For U.S. and Canadian homeowners, spring rainy season is appreciated before the looming long, hot summer. These days, even people living in regions that didn’t have water-conservation efforts are rethinking their water usage.
As precipitation becomes more precious, it begs the question: Are there simple ways homeowners can utilize spring rainwater and winter ice and snow melt for their own purposes to help alleviate the strain of water scarcity?
The fact is collecting rainwater is one of the most accessible and economically viable options available to deal with the freshwater crisis. However, unlike residential solar systems that have become relatively mainstream, there is still room or improvement when it comes to architects, designers and remodelers proactively advising their clients to install rainwater harvesting systems to improve residential sustainability.
RAINWATER HARVESTING 101
The good news is installing a rooftop rainwater harvesting is relatively straightforward. Basically, rainwater harvesting is collecting precipitation runoff from a roof via gutters designed to channel water into a storage vessel. Storage can be small, simple rain barrels that keep a few gallons of non-potable water handy for watering plants and the like, or they can be elaborate, large cisterns that supply an entire household’s potable needs (when properly filtered, disinfected and tested). (Consider other rainwater uses.)
When considering a residential rainwater harvesting system, a home’s roof is a very important component. Roofs made from a variety of materials, including metal, asphalt, slate and tile, can be used for collecting rainwater.
A roof’s angle, or slope, will determine the speed and rate at which water can be collected. A steep-slope roof will shed water more quickly and help keep debris and other foreign materials at a minimum. The greater the slope, the better the roof will prevent stagnant water buildup and contaminants.
Although research varies about whether toxins may leach from roofing materials (see “Roofing Materials and Water Quality”, below), a major concern when it comes to rainwater harvesting is how best to reduce the potential contaminants that grow on the roofing material itself. Metal roofs from reputable manufacturers who use high-quality coatings are a good option because they feature antimicrobial paint systems. Not only will these roofs shed larger organic matter, like leaves and pine needles, via the wind, metal roofs’ coating systems won’t allow harmful micro-organisms to grow. Galvanized and Galvalume roofs also are well suited for rainwater collection because they are coated with a layer of zinc that seals the material, preventing rust and lowering levels of iron in the water.
It’s worth mentioning, rainwater harvested from any type of roof, including metal, always should be filtered and decontaminated before consumption.
ROOFTOP COMPONENTS
Although rainwater collection systems can be installed at any time, the best time to plan for them is when a new roof (new construction or a roof replacement) is installed. Here are key things to keep in mind:
- Rooftop rainwater can be collected with any type or shape of gutter.
- The gutters should have protection screening to help keep large debris out.
- An additional filtration opportunity is available with the installation of a rain head (downspout filter) that allows for self-cleaning. A first-flush diverter also helps prevent the first flush of contaminated rainwater from entering the storage container/tank.
- Have a storage plan in place so downspouts and connection points can be designed or retrofitted as appropriate.
- For ongoing maintenance, advise your client to annually clean and perform routine rooftop maintenance.
As we face an ever-changing climate, now is the time for architects, designers and remodelers to advise their clients about the benefits of rainwater harvesting. Even harvesting on a smaller scale can make a big difference. For example, 1 inch of rainfall on a 1,000-square-foot roof yields an incredible 623 gallons of water!
Rainwater harvesting systems don’thave to be expensive or complicated. Simple planning can make an amazing contribution to a home’s personal water supply.
Roofing Materials & Water Quality
Learn more about the effects of roofing materials on water quality within rainwater collection systems by visiting the following websites:
- www.twdb.texas.gov/innovativewater/rainwater/projects/rainquality/2011_02_rainquality_final_rpt.pdf
- www.sciencedaily.com/releases/2011/03/110307142229.htm
- www.buildwithrise.com/stories/best-roofs-for-rainwater-collection
The Metal Roofing Alliance
The Metal Roofing Alliance was established in 1998 to provide accurate information, comprehensive research and examples of quality metal roofing in action. Learn more.
PHOTOS: courtesy Metal Roofing Alliance unless otherwise noted
