Biochar is rapidly replacing perlite as the medium-of-choice for green roofs, and biochar is an ideal soil-less component to green roof installations, particularly for its characteristics of high surface area, high activity, porosity and very light weight.
Green Roof Benefits Range from Runoff Filtration to Providing Natural Habitats
Green roofs are building roofs that are partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. Green roofs may also include layers such as root barriers/drainage systems. More info on green roof systems at GreenRoofs.org
Green roofs serve many purposes such as adsorbing rainwater, providing insulation, creating a habitat for wildlife, and helping to lower urban air temperatures mitigating what is known as the heat island effect. Green roofs also provide benefits such as:
- Reduction of stormwater runoff
- Creating a natural habitat or “urban wilderness”
- Filter pollutants and CO2 from the air
- Contributing to LEED points
- Enhancing building aesthetics
- Increasing agricultural space, and
- In high densities, reduction of city’s average temperature during the summer.
Use BioChar Prime™ in your next green roof install Contact Us
Green Roof Types and Construction
There are two types of green roofs for buildings; intensive roofs, which are thicker and require more maintenance, and extensive ones, which are lighter, have less vegetation and require less maintenance. Structurally, green roofs are comprised of native vegetation, planting medium (soil-less), filter fabric, drainage/storage layer, insulation, waterproof membrane, protection board and roof deck.
Incorporating Biochar Into Green Roof Design
Green roof growing media need to be designed to insure low concentrations of nutrients in storm water runoff. An important study run by Portland State University’s Debbie Beck, concluded that green roofs containing biochar showed significant water retention and decreases in discharge of nitrogen & phosphorus. The addition of biochar is a sustainable way to retain nutrients in the soil and improve water quality. Biochar can also prevent Cu (copper), Zn (zinc) and Al (aluminum) that are often associated with runoff from green roofs and green walls.
Given the need to keep the per/sq foot weight of the green roof installation low, biochar is ideal due to the fact that it is a very light media, yet has a very great WHC (water holding capacity), lessening water and irrigation needs. CharGrow’s Biochar Prime™ can weighs as little as 7 pounds per cubic foot (dry bulk density), while having a WHC of over 90%.
Potential LEED Credit Categories
When incorporating biochar into green roof systems, additional LEED credit opportunities are presented.
- Sustainable wastewater management
- Outdoor water use reduction
- Design for Enhanced Resilience
- Local food production
- Green power and carbon offsets
- Rainwater management
USDA Certified 100% Biobased Biochar for Green Roofs
CharGrow sells BioChar Prime™, a pure wood biochar for green roofs that is certified by the USDA BioPreferred Program as 100% Biobased, and is sourced as a by-product of sustainable forestry management practices. BioChar Prime™ is sold by the cubic yard in bulk poly woven bags or loose by the dump truck load. Contact us for biochar performance specs and pricing for your next pilot project or full green roof installation.
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