Green roofs succeed when they achieve the ideal balance of weight, water infiltration and soil balance to sustain desired plantings. Here are some key performance areas for soils and green roofs that JBC applies in the design process:
Infiltration rate: The amount of permeability in the soil. The higher the infiltration rate, the faster water will pass through the soil.
Bulk density: The weight of a given volume of soil, including air/water pockets known as “pore spaces.” The higher the bulk density, the more compacted the soil.
Total pore space: The nonsolid space in soil mixes often filled with air or water. The lower the total pore space, the more compacted the soil.
Water release curves: A method of determining the amount of water usable for plant roots in the soil, particularly to see if the water in the soil “perches” at a certain level over a period of time.
Organic matter content: The dry weight of organic matter in the soil blend to sustain plantings. Measured as a percentage of overall soil blend weight.
Biological soil conditioner: Any natural (nonsynthetic) product used to improve the physical properties of the soil.
Mycorrhizal innoculant: A biological soil conditioner comprised principally of a microorganism that attaches to roots which promotes optimal energy exchange with soils.