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 EngineeringFall 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 storm water

retention– Longer membrane life

• Disadvantages– Greater weight loading– Need for irrigation and drainage system – energy– Higher maintenance costs

Layers of Green Roof

1. Plant layer2. Growing Medium3. Drainage Layer4. Root Barrier5. Waterproof Layer6. Structural Support

(Roof)

Types of Green Roof Plants

• Mosses• Grasses• Herbs• Succulents

• Contains both organic & inorganic materials.

• Provides fertilizers for plant growth.

• Provides stability to plants.

• Retains water for plants.

• Restricts weed growth.

Growing Medium

• Locks water

• Drains excess water

• Provided for roofs with

slope angle <10°

• Supports growing medium

Drainage Layer

• Placed below drainage layer

• Prevents root migration

• Protects waterproof layer

• Avoids water from damaging the roof

Root Barrier & Waterproof Layer

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 StudyToledo 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 AccreditationSustainable 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

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

Energy and Atmosphere

Credits Description Points

1 Optimize Energy Performance

Insulating properties of the green roof reduced energy demand.

1

LEED Accreditation

*continued from prior page

Life Cycle Analysis ResultsImpact 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