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Life Cycle Assessment and the Building Envelope: Balancing
Durability & Environmental Impact
Dr. James L. HoffCenter for Environmental Innovation in Roofing
Agenda
• Sustainability: Balancing Time & Impact
• Life Cycle Assessment
• Durability
• LCA and Durability: Critical Issues
• Durability Tools for a Sustainable Future
• Recommendations Going Forward
What is Sustainability?
“A state that can be maintained at a certain level indefinitely” (Merriam-Webster Online Dictionary)
“Meeting the needs of the present without compromising the ability of future generations to meet their own needs” (U.N. Brundtland Commission, 1987)
Measuring Sustainability
When evaluating the relative sustainability of a product or a system, the key questions are:
Sustainability =ImpactTime
1. How long (time) can the product or system last?
2. What is the cost (impact) to last that long?
Sustainability: The Core Issue
TIMEIMPACT
Balancing Impact and Time
Looking at Impact:Life Cycle Assessment
(LCA)
Looking at Longevity:Durability
What is LCA?
“… a scientific approach to identify and evaluate the environmental impact of a product throughout its life cycle.”
Office of the Federal Environmental Executive (OFEE)http://ofee.gov/gs/gs.asp
What is LCA?• A Scientific Approach: Based on measurable and
predictable attributes
• To Identify & Evaluate: Intended to compare alternatives, not provide absolute values
• Focused on Impact: What is the net result to the environment?
• Throughout the Life Cycle: A “cradle-to-grave”… or “cradle-to-cradle” approach
Why is LCA Important?
• LCA is a globally recognized procedure based on established ISO standards
• LCA will be incorporated into the LEED®
Green Building Rating System in 2010 / 2011
• LCA is a necessary measure to support emerging global warming initiatives such as carbon cap-and-trade
1. Establish the Time Period
2. Describe the Life Cycle System
3. Identify & Measure the Impacts
4. Assess the Impacts
Key LCA Steps
10 Years
15 Years
20 Years
30 Years
39 ½ Years
60 Years
Typical Commercial Roof Warranty Length
U.S. Taxable Building Depreciation Period
USGBC Life Cycle Task Force Recommendation
Step 1: Establish the Time Period
Step 2: Describe the Life Cycle System
• Inputs
• Processes
• Outputs
• System Boundary
Raw Materials Acquisition
Manufacturing
Operation / Maintenance
Recycling / Waste Mgmt.
Inputs:
Raw Materials
Energy
Outputs:
Atmospheric Emissions
Waterborne Waste
Solid Waste
Co-Products
Other ReleasesSystem Boundary
Processes:
Transportation & Handling
Installation / Assembly
The Product Life Cycle
Time
Impact
Step 3: Measure the Impacts
• Identify the Significant Impacts
• Establish Meaningful Measures
Impact:
Global Warming Potential
Ozone Depletion Potential
Photochemical Oxidant Potential
Acidification Potential
Eutrification
Health Toxicity (Cancer)
Health Toxicity (Non-Cancer)
Health Toxicity (Air Pollutants)
Eco-Toxicity Potential
Linked To:
Global Climate Change
Degradation of Ozone Layer
Ground-Level Ozone
Acid Rain
Algae Blooms
Cancer Frequency
Non-Cancer Disorders
Breathing-Related Illnesses
Reproductive & Genetic Disorders
Measuring Environmental Impacts
The TRACI Model
Measuring Environmental Impacts
The TRACI Model
Meaningful Measure:
kg CO2 Equivalent
kg CFC Equivalent
kg NOX Equivalent
H+ Moles Equivalent
kg Nitrogen Equivalent
kg Benzene Equivalent
kg Toluene Equivalent
kg: DALYs Equivalent
kg 2,4-D Equivalent
Impact:
Global Warming Potential
Ozone Depletion Potential
Photochemical Oxidant Potential
Acidification Potential
Eutrification
Health Toxicity (Cancer)
Health Toxicity (Non-Cancer)
Health Toxicity (Air Pollutants)
Eco-Toxicity Potential
• Weigh the Impacts– Which impacts are most important in the assessment?
• Compare Alternatives– Which alternative provides the optimal benefit?
• Look for Improvement Opportunities– How can the impacts be reduced?
Step 4: Assess the Impacts
• Avoids Shifting of Impacts
• Allows Consideration of Trade-Offs
• Promotes Situation-Based Decisions
LCA Benefits
LCA Limitations• LCA is Expensive
– Requires time & money
• LCA is Complex– Difficult to understand & communicate
• LCA is Not Absolute– Useful for reference or comparison– Cannot by itself determine cost-
effectiveness or practicality
What is Durability?
A dictionary definition:
“… the ability to exist for a long time without significant deterioration.”
Merriam-Webster Online Dictionary
What is Durability?A building standards definition:
“… the ability of a building or any of its components to perform its required functions in its service environment over a period of time without unforeseen cost for maintenance or repair.”
Canadian Standards Association “Guideline on Durability in Buildings” (CSA S478-95, Rev. 2001)
The ability of a building or any of its components to:
1. perform its required functions
2. in its service environment
3. over a period of time
4. without unforeseen cost for maintenance or repair
What is Durability?
Roof Durability Characteristics
Performing Required Functions• Resist and re-direct moisture
• Resist air & vapor movement
• Resist thermal transfer
• Resist fire, wind, hail, and other loads
• Serve as a working platform for:– Rooftop mechanical equipment– Solar / PV installations– Garden roofing installations
Roof Durability Characteristics
In Its Service Environment
• Climatic Environment– High wind / wind-blown debris zones– Severe hail zones– Cold climates / severe freeze-thaw zones– Warm climates / high uv zones
• Operating Environment– Frequency / density of use– Occupant capabilities / attitudes– Frequency / complexity of maintenance
Roof Durability Characteristics
Over a Period of Time
Period of Time =
Intended Service Life
Roof Durability Characteristics
Without Unforeseen Cost
Implies Some Level of Cost Should Be Foreseen!
Implies Planning Is Necessary!
“The majority of green building assessment systems focus on the design of the constructed building, with little focus on the effect of the building system’s life during operation. This tendency has resulted in a failure of many rating systems to properly consider durability, lifecycle cost, and the effects of premature building envelope failures.”
Durability &Green Rating Systems
“Green Assessment Tools: The Integration of Building Envelope Durability. “ (McCay, 2008, p. 1)
Too much focus on design, too little focus on operation…
... resulting in a failure to address:
– True life cycle cost
– Risk of premature failures
Durability &Green Rating Systems
• Incorporating Vital Service Features into LCA
• Incorporating Realistic & Achievable Service Life Expectations into LCA
Balancing Impact &Durability: The Key Issues
Example:
Installing a High Density Cover Board over Low Density Roof Insulation
MembraneCover Board
Insulation
Environmental Benefits:+ Reduced Damage+ Longer Service Life+ Lower Life Cycle Impact
Environmental Costs:– Added Materials– Added Energy– Added Waste
Balancing Impact & Durability
Vital Service Functions
Thicker roofing membranes
Redundant flashing details
Will the LCA recognize the added value of such enhanced service features?
Balancing Impact & Durability
Vital Service Functions
Other Examples:
Balancing Impact & Durability
Service Life Expectations
How do we identify service life today?• Anecdotal field reports
• Opinion surveys
• Historical end-of-service studies
• Agency approval reports
• Manufacturer warranty offerings
Opinion Survey1
16.6
16.6
N/A2
14.1
No Data
System Type
Asphalt BUR
SBS Modified
PVC
EPDM
TPO
Historical Study3
13.6
17.3
N/A2
16.8 – 18.4
No Data
Agency Report4
20
20
35
20
20
Warranty Offering5
20
20
15
30
30
Data Source
1Mean service life from Cash (1997), based on an opinion survey of industry participants.2Data from the Cash & Schneider studies involved discontinued formulations of PVC that do not allow the data to be meaningful.3Mean service life from Schneider & Keenan (1997), based on end-of-service field reports.4Estimated service life from British Board of Agrément Technical Approvals (BBA, 2008):5Published warranty offerings from NRCA Low Slope Roofing Materials Guide, 2006-07, Vol. 2, Section 5 Roof Membrane Warranties.
Service Life Expectation Example:
Low-Slope Roofing SystemsEstimated Service Life (Years)
Different Estimates – Different Assumptions:
• Time Assumptions– Backward looking: Expecting no change– Forward looking: Expecting improvement
• Quality Assumptions– Uncontrolled sample: Assuming the worst– Controlled sample: Assuming the best
Durability & LCA
Service Life Expectations
The contrast between forward-looking versus backward-looking service life estimates and average versus high quality levels help identify two critical questions for the building envelope industry:
Durability & LCA
Where Do We Go From Here?
1. Should we move forward with the assumption that the building envelope components installed on the sustainable buildings of the future will be average in performance, or should the expectation be set higher?
2. And if we decide to move forward with higher expectations, how do we develop and implement processes and controls to assure this higher level of performance is attained?
Durability & LCA
Durability Tools for a Sustainable Future
• Performance Standards
• Durability Planning
Durability Tools
Performance Standards
• Prove Their Value through Research– Drawing from the past– Adding certainty to the future.
• Identify Their Value with Measurement– Providing measurable and reproducible value– Balancing environmental impact with added performance.
In order to effectively address vital service functions, performance standards must…
• Failure Analysis (e.g. Bailey & Bradford field studies)
• Destructive Testing (e.g. Koontz et al. hail testing)
• Performance Testing (e.g. ORNL thermal testing)
Performance Standards
Research Examples & Options(Low Slope Roofing)
What is the measurable value (benefit less impact) of:
– Multiple & staggered insulation layers?
– Cover boards?
– Increased membrane thicknesses?
– Redundant flashing details?
Performance Standards
Features Needing Measurable Value:
• An Up-To-Date & Active Research Agenda– To identify & address the critical “gaps”– To identify resources & funding– To monitor & measure progress
• A Research-Driven Standards Process– A consensus process … – Using research results to validate industry practice
Performance Standards and the Building Envelope
What We Need:
Durability Tools
Durability Planning
• Emphasis on Process– A management system– Similar to ISO 9000 & ISO 14000
• Emphasis on Shared Responsibility– Identifies stakeholders– Identifies roles
Durability Tools
Durability Planning and Canadian Standard S478-95
Three Basic Steps:
1. Identify Durability Determinants
2. Identify Durability Interventions
3. Develop Action Plan & Timetable
Step1: Identify Durability Determinants
• Providing the Required Functions
• In the Service Environment
• By Key System Element
Durability Planning
Canadian Standard S478-95
Step 2: Identify Durability Interventions
Durability Planning
Canadian Standard S478-95
• During Design
• During Material Selection
• During Application & Commissioning
• During Service Life
• At End of Service
Step 3: Develop Action Plan & Timetable
Durability Planning
Canadian Standard S478-95
• Periodic & Ongoing
• At Critical Specified Times
Durability Planning Matrix
Durability Planning & Green Building Envelope Design
The Service Environment
Required Functions
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Durability Planning
Model Durability Planning Matrix
The Service Environment
Required Functions
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Durability Planning
Model Durability Planning Matrix
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Durability Planning
Model Durability Planning Matrix
Operating / Maintenance Criteria
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Balancing Impact & Durability
Going Forward…• Try to reach agreement on realistic, but achievable service
life periods that support long-term building sustainability
• Establish an up-to-date and active industry research agenda
• Increase research activity, emphasizing key component & detail functions
• Re-invigorate standards activity with new research & new commitment
• Begin incorporating durability planning into building envelope specifications
• Continue to advocate the importance of durability
Life Cycle Assessment and the Building Envelope: Balancing
Durability & Environmental Impact
Dr. James L. HoffCenter for Environmental Innovation in Roofing