Installation of a Green Roof
The Use of a Literature Review, Engineering
Analysis, and Life Cycle Analysis to Determine
Sustainable Benefits
CIVE 6900 Sustainability Science and Engineering
Fall 2008 Professor Apul
Presented by: Katie Puffenberger,Erik
Lange,Prasad Bollineni,Zongsu Wei
School of Art, Design and Media
at Nanyang Technological University
An intensive green roof on the Coast Plaza Hotel
in Vancouver, British Columbia
Portion of a 10.4-acre extensive green roof on an assembly plant
at Ford Motor Company in Dearborn, Mich.
Fukuoka City, Japan
Stakeholders of this Project
• University of Toledo wishes to update the
North Engineering Building
• SSOE is fast tracking design plans
• UT Students will be benefited by aesthetically
pleasing study areas
• Society benefits from silver standards of LEED
certification
Objectives
• Engineering analysis for installing a green roof
– Far reaching background information
– Analyze possible LEED credits
– Life cycle analysis
Introduction
Green Roof
•
•
•
•
Developed in Germany in the 1960s
Water-proof structures covering buildings
Energy savings
Used to combat the urban island
effect.
• Decrease air pollution
• Provides habitat
Extensive Green Roof
• Advantages
– Lightweight
– Used in large
areas
– Low
maintenance
– No need for irrigation
• Disadvantages
– Less energy efficient and storm water retention
– Limited choice of plants
– Unattractive during the winter
Intensive Green Roof
• Advantages
– Good insulation
– Very attractive
– Energy efficiency and
water retention
– Longer membrane life
storm
• Disadvantages
– Greater weight loading
– Need for irrigation and drainage system – energy
– Higher maintenance costs
Layers of Green Roof
1.
2.
3.
4.
5.
6.
Plant layer
Growing Medium
Drainage Layer
Root Barrier
Waterproof Layer
Structural Support
(Roof)
Types of Green Roof Plants
•
•
•
•
Mosses
Grasses
Herbs
Succulents
Growing Medium
• Contains both organic & inorganic materials.
• Provides fertilizers for plant growth.
• Provides stability to plants.
• Retains water for plants.
• Restricts weed growth.
Drainage Layer
• Locks water
• Drains excess water
• Provided for roofs with
slope angle <10°
• Supports growing medium
Root Barrier & Waterproof Layer
• Placed below drainage layer
• Prevents root migration
• Protects waterproof layer
• Avoids water from damaging the roof
Methods and Modeling
Approach
Analysis Methods
• Much of the modeling analysis was done using
site-adjusted published figures
• Specific numbers were found for the North
Engineering Building Roof
• Literature review was very important for data
gathering
• Site drawings and roof visits were important
for visualization
LITERATURE
REVIEW
Insulation Effect
• Lowering Thermal Conductance in Roofs is the
Key to Energy Savings
• Studies have found between 37% to 48%
Energy Savings due to Insulation of Green
Roofs
Air Quality Effect
• In U.S., there are 3,700
premature deaths per year
that can be directed contributed
to air pollution
• Reducing air pollution does not always equate to lower
monetary costs
• Ozone, nitrogen oxide, sulfur dioxide, and PM10
(particulate matter) are examples of pollutants that
have been shown to be removed by plants that have
been installed on green roofs
• Each hectare of green roof installed has been found to
remove 85 kilograms of air pollution in one year
Monetary Effect
• Green roofs cost approximately $150 per
square meter to install
• Energy costs are substantially less for buildings
with green roofs
• Cost analyses must be done on each site due
to a number of differing factors including
existing insulation and building configuration
LIFE CYCLE
ANALYSIS
LCA Goals and Scope
• Goal of LCA was to quantify and clarify the
environmental and monetary costs and saving of
installing a green roof versus leaving the existing
roof
• The functional unit was the entire roof
• The life was determined to be thirty years
LCA Scope: Boundaries
• Included in the LCA was energy used,
monetary cost, and any pollution
removed or added during the
manufacture, construction, or operation
phases
• No results in other impacted sectors or
results from the maintenance or
demolition phases were considered.
LCA: Life Cycle Inventory
• Comparison Categories (from the functional unit):
–
–
–
–
Global Warming Potential (GWP-carbon dioxide equivalence)
Monetary Costs (U.S. dollars)
Air Pollution Removal (kilograms of total pollutants)
Energy Saving (terajoules)
• Analysis for each category was done using a mix of
process-based LCA and EIOLCA
• Most of the inventory was done using site-adjusted
published figures
• Multiple outputs were evaluated from each phase
within the boundaries
Results and Interpretation
A Local Case Study
Toledo Lucas County Public Library
Toledo Lucas County Public Library
• Serving the Public since 1993.
• Intensive Green Roof.
• Green Roof Covers 0.5 acres of the roof.
• Consists of Turf, Shrubs, & Trees.
• Grid System Implemented for Roof.
• Uses Potable
Water for Watering
Plants.
Baseline Scenario
• Water
• There is approximately 5,150
square yards of roof was
examined
• Using average annual rainfall data,
this area of roof catches
approximately 4,580 cubic yards
of water each year.
• This water is currently being
wasted
Layout and Drainage Patterns
• The 50-year, 24-hour storm was the basis of
design
• Existing Drains will remain intact only as
emergencies
Layout and Drainage Patterns
• The new roof shall not need to be re-sloped
• The roof layers and plants shall be designed to
hold the design storm
• The saw-toothed structures shall work as they
do currently
Roof Type Determination
• Extensive Green Roof
– No supplemental
irrigation
– Maintenance free
– Less design load
• Why Intensive Roof was not chosen
– Difficult and expensive to reconstruct the roof
– Planting media requires more maintenance
Introduction to LEED Building
Rating System
LEED (Leadership in Energy and Environmental
Design) was developed as a national standard
for building environmental minded and
sustainable buildings. LEED was developed
and continues to be administered by the U.S.
Green Building Council. The first pilot version
of LEED was released in 1999.
LEED Sections and Points per Section
(Source: www.usgbc.org)
LEED-NC
Section Points
Sustainable Sites (SS)
14
Water Efficiency (WE)
5
Energy and Atmosphere (EA)
17
Materials and Resources (MR)
13
Indoor Environmental Quality
(EQ)
15
Innovation and Design Process
5
LEED Accreditation
Sustainable Sites
Credits
Description
Points
5.1 Reduced Site
Disturbance
Local plants and vegetation used on the
green roof for habitat creation and
restoration.
1
5.2 Reduced Site
Disturbance
The green roof is an open place for students
and faculties.
1
6.1 Storm Water
Management
Rainwater and runoff are collected on the
roof.
1
7.1 Landscape &
Exterior Designed to
Reduce the Heat
Islands
The green roof helped to reduce the heat
island effect.
1
*continued on next page
LEED Accreditation
Water Efficiency
Credits
Description
Points
1.1 Water Efficiency
Landscaping
Water was not directed to storm sewers.
1
1.2 Water Efficiency
Landscaping
No potable water was used for irrigation of
plants on the green roof because native
plants were chosen.
1
Credits
Description
Points
1 Optimize Energy
Performance
Insulating properties of the green roof
reduced energy demand.
1
Energy and
Atmosphere
*continued from prior page
Life Cycle Analysis Results
Impact Assessment
• Totals (inclusiveness of all within boundaries):
Comparison Category
Installing a Green Roof
Allowing Existing Roof to
Remain
Money
$752,100
$542,025
GWP
3,766 GWP
5,700 GWP
Energy Saved
43.5 TJ
65.7 TJ
Air Pollution Removal
697 kg of total pollutants
0 kg of total pollutants
LCA Interpretation Phase
• Over life cycle, monetary costs are not
recovered from high installation cost of green
roof
• Other categories evaluated decidedly favor
green roof installation
• Tough to compare to other LCAs performed on
green roofs due to unique functional unit
Take Home Messages
1.University of Toledo can benefit from the
installation of a green roof, because LEED
many accreditation points can be accumulated
2 Cost of installing a green roof on an existing
structure will not be met by energy savings
costs
3.Other than monetary cost, all other areas of
the LCA favored green roof installation
Questions
Thank You