Green Roofs
Getting Started
What is a Green Roof?
In the simplest of terms, a green roof is a roof with plants on top of it. There are different types of green roofs, but most green roofs are made of the following components: a layer of insulation; a waterproof membrane; a root barrier to prevent the plant roots from penetrating the waterproof membrane; a drainage layer; a geotextile or filter mat; a growing medium; plants; and sometimes a wind blanket.
Why install a green roof?
The benefits of green roofs are numerous, ranging from
cost-savings to improved air quality.
Green roofs decrease the Heat Island Effect; provide a layer of
insulation on the roof; keep the building cooler in the summer and
warmer in
the winter; save energy and reduce energy bills; extend the life of the
roof; provide
additional green space; support local bee colonies which in turn
facilitate plant
fertilization (without plant fertilization, we would have no trees, no
crops,
no plants); improve air quality; and decrease the amount of stormwater
drainage
from a property.
Steps to install a green roof
Installing a green roof is a big decision, and one that requires planning. Here are a couple topics to explore as you decide if installing a green roof is right for you:
Determine the structural capacity of your roof. In order to do this, you must hire a licensed structural engineer or architect to conduct a structural analysis.
Type
of green roof. There are two
types of green
roofs, extensive and intensive, which differ based on weight, cost,
plant
diversity, and maintenance.
Weight
of the green roof. A licensed
structural engineer or
architect should determine the maximum weight your roof can handle. The poundage per square foot of a green
roof
can differ drastically.
Cost
of the green roof. Green roofs
cost more than
conventional roofs, but they increase the life of the roof by 50%, they
provide
energy savings, and they enhance your local ecosystem.Costs to install a green roof include
permitting fees, experts’ fees, plants, soil, growing material,
irrigation
materials, water, installation fees, and membrane layers.
As you plan to install a green roof, remember to include the following steps in your project plan:
Hire a
structural engineer or architect, as well as a licensed plumber or
irrigation contractor to assess and design an irrigation system on
your
roof.Identify
how people (ie: contractors, tenants, you) and materials can safely
get
from the ground to the roof, pre and post installation. Identify
green proof providers in your area.Make
sure to apply for a permit with the Department of Construction and
Permits.Research
what native plants you can use on your green roof.
Also consider when your conventional roof needs to be replaced, because the ideal time to install a green roof is when your conventional roof’s life has come to an end.
Additional Resources
City of Chicago Guide to Rooftop Gardening
Guide for Building Green Roofs in Chicago