Draining and root stopping 1.
Soil on roof for insulation.
It s r value range of 5 6 6 5 for 1 of material is the highest of the primary rigid insulation types hence it s highest cost.
The deeper the growing medium on your green roof the better it will insulate.
Pour on the bags of gravel your looking to get just a single layer cover over the entire roof 2.
Roll over the root membrane.
In a cold climate using rigid foam insulation has the additional benefit of warming the soil even if just a bit beneath the insulation and next to the foundation well draining soil is placed over the sheet material up to grade where a large diameter topping material such as pea stone or wood mulch helps to break up the falling water and reduce splashback to the building.
If we take insulation to be a bit more specific say the most commonly used material fiberglass that s about r3 inch for fiberglass or if we believed the soil r value rule of thumb about dirt that s about 24 3 about r 0 8 for arbitrary dirt insulation value.
After ensuring you have proper water management in place up to 20 inches of soil or growing medium is added to the roof followed by the plants and trays.
To hold them up you need a really beefy building with a well supported roof.
A sedum green roof is not quite as good an insulator as a wildflower green roof.
Keep in mind that an intensive green roof uses more soil so it won t need the same insulation as other types of green roofs.
Brush into place 3.
Deep layers of substrate growing medium are extremely heavy.
However there s a compromise here.