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SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING ENVELOPE DURABILITY Dr. James L. Hoff Center for Environmental Innovation in Roofing / TEGNOS Research, Inc. 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. 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) 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 What is Durability? 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) 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 Roof Durability Characteristics Perform 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 … More to Follow Roof Durability Characteristics Without Unforeseen Cost… Implies Some Level of Cost Should Be Foreseen! Implies Planning Is Be Necessary! Roof Durability Characteristics Without Unforeseen Cost for.. • Maintenance – Frequent & ongoing – Includes inspection, assessment, service, & minor repairs • Repair – Infrequent, but generally planned – Includes renovation, retrofitting, component replacement Durability & Green Building Design The Major Issues • Justifying Vital Service Functions in Green Design Assessment • Incorporating Reliable Service Life Expectations into Green Design Durability & Green Building Design Vital 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 Membrane Cover Board Insulation Environmental Costs: – Added Materials – Added Energy – Added Waste 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 Membrane Cover Board Insulation Environmental Costs: – Added Materials – Added Energy – Added Waste Durability & Green Building Design Vital Service Functions Other Examples: • Thicker roofing membranes • Redundant flashing details Will the project assessment recognize the added value of such enhanced service functions? Durability & Green Building Design Incorporating Vital Service Functions Performance Standards Durability & Green Building Design Performance 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. Durability & Green Building Design Performance 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) Durability & Green Building Design Performance 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? Durability & Green Building Design Performance 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. Durability & Green Building Design Performance 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. Durability & Green Building Design Performance 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 Durability & Green Building Design Service Life Expectations How do we identify service life today? Durability & Green Building Design Service 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 Durability & Green Building Design Service Life Estimates for Low-Slope Roofing Systems (Years) Data Source System Type Opinion Survey1 Historical Study3 Agency Report4 Warranty Offering5 Asphalt BUR 16.6 13.6 20 20 SBS Modified 16.6 17.3 20 20 PVC N/A2 N/A2 35 15 EPDM 14.1 16.8 – 18.4 20 30 No Data No Data 20 30 TPO 1Mean service life from Cash (1997), based on an opinion survey of industry participants. 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. 2Data Durability & Green Building Design Service Life Estimates Different Estimates – Different Assumptions: • Time Assumptions – Backward looking – Forward looking • Quality Assumptions – Uncontrolled sample: Assuming the worst – Controlled sample: Assuming the best Durability & Green Building Design Service 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. Durability & Green Building Design Incorporating Service Life Expectations Durability Planning Durability & Green Building Design Durability Planning • Emphasis on Process – A management system – Similar to ISO 9000 & ISO 14000 • Emphasis on Shared Responsibility – Identifies stakeholders – Identifies roles Durability & Green Building Design Durability Planning and Canadian Standard S478-95 Three Basic Steps: 1. Identify Durability Determinants 2. Identify Durability Interventions 3. Develop Action Plan & Timetable Durability & Green Building Design Durability Planning 1. Identify Durability Determinants: • Provide the Required Functions • In the Service Environment • By Key System Element Durability & Green Building Design Durability Planning 2. Identify Durability Countermeasures: • During Design • During Material Selection • During Application & Commissioning • During Service Life • At End of Service Durability & Green Building Design Durability Planning 3. Develop Action Plan & Timetable • Periodic & Ongoing • At Specified Times Durability & Green Building Design Durability Planning A Suggested Durability Planning Matrix (See Appendix A) Durability & Green Building Design Durability Planning Matrix Service Environment Required Function Special wind / storm considerations? Hail zone? Exposure to contaminants? Extent of expected roof traffic? o Pre-commissioning o Post-commissioning Interior environment? o Humidity o Pressure o Special (pool, cold storage, etc.) Building features? o Large openings o Deck type/condition o Deck capacity (Deal Load / Live Load) Protect building interior from moisture Support maintenance of the desired interior environmental conditions Provide fire rated system: Class xx Finished roof shall have positive drainage Roof system shall be removable and recyclable. Building importance factor (critical services facility?) Roof System Element Required Functions Design Criteria Materials Criteria Application Criteria Commissioning Criteria None None None If slope for drainage is not part of the structure, include tapered insulation with crickets and saddles designed to provide at least ¼ in per foot slope. Field applied tape seams All T-joints shall be overlaid at least 5 inches in all directions None 08. Membrane Securement 10 lb/sf ASTM xxxx, #4, smooth, rounded, water worn gravel 07. Membrane 06. Insulation Overlayment (incl fastening) Nominal .060 inch thick Criteria assume project is not prone to hail or frequent traffic Overlayment should be included (staggered joints) when the project is prone to hail or frequent traffic, to avoid insulation damage and loss of R Hard surface overlayments (e.g., DensDeck, OSB, gypsum, etc.) are not acceptable directly beneath a ballasted membrane. Polyisocyanurate foam insulation Half the desired R value Polyisocyanurate foam insulation Half the desired R value None None Criteria assume condensation will not occur in the roofing system Vapor retarder (by designer) should be included when justified by building environment to avoid condensation within the roofing system Steel Criteria assume deck is suitable for loads. ASTM D4637, Type I None Membrane terminations on a vertical wall shall be counterflashed Roof edge metal installation shall be installed according to SPRI-ES-1 Fabricate seams per manufacturer’s specifications Adhere T-joint overlay with primer/100% solids, cured tape Secure membrane to the building at penetrations and the perimeter of roof sections Attachment detail shall not penetrate the membrane when such an option is sanctioned by the membrane system manufacturer None ASTM xxxx loose laid, staggered joints ASTM xxxx loose laid None None None None None None 11. Field Applied Coating 10. Membrane System Upgrade Roof System Elements The Service Environment 09. Membrane Seaming 05. Insulation (incl fastening) 04. Insulation (incl fastening) 03. Underlayment 02. Vapor control 01. Deck L PRE Primer/100% solids, cured seam tape, 3in wide T-joint cover shall be field curing EPDM membrane RY A N IMI AFT R D ATA D – None OM INC TE E L P Seams to be left uncovered until inspected Verify ballast gradation and application rate Check membrane labeling None Durability & Green Building Design Durability Planning Matrix (cont.) Service Environment Required Function Special wind / storm considerations? Hail zone? Exposure to contaminants? Extent of expected roof traffic? o Pre-commissioning o Post-commissioning Interior environment? o Humidity o Pressure o Special (pool, cold storage, etc.) Building features? o Large openings o Deck type/condition o Deck capacity (Deal Load / Live Load) Protect building interior from moisture Support maintenance of the desired interior environmental conditions Provide fire rated system: Class xx Finished roof shall have positive drainage Roof system shall be removable and recyclable. Building importance factor (critical services facility?) The Service Environment Roof System Element Materials Criteria Application Criteria Commissioning Criteria None None None If slope for drainage is not part of the structure, include tapered insulation with crickets and saddles designed to provide at least ¼ in per foot slope. Field applied tape seams All T-joints shall be overlaid at least 5 inches in all directions None 08. Membrane Securement 10 lb/sf ASTM xxxx, #4, smooth, rounded, water worn gravel 07. Membrane 06. Insulation Overlayment (incl fastening) Nominal .060 inch thick Criteria assume project is not prone to hail or frequent traffic Overlayment should be included (staggered joints) when the project is prone to hail or frequent traffic, to avoid insulation damage and loss of R Hard surface overlayments (e.g., DensDeck, OSB, gypsum, etc.) are not acceptable directly beneath a ballasted membrane. Polyisocyanurate foam insulation Half the desired R value Polyisocyanurate foam insulation Half the desired R value None None Criteria assume condensation will not occur in the roofing system Vapor retarder (by designer) should be included when justified by building environment to avoid condensation within the roofing system Steel Criteria assume deck is suitable for loads. ASTM D4637, Type I None Membrane terminations on a vertical wall shall be counterflashed Roof edge metal installation shall be installed according to SPRI-ES-1 Fabricate seams per manufacturer’s specifications Adhere T-joint overlay with primer/100% solids, cured tape Secure membrane to the building at penetrations and the perimeter of roof sections Attachment detail shall not penetrate the membrane when such an option is sanctioned by the membrane system manufacturer None ASTM xxxx loose laid, staggered joints ASTM xxxx loose laid None None None None None None 11. Field Applied Coating 10. Membrane System Upgrade Roof System Elements Design Criteria Required Functions 09. Membrane Seaming 05. Insulation (incl fastening) 04. Insulation (incl fastening) 03. Underlayment 02. Vapor control 01. Deck L PRE Primer/100% solids, cured seam tape, 3in wide T-joint cover shall be field curing EPDM membrane RY A N IMI Design Criteria AFT R D ATA D – Material Criteria None OM INC TE E L P Application Criteria Seams to be left uncovered until inspected Verify ballast gradation and application rate Check membrane labeling None Commissioning Criteria Durability & Green Building Design Durability Planning Matrix (cont.) Operating / Maintenance Criteria Management Beginning with Commissioning Service Environment Required Function Control roof access; maintain access log; Inspect roof every spring/fall, after threatening activities on, above or near the roof, after new equipment or penetrations are installed, and after any activity that may have jeopardized the roof Log leak reports along with related conditions Confirm clean drains and good roof drainage Any new rooftop installation shall be reviewed with the roofing contractor for its impact on the roof system Roof System Element 11. Field Applied Coating 10. Membrane System Upgrade At 20 Years Beginning with Commissioning At 20 Years Review roof traffic patterns and add walkway pads where needed Peel up walk pads; recycle (similar to tires) Cut seams out of membrane (6” per 30-50 ft width); recycle as energy source or into application to be developed Vacuum ballast; stockpile for re-use No fasteners; inspect boards for reuse or route to existing recycling applications No fasteners; inspect boards for reuse or route to existing recycling applications None None Do not remove unless necessary ballast for points of scour and evenly redistribute ballast to original coverage 02. Vapor control None ATA –D T RAF D Y Removal/Recycling E LET P M O INC At 40 Years R INA After a high wind event inspect roof 07. Membrane 06. Overlayment (incl fastening) 05. Insulation (incl fastening) 04. Insulation (incl fastening) 03. Underlay ment At 60 Years 09. Membrane Seaming 08. Membrane Securement At 40 Years IM REL P Route to processor for grinding and incorporation into walk pads or other application to be developed None 01. Deck Ongoing & Periodic At X Years At X+ Years At End of Service Durability & Green Building Design Recommendations 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 SUSTAINABLE BUILDINGS: ADDRESSING LONG-TERM BUILDING ENVELOPE DURABILITY Dr. James L. Hoff Center for Environmental Innovation in Roofing / TEGNOS Research, Inc.