedom and "choice" at this Energy Committee hearing, as if unrestricted individual self-interest, unmediated by governmental intervention, somehow preserves environmental resources and promotes national wealth:

Alternatively, one can watch Kramer and Newman conspire to purchase black market showerheads in this Seinfeld episode:

...or, best of all, just read this piece by humorist Dave Barry.

WE Prerequisite 3: Building-level water metering

Intent: Find ways to use less water by tracking its use (benefits on both ends — less strain on local supply, plus less impact on local wastewater systems).

Requirements: Track overall building water use on a monthly and annual basis by installing a water meter and — either manually or automatically — noting monthly and annual consumption. Additionally, building owners must agree to supply USGBC with data on water use for 5 years (or until the building is sold, whichever comes first).

WE Credit 1: Outdoor water use reduction (1-2 points)

Intent: Use less "outdoor" water (benefits on both ends — less strain on local supply, plus less impact on local wastewater systems).

Requirements: Similar to the prerequisite. There are two options for compliance. In the latter case, nonvegetated surfaces are not counted in landscape area calculations. Vegetated play fields and food gardens may or may not be included.

Option 1. No irrigation required (Satisfying this option gets you 2 points). Note that it is permissible to irrigate for up to two years, just to get the vegetation started.

Option 2. Reduced irrigation: Using smart species selection and advanced irrigation technology, show that outside water use is reduced 50% from the "baseline," at least during the "peak watering month." Calculations are based on the Environmental Protection Agency (EPA) WaterSense Water Budget Tool. Since the prerequisite already requires a 30% reduction (i.e., no more than 70% of baseline water use), this credit is achieved by using no more than 72% of the water allowed under the prerequisite — in other words, 72% of 70% is 50%.

Rather than reducing actual water use for irrigation, LEED permits the building owner to use unlimited quantities of water for irrigation as long as this water is derived from "alternative sources" such as graywater, reclaimed wastewater, refrigeration system condensate, and so on.

WE Credit 2: Indoor water use reduction (1-6 points)

Intent: Use less "indoor" water (benefits on both ends — less strain on local supply, plus less impact on local wastewater systems).

Requirements: Like the prerequisite (which required a 20% reduction), indoor water use must be reduced from "baseline" values for both building water as well as for appliance and "process" water use. The necessary reduction in building water use from the baseline in order to get points is as follows: 25% for 1 point, and an additional point for each 5% improvement, up to 6 points for a 50% reduction. As in the prerequisite, alternative water sources can be used without penalty — i.e., it is not the "actual" water use that is being constrained, but only conventional "potable" water.

WE Credit 3: Cooling tower water use (1-2 points)

Intent: Use less water in cooling towers, while still protecting occupants against "microbes" (disease-causing organisms that might originate in such places) and HVAC system inefficiencies.

Requirements: Cooling towers reuse (cycle, or circulate) water in order to get rid of building heat, primarily through evaporation. To maximize the number of such cycles, thereby minimizing the amount of replacement water that would otherwise be needed, it is necessary to test the system to see how much mineral and other content is actually dissolved in the potable water used in the system. Such a test is important since such minerals can be deposited as "scale" on the surfaces of the tower elements, reducing efficiency (and thereby requiring more energy), if not diluted adequately. LEED establishes maximum concentrations of such things (1000 ppm of both Ca in the form of CaCo3, and total alkalinity; 100 ppm SiO2; 250 ppm of Cl; and 2000 micro siemens per centimeter of conductivity) and then requires that the maximum number of "cycles of concentration" be no more than the maximum allowable concentration divided by the concentration found in the make up water. Since there are 5 parameters being tested (calcium, alkalinity, SiO2, chloride, and conductivity), one takes the lowest number of the five ratios as the maximum number of cycles permitted.

Why the lowest and not the highest? Because the assumption is that if the make-up water contains, for example, 100 ppm of calcium, then it would take 10 "cycles" for the mineral concentration to reach the limit of 1000 ppm. The concentration of calcium increases with each cycle because the make-up water, containing additional minerals, is replacing "pure" water lost via evaporation. But if the make-up water also contains 50 ppm of chloride, then the system would reach its limit for this mineral after only 5 cycles (i.e., it would reach 250 ppm). The lower number of cycles governs since 5 cycles works for all the parameters, whereas 10 cycles works only for the calcium, but would cause the chloride levels to exceed the maximum allowed by a factor of two.

I'm hardly an expert on cooling tower management, but the LEED guidelines seem a bit superficial, as they only require a one-time check to assess the composition of make-up water. The Office of Energy Efficiency and Renewable Energy has what appears to be a more useful set of recommendations, including the idea of installing a "conductivity controller to automatically control blowdown."

The "intent" of this credit mentions control of microbes (i.e., water-borne disease) but this intention does not seem to generate any further discussion within the credit guidance or explanation sections. The most famous instance of cooling tower disease-causing problems was the 1976 outbreak of Legionnaires' Disease in Philadelphia. As of this writing (July 8, 2014) a new Standard 188 is being developed by ASHRAE to address the "prevention of Legionellosis associated with building water systems," but this standard is not referenced in LEED v4, presumably because it did not exist when v4 was being developed. [Update 6 August 2015: The new Standard 188 has been published: we'll see what USGBC does with it, especially in light of continuing problems with cooling towers.]

Even so, a growing body of research suggests that prevailing protocols for preventing Legionellosis are wholly inadequate, and that methods already exist that could easily be implemented on a building-by-building basis — a process that is consistent with LEED's approach to sustainability. Henry I. Miller writes in Forbes (22 July, 2014): "The only way to determine whether a water source is a high-risk Legionella-contaminated system is to take samples of the water to see whether the bacteria grow in a simple and inexpensive culture test in a laboratory" (emphasis added). It is remarkable that such a requirement is not part of this credit.

WE Credit 4: Water metering (1 point)

Intent: Find ways to use less water by tracking its use (benefits on both ends — less strain on local supply, plus less impact on local wastewater systems).

Requirements: The prerequisite already requires a main water meter for the building as a whole. For this credit (1 point), additional sub-metering is required for at least two of the following systems:

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