Designing a LEED Silver building here in DC, and had a question about landscape irrigation. We were planning on using no (0%) potable water for our landscape irrigation. All of our irrigation water was supposed to come from AHU condensate.
Our engineer says that on a hot summer day, we will generate 5,000 gallons of water from condensate, and we have sized our tanks to accommodate this amount. Our irrigation consultant says that 5,000 gallons a day is just enough (they need ~4,900 gallons/hot day).
Our landscape architect and irrigation consultant would prefer that there be domestic water available as make up "just in case". Neither has ever done a system that used only AHU condensate, and they are nervous that there may be times when the plants need water and condensate isn't available.
We would lose 1 LEED point if we provided such water.
Anyone out there had any experience with irrigation water coming solely from condensate? How did it work out?
good question & great solution for irrigation. I've read case studies of such systems but can't cite them from memory. Having a make up water supply automatically eliminate a credit, since credit is based on the amount of water used from each source and calculations on 'normal' irrigation needs. check the CIRs & LEED reference guide...
I'd recommend a increasing your cistern capacity to 200% via rainwater harvesting to provide back up capacity (and the water quality will be better for plants cause of the pH of rainwater versus condensate). Since you don't want to allow the water to get stagnant, don't go much bigger then that - look into adding some filtration, especially if you mix rainwater. Also get info from the MEP about the quality of the condensate - are there any potential contaminants or chemicals being added?
LEED NC2.1 (no relevant CIRs from NC2.2)
Per WEc12 CIR Ruling 4/4/2005, it is acceptable for projects to provide potable water as backup irrigation
&
To achieve WEc1.2, the project must demonstrate that no potable water is necessary throughout the year. Calculate the supply and demand balance for every month of the year to demonstrate the rainfall/storage/demand interplay over a typical annual hydrologic cycle
&
installation of exterior hose bibs does not preclude a project from claiming zero potable water use for irrigation.
have you LA get a sustainable design consultant to hold their hands. Seems that you need a better team. if you only are aiming for silver, one point won't kill you. But why aim so low?
Good find on the CIR for 2.1, I am asking around to see if it will also apply to 2.2. If so, then we are good to go.
We unfortunately do not have the space to provide more capacity than is necessary, as we are already at our code minimum for parking spaces.
The condensate will be filtered before going out to the plants, so no worries there.
Silver is the minimum stipulated in our contract, though we currently have enough points for gold. With 2 months left before final drawings go out, I am trying to hang on to all the points we shot for, so that we can achieve gold.
I understand the risk involved with making LEED a contractual obligation, but I think the benefits out way the risk. I think it is important for us to guarantee performance of our buildings.
In DC, they passed a law (in 2006) mandating LEED certification for any building above a certain amount of sf (50,000?). It covers both private and public buildings, and goes into effect 2009. We are the first city in the country to mandate LEED for private and public.
namhenderson & Just Why
The cisterns will be located on the B2 level (parking is on B2 and B1). We are using two (2) 2,500 gallon tanks per building.
Each building has ground floor retail and 7 levels of office space above. The GBA is 480,000 SF for one and 570,000 SF for the other.
reed- I'll be remembering your volume of condensate the next time I'm starting to figure out alternative water sources in a humid subtropical location.
good numbers and good luck. LEED Gold for 1m sf is impressive. very impressive. We should talk.
I also just started working on a LEED project in DC with similar characteristics, although I haven't found a cistern yet if there is one in the project. To echo tk, we should talk.
This is the cistern we have currently spec'd. Though it probably won't be the one we use in the end, as it has no opening for an overflow valve or for a water meter.
We liked it because it was cheap, and short enough to fit in our parking garage. Like I said before, we have two of these 2,500 gallon tanks per building.
i don't know what the climate patterns are like at your end, but the other side of the equation can also be tampered with. so the choice of planting and design would reflect how much water (ahu+rainwater+ perhaps treated grey water? this also depends on your state/country ) you would be able to provide. so for instance, instead of using conventional grass that requires a lot of water, u could use paspalum grass..etc
oh, LEED doesn't disqualify a project from the no irrigation landscape credits if temporary irrigation is needed the first growing season or two to establish the plants.
Irrigation from AHU condensate?
Designing a LEED Silver building here in DC, and had a question about landscape irrigation. We were planning on using no (0%) potable water for our landscape irrigation. All of our irrigation water was supposed to come from AHU condensate.
Our engineer says that on a hot summer day, we will generate 5,000 gallons of water from condensate, and we have sized our tanks to accommodate this amount. Our irrigation consultant says that 5,000 gallons a day is just enough (they need ~4,900 gallons/hot day).
Our landscape architect and irrigation consultant would prefer that there be domestic water available as make up "just in case". Neither has ever done a system that used only AHU condensate, and they are nervous that there may be times when the plants need water and condensate isn't available.
We would lose 1 LEED point if we provided such water.
Anyone out there had any experience with irrigation water coming solely from condensate? How did it work out?
good question & great solution for irrigation. I've read case studies of such systems but can't cite them from memory. Having a make up water supply automatically eliminate a credit, since credit is based on the amount of water used from each source and calculations on 'normal' irrigation needs. check the CIRs & LEED reference guide...
I'd recommend a increasing your cistern capacity to 200% via rainwater harvesting to provide back up capacity (and the water quality will be better for plants cause of the pH of rainwater versus condensate). Since you don't want to allow the water to get stagnant, don't go much bigger then that - look into adding some filtration, especially if you mix rainwater. Also get info from the MEP about the quality of the condensate - are there any potential contaminants or chemicals being added?
LEED NC2.1 (no relevant CIRs from NC2.2)
Per WEc12 CIR Ruling 4/4/2005, it is acceptable for projects to provide potable water as backup irrigation
&
To achieve WEc1.2, the project must demonstrate that no potable water is necessary throughout the year. Calculate the supply and demand balance for every month of the year to demonstrate the rainfall/storage/demand interplay over a typical annual hydrologic cycle
&
installation of exterior hose bibs does not preclude a project from claiming zero potable water use for irrigation.
have you LA get a sustainable design consultant to hold their hands. Seems that you need a better team. if you only are aiming for silver, one point won't kill you. But why aim so low?
Treekiller-
Good find on the CIR for 2.1, I am asking around to see if it will also apply to 2.2. If so, then we are good to go.
We unfortunately do not have the space to provide more capacity than is necessary, as we are already at our code minimum for parking spaces.
The condensate will be filtered before going out to the plants, so no worries there.
Silver is the minimum stipulated in our contract, though we currently have enough points for gold. With 2 months left before final drawings go out, I am trying to hang on to all the points we shot for, so that we can achieve gold.
tim-
not that you had any say, but next time a contract is drafted up - avoid at all costs, any stipulation of minimum certification levels.
good luck with the rest of the certification process- 5000 gallons is a large tank. any space left under the parking?
Woah - I had no idea that the AHU's would generate 5,000 gallons of water on a hot day!
I'm curious, timothy, where will the cistern be located?
Yeah. Wow that seems like a large amount of condensate.
How large of a commercial system is this?
barry lehrman -
I understand the risk involved with making LEED a contractual obligation, but I think the benefits out way the risk. I think it is important for us to guarantee performance of our buildings.
In DC, they passed a law (in 2006) mandating LEED certification for any building above a certain amount of sf (50,000?). It covers both private and public buildings, and goes into effect 2009. We are the first city in the country to mandate LEED for private and public.
namhenderson & Just Why
The cisterns will be located on the B2 level (parking is on B2 and B1). We are using two (2) 2,500 gallon tanks per building.
Each building has ground floor retail and 7 levels of office space above. The GBA is 480,000 SF for one and 570,000 SF for the other.
reed- I'll be remembering your volume of condensate the next time I'm starting to figure out alternative water sources in a humid subtropical location.
good numbers and good luck. LEED Gold for 1m sf is impressive. very impressive. We should talk.
threads like this truly demonstrate both the power and the value of a forum like archinect ... great thread ...
architects helping other architects, in a civil, professional way ... who knew that was possible?
I also just started working on a LEED project in DC with similar characteristics, although I haven't found a cistern yet if there is one in the project. To echo tk, we should talk.
This is the cistern we have currently spec'd. Though it probably won't be the one we use in the end, as it has no opening for an overflow valve or for a water meter.
http://plastic-mart.com/class.php?item=668
We liked it because it was cheap, and short enough to fit in our parking garage. Like I said before, we have two of these 2,500 gallon tanks per building.
i don't know what the climate patterns are like at your end, but the other side of the equation can also be tampered with. so the choice of planting and design would reflect how much water (ahu+rainwater+ perhaps treated grey water? this also depends on your state/country ) you would be able to provide. so for instance, instead of using conventional grass that requires a lot of water, u could use paspalum grass..etc
Noctilucent- We are using native, drought-resistant species. Our LA chose trees, bushes, plants, and sedum that didn't require too much water.
oh, LEED doesn't disqualify a project from the no irrigation landscape credits if temporary irrigation is needed the first growing season or two to establish the plants.
yay! I found the cistern on our project today!
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