On the Sustainable Building Advisor discussion board…

Expert instructor Ann Edminster discusses greywater uses and the often intangible, but very important ‘non-energy’ returns on investments.


Student 1: Has anyone heard of greywater solutions for dust mitigation? It is common in construction to have a water truck drive around a few times a day spraying potable water on the ground to hold down dust.

Ann Edminster: In areas where there is reclaimed water, it can be obtained for purposes like that. In our area, I believe we have tertiary treated wastewater that is used for dust control. In general, greywater is limited to subsurface application to avoid releasing airborne microbes that may be in the greywater. It does seem criminal to use potable water for dust control!

Student 2: This week’s readings have inspired me to look more into how I can recycle our greywater. If it can filter into an underground irrigation system… this would solve some of the water management issues we face. We already harvest rainwater, but the problem is, of course, storage. One monsoon storm will fill up our 40,000 liter tank, but the months preceding monsoon are hot and dry. The water has to last all year until we are desperate for it! It is a challenging balance. But greywater is relatively consistent. And if it is directly supplied to the roots, limiting evaporation? Brilliant!

Ann Edminster: Here’s a great resource site for you, Student 2: Greywateraction.org. Applying water to the roots not only greatly reduces evaporative losses, it also allows soil microorganisms to process the organics in the greywater, and limits issues related to airborne contaminants.


Student 3: I read a couple of the articles and thought I should share this. I just recently wrote up a change order on our project to substitute 40,000 sf of asphalt for our parking area with porous pavement. It is a change totaling $1.2 million. It mentioned in the article that these types of systems help filter pollutants and toxins from entering into the water stream. My question is, why spend so much money on a system like this when it only rains once every three months? Obviously, I am all for implementing this type of system… but am I wrong to say maybe the money should have been spent towards a solar betterment?

Student 4: Just thinking out loud… I can only imagine how many pollutants and toxins a parking lot can accumulate over the course of 3 months, and the associated cost of having to filter blackwater from water streams. I think in the long term it will have more monetary benefits in comparison to solar. It would probably take extensive research and time after implementing before you’ll actual have enough data to know for sure.

Student 3: Thanks for the response, Student 4. This was just a general thought because as we learn to develop different sustainable solutions we also have to develop financial profiling to outline the long-term economic and environmental benefits. Without that, the majority will not feel comfortable funding any sort of sustainable change. By packaging a return on investment (ROI) to the project owner, designer and contractor, it becomes clear where the money is going and what the benefits are in the long-run. As for now all I have is a $1.2 million bill for toxin control of rain water during a drought. I hate to play devil’s advocate but I think it’s important to keep in mind the naysayers.

Ann Edminster: A mid-state California Lumber company took on a LEED project a number of years ago (a production facility, I think) and found that switching to pervious paving allowed them to eliminate a retention basin that would otherwise have been required; the net effect was a significant monetary savings. They also got a more attractive parking lot and a larger landscaped area.

It’s important in every project to weigh costs vs. benefits; sometimes the benefits include attractive ROI, sometimes there are other benefits that are harder to quantify, or harder to express in traditional monetary terms. That doesn’t mean they don’t have value.

One important concept that comes up a lot in the energy efficiency community is ‘non-energy benefits’ — e.g., comfort, health, durability, etc. Sometimes those benefits have more perceived value (even to investors) than a traditional metric like ROI. There are analogous non-qualitifiable, non-monetary benefits across every aspect of sustainable building.

An important early step in every sustainable building project is to establish goals and priorities. Without understanding the owner’s, developer’s, and/or occupants’ goals and priorities, it can be difficult to arrive at helpful conclusions from a cost:benefit comparison. Maybe ROI is important; maybe it isn’t, or maybe there are other things that are equally important. If you don’t know what matters to them, how do you make good decisions?

Ideally, devote a good chunk of time in a project kickoff charrette (all-hands workshop) to goals and priorities.

Enroll in Sustainable Building Advisor with expert Ann Edminster today! After successfully completing the 9-week online course, passing the final exam, and receiving instructor approval of your field project, you will earn the Sustainable Building Advisor (SBA) distinction, while receiving  32 AIA LU/HSW Credits and a 1-year membership to the full BuildingGreen.com educational library.

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About instructor Ann Edminster – owner/founder, Design AVEnues LLC

Ann V. Edminster, M. Arch, founder/principal of Design AVEnues, is an expert residential net-zero energy consultant, green building teacher, speaker, and author. She consults with builders, developers, software startups, design firms, investors, utilities, public agencies, and homeowners, providing unmatched knowledge of sustainable and regenerative design and construction. She has 35 years of design experience and has guided project teams in the creation of hundreds of award-winning, high-performance homes. Her leadership and contributions – including facilitation, research, and analysis that shaped the LEED for Homes rating system – create healthy, vibrant living spaces, protect the environment, and provide economic benefits.