Achieving Leadership in Energy and Environmental Design (LEED) certification for a project is not an easy task. It requires the design team to review every discipline to provide the project with the smallest environmental impact possible.

When it comes to storm drainage, less than 1% of projects understand the overwhelming benefits siphonic roof drains bring to a project to seamlessly take it from silver to gold certification. 

By using siphonic roof drains, LEED points can be awarded for reducing material, eliminating site disturbance, and further compounded when a rainwater harvesting system is incorporated. 

For those unfamiliar with LEED, it was created by the U.S. Green Building Council to raise awareness of and promote integrated “green” building projects. The LEED Green Building Rating System was devised as a voluntary, consensus-based national standard for developing high-performance, sustainable buildings. 

To become LEED-certified, a building is rated in six categories:

Creating a sustainable site (up to 10 points);

Conserving water (up to 10 points);

Reducing the depletion of natural resources and materials (up to 14 points);

Improving indoor environmental quality (up to 15 points);

Use of innovative design (up to 6 points);

Reducing energy consumption (up to 35 points).

Within each category, points are awarded based on the LEED Green Building Rating System. The number of points available within each category may depend on the specific rating system used (e.g., LEED v4, LEED v4.1, etc.). The total number of possible points in a LEED certification project ranges from 40 to 110 points, depending on the rating system.

For those new to siphonic drainage, the system operates by eliminating air from entering the pipework, which then reduces the storm pipe diameter to roughly half the size of traditional gravity drainage. Even more impactful, siphonic storm drainage allows the pipe to install with zero slope. This provides routing options traditional gravity drainage isn’t even capable of hydraulically. 

Lastly, siphonic drains directly remove the debris from the roof, saving on recurring maintenance costs over the lifetime of the building. 

Although not required, a siphonic system allows for ideal routing to a rainwater harvesting system. The rain can be stored and used for nonpotable applications such as irrigation, toilet and urinal flushing, process cooling towers or janitorial needs. By introducing a rainwater harvesting system to a project, several additional LEED credits become available.

It’s important to note that the thresholds and point values listed here are subject to change and may vary depending on the specific version of the LEED rating system being used. Additionally, achieving LEED certification requires earning a minimum number of points across different credit categories, so it’s important to consider the overall sustainability goals of a project when selecting strategies to pursue LEED credits.

Siphonic Drainage and LEED Credits Explained

• Sustainable Sites Credit 5.1, Site Development: Protect or Restore Habitat. This credit is worth up to one point for minimizing the impact of development on ecosystems, maintaining or restoring habitats and promoting biodiversity.

Siphonic drainage can reduce the amount of site disturbance compared to conventional stormwater management systems, which could be used to increase the amount of open space or restore damaged ecosystems. Additionally, piping in a siphonic system runs with no pitch, creating a shallow, linear trench.

• Sustainable Sites Credit 5.2, Site Development: Maximize Open Space. This credit is worth one point, which is awarded for preserving or restoring at least 50% of the site as open space.

Siphonic drainage systems can help reduce the need for traditional stormwater management features, such as retention ponds and swales. This can free up space on a project site for other use by routing the stormwater to the designer’s preferred discharge location.

• Sustainable Sites Credit 6.1, Stormwater Design: Quality Control. This credit is worth up to two points, with one point awarded for achieving a 25% reduction in stormwater runoff volume and an additional point awarded for achieving a 50% reduction.

Siphonic drainage systems can help reduce stormwater runoff and improve water quality by efficiently conveying rainwater to storage tanks, infiltration systems or other rainwater harvesting systems.

• Water Efficiency Credit 1: Water-Efficient Landscaping. This credit is worth up to two points, with one point awarded for reducing landscape water use by 50% and an additional point awarded for reducing landscape water use by 75%.

By reducing stormwater runoff and reusing it for landscaping purposes, siphonic drainage systems can help reduce the overall water consumption of a building or project site.

• Water Efficiency Credit 2: Innovative Wastewater Technologies. This credit is worth two points, with both points awarded for implementing an innovative wastewater technology that reduces potable water demand by at least 50%.

Siphonic drainage systems can be used as an innovative wastewater technology to help reduce the demand on municipal wastewater treatment plants by capturing and reusing rainwater.

• Water Efficiency Credit 3: Water Use Reduction. This credit is worth up to four points, with the number of points awarded based on the percentage reduction in water use achieved compared to a baseline building.

By reducing the overall demand for potable water through the reuse of stormwater for nonpotable uses, such as flushing toilets or irrigating landscaping, siphonic drainage systems can help contribute toward meeting the water use reduction requirements for this credit.

• Materials and Resources Credit 2: Construction Waste Management. This credit is worth up to two points, with one point awarded for diverting at least 50% of construction waste from landfill or incineration and an additional point awarded for diverting at least 75% of construction waste.

Siphonic drainage systems can be prefabricated off-site, which can help reduce the amount of construction waste generated during the installation process. 

• Materials and Resources Credit 4: Recycled Content. This credit is worth up to two points, with one point awarded for using materials with recycled content contributing to 10% of the total value of the materials used in the project and an additional point awarded for using materials with recycled content contributing 20% of the total value.

Siphonic drains and the pipework within the system can be made from recycled materials such as cast iron, which can help contribute toward the use of recycled content in construction materials.

• Indoor Environmental Quality Credit 3.1: Construction Indoor Air Quality Management Plan. This credit is worth one point, which is awarded for implementing an Indoor Air Quality Management Plan during construction that meets the requirements outlined in the credit.

Siphonic drainage systems require less site disturbance to the surrounding environment, which can help minimize the release of pollutants during the construction process. Pipe is installed in the ceiling, eliminating the need for internal excavation. 

• Innovation in Design Credit 1: Innovation in Design. This credit is worth one-to-five points, depending on the level of innovation demonstrated by the project team above the requirements set by the LEED Green Building Rating System.

Siphonic drainage systems can be considered innovative technology to help improve the overall sustainability of a building or project.

• Innovation in Design Credit 2: LEED Accredited Professional. This credit is worth one point, which is awarded for having a LEED Accredited Professional on the project team.

By working with a LEED Accredited Professional during the design and construction process, a project team can ensure that its siphonic drainage system is optimized to achieve maximum sustainability benefits, which can contribute toward earning this credit. 

Brennan Doherty is the director of siphonic drainage for MIFAB HydroMax. In his current role, he is responsible for educating owners, engineers, design-build contractors and architects on the many technical, design and cost-saving benefits of siphonic roof drainage. Doherty’s expertise in siphonic drainage is well-established, having helped to introduce the technology into the ASPE Design Handbook V2 and obtaining BMEC approval for Ontario. He has also published multiple articles and delivered presentations at both national and local levels for organizations such as ASPE, Tilt-Up, MCAA, PHCC, and IAPMO.