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Bridger Steel Project News, Highlights & Helpful Tips

Rainwater Harvesting & Metal Roofs

[fa icon="calendar"] 02/18/2020 / by Kaylee Beattie

Rainwater harvesting is becoming increasingly popular across the country — and for many good reasons. Both residential and commercial building owners are adding the practice of rainwater collection to their homes in order to become more self-sufficient and sustainable. Metal roofs are the optimal catchment choice for rainwater harvesting off a rooftop surface.

rainwater harvesting on a metal roof

What is Rainwater Collection?

Rainwater harvesting is the process of collecting run-off rainwater from a building in order to store it for later use. Typically, a roof acts as the main collection source. The water is collected in the gutters, moves through the downspouting, and then finally collects in some sort of storage container. Rainwater can be stored in rain barrels for later use or moved directly into cisterns so it can be used right away.

Rainwater collection is a big part of the Leadership in Energy and Environmental Design (LEED) process. It helps reduce the volume of runoff and improves water quality on sites. In order to effectively capture rainwater for redistribution, the rainwater collection system must capture up to 25% of the water from impervious or hard surfaces (like a roof). Then, the water should be filtered, decontaminated, and reused in the building’s water system or released into a public water treatment facility.

Metal Roofs for Rainwater Collection

A metal roof for rainwater collection is a prime choice, especially when the appropriate paint system is incorporated. When designing a rainwater collection, you have to consider its durability. Your roof needs to be able to withstand the weight of heavy snow and rain. A rainwater collection roof also needs to be designed with an easy path for the water to follow — ideally using steep-sloped roof. A steep-sloped roof performs better as a catchment area because it prevents stagnant water buildup, sheds debrid more quickly, and possible contaminants from building up.

While there are a lot of roofing materials out there that can be used as rainwater collection systems, metal roofs are oftentimes the preferred system. Mainly due to the fact that metal roofs have much lower concentrations of dissolved organic carbon and other bacteria. Metal roofing can reduce the amount of potential contaminants that may grow on the roofing materials, especially when compared to asphalt, slate, and tile roofs. They’re often coated in anti-microbial paint systems and are able to shed large debris without the chance of it getting stuck in cracks and crevices.

All in all, a metal roof rainwater collection system produces more water with less chance of disease-causing microorganisms. Galvanized metal roofs are even more highly recommended because of their zinc coating. Zinc seals the metal, which prevents rusting and lowers the levels of iron in your run-off.

No matter what roofing material or finish you choose, including metal roofs, any rainwater collected should always be filtered and decontaminated before you use it. This is especially true and even more important if you plan on using the rainwater you collected inside your home or as a drinking source.

rainwater collection on a metal roof

Advantages of Collecting Rainwater

Rainwater harvesting has many advantages that are making more and more residential and commercial building owners incorporate the practice into their properties. Some advantages of collecting rainwater include:

  • It’s Free — Collecting rainwater provides your property a completely free source of water. You also have complete control over the supply of water, which is ideal for towns or cities with water restrictions.
  • Environmental Benefits — Not only is rainwater harvesting good for your home, it’s also good for the environment. It’s a self-sufficient and energy-efficient way for you to conserve water. Rainwater harvesting also reduces run-off, which can help solve drainage issues, reduce streambank erosion, and is better for your surrounding environment, including gardens and plants, because the water isn’t treated with any chemicals or chlorine.
  • Tons of Uses — The rainwater that you harvest can be used for so many things, with the three main categories of use being indoor, outdoor, and irrigation. Everything from watering your garden to filling your sprinkler system to washing your pets, the rainwater you’ve collected won’t go to waste and the possibilities are endless.
  • Ideal for Emergencies — The rainwater you’ve harvested is the perfect back-up source of water. If there’s ever an emergency, rainwater harvesting can provide you and your home with a large supply of water.
  • Simplicity — Using and maintaining a rainwater collection system is simple. Most systems and their technology are basic and easy to use. They can also usually be fitted onto an existing building and are easy to build during new construction. If you ever need to relocate or reconfigure your rainwater collection system, most are also very flexible and can be easily moved.

There are many more advantages of collecting rainwater. It’s becoming more popular for a reason!

How Much Rainwater Will I Be Able to Collect?

You can determine how effective your rainwater collection system will be and how much rainwater you can expect to harvest by using the following formula:

Catchment Area (sq. ft.) X Rainfall Depth (in.) X 0.623 (conversion factor) = Gallons of Harvested Water


If you’re interested in learning more about a metal roof for rainwater collection, get in touch with any of our Product Specialists today. Our team helps to provide eco-friendly builders and building owners with an ideal rainwater collection roof.


Topics: Metal Roofing, Sustainability

Kaylee Beattie

Written by Kaylee Beattie