LEED v4.1
Hospitality – NC
Water Efficiency
Optimize Process Water Use

LEED CREDIT

# Hospitality-NC-v4.1 WEc3: Optimize Process Water Use1-2 points

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#### Requirements

##### Option 1. Cooling Tower and Evaporative Condenser Cycles of Concentration (1-2 points except CS, 1-3 points CS)

For cooling towers and evaporative condensers, conduct a one-time potable water analysis, measuring at least the five control parameters listed in Table 1.

Table 1. Maximum concentrations for parameters in condenser water
Parameter Maximum level
Ca (as CaCO3) 600 ppm
Total alkalinity 500 ppm
SiO2 150 ppm
Cl- 300 ppm
Conductivity 3300 µS/cm

ppm = parts per million
µS/cm = micro siemens per centimeter

Calculate the maximum number of cooling tower cycles by dividing the maximum allowed concentration level of each parameter by the actual concentration level of each parameter found in the potable makeup water analysis. Limit cooling tower cycles to avoid exceeding maximum values for any of these parameters.

The materials of construction for the water system that come in contact with the cooling tower water shall be of the type that can operate and be maintained within the limits established in Table 1.

Table 2. Points for cooling tower cycles
Cooling tower cycles Points (all except CS) Points (CS)
Maximum number of cycles achieved without exceeding any maximum concentration levels or affecting operation of condenser water system 1 1

Meet the maximum calculated number of cycles to earn 1 point, and increase the number of cycles by a minimum of 25% by increasing the level of treatment and/or maintenance in condenser or make-up water systems

OR

Meet the maximum calculated number of cycles to earn 1 point and use a minimum 20% recycled nonpotable water

2 2

Meet the maximum calculated number of cycles to earn 1 point, and increase the number of cycles by a minimum of 30% by increasing the level of treatment and/or maintenance in condenser or make-up water systems

OR

Meet the maximum calculated number of cycles to earn 1 point and use a minimum 30% recycled nonpotable water

-- 3

Minimum percentage recycled nonpotable water used in cooling tower makeup should be based on water use during the month with the highest demand for make-up water.

Projects may consider using water reclaimed from another process as a source of makeup water for evaporative cooling equipment as long as the resultant circulating water chemistry conforms to the parameters established in Table 1.

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 1 if the district cooling system complies with the above requirements.

OR
##### Option 2. Optimize Water Use for Cooling (1-2 points, 1-3 points CS)

To be eligible for Option 2, the baseline system designated for the building using ASHRAE 90.1-2016 Appendix G Table G3.1.1 must include a cooling tower (systems 7, 8, 11, 12, and 13).

Achieve increasing levels of cooling tower water efficiency beyond a water-cooled chiller system with axial variable-speed fan cooling towers having a maximum drift of 0.002% of recirculated water volume and three cooling tower cycles. Points are awarded according to Table 3.

Table 3. Points for reducing annual water use compared to Water-Cooled Chiller System
Percentage Reduction Points (BD+C) Points (CS)
25% 1 1
50% 2 2
100% - 3

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 2 if the district cooling system complies with the above requirements.

AND/OR
##### Option 3. Process Water Use (1-2 points except CS, 1-3 points CS)

Demonstrate that the project is using minimum 20% recycled alternative water to meet process water demand for 1 point, or using minimum 30% recycled alternative water to meet process water demand for 2 points. Ensure that recycled alternative water is of sufficient quality for its intended end use.

Minimum percentage of recycled alternative water used should be based on water use during the month with the highest water demand.

Process water uses eligible for achievement of Option 3 must represent at least 10% of total building regulated water use and may not include water used for cooling. Eligible subsystems may include:

• Boilers
• Humidification systems
• Other subsystems using process water

Projects served by district systems are eligible to achieve Option 3 if the district system complies with minimum thresholds for recycled alternative water use.

CS projects:

Demonstrate that the project is using minimum 20% recycled alternative water to meet process water demand for 1 point, using minimum 30% recycled alternative water to meet process water demand for 2 points, or using minimum 40% recycled alternative water to meet process water demand for 3 points. Ensure that recycled alternative water is of sufficient quality for its intended end use.

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This information is also available in a full PDF download in The Cost of LEED v4 report.

4/9/2021Updated: 4/20/2021
Rating System Correction
Description of change:
WE credit Optimize Process Water Use:
- revise Intent to read: "To conserve low cost potable water resources used for mechanical processes while controlling, corrosion and scale in the condenser water system."
Campus Applicable
No
Internationally Applicable:
No
11/9/2020Updated: 2/3/2021
Form Update
Description of change:
Updated to align with v4.1 November 2020 Addenda
Campus Applicable
No
Internationally Applicable:
No
11/10/2020Updated: 11/30/2020
Rating System Correction
Description of change:
1. Credit name: revise credit name from "Cooling Tower and Process Water Use" to "Optimize Process Water Use"

2. Credit Intent: delete "and cooling tower makeup" and "microbes" so that the sentence reads as follows: "To conserve water used for mechanical processes while controlling corrosion and scale in the condenser water system."

3. Revise title of Option 1 to "Cooling Tower and Evaporative Condenser Cycles of Concentration"

4. Revise the maximum levels for all parameters in Table 1. Maximum concentrations for parameters in condenser water as follows:
Parameter Maximum level
Ca (as CaCO3) 600 ppm
Total alkalinity 500 ppm
SiO2 150 ppm
Cl- 300 ppm
Conductivity 3300 µS/cm

5. Above Table 2. Points for cooling tower cycles, add the following sentence: "The materials of construction for the water system that come in contact with the cooling tower water shall be of the type that can operate and be maintained within the limits established in Table 1."

6. In Table 2. Points for cooling tower cycles, revise the text in the first row of the "Cooling Tower Cycles" column: replace the word "filtration" with "maximum concentration".

7. After the sentence "Minimum percentage recycled nonpotable water used in cooling tower makeup should be based on water use during the month with the highest demand for make-up water." add the following sentence: "Projects may consider using water reclaimed from another process as a source of makeup water for evaporative cooling equipment as long as the resultant circulating water chemistry conforms to the parameters established in Table 1."

8. Replace the text "Option 2. No Cooling Tower (2 points)" with the following: "Option 2. Optimize Water Use for Cooling (1-2 points except CS, 1-3 points CS)

9. Replace all requirements in Option 2 with the following:

"To be eligible for Option 2, the baseline system designated for the building using ASHRAE 90.1-2016 Appendix G Table G3.1.1 must include a cooling tower (systems 7, 8, 11, 12, and 13).

Achieve increasing levels of cooling tower water efficiency beyond a water-cooled chiller system with axial variable-speed fan cooling towers having a maximum drift of 0.002% of recirculated water volume and three cooling tower cycles. Points are awarded according to Table 3.

Table 3. Points for reducing annual water use compared to Water-Cooled Chiller System
Percentage Reduction Points (BD+C) Points (CS)
25% 1 1
50% 2 2
100% -- 3

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 2 if the district cooling system complies with the above requirements."

10. Add "AND/" in front of the "OR" above Option 3.

11. In the Option 3 sentence that begins "Process water uses eligible for achievement of Option 3..." add the word "regulated" before "building water use" and add the phrase "and may not include water used for cooling" to the end of the sentence.

12. Under the three bullet points in Option 3, revise the sentence that begins "Projects whose cooling is provided by district cooling systems..." to read as follows: "Projects served by district systems are eligible to achieve Option 3 if the district system complies with minimum thresholds for recycled alternative water use."
Campus Applicable
No
Internationally Applicable:
No
11/10/2020Updated: 11/30/2020
Reference Guide Correction
Description of change:
Behind the Intent:

1. Replace the sentence "In some climate zones, efficient systems design can eliminate the need for a cooling tower by decreasing the water intensity of the building cooling process." with the following text:

"Evaporative cooling is the most energy efficient method to reject heat from a process (1 lb. of water removes almost 1,000 BTU’s (970 BTU/lb.) with the added benefit of reducing greenhouse gas emissions. Cooling towers and evaporative condensers utilize evaporative cooling to operate with maximum energy efficiency; to preserve this energy savings, it is important to conserve the water these system use, especially in water stressed regions. In some climate zones, heat rejection system designs can help to decrease the water intensity of the building cooling process using a combination of wet, dry or adiabatic cooling. In some cases, 100% dry operation is possible.

For wet cooling systems, this credit addresses water conservation strategies while still saving energy. This strategy includes maximizing cycles of concentration in cooling towers and evaporative condensers and make-up water reduction strategies including the use of reclaimed water and hybrid cooling."

2. In the sentence that begins "Core and Shell projects can now earn up to 3 points..." replace the words "Cooling Tower and Process Water Use" with "Optimize Process Water Use".

Step-by Step Guidance:

3. Add the following text to the beginning of the Step-by-Step Guidance section:
"Option 1. Cooling Tower and Evaporative Condenser Cycles of Concentration

Refer to the v4 BD+C reference guide with the following addition:

Step 6. Address construction materials for cooling system
Share the results of the potable water analysis with the cooling system manufacturer and ensure that the materials of construction for all components of the water-cooled system that come in contact with the cooling loop can operate and be maintained within the limits established in Table 1. The evaporative cooled system equipment must be designed to accommodate the targeted cycles of concentration calculated for the cooling tower or evaporative condenser."

4. Revise the title of Option 2 to read "Optimize Water Use for Cooling". Beneath the Option 2 title, add the following:
"Option 2 is limited to projects that use water-cooled systems in the ASHRAE 90.1-2016 baseline design. ASHRAE 90.1 Appendix G identifies baseline system types that are standard practice for similar, newly constructed buildings."

5. Revise the first sentence in Step 1: add an "s" after "include" and add the phrase "or evaporative condenser (systems 7, 8, 11, 12, and 13)" to the end of the sentence.

6. Add the following sentence to the end of Step 1: "If the above conditions are met and the project team eliminates the need for cooling towers or evaporative condensers in the proposed building design, then the project team may document a 100% reduction in water use for cooling."

7. Revise the text of Step 2. Develop building cooling systems design so that it reads as follows:
"Consider viable on-site alternatives to 100% evaporative cooled water-cooled systems for the building and the impacts of the cooling systems design on building energy use. Hybrid water-cooled system options may be used to reduce water usage while saving energy."

Delete the sentence "Projects receiving thermal energy from District Cooling Systems may not pursue Option 2."

8. For Step 3. Document compliance, delete the sentence "Demonstrate that building mechanical systems design eliminates the need for a cooling tower or other system that uses the latent heat of the evaporative cooling of water." and add the following text:
"If the project includes systems that use the latent heat of evaporative cooling, calculate annual water savings as compared to a 100% water-cooled chiller system, based on proposed cooling loads for spaces served by systems 7, 8, 11, 12, or 13 in the baseline. The system performance for the reference shall be calculated based on a 100% water-cooled chiller system with axial variable-speed fan cooling towers having a maximum drift of 0.002% of recirculated water volume and three cooling tower cycles.

Some energy simulation software has the capability of simulating cooling tower water usage within the software. To perform the calculations within the energy model, the proposed case model shall be modeled consistent with the project design to demonstrate the total water usage associated with evaporative cooling in the proposed design.

To determine the reference case performance, the proposed case model shall be updated with a water-cooled chilled water system serving all spaces served by systems 7, 8, 11, 12, or 13 in the ASHRAE 90.1 Baseline model. All proposed parameters (such as fan power, fan control, economizer control, demand control ventilation, energy recovery, dedicated outside air supply, quantity of systems, etc.) shall remain identical, except that the cooling type shall be revised to water-cooled chillers matching those stipulated in ASHRAE 90.1 Appendix G.

If performing the cooling tower water usage calculations outside the energy model, cooling tower and evaporative condenser manufacturers have water usage programs based on design conditions, building load and water chemistry. To calculate the water usage with the manufacturer’s data, the design cooling loads from the proposed model for spaces served by systems 7, 8, 11, 12, or 13 in the baseline shall be exported from the energy model, and supplemental calculations shall be documented based on the proposed building cooling load and water use data sheets from equipment suppliers. Any assumptions used for the calculations shall be submitted with the calculations.

The manufacturer’s program used for calculating water usage must incorporate the hourly load profile from the energy model or be based on climate-specific load profiles for the project’s building type. If hourly load profiles and hourly weather profiles are not used, the calculations shall include “bins” that account for variations in the load profile and water usage dependent on outdoor air drybulb temperature, outdoor air wetbulb temperature, and building cooling load. The load profile must be identical in the proposed and reference case."

9. Option 3. Process Water Use: In Step 1. Identify water subsystems, add the word "regulated" before "building water use" in the first sentence. After the first sentence, add the following sentence: "Water used for cooling is not eligible for Option 3."

10. Option 3. Process Water Use: In Step 3. Calculate subsystem water use, add the words "regulated" and "use" to the first bullet point so that it reads as follows: "To be eligible for Option 3, the subsystem must represent at least 10% of total building regulated water use annually."

11. After the Step-by-Step section, add a new beta guide section with the title "Project Type Variations". Beneath this new section, add the following text:
"District Energy Systems

Option 2. Optimize Water Use for Cooling
For projects connected to a district cooling system, the project shall demonstrate that any on-site cooling equipment meets the credit requirements and that upstream systems meet the credit requirements.

To pursue this option, the baseline system designated for the building in accordance with ASHRAE 90.1-2016 Appendix G Table G3.1.1 (prior to modeling purchased energy) must include a cooling tower (systems 7 &, 8, 11, 12, and 13).

For upstream equipment from the District Energy System, provide a narrative describing how the system is operated and specifically describing the district energy cooling equipment, including capacities, equipment type, etc.

If cooling towers, evaporative condensers, evaporative cooling systems, and other evaporative cooling systems are not used in the district cooling system serving the project, or are used in conjunction with compressor-based cooling equipment to supply no more than 10% of the total cooling energy generated by the District Energy System, then the project automatically qualifies for 2 points under the credit (Core and Shell projects automatically qualify for 3 points) and does not need to provide calculations. Provide a narrative description of how the district cooling system is operated and confirm that there is no evaporative cooling equipment in the district energy system.

If the district cooling system does use evaporative cooling, the project team must provide calculations demonstrating achievement of the Option 2 requirements based on total district cooling capacity and cooling load profile for the entire district system (building cooling loads shall not be used to document performance).

The program or supplemental calculations used for calculating water usage must either incorporate the hourly load profile from the District Energy System, or include “bins” that account for variations in the District Energy Plant load profile and water usage dependent on outdoor air drybulb temperature, outdoor air wetbulb temperature, and District Energy thermal cooling load. The load profile must be identical in the proposed and reference case.

Option 3. Process Water Use
For projects where heating is provided by a district heating system, the project team must pro-rate the district heating system’s total water usage to the building to determine whether it represents at least 10% of total building regulated water use.
For example, if the district heating system consumes 500,000 gallons of water annually and the LEED project uses 1% of the district heating system annual heat generation, the total prorated water consumption from the district heating system is 500,000 gallons x 1% = 5,000 gallons. This must represent at least 10% of the total building water consumption, meaning that the total building consumption must be less than or equal to 50,000 gallons."

12. Make the following edits to the Required Documentation table:
- Revise the text "Documentation showing that project is designated as systems 7 or 8 under ASHRAE 90.1-2016 Appendix G Table G3.1.1" so that it reads as follows: "Documentation showing that project Baseline system is designated as systems 7, or 8, 11, 12, or 13 under ASHRAE 90.1-2016 Appendix G Table G3.1.3"
- Beneath the row that begins "Documentation showing that project Baseline system is designated", add a new row with the following text: "Calculations demonstrating percent reduction in cooling tower water usage for systems where the proposed design uses the latent heat of evaporative cooling of water" and add add an "x" in the Option 2 column in this new row

13. After the Required Documentation table, add new section "Exemplary Performance". Beneath this new section, add the following text:
" Option 2. Demonstrate a 100% reduction in annual water use compared to a water-cooled chiller system.

 Option 3. Use minimum 40% recycled alternative water to meet process water demand (all projects except Core and Shell). Core and Shell: use minimum 50% recycled alternative water to meet process water demand."

14. After the new section "Exemplary Performance", add a new section "Referenced Standards". Beneath this new section, add the following text:
" ASHRAE Standard 90.1-2016"
Campus Applicable
No
Internationally Applicable:
No

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#### Requirements

##### Option 1. Cooling Tower and Evaporative Condenser Cycles of Concentration (1-2 points except CS, 1-3 points CS)

For cooling towers and evaporative condensers, conduct a one-time potable water analysis, measuring at least the five control parameters listed in Table 1.

Table 1. Maximum concentrations for parameters in condenser water
Parameter Maximum level
Ca (as CaCO3) 600 ppm
Total alkalinity 500 ppm
SiO2 150 ppm
Cl- 300 ppm
Conductivity 3300 µS/cm

ppm = parts per million
µS/cm = micro siemens per centimeter

Calculate the maximum number of cooling tower cycles by dividing the maximum allowed concentration level of each parameter by the actual concentration level of each parameter found in the potable makeup water analysis. Limit cooling tower cycles to avoid exceeding maximum values for any of these parameters.

The materials of construction for the water system that come in contact with the cooling tower water shall be of the type that can operate and be maintained within the limits established in Table 1.

Table 2. Points for cooling tower cycles
Cooling tower cycles Points (all except CS) Points (CS)
Maximum number of cycles achieved without exceeding any maximum concentration levels or affecting operation of condenser water system 1 1

Meet the maximum calculated number of cycles to earn 1 point, and increase the number of cycles by a minimum of 25% by increasing the level of treatment and/or maintenance in condenser or make-up water systems

OR

Meet the maximum calculated number of cycles to earn 1 point and use a minimum 20% recycled nonpotable water

2 2

Meet the maximum calculated number of cycles to earn 1 point, and increase the number of cycles by a minimum of 30% by increasing the level of treatment and/or maintenance in condenser or make-up water systems

OR

Meet the maximum calculated number of cycles to earn 1 point and use a minimum 30% recycled nonpotable water

-- 3

Minimum percentage recycled nonpotable water used in cooling tower makeup should be based on water use during the month with the highest demand for make-up water.

Projects may consider using water reclaimed from another process as a source of makeup water for evaporative cooling equipment as long as the resultant circulating water chemistry conforms to the parameters established in Table 1.

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 1 if the district cooling system complies with the above requirements.

OR
##### Option 2. Optimize Water Use for Cooling (1-2 points, 1-3 points CS)

To be eligible for Option 2, the baseline system designated for the building using ASHRAE 90.1-2016 Appendix G Table G3.1.1 must include a cooling tower (systems 7, 8, 11, 12, and 13).

Achieve increasing levels of cooling tower water efficiency beyond a water-cooled chiller system with axial variable-speed fan cooling towers having a maximum drift of 0.002% of recirculated water volume and three cooling tower cycles. Points are awarded according to Table 3.

Table 3. Points for reducing annual water use compared to Water-Cooled Chiller System
Percentage Reduction Points (BD+C) Points (CS)
25% 1 1
50% 2 2
100% - 3

Projects whose cooling is provided by district cooling systems are eligible to achieve Option 2 if the district cooling system complies with the above requirements.

AND/OR
##### Option 3. Process Water Use (1-2 points except CS, 1-3 points CS)

Demonstrate that the project is using minimum 20% recycled alternative water to meet process water demand for 1 point, or using minimum 30% recycled alternative water to meet process water demand for 2 points. Ensure that recycled alternative water is of sufficient quality for its intended end use.

Minimum percentage of recycled alternative water used should be based on water use during the month with the highest water demand.

Process water uses eligible for achievement of Option 3 must represent at least 10% of total building regulated water use and may not include water used for cooling. Eligible subsystems may include:

• Boilers
• Humidification systems
• Other subsystems using process water

Projects served by district systems are eligible to achieve Option 3 if the district system complies with minimum thresholds for recycled alternative water use.

CS projects:

Demonstrate that the project is using minimum 20% recycled alternative water to meet process water demand for 1 point, using minimum 30% recycled alternative water to meet process water demand for 2 points, or using minimum 40% recycled alternative water to meet process water demand for 3 points. Ensure that recycled alternative water is of sufficient quality for its intended end use.

### LEEDuser expert

#### Maeve Donohue

LEED AP BD+C, WELL AP, LFA, Fitwel Ambassador

Introba
Consultant