Over the summer, we worked with clients who sought out our services to modify a set of plans for a home design they purchased from the Internet. It was a rewarding effort to help them reach their goal of achieving a net-zero energy home for ‘living their values’ today and into retirement. Beyond achieving net-zero energy, they wanted the property to be as self-sustaining as possible. These extra features include a permaculture garden, raising livestock, installing an off-grid photovoltaic system, and harvesting rainwater.
We performed a rainwater harvesting analysis to help the clients understand the quantities of rainwater they could expect to harvest so their cisterns could be properly sized. We utilized formulas developed by Brad Lancaster, an expert in rainwater harvesting and permaculture teacher, combined with localized annual rainfall data from the National Oceanic and Atmospheric Administration (NOAA). When rainfall data was entered into the formulas and applied to the total square footage of roof area available, we were able to estimate the maximum potential net rainwater volume for the entire year, or any given month. In this particular case, it was almost 22,000 gallons annually - not too shabby for a 1,500 s.f. home situated on a high-desert plain at nearly 8,000 feet in elevation.