Living roofs are rooftops that are partially or completely covered with vegetation. They have been gaining popularity in Europe, where one-third of new roofs in some areas are now living roofs. Living roofs can provide insulation, help regulate rooftop temperatures, increase habitat for wildlife, and beautify buildings. They are categorized as either extensive or intensive based on soil depth and plant types supported. Creating a living roof involves installing multiple layers like a waterproof membrane, root barrier, drainage system, and growing medium before planting vegetation suited to the roof environment.

1. Living Roofs
AK Townsend
Living roofs are rooftops that are partially or completely covered with vegetation.
Once nearly unheard of, living roofs can be found on a growing number of
buildings around the world. It has been reported that one-third of all new roofs
in some parts of Europe are living roofs.
The history of the living roof can be traced back a few hundred years to Iceland,
where buildings were topped with sod for insulation and protection from the
elements. The idea appears to have spread to Scandinavia and, then, to the rest
of Europe, where it has gained popularity over the past few decades.
Living roofs have several benefits. On hot summer days, they can reduce rooftop
temperatures by several degrees, keeping buildings and cities cooler. They also
keep buildings warmer in the winter. Living roofs act as air and water filters.
They also increase habitat for songbirds and insects and beautify homes and
commercial buildings. Living rooftop gardens can be created for a peaceful, cool,
park-like atmosphere above the noise and busyness of the city below.
Living roofs can be divided into two categories. “Extensive” living roofs need
between one and five inches of soil and support plants with shallow roots. They
generally add from 15-50 pounds of weight per square foot onto the roof and do
not need any special rooftop construction to support their additional weight.
Seeds can be planted by hand or purchased in sheets. These roofs require little to
no maintenance.
“Intensive” living roofs can support trees and shrubs. Grown in at least one foot
of soil, these living roofs can add from 80-150 pounds of weight per square foot
to the roof. Building owners will need to ensure that their roofs are strong
enough to hold the added weight. These roofs require more maintenance.
Living roofs typically are created using several layers of materials. The bottom
layer, sloped slightly to prevent pooling, is a waterproof membrane that is laid on
the roof to keep moisture in the soil from seeping into the building. A root
barrier is added to keep plant roots from digging into the roof. Other layers
include special insulation, drainage, and filtration layers. A water storage and
irrigation layer helps to ensure that the plants’ roots do not dry out. Finally, soil
is added, and vegetation is planted. A wide variety of plant species can be grown
on living roofs. Plants that can thrive in strong sun, wind, and drought are good
choices.
For those who want the benefit of a living roof but cannot spare the space or the
expense, partial living roofs are an option. The GreenGrid roof consists of
portable, 2-inch-deep containers that can be placed anywhere providing the roof
will bear their weight, which can be 15 pounds per square foot when wet. Deeper
containers are available as well.

2. Some of the most advanced and least expensive living roof technology has been
developed in Germany. Currently, the Ford Motor Company is constructing the
world’s largest living roof on one of its manufacturing plants. It will stretch
across 10.4 acres of rooftop.
If you are interested in constructing a partial or full living roof on your home,
hotel, or office building, you can contact the companies below for information,
supplies, and installation.
For Additional Information
Germany: Xero Flor - http://www.xeroflor.de/index2.html
Optigun - http://www.optigruen.de/2003/start.html
UK: Miller Roofscapes - http://www.miller-roofing.com/roofscapes.htm
Green Roof Systems Consultancy – http://www.roof-garden-
consultancy.co.uk/home.htm
USA: GreenGrid - http://www.greengridroofs.com/
http://www.archibio.qc.ca/pages/roof.html