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Sustainable Buildings: Addressing Long-Term Envelope Durability

Explore the importance of durability in achieving sustainability and how green rating systems fall short. Learn about vital service functions and incorporating durability in green building design.

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Sustainable Buildings: Addressing Long-Term Envelope Durability

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  1. SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING ENVELOPE DURABILITY Dr. James L. Hoff Center for Environmental Innovation in Roofing / TEGNOS Research, Inc.

  2. Durability & Green Rating Systems Durability is a necessity to achieve long-term sustainability … … but many green building rating systems provide little assurance that durability is adequately addressed.

  3. Durability & Green Rating Systems “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.” “Green Assessment Tools: The Integration of Building Envelope Durability. “ (McCay, 2008, p. 1)

  4. Durability & Green Rating Systems Too much focus on design, too little focus on operation… ... resulting in a failure to address: • True life cycle cost • Risk of premature failures

  5. What is Durability?

  6. What is Durability? A dictionary definition: “… the ability to exist for a long time without significant deterioration.” Merriam-Webster Online Dictionary

  7. 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)

  8. What is Durability? 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

  9. Roof Durability CharacteristicsPerform 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

  10. Roof Durability CharacteristicsIn 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

  11. Roof Durability CharacteristicsOver a Period of Time Period of Time = Intended Service Life … More to Follow

  12. Roof Durability CharacteristicsWithout Unforeseen Cost… Implies Some Level of Cost Should Be Foreseen! Implies Planning Is Be Necessary!

  13. Roof Durability CharacteristicsWithout Unforeseen Cost for.. • Maintenance • Frequent & ongoing • Includes inspection, assessment, service, & minor repairs • Repair • Infrequent, but generally planned • Includes renovation, retrofitting, component replacement

  14. Durability & Green Building DesignThe Major Issues • Justifying Vital Service Functions in Green Design Assessment • Incorporating Reliable Service Life Expectations into Green Design

  15. Durability & Green Building DesignVital Service Functions Example: Installing a High Density Cover Board over Low Density Roof Insulation • Environmental Benefits: • Reduced Damage • Longer Service Life • Lower Life Cycle Impact • Environmental Costs: • Added Materials • Added Energy • Added Waste Membrane Cover Board Insulation

  16. Durability & Green Building Design Vital Service Functions Unless the benefits of the cover board are recognized in the overall project assessment, the cover board may be viewed only as adding to environmental costs: • Environmental Benefits: • Reduced Damage • Longer Service Life • Lower Life Cycle Impact • Environmental Costs: • Added Materials • Added Energy • Added Waste Membrane Cover Board Insulation

  17. Durability & Green Building DesignVital Service Functions Other Examples: • Thicker roofing membranes • Redundant flashing details Will the project assessment recognize the added value of such enhanced service functions?

  18. Durability & Green Building DesignIncorporating Vital Service Functions Performance Standards

  19. Durability & Green Building DesignPerformance Standards In order to incorporate vital service functions, performance standards must… • 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.

  20. Durability & Green Building DesignPerformance Standards Research examples & options: • Failure Analysis (e.g. Bailey & Bradford field studies) • Destructive Testing (e.g. Koontz et al. hail testing) • Performance Testing (e.g. ORNL thermal testing)

  21. Durability & Green Building DesignPerformance Standards Benefits Needing Definition: (Examples) • What is the measurable value(benefit less impact) of: • Multiple & staggered insulation layers? • Cover boards? • Increased membrane thicknesses? • Redundant flashing details?

  22. Durability & Green Building DesignPerformance Standards and the Roofing Industry By definition, sustainable buildings must be buildings that perform: so performance standards are more important than ever … … but without credible roofing industry performance standards, others may establish the standards for us.

  23. Durability & Green Building DesignPerformance Standards and the Roofing Industry A spirit of industry cooperation is emerging that could foster expanded performance standards activities … … but credible roofing industry standards may require a much higher level of research activity and funding.

  24. Durability & Green Building DesignPerformance Standards and the Roofing Industry What The Industry Needs: • 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

  25. Durability & Green Building DesignService Life Expectations How do we identify service life today?

  26. Durability & Green Building DesignService Life Expectations How can we identify service life today? • Anecdotal field reports • Opinion surveys • Historical end-of-service studies • Agency approval reports • Manufacturer warranty offerings

  27. Durability & Green Building DesignService Life Estimates for Low-Slope Roofing Systems(Years) Data Source Opinion Survey1 16.6 16.6 N/A2 14.1 No Data 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 System Type Asphalt BUR SBS Modified PVC EPDM TPO 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.

  28. Durability & Green Building DesignService Life Estimates Different Estimates – Different Assumptions: • Time Assumptions • Backward looking • Forward looking • Quality Assumptions • Uncontrolled sample: Assuming the worst • Controlled sample: Assuming the best

  29. Durability & Green Building DesignService Life Assumptions: Going Forward • Time Assumptions: Roofs perform in the future, not the past … … but the future is never certain. • Quality Assumptions: Assuming the best may be overly optimistic … … but assuming the worst understates the value of good design, installation and maintenance. • Mixed Assumptions: Only increase marketplace confusion.

  30. Durability & Green Building DesignIncorporating Service Life Expectations Durability Planning

  31. Durability & Green Building DesignDurability Planning • Emphasis on Process • A management system • Similar to ISO 9000 & ISO 14000 • Emphasis on Shared Responsibility • Identifies stakeholders • Identifies roles

  32. Durability & Green Building DesignDurability Planning and Canadian Standard S478-95 Three Basic Steps: • Identify Durability Determinants • Identify Durability Interventions • Develop Action Plan & Timetable

  33. Durability & Green Building DesignDurability Planning 1. Identify Durability Determinants: • Provide the Required Functions • In the Service Environment • By Key System Element

  34. Durability & Green Building DesignDurability Planning 2. Identify Durability Countermeasures: • During Design • During Material Selection • During Application & Commissioning • During Service Life • At End of Service

  35. Durability & Green Building DesignDurability Planning 3. Develop Action Plan & Timetable • Periodic & Ongoing • At Specified Times

  36. Durability & Green Building DesignDurability Planning A Suggested Durability Planning Matrix (See Appendix A)

  37. Durability & Green Building DesignDurability Planning Matrix The Service Environment Required Functions Roof System Elements

  38. Durability & Green Building DesignDurability Planning Matrix (cont.) The Service Environment Required Functions Roof System Elements Design Criteria Material Criteria Application Criteria Commissioning Criteria

  39. Durability & Green Building DesignDurability Planning Matrix (cont.) Operating / Maintenance Criteria Ongoing & Periodic At X Years At X+ Years At End of Service

  40. Durability & Green Building DesignRecommendations Going Forward • Establish and an Up-To-Date and Active Industry Research Agenda • Increase Research Activity, Emphasizing Key Roofing Components & Details • Re-Invigorate Consensus Standards Activity with New Research & New Commitment • Start Incorporating Durability Planning in Roofing Specifications • Continue to Advocate the Importance of Roof Durability

  41. SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING ENVELOPE DURABILITY Dr. James L. Hoff Center for Environmental Innovation in Roofing / TEGNOS Research, Inc.

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