Karen Peck Katz Conservation Education Center at the Milwaukee County Zoo
Green
roofs offer benefit to a building owner and to the community. Before a building
owner decides that a green roof is right for them, it is important for them
to understand the initial and long-term benefits, types, maintenance requirements,
and costs of installing a green roof. Explore green roofs on this website
and other websites alike.
Table of Contents
Thinking of building a green roof?
Whether you are considering retrofitting a green roof on your existing building
or making it a part of a new building, it is important to understand the process
of installing a green roof. Below are some guidelines to help you through
the green roof implementation process.
What is the purpose of your green roof (based on your needs and budget)?
ABC Supply, Co., Beloit, Wisconsin
Image courtesy Weston,
Inc. |
- Aesthetics: To
provide company’s employees with an aesthetically-pleasing
environment to meet, lunch, or recreate.
- Therapy and health: Hospitals and health facilities utilize the
therapeutic benefits of green roofs. These facilities sometimes use gardening
as a tool to enhance the healing process for patients. Plus, the person
can enjoy the comfort, fresh air, and landscape while restoring their health.
- Reduction of capitol costs: Industrial
companies or other businesses build green roofs to reduce costs on energy
and roof upkeep. Green roofs insulate and protect buildings (E.g. weather
conditions and sun’s
U.V. radiation), which reduces energy consumption and increases the durability
of the roof.
Environmental: Green
roofs provide partial solutions to several environmental problems, which
are common in urban locations including: storm-water management, reduction
of pollution, improved air quality, reduction of ‘Urban
Heat Island Effect’, decreased noise pollution, and quality habitats
for insects and birds due to less available green space on the ground. For
example, Great Lakes WATER Institute, located in Milwaukee, Wisconsin is
currently using a weather station to collect real-time weather data to monitor
precipitation. (See Figure 5 to right.) The weather station measures the
following:
- Wind Direction
- Wind Speed
- Temperature
- Barometric Pressure
- Rainfall
- Relative Humidity
Upgrade existing roof or build a new roof?
Determine whether
the green roof will be retrofitted on an existing building or addedto a
newly constructed building.
-
Formerly a run-down automobile repair shop, now
the Garden Room, Shorewood, Wisconsin |
Upgrade? The best time to build a green roof is when an existing
roof needs repair or to be replaced.
- New building? Developing a new building with a green roof will
double the life of the roof membrane and reduce energy costs and consumption.
Hire
structural analysis consultants
Before any construction can take place, it is very important to hire licensed structural
engineers or architects to determine if the site can support
a green roof. These consultants will analyze the building and roof to find
the following information to complete the structural analysis. (Green Roofs
for Healthy Cities)
- Building: Position and structural weight loading capacity
- Existing Roof: Type of roof membrane, year of installation, current
condition (Are there any leaks or damage that need to be repaired?), height
above ground, roof pitch (slope), and orientation
- Is there electrical and water supply in place?
- Is the roof accessible for installation and maintenance? Determined
by the type of green roof that is in place.
Choose
the site
Choose the building or portion of the structure where the green roof will
be installed based on the structural analysis by the consultants.
Great Lakes WATER Institute, University of Wisconsin-Milwaukee
Obtain
required permits from the Department of Construction and Permits
Permits needed
for building a green roof can vary from city to city due to differences
in climate, zoning, and building codes. It is the owner’s
responsibility to be familiar with their particular communities’ zoning
laws and building codes.
Note: Some cities in the United States (E.g. Portland, Oregon and
Chicago, Illinois) are offering incentives for building green roofs to promote
the benefits of sustainable green building. These incentives may make the
permits more accessible to those interested. (City of Chicago, Green Roof
Basics)
Links:
Research
green roofs designers and installation companies
Preparing Green Grid™ green roof design, planting
scheme, and landscape to meet client goals
Image courtesy Weston,
Inc. |
The company chosen to design and install your green roof should be based
on the following:
- Experience and expertise
- Design features offered
- Costs
Landscape
contractors usually design and install green roofs. As of 2004, ten green
roof installation companies are located in the United States.
Green Roof
Providers in North America
(Source: City
of Chicago)
American Hydrotech, Inc.,
located nationwide |
http://www.hydrotechusa.com/START.HTM |
Barrett Company, Millington, NJ |
http://www.barrettroofs.com/ |
Green Tech, Inc.,
Roswell, GA |
http://www.greentechitm.com/ |
Sarnafil, Inc., located nationwide |
http://www.sarnafilus.com/ |
Green Grid/Weston/ABC Supply, Chicago,
IL |
http://www.greengridroofs.com/default.htm |
W.P. Hickman Systems, Inc., Solon,
OH |
http://www.wphickman.com/index.html |
American
Wick Drain Corporation, Monroe,
NC
|
http://www.americanwick.com/ |
The Garland Company, Cleveland, OH |
http://www.garlandco.com/index.html |
Roofscapes, Inc., Philadelphia, PA |
http://www.roofmeadow.com/ |
Soprema, Inc., (located nationwide) |
http://www.soprema.us/index.html |
Determine
the type of Green Roof
The type of green roof is determined by the load that the building can support.
The structural engineer or architect can help decide which type of system
is best suited to your facility based on the structural analysis of the building
- Extensive green roofs: Much lighter than intensive green roofs. Soil
depth is 1-6 inches and weight load 15 – 50 pounds per
square foot.
- Intensive green roofs: Much heavier than extensive green roofs. Soil
depth is typically 6-24 inches (or more) and weight load is
80-150 pounds per square foot.
Plant
Selection
Green roof plants are selected based the type of green roof selected, soil
depth, loading capacity, climate, type of irrigation system, and height and
slope of the roof itself.
- Extensive green roofs: Plants such as sedums and prairie flowers
are utilized because they are low to the ground, will not be destroyed by
nesting birds, require less maintenance (requiring occasional weeding and
watering) and can tolerate almost any kind of weather conditions (E.g. wind
and temperatures).
- Intensive green roofs: Allow for a greater variety of plants including
hardy perennials, native flowers (more expensive), shrubs, and even trees.
These plants require regular maintenance including watering and weeding.
Irrigation
system
Whether your green roof is the extensive or intensive type, it is important
to determine the type of irrigation system needed. Often the green roof installation
company will know how to install the appropriate irrigation system for your
type of green roof, but if not, you can hire a licensed irrigation specialist
or contractor to design and install the watering system for your green roof.
Irrigation
systems are determined by:
- Green roof type: extensive or intensive
- Climate
- Vegetation planted
Costs
Although the initial costs of installing a green roof are greater than a
conventional roof system, the long-term benefits and the energy savings outweigh
the original investment (E.g. increased longevity of the roof and savings
on energy expenditures). The costs of your green roof will depend upon the
design of the green roof such as the type (extensive or intensive), climate,
and plant selection.
Depending on the green roof technology used initial cost for a green
roof is:
Extensive
green roof: $8 to $20 per square foot
Target, Chicago, Illinois
Image courtesy Weston,
Inc.
Intensive
green roof: $15 to 25 per square foot
ABC
Supply Co., Inc., Beloit, Wisconsin
Image courtesy Weston,
Inc.
The
costs will usually include:
- Consultant fees: Structural analysis, designers, landscapers, and
contractors fees
- Structural analysis recommendations: Safety and repairs needed
before installation of green roof.
- Irrigation system: Drip system (permanently installed) or sprinkler
and drainage costs
- Garden materials: Growing medium, plants, fertilizers, substrate
containers (extensive green roofs), and pavers (to prevent spread of fire
and allow accessibility).
- Plants: Typically, Production costs of cultivating plants are higher
in the United States than in Europe because green roof technology is relatively
new here (Beattie and Berghage, 2004).
- Maintenance: Initial (extensive green roofs) and
sometimes long-term (intensive green roofs) maintenance costs
depending on the size and type of green roof installed. For example, extensive
green roofs regular maintenance is only needed for 6-12 months (after plants
are established) after which watering a weeding once a season is sufficient.
- Transportation of materials and services: Based on the location
and types of materials (I.e. some roofing membranes need to be imported
from Europe and some substrate materials come from concrete manufacturing
companies far away) needed. (Beattie and Berghage, 2004)
- Professional assistance and permits: The zoning and building codes
are different in every city.
Green
Roof Costs: An Example of the Typical Extensive Green Roof
# |
Component |
Costs |
Cost Factors |
1 |
Design & Specifications |
5 - 10 % (of total roofing cost) |
The size/complexity of the project and the
number/type of consultants needed. |
2 |
Project
Administration & Site Review |
2.5 - 5 % of total roofing cost |
The size/complexity of the project and the
number/type of consultants needed. |
3 |
Re-roofing with root-repelling membrane |
$ 10.00 - $15.00 / ft 2 |
The type of existing roof, type of new roof
system, and roof accessibility. |
4 |
Green Roof System (drainage, filtering,
paving, growing medium) |
$ 5.00 - $10.00 / ft 2
|
Growing medium (type and depth), pavers
(size and type), and square footage of the green roof (project size). |
5 |
Plants |
$ 1.00 - $3.00 / ft 2 |
Season of installation, type of plants,
and size of seeds being planted. |
6 |
Installation and Labor
|
$ 3.00 - $8.00 / ft 2 |
Equipment necessary to move materials on
to the roof (E.g. crane, if rented is: $ 4,000.00 /day), project size,
design, and planting methods. |
7 |
Maintenance |
$ 1.25 - $2.00 / ft 2 (only for the first
two years) |
Project size, installation schedule, irrigation
system, and plants (type and size) used. |
8 |
Irrigation System |
$ 2.00 - $4.00 / ft 2 |
Since extensive roofs require little irrigation
(E.g. sprinkler system or drip system), this component is optional. |
Note: The
above costs are based on completion of the structural analysis. In this
example, the building is in need of a roof upgrade and does not require
added structural support. In addition, the roof is accessible for maintenance
by ladder. Depending on the size of the green roof project, costs may vary.
Source: Design
Guidelines for Green Roofs, by Steven Peck and Monica Kuhn, B.E.S. Arch,
O.A.A
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