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Two options, but three choices
The intent of this credit is to reduce the amount of potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. used for flush fixtures and to minimize the amount of wastewater conveyed to the municipal system. For credit compliance, you have two options:
Option 1: Reduce the quantity of potable water used for flush fixtures (water closet and urinals only) by 50%. You have two ways to make this reduction:
- use low-flow fixtures;
- use non-potable water such as graywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area. or rainwater, or combine both strategies.
Option 2: Treat 50% of wastewater onsite to tertiary standards and infiltrate it, or reuse the treated wastewater onsite.
Establish a baseline
To determine your percentage reduction, compare a baseline case with the design case. Note that the baseline for WEc2 is not the same as the baseline for WEp1 and WEc3: Water Use Reduction. Whereas WEp1 and WEc3 count flow (shower, lavatory and kitchen sink) and flush fixtures (toilets and urinals), WEc2 only counts toilets and urinals. The data that you enter on flush fixtures in the LEED Online credit form in WEp1 will automatically populate the credit form for WEc2.
The calculations for wastewater use are based on the number of full-time equivalentFull-time equivalent (FTE) represents a regular building occupant who spends 40 hours per week in the project building. Part-time or overtime occupants have FTE values based on their hours per week divided by 40. Multiple shifts are included or excluded depending on the intent and requirements of the credit. (FTEFull-time equivalent (FTE) represents a regular building occupant who spends 8 hours a day (40 hours a week) in the project building. Part-time or overtime occupants have FTE values based on their hours per day divided by 8 (or hours per week divided by 40). Transient Occupants can be reported as either daily totals or as part of the FTE. Residential occupancy should be estimated based on the number and size of units. Core and Shell projects should refer to the default occupancy table in the Reference Guide appendix. All occupant assumptions must be consistent across all credits in all categories.) occupants. FTE calculations can sometimes be confusing in certain building types or occupancy types—see WEp1 for more information.
Fixture choice is the cheapest option, if you can make it workGenerally, the easiest and cheapest way to achieve this credit is to install low-flow and waterless fixtures. Using waterless urinals or pint-per-flush urinals in combination with ultra-low-flow toilets (1.0 gpf) or aggressive, dual-flushA type of water-saving toilet that gives a choice of flushes depending on the type of waste solid or liquid. toilets (1.28/0.8 gpf) can work, although it depends on your project occupancy and will need to be verified for each project.
If your project comes up just a little short, consider supplementing some of your potable water use with graywater or rainwater, or installing composting toiletsComposting (or Nonwater) toilet systems are dry plumbing fixtures and fittings that contain and treat human waste via microbiological processes..
Treating wastewater onsite is great—if it’s right for your project
Onsite wastewater treatment has a number of environmental and educational benefits, but treating to tertiary standards can be challenging for some projects, especially if they have limited space. The Solaire, a LEED Gold market-rate apartment building in Battery Park City in Manhattan, located wastewater treatment facilities in the basement because above-grade space was at a premium.
Treating to tertiary standards involves extra filtration or biological activity to remove nutrient pollutants such as nitrogen and phosphorus, and it may also involve disinfection. Treating wastewater to this level goes beyond code in most places. Consider technologies that are passive or low-tech in order to minimize operation and maintenance costs.
Once the wastewater has been treated to tertiary standards, you’ll need to determine the best reuse method. Many projects prefer to use it landscape irrigation. This will generally be your cheapest and easiest reuse method. If your project doesn’t have landscaping, consider reusing the treated wastewater for toilet flushing.
Notes on specific building types
Office—In order for office spaces or other buildings to meet the credit through fixtures alone, they will most likely need to include waterless urinals. (Depending on your project, one-pint-flush urinals may work.)
Multifamily and Hotel—Residential and hotel projects, which don’t have urinals in private bathrooms, cannot meet this credit with low-flush fixtures alone, so they have to provide nonpotable waterNonpotable water: does not meet EPA's drinking water quality standards and is not approved for human consumption by the state or local authorities having jurisdiction. Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals, or infective agents. or treat wastewater on site to earn the credit.
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FAQs for WEc2
The credit language says the Option 2 involves a reduction in wastewater. Does that mean that all water, including process water, should be included?
The WEc2 calculations are based on the annual generation of blackwaterBlackwater is wastewater containing urine or fecal matter that should be discharged to the sanitary drainage system of the building or premises in accordance with the International Plumbing Code, or sewage, from flush fixtures as documented in WEp1. Note that the scope is not the same as WEp1, which includes both flush and flow fixtures.
Can project teams include reclaimed water systems that are planned and funded, but not completed?
Yes, per LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #10012 made on 05/09/2011, "projects may only count future infrastructure such as reclaimed water systems so long as they will be completed and functional within 1 year." Anything further out than one year may not be counted, however.
Legend
- Best Practices
- Gotcha
- Action Steps
- Cost Tip
Design Development
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Remember that this credit is based on EPAct 1992 and subsequent rulings of EPAct 2005, the 2006 Uniform Plumbing Code, and the International Plumbing Code. The baseline case for this credit includes these standards:
USGBC
Excerpted from LEED 2009 for New Construction and Major Renovations
WE Credit 2: Innovative wastewater technologies
2 Points
Intent
To reduce wastewater generation and potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. demand while increasing the local aquifer recharge.
Requirements
Option 1
Reduce potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. use for building sewage conveyance by 50% through the use of water-conserving fixtures (e.g., water closets, urinals) or nonpotable waterNonpotable water: does not meet EPA's drinking water quality standards and is not approved for human consumption by the state or local authorities having jurisdiction. Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals, or infective agents. (e.g., captured rainwater, recycled graywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area., on-site or municipally treated wastewater).
OR
Option 2
Treat 50% of wastewater on-site to tertiary standards. Treated water must be infiltrated or used on-site.
Potential Technologies & Strategies
Specify high-efficiency fixtures and dry fixtures (e.g., composting toilet systems, nonwater-using urinals) to reduce wastewater volumes. Consider reusing stormwater or graywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area. for sewage conveyance or on-site mechanical and/or natural wastewater treatment systems. Options for on-site wastewater treatment include packaged biological nutrient removal systems, constructed wetlands and high-efficiency filtration systems.
Publications
Terry Love’s Consumer Toilet Reports
This website offers a plumber’s perspective on many of the major toilets used in commercial and residential applications.
Water Closet Performance Testing
This site provides two reports on independent test results for a variety of toilets’ flush performance and reliability.
American Rainwater Catchment Systems Association
ARCSA was founded to promote rainwater catchment systems in the United States. The ARCSA website provides regional resources, suppliers, and membership information, and publications such as the Texas Guide to Rainwater Harvesting.
Technical Guides
US EPA, On-Site Wastewater Treatment Systems Manual
This manual provides a focused and performance-based approach to on-site wastewater treatment and system management. It also includes information on a variety of on-site sewage treatment options.
Organizations
WaterSense
WaterSense is a U.S. Environmental Protection Agency program designed to encourage water efficiency in the United States through the use of a special label on consumer products. It was launched in 2006. The WaterSense website offers information on certified products, and other water conservation information from its partners.
Example Calculations
The LEED Online credit form offers a useful calculator for this credit that we recommend. The scenarios shown in these sample calculations show how this credit can play out with percentage savings based on fixture selection alone.
Samples
LEED Online Forms: NC-2009 WE
The following links take you to the public, informational versions of the dynamic LEED Online forms for each NC-2009 WE credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.
Version 4 forms (newest):
Version 3 forms:
- WEp1: Water Use Reduction
- WEc1: Water Efficient Landscaping
- WEc2: Innovative Wastewater Tech.
- WEc3: Water Use Reduction
These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictions on these forms; for more information, visit LEED Online and click "Sample Forms Download."
Design Submittal
Documentation for this credit can be part of a Design Phase submittal.
LEEDuser is produced by BuildingGreen, Inc., with YR&G authoring most of the original content. LEEDuser enjoys ongoing collaboration with USGBC.
75 Comments
Rainwater collection and reuse on campus
Hello,
Our project is a new building on a school campus. The Engineers are proposing collecting rainwater from the building's roof, storing this is a big common water tank next to the building, and then reusing this water for flushing purposes for all buildings on campus.
So let's say the project building is collecting 200,000 gallons per year, and another building is collecting 300,000 gallons per year. These 500,000 gallons will be stored together and pumped to 3-4 buildings on campus (including those which they were collected from).
How can the collected rainwater contribute to the LEED water calculations of this project?
The Engineers are confident that all the collected rainwater will be used on campus, but they cannot be 100% sure all the collected rainwater will be used specifically on this building.
Any tips on the best way to proceed?
Thanks!
Be sure to look into SS 6.1 and 6.2 as well if this reuse approach will be used.
I know there have been CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide's relating to campus-wide credit applications, I am not positive if WEc2 was one of them, but it is worth a look.
Combined approach to WEc2
We have a project where, through efficient fixtures, we will reduce wastewater (WCs, lavatories, and showers) conveyance by approximately 45%. This represents a significant reduction in potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. demand and sewage conveyance. At the same time, we are capturing all greywater, treating it to tertiary standards, and using it for irrigation. This further reduces sewage conveyance, for a net reduction in sewage conveyance by well over 50%. It seems like we are meeting the intent and performance threshold of the credit, yet we do not comply via either path. Has anyone tried this approach and succeeded in earning the points?
Michael, you're overthinking it—you are meeting Option 1 through the combination of strategies mentioned in the credit language (see above).
Option 2 provides a way to comply with the credit without necessarily reducing the overall flow of wastewater. I do see how the language could be confusing.
I may very well be overthinking it, but the credit language and form do not seem to allow our approach.
Per Option 1, you must reduce potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. use for sewage conveyance by 50%. We are reducing potable water use for sewage conveyance by 45% through efficient fixtures. We're then further reducing net sewage conveyance (but not potable water use for sewage conveyance) by diverting greywater from the sanitary sewer, treating it, and using it for irrigation.
The catch is we are not taking our treated greywater and using it to flush toilets or otherwise offset 'potable water for sewage conveyance.' We're using it to offset potable water for irrigation!
In any case, I think we'll submit a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide and see what response we get. I feel confident that we meet the intent although our approach does not seem to conform to the standard criteria.
Michael, yes, I see you're right. I think that on the face of it, you would not meet the WEc2 requirements, but would have to take solace with a strong showing in WEc1 and WEc3, unless GBCI sees a path for you. Rather than submit a CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide, though, I'd start with contacting them via their website for a quicker opinion.
Water quality examples
Does anyone have a good resource for expected water quality/colour of collected rainwater for toilet flushing? I have a few photo examples but need some more to convince an owner to use the strategy.
Thanks,
Mitch
Mitch, I don't have any photographic examples, but in my experience it will typically look no different than regular toilet water. Rainwater itself looks like normal potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems.. It can pick up some particular matter or mineral coloration depending on the collection method and location, but some filtration can (and probably should) easily remove this.
One single treatment plant for two LEED projects
We have a project in which site two independent buildings will apply for LEED certification.
In this case, (when the treatment plant is shared by the two LEED buildings), is there any special consideration we need to take into account for the LEED certification process?
Building 1 + Building 2 will treat 100% of the waste water to tertiary standards.
100% of all treated water effluent will go to building 1 to supply water for cooling towers.
Will we be fulfilling WEc2 for the two LEED buildings?
Michael, you haven't mentioned where the treatment plant is located, but I assume onsite. I think both buildings would be in compliance with WEc2. You will have some considerations to figure out with MPR3, but that seems doable.
Hello Tristan,
For this project a LEED Boundary will be placed accordance to the property line. Whithin this LEED Boundary/property line the treatment plant will be located.
Both LEED Buildings will be located inside the LEED Boundary/property line.
So yes, the treatment plant will be on site. Thank you very much for your comments Tristan.
Just in case someone is facing this situation, this was the GBCI response on this issue:
Dear David,
Thank you for contacting the Green Building Certification Institute about treating wastewater on a site with 2 buildings and using all of the water for the cooling tower in 1 building.
Appendix A to the
2010 LEED Application guide for Multiple Buildings and On-Campus Building Projects (AGMBC) October 31, 2011 , indicates, on page 14, that WEc2 can be pursued as a group credit but not as a campus credit.
If these 2 buildings will be built at the same time, under the same contract and using the same rating system, they may be certified as a group.
If that is not the case, then making a formal inquiry about a campus application may be worthwhile. It would require that you register a Master Site as well as the 2 projects. The argument to make is that you are treating 100% of the water from both buildings, and using all of it on the campus. Formal Inquiries may be submitted through LEED Online . Instructions can be found at this link; .
If you do not need the entire amount of water generated, you might consider infiltrating it within the LEED Project Boundary of the building fin which you are not using any of it. Please also remember that 100% treatment entitles you to an exemplary performanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. credit that you may use as an ID credit.
I hope that helps, but if you have any further questions or concerns, please feel free to use the contact form at http://www.gbci.org/contactus and select "Follow up to GBCI Response," inputting your case number from this email's subject line.
groundwell non potable saline water
We are trying to pursue this credit, by using municipal 'brackish' water for irrigation and toilet flushing. The source of the municipal brackish water is groundwater pumped up from wells that is non-potable that is used throughout the region for irrigation. What is the definition for "municipal wastewater"? Can someone please advise if this will be accepted as wec2 and wec1 credit?
In addition, our engineer says a polishing plant would be required before this water can be used for toilet flushing. Any advice on this?
Natalie, according the LEED requirements, this is explicitly not allowed. However, there is a case to be made that it should be, but you'd probably need an official ruling via CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide or LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org..
Rainwater Harvesting Calculator
Does anybody know of a good rainwater harvesting calculator online anywhere? Most of the ones I have found do not let you adjust enough of the inputs to be useful.
Changes to system after project has been certified, what to do?
What is your experience with LEED projects that remove a specific technology (project did earn a LEED point) due to another recommendation, say a third party energy audit after the project was already LEED certified?
For example, a third party is benchmarking a LEED platinum project in update New York that captures stormwater runoff from the roof, collects the water in a big tank, and uses it to flush the toilets. Before the water is used to flush the toilets, it runs through a water purification systems that includes both filtration and UV (WEc2- Option 2, treat on-site wastewater to tertiary standards). The third party energy auditor would like to recommend unplugging the purification system in order to save energy (ECMEnergy conservation measures are installations or modifications of equipment or systems intended to reduce energy use and costs. in report). My question is, how would this affect their LEED credit? or would it? - the project was certified in 2010. I am a little confused. Thanks!
Courtney,
If your project is collecting rainwater and using it to flush the toilets then your project probably did or should have gone with WEc2 Option 1 - reduce potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. use for sewage conveyance by 50% through the use of nonpotable waterNonpotable water: does not meet EPA's drinking water quality standards and is not approved for human consumption by the state or local authorities having jurisdiction. Water that is unsafe or unpalatable to drink because it contains pollutants, contaminants, minerals, or infective agents. (e.g., captured rainwater). In which case if you remove the purification system it wouldn't affect your LEED credit intent.
In addition, if your project is already certified LEED NC, I've never heard of it being taken away regardless of what happens during occupancy.
Option 2 is if you are treating the water after it has been flushed (wastewater) and reusing it onsite.
Thanks a lot, Dylan. For some reason, every time I read this credit, I always get confused and automatically think Option 2 when captured rainwater is discussed. And then treating rainwater to tertiary standards seems way overkill!
Treated wastewater definition.
Hi,
working on an office building project, we r pursuing this credit through option 2 : "Treat 50% of wastewater on-site...etc."
Through the design Preliminary Review we received a comment stating that the wastewater should be generated from the flush fixtures not the lavatories as we did in the design.
My question is : Does anyone have an information (a definition in the reference guide) that state that the wastewater is water generated from flush fixtures only? because we have an intention to send a clarification stating that nothing in the guide state this. Please advise.
Water from lavatories and showers is considered wastewater by code definition. It is unlikely, however, in an office building that the lav and shower waste would add up to 50% of the total wastewater.
Here is a sentence from the ref guide "GraywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area. systems reuse the wastewater collected from sinks, showers, and other sources for flushing toilets..."
Waste Water Calculation for Option 2
LEED template use the flush fixture water which calculated based on occupant usage. But our plumbing design is based on fixture unit which includes both flush and flow fixture into the WWTP sizing.
Our plumbing engineer comes up with the annual waste water of 19,000 kgal but the annual flush fixture water from LEED template is only 600 kgal. How can we fill in the LEED template?
Actually, all waste water will be treated by the WWTP and reused on site. We should achieve LEED credit requirement, shouldn't we?
Sompoche, you should be able to earn the credit with that system, provided you meet the specific detailed credit requirements.
I don't know how your plumbing engineer and the LEED template are so far off from each other. Have you looked at the differences of what they are assuming? You should fill in the LEED template based on the LEED protocols, even if that's different from your engineering figure, but I would closely look to make sure something isn't missing.
Should I consider process water?
Hi,
My project is a pharmaceutical facility. For their industrial process, they use a fairly large amount of water. I was wondering if process waterProcess water is used for industrial processes and building systems such as cooling towers, boilers, and chillers. It can also refer to water used in operational processes, such as dishwashing, clothes washing, and ice making. is considered for this credit.
Our intent is to use some of this water on flush fixtures and irrigation. The spare amount would be conducted to a large soakaway pit.
Would that comply with WEc2 and WEc3 (assuming we have a 50% efficiency in fixtures, considering the use of process water)?
Thank you.
If the process waterProcess water is used for industrial processes and building systems such as cooling towers, boilers, and chillers. It can also refer to water used in operational processes, such as dishwashing, clothes washing, and ice making. has been used and recaptured then it would be considered non-potable. Then you would be meeting the requirements of Option 1: Potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. reduction.
Dylan,
Thank you for your reply. Nevertheless, I would still like to know, if we would pursue option 2 for this credit, would we have to consider the whole amount of water to achieve the 50% reduction, including the process waterProcess water is used for industrial processes and building systems such as cooling towers, boilers, and chillers. It can also refer to water used in operational processes, such as dishwashing, clothes washing, and ice making.? Thank you.
Nadia, I see why the question comes up, but the scope for wastewater under Option 2 here is identical to the scope of WEp1/c3. This is spelled out in places like LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org. #5186 made on 02/10/2009.
Determining the number of full time equivalent (FTE) occupants
To determine the demand for water, what number should be used for FTEFull-time equivalent (FTE) represents a regular building occupant who spends 8 hours a day (40 hours a week) in the project building. Part-time or overtime occupants have FTE values based on their hours per day divided by 8 (or hours per week divided by 40). Transient Occupants can be reported as either daily totals or as part of the FTE. Residential occupancy should be estimated based on the number and size of units. Core and Shell projects should refer to the default occupancy table in the Reference Guide appendix. All occupant assumptions must be consistent across all credits in all categories. occupants - the number of occupants that the building is being designed for, or the maximum number of occupants calculated using SF/person units for egress code compliance?
Hi Rudolph,
Above it states: "The calculations for wastewater use are based on the number of full-time equivalent (FTE) occupants. FTE calculations can sometimes be confusing in certain building types or occupancy types—see WEp1 for more information. "
Rudolph, FTEFull-time equivalent (FTE) represents a regular building occupant who spends 8 hours a day (40 hours a week) in the project building. Part-time or overtime occupants have FTE values based on their hours per day divided by 8 (or hours per week divided by 40). Transient Occupants can be reported as either daily totals or as part of the FTE. Residential occupancy should be estimated based on the number and size of units. Core and Shell projects should refer to the default occupancy table in the Reference Guide appendix. All occupant assumptions must be consistent across all credits in all categories. should be the intended number for the project building. I would keep this number grounded in the reality of the project—not a theoretical code-based number. If the FTE number is not known for the project (as in CS), there are default numbers to use, from the LEED Reference Guide.
Rainwater Harvesting Tank Calculations
Has anyone found a good spreadsheet/website that calculates the approximate size of a rainwater tank needed for a given roof areaRoof area is the area of the uppermost surface of the building which covers enclosed Gross Floor Area, as measured when projected onto a flat, horizontal surface (i.e. as seen in Roof Plan view). ‘Roofs’, or portions of roofs, covering unenclosed areas (e.g. roofs over porches and open covered parking structures) are not included in the areas used to evaluate compliance with SSc7.2, though they may be applicable to SSc7.1. and water usage? I have made my own but am unsure of how accurate it is. Does anyone know how detailed the supporting documentation needs to be for this credit? I am going on average rainfall per month and 80% efficiency. The project is located in Ireland.
Thanks so much.
S W, did you ever find any useful resources? Was your documentation approved?
There are some interesting rainwater harvesting simulation graphs available at www.architectscience.com that show the basic relationship between tank size, daily use and the quantity of rainwater harvested over a twenty year period in Washington DC, Philadelphia and New York City. Ideally, rainwater tanks should be sized according to a simulation based on long term historical rainfall data of the project location.
Also available from Virginia Stormwater BMPBest Management Practice Clearinghouse is a non-proprietary Excel spreadsheet that uses a 30 year rainfall database to generate tables and graphs indicating the quantity of harvested rainwater (developed by Rainwater Management Solutions). http://vwrrc.vt.edu/SWC/nonproprietarybmps.html
onsite waste water treatment plant
if our building is part of a bigger development which has a central waste water treatment plant does this count as being an onsite plant and will it count towards option 2.reducing 50% of building sewage conveyance?
Razan, I would review the LEED Minimum Program Requirements supplemental guidance document for some perspective on this question. There are cases (like with parking) where something can contribute to a credit without being in the LEED boundary. I would consider this a good possibility in your situation.
Hi Razan! We had the same case in a project. They awarded us WEc2 but not WEc3. They said that all water coming from this treatment plant (in a university campus, in which our building was located) counted as "municipally treated", not "on-site" and would qualify only to earn WEc2. Hope it helps.
Hello, I have the same question. My project is located at an industrial park and they have a Central treatment water plant outside of my LEED boundary and the water is for the all the irrigation areas in the park. Does this count for the credit?
Dario, as I mentioned earlier, please review the MPRs, especially MPR3. There is a relevant exception in MPR3, and while I don't know if it has been applied in this type of situation, it seems like it should work.
For our factory project, We DID have an exterior treatment plant, but it was on adjacent land owned by the same owner. So--between Nadia's answer and mine you can see what is allowable and not allowable for this credit. Please note: for our credit compliance, we had to show in detailed calculations that the capacity of the treatment plant was enough for all recycled water needs,AND that the INPUT to the system from our project was sufficient for the OUTPUT requirements (so it was calculated as if it was a stand-alone treatment plant).
Using well water for WEc2
Our MEP has recommended drilling a well and using local well water to flush the tolleits instead of using municipally supplied potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems.. Based on the intent of this credit, I am not sure that using well water is a viable strategy. What is your opinion on this strategy?
Use of well water is specifically mentioned as non-compliant in the Reference Guide for WEc1. Although not specifically mentioned in the same way for WEc2, I don't see that it would be any different. Do you?
Tristan, I agree. If well water is non-compliant for WEc1, I would think that it is non-compliant for Wec2.
Annual Captured Rainwater
Hello,
The Mechanical and Plumbing engineers working on our project have provided us with the capacity of the rainwater tank as well as the volume of captured runoff in a 2 year 24 hour design storm (cf/storm) (needed for SS credit 6.1)
My question is, which methodology should be used in order to compute the annual captured rainwater and deduct it from the calculated flush fixture water use annual volume ?
Many thanks,
The engineer should be able to provide an expected amount of annually captured rainwater based on rainwater data and the rainwater management plan.
Rainwater harvesting Calcs.
Has LEED set in precedent for rainwater harvesting efficency rates? My research has shown to assume you will actually capture 60%-90% of your potential rainwater harvest. But 60-90% is quite a range. Any thoughts on the norm or what GBCI would consider acceptable?
Thanks in advance!
I think the range is so wide because it depends a lot on your system—what kind of roofing or collection surface, how it's collected, etc. Is there someone designing your system who can provide input?
Pursuing both Option 1 & 2?
Does anyone know if it is possible to pursue both option 1 & 2? I am working on a project that is treating 100% of it's waste water on site via a spetic tank and leech field AND is also using low-flow fixtures and flushing with only captured rainwater and cooling condensate water. So can we purse both options? And exemplary preformance? Any thoughts on the best approach to this to get the max points?
Perhaps purse option 1 under the credit and take exemplary preformance for it. Then apply for an ID credit for our waster water system?
You're going to be able to earn three points here—or four if this is an RPc1 credit in your zipcode.
You can use one or both options to earn two points through credit compliance, and then one Exemplary PerformanceIn LEED, certain credits have established thresholds beyond basic credit achievement. Meeting these thresholds can earn additional points through Innovation in Design (ID) or Innovation in Operations (IO) points. As a general rule of thumb, ID credits for exemplary performance are awarded for doubling the credit requirements and/or achieving the next incremental percentage threshold. However, this rule varies on a case by case basis, so check the credit requirements. point via IDc1.
Does this answer your question?
No RP credits because this an international project. Yes I think I will just use option 1 for 2 pts plus 1 EP point. I was just asking about gettin more points because we are also doing option 2 (treating 100% of wasterwater and infiltrating on site). Perhaps I can take the 3 pts and apply for and ID for pt. for option 2? But I'm pretty sure you can only get 1 ID point per credit. I just feel like we should get more points since we are meet both options 1 & 2 100%. And really both have very measurable positive environmental effects.
Nelina, I think you'll be happy to read this news that RPc1 is available for international projects. There's your fourth point for WEc2!
We are flushing with captured rainwater AND on site septic, attempting to go for two points and an EP. However I am unable to select both option 1 and option 2 simultaneously. Is there any trick to overriding the template?
Onsite wastewater treatment
I have a Project where the land field has very little infiltration and naturally rainwater runs off to the sea. There is no municipal sewer, but water will be treated. Is it possible to obtain this credit by treating the water and not infiltrating it? Instead treated water goes to the sea.
Interesting situation. This seems to be not possible according to the credit language, but I could imagine it being possible, in theory, if you're able to make a case that it's not environmentally damaging in any way, and meets the same credit intent. Do you think you have a shot at doing that?
Yes, I think it might be possible. The only downside that I see is mixing potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. with sea water. Even though it is the natural hydrology of the location, theoretically by doing that I would be reducing the potable water source, (though I´ll try anyway).
The intent of the credit is to “reduce generation of wastewater and potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. demand, while increasing the local aquifer recharge.” I think that what you are doing with wastewater is interesting and does have environmental benefit, but it may not meet the credit intent because your are not reducing potable water demand. If you are, make sure to explain this in your narrative very well and back it up with solid calculations. You may be indirectly recharging the local aquifer by discharging to the sea and could potential make this reasoning if you were able to back it up with some hydrologic cycle information specific to the site. Seems like a long shot....maybe consider an Innovation credit for which you'd need to demonstrate environmental benefits convincingly. Regardless, it's a beneficial strategy as long as quantities of treated water released to salt water is not excessive--as you point out it occurs naturally.
Recycled water from Local Government
Hi all,
If we use non-potable recycled water supplied by local government, can it be eligible for the point?
The recycled water is still not available for the whole country (Singapore) now, but in next few years, it may be available for all areas.
Thanks and regards,
Erika
Yes, municipal treated wastewater is one of the options for this credit.
dual flush calculation
total daily uses # of FTEFull-time equivalent (FTE) represents a regular building occupant who spends 8 hours a day (40 hours a week) in the project building. Part-time or overtime occupants have FTE values based on their hours per day divided by 8 (or hours per week divided by 40). Transient Occupants can be reported as either daily totals or as part of the FTE. Residential occupancy should be estimated based on the number and size of units. Core and Shell projects should refer to the default occupancy table in the Reference Guide appendix. All occupant assumptions must be consistent across all credits in all categories. is 3. residential is 5.
3 = (1 full + 2 low)
within 5 uses for residential, how many is full, how many is low?
Direction on this is not included in the reference guide, so I would use a reasonable estimate and explain it. With 5 total uses, I would estimate 2 full, 3 low. You might try 4/1 but that could be viewed as gaming the credit; 3/2 is a little more cautious and reasonable.
Cistern Capacity
Hi,
My question is in regards to calculating the cistern capacity to reduce sewage conveyance. When completing the LEED letter template, is it based on the capacity of the cistern or the collection of rainwater over a year?
I'm looking at the LEED-2009 WEc2 LEED Online form, and it asks for "annual quantities" of captured rainwater, recycled graywaterGraywater is untreated household waste water which has not come into contact with toilet waste. Graywater typically includes used water from bathtubs, showers, bathroom wash basins, and water from clothes-washer and laundry tubs, though definitions may vary. Some states and local authorities also allow kitchen sink wastewater to be included in graywater. Project teams should comply with the graywater definition established by the authority having jurisdiction in the project area., etc. So it seems to be looking for a quantity of water, not a cistern size. Which makes sense, because LEED wants to know how much potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. you're replacing—the system capacity you use to do it is of less interest.
Tristan, you are correct on that, but in regards to this question, If the cistern does not have the capacity to capture all this rainwater, the rest of the water is going to be lost and not able to replace some of the potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. for the flush systems. In our case we have an annual rainwater of 869kGal, but the cistern capacity is around 17kGal. Therefore tecnically the annual "captured" rainwater should be calculated in some type of spreadsheet based on the capacity, is that correct? If that's the case, does anybody know of a spreadsheet where we can calculate this?
Victor, it sounds like what you need is the help of an engineer who has developed an appropriate calculation method. I'm not aware of a spreadsheet out there that can do this for you—or if there is one, I would imagine that it requires some expertise to use.
LEED in Vietnam
Dear all,
regarding this credit it is required to (Option 2) to treat 50% of wastewater on-site to tertiary standard. In Vietnam we have different standard for wastewater treatment for different purpose. One of these is treat the sewage treatment water from effluent for irrigation (tertiary). However the limit of the parameter such BOD5 and TSSTotal suspended solids (TSS) are particles that are too small or light to be removed from stormwater via gravity settling. Suspended solid concentrations are typically removed via filtration. are higher than the ones indicated in the "Definitions" paragraph for tertiary standard treatment since we are in Vietnam. Do you think we can still apply for this credit?
Thanks
Given that this is an international project, I strongly suggest that you submit an inquiry to your LEED reviewer. Theoretically, the LEED standards are to be applied consistently throughout the world as it's adopted in other countries. However, this may be infeasible in certain cases but only GBCI can make that determination. My bias would be to agree with you because the water is treated to tertiary standards of the local governing agencies for the intended use (landscaping) and as long as you meet the overall goal of treating 50% of wastewater on site and reuse it or let it infiltrate you meet the intent of the credit, and this reuse would also contribute to WEc1.1 and 1.2, if you use no potable waterPotable water meets or exceeds EPA's drinking water quality standards and is approved for human consumption by the state or local authorities having jurisdiction; it may be supplied from wells or municipal water systems. for irrigation.
Septic Systems
Do septic systems count as on-site wastewater treatment? Our automotive dealership project will treat 100% of their wastewater via a septic system. Floor drains in shop areas will go through an oil/water separator and then into an underground collection tank for later removal by a tanker truck.
Septic systems do count as on-site wastewater treatment, however, for WEc2 purposes you still need to reduce potable waste water quantities for flushing by 50% through standard methods like waterless and ultra-low flow fixtures, or by using recycled grey water, captured rainwater or municipal reclaimed water. Typically, septic systems do not provide a source of tertiary treated grey water for reuse, though you may be able to incorporate this feature in your septic system.
Where is this requirement that in addition to a septic system (leech field) you have to reduce waste water for flushing by 50%? The ref guide gives you two options, and doesn't require that you do both (as far as I can tell).
You are correct, you do not have to do both if you are using option 2, however, you do have to demonstrate that at least 50% of your total wastewater is diverted to the on-site system. This is probably self-evident in most cases, but just to be clear for the reviewers make sure to clearly state the facts. I would also add that even though it's not required to reduce flushing by 50% it's still a good idea.
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