I was wondering if anyone had already used a roof garden including the perlite.
Perlite is a volcanic rock effusive varying in color between gray and pink, whose chemical composition is similar to that of dacites and rhyolites. It has the ability to expand its volume up to 20 times when compared to the original flow rate.
The peculiarities of the system including the perlite is due to the limited thickness of the package that allows engraftment and development of plant species provided in 11 cm thickness, bringing the storage value total water up to 45 l / m2 (perlite's saturation value)
I think this roof system can be included into WEc1 calculation by reducing the Ks factor since this is not a typical cistern or pond retention system but it releases water directly at the roots without use of any irrigation system.
Any suggestion?
Alexia Anastassiadis
9 thumbs up
July 27, 2015 - 5:20 pm
Hello Fabio,
Ks is the Species Factor, it is a characteristic of the plants you will use, the soil type should not affect the Ks.
We do lots of projects with green roofs, all of them have special substrates that we engineer, according to the type of planting, exposure, rainfall patterns, etc and we still use a High Microclimate factor for the green roofs, since the conditions there are usually far worse than those on the ground, still what substrate engineering allows us to do, is to still use low Ks species and no permanent irrigation on those roofs, so that's plenty of help in making a low water consumption project.
What we do in such cases is that we declare the area a non-irrigated and leave the Ks space blank and the irrigation space blank so you don't add a water consumption for that category on the LEED form.
For instance, lets say that your project earns credit SSc2 (if not, you can not include the green roof in your calculations) and have an irrigated garden in the ground level and then the non-irrigated green roof (usually an extensive green roof is all made up of ground covers).
So, you would have all the irrigated categories of your garden (trees, shrubs, mixed, groundcovers, etc) and then the Non-Irrigated Groundcovers of your roof, with a 0 Ks value and no irrigation (the plants don't have 0 ks, it is just what you do in order to fill the form and have zero consumption for that category).
Hope this helped!! All the best!