Blue Roofs combined with Green Roofs as Tools for Low Impact Stormwater Management

Learn more about Blue roofs and green roofs on our website: http://liveroof.com/roofblue

This video explains how to design and install blue roof technology in combination with the LiveRoof brand green roof system using the RoofBlue riser and a control flow drain system.

The RoofBlue solution allows for a combination of green and blue roofing technology to be used in the same space. RoofBlue risers elevate the LiveRoof system and allow for additional stormwater detention below the green roof system.

This allows building owners to manage more stormwater on their rooftops, minimizing or possibly eliminating the need for additional ground-level water management tools such as detention ponds and cisterns.

How does it work?

RoofBlue risers create a gap between the LiveRoof modules and the membrane, where water can be temporarily detained using a control flow drain system.

During periods of heavy rainfall, peak flow is initially delayed as the green roof plants and soil absorb water. Overflow runoff collects beneath the green roof system, where it moves slowly through a drain with narrow openings that meter the flow of water.

Reducing the flow of water provides stormwater management systems with more time to treat runoff, preventing untreated water from entering local waterways.

During exceptionally heavy storms, water may overflow above the top of the drain into an opening for faster flow. This prevents the live water load from over-loading the system.

Most manufacturers will have specific requirements for blue roof applications. In the early stages of design, it is critical for architects and engineers to consult with the preferred membrane manufacturer to ensure the roofing system will be suited for detained water use.

Also, confirm that the roofing system proposed complies with local codes. Some municipalities may require secondary, redundant waterproofing membranes or have other provisions for rooftop water detention.

Control flow drains and inserts are available from a number of manufacturers – consult your preferred drain supplier for options, spacing and sizing recommendations and installation instructions.

RoofBlue risers allow for a maximum of 3.5” of water retention below the green roof. The risers provide 90% void space, for maximum detention of approximately 2 gallons (or 7.4 liters) per square foot.

Designers and contractors must ensure that the water levels never exceed the height of the RoofBlue risers at the lowest point of slope in the vegetated area. If the water levels rise above the height of the risers, the root systems of the green roof plants would be submerged. Prolonged root immersion in standing water can lead to root rot and plant death.

Installation of RoofBlue is simple. Risers arrive on a separate pallet from the green roof system. To ensure that LiveRoof module lips meet up, install modules and risers from right to left.

One installation team member lays out RoofBlue risers in a row, while another member sets LiveRoof modules atop the risers and pushes them tightly into place.

As with all LiveRoof Installations, be sure to pull soil elevators from the previous row as each row is set. And, avoid walking on the plants so as to prevent damage.

When used in conjunction with the LiveRoof Lite system, use LiveRoof Deep edging at the perimeter.

LiveRoof Standard systems atop RoofBlue risers require LiveRoof Maxx edging at the perimeter.

For LiveRoof Deep and Maxx modules atop RoofBlue Risers, there are two options for perimeter treatment:

1. Use LiveRoof Standard modules atop RoofBlue risers with Maxx edging for the perimeter rows. Then transition to the deeper soil profile. The module bases for Standard, Deep and Maxx systems are the same height and integrate seamlessly without the need for edging. This creates an attractive natural mounding effect.

2. Source or construct a custom perforated, corrosion-resistant edge treatment of sufficient height to contain the soil level above the RoofBlue Risers.

As an added measure against displacement, LiveRoof recommends that RoofEdge be fastened to perimeter modules using blind rivets.

Every 12 inches, pre-drill holes through the edging and into the plastic module sidewall. Install blind rivets with a hand riveter or pneumatic rivet gun.

On wind-challenged applications, designers may choose to use WindDisc to connect modules together atop the RoofBlue risers.

Using a rubber mallet, tap disc into place after each row of modules and risers are installed. Then, slide the next row of risers and modules into place, and push hard to engage the discs fully into the module corner slots.

If needed, RoofBlue risers may be custom cut using a chop saw or a reciprocating saw with a long blade. Be sure to choose blades recommended for plastic.