CS-v4.1 WEc3: Optimize Process Water Use 1-3 points

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"