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Conventional Roofing - Impacts of Insulation Strategy and Membrane Color

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Presentation given at the Philadelphia BEC luncheon in September 2014 on a multi-year field study looking at the performance of conventional insulated roofing assemblies and the impacts of different roof membrane colors and insulation types. Full report and papers available at www.rdh.com

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Conventional Roofing - Impacts of Insulation Strategy and Membrane Color

  1. 1. Conventional Roofing Assemblies: Measured Benefits of Light to Dark Roofing Membranes & Alternate Insulation Strategies PHILADELPHIA BEC – SEPTEMBER 16 2014 GRAHAM FINCH, MASc., P.ENG – PRINCIPAL, BUILDING SCIENCE RESEARCH SPECIALIST
  2. 2. “RDH Building Sciences” is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
  3. 3. Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited.
  4. 4. Learning Objectives At the end of this program, participants will be able to: 1. Understand how to evaluate and select an appropriate conventional roof membrane type and color for various climate zones 2. Understand how to evaluate and design the most appropriate insulation strategy for a conventional roof. Learn how different insulation materials and hybrid insulation combinations will behave differently in-service and have a varying effective R-value depending on temperature. 3. Understand how different insulation strategies and roofing membranes affect heating and cooling energy consumption in different building types. 4. Observe case studies where recommended roofing membrane and insulation designs have been implemented.
  5. 5. Presentation Outline  Conventional Roofing Designs and Current Issues  Conventional Roofing Field Monitoring and Research Program  Field Results – Membrane & Insulation Strategies  Selecting Optimum Roofing Color and Insulation Strategy for Energy Efficiency  Case Studies
  6. 6. Conventional Roofing Designs & Current Issues
  7. 7. Recap: Conventional Insulated Roofs  Most common low-slope roof application in North America  Insulation installed above structure, protected by roofing membrane - Insulation is typically foam plastic (polyiso, EPS), though mineral fiber also used  Roofing membrane is exposed to temperature, UV, traffic – needs to be durable  Roof slope typically achieved by tapered insulation unless the structure is sloped  Attachment of membrane/insulation can be: adhered, mechanically attached, loose laid ballasted, or combination to resist wind uplift  Wood, concrete, or steel structure substrate  Air barrier and vapour control layer below insulation on top of structure (depending on climate/design)
  8. 8. Current Issues With Conventional Roofs  Roofing membrane issues  Insulation movement – Thermally induced  Causes membrane ridging and stresses  More movement with thicker amounts of insulation (becoming more common) and certain insulation types  More movement in roofs with darker colored membranes  Insulation movement - Long term shrinkage, expansion, contraction  Gaps between insulation boards, induced membrane stresses  Cover board /protection board failure – delamination, softening, organic growth, fastener corrosion  Moisture trapped in insulation and roof assembly from wetting during construction or from small leaks in-service  Becoming more common to install leak detection monitoring within conventional roofs and find this out – what to do about it? How to adjust monitoring?
  9. 9. Membrane Ridging & Insulation Movement TPO over gypsum board and polyiso SBS over wood fiberboard and XPS
  10. 10. Membrane Ridging & Insulation Movement 2 ply SBS over Fiberboard & XPS
  11. 11. Insulation Movement & Membrane Failure 2 ply SBS over EPS
  12. 12. Insulation Movement & Membrane Failure 2 ply SBS over Polyiso over EPS taper package
  13. 13. Wood Fiberboard Coverboard Issues Wood fiberboard cover-board wetting and delamination
  14. 14. Cover Board Failures & Membrane Delamination
  15. 15. Gypsum Cover Board Issues Wetting, Softening & Facer delamination Wetting & Fungal growth Wetting & accelerated fastener corrosion
  16. 16. Insulation Shrinkage & Heat Loss 2 ply SBS over single layer of mechanically attached Polyiso
  17. 17. Insulation Shrinkage Study  Polyiso has had a reported history of board shrinkage – both initial and long-term  Related to manufacturer, mix, temperature, moisture, and age  Results in gaps between the insulation boards and induces stresses introduced into roof membranes  Past monitoring shows varying amounts of ongoing shrinkage – primarily influenced by age of product when installed
  18. 18. Polyiso Shrinkage Monitoring Study  Year 1 – 0.2% (2 mm in 1200 mm) Shrinkage-mm 20102009 0 2 1 3 1/8”
  19. 19. Polyiso Shrinkage Monitoring Study  Year 4 – 0.2% to 0.7% (2-8 mm in 1200 mm) Shrinkage-mm 8 0 2 4 6 2009 2013 Year 1 1/4”
  20. 20. Roof Membrane Color Considerations  Roof membrane or ballast color (solar absorptivity) influences surface temperature  Darker colors (more absorptive, less reflective) results in higher temperatures, more assembly movement and membrane stress, higher cooling loads, lower heating loads  Lighter colors (less absorptive, more reflective) results in lower temperatures, less assembly movement and membrane stress, lower cooling loads, higher heating loads  Balance needed between membrane durability, assembly movement, heating and cooling loads  Programs such as LEED have points for use of highly reflective roofs regardless of energy implication and local climate.  Long term impacts and soiling of light colored roofs
  21. 21. Membrane Soiling – 5 years, Poor Slope TPO
  22. 22. Conventional Roofing Field Monitoring Study
  23. 23. Guiding Purpose of the Study – Why?  Quantify performance of different colors of exposed roof membrane (white, grey, black)  What impact does LEED have on roof energy performance  Quantify performance differences of different insulation types: stone wool, polyiso and hybrid insulation combinations  Quantify combined impact of membrane color and insulation strategy  Observe impact of the long-term soiling of white SBS cap sheets  Monitor long-term shrinkage/movement of insulation and relative humidity/moisture levels within insulation  Laboratory testing of material properties we didn’t know  While Certain materials used for Phase 1 of study – key findings are applicable to all membrane & insulation types
  24. 24. Roof Membrane Colors  3 different 2-ply SBS roof membrane cap sheet colors (white reflective, grey, black) White Reflective Cap Sheet: SRI 70, Reflectance 0.58, Emittance 0.91 Grey Cap Sheet: SRI 9, Reflectance 0.14, Emittance 0.85 Black Cap Sheet: SRI -4, Reflectance 0.04, Emittance 0.85
  25. 25. 3 Different Insulation Strategies Stone wool - R-21.4 (2.5” + 3.25”, adhered) Polyiso - R-21.5 (2.0” + 1.5”, adhered) Hybrid - R-21.3 (2.5” Stone wool + 2.0” Polyiso, adhered) Design target: Each Assembly the same ~R-21.5 nominal
  26. 26. Insulation and Cap Sheet Layout  9 unique roof test areas, each 40’ x 40’ and each behaving independently  Similar indoor conditions (room temperature) and building use (warehouse storage)  Climate Zone 4 Polyiso Hybrid Stone wool 120’ 120’ Grey White Black Polyiso Hybrid Stonewool
  27. 27. Sensor Selection and Installation  Temperature  Heat Flux  Relative Humidity  Moisture Detection  Displacement  Solar Radiation Heat Flux Relative Humidity & Moisture Detection Displacement Temperature Solar Radiation
  28. 28. Sensor Positioning T - Temperature RH - Relative Humidity HF - Heat Flux M - Displacement M M
  29. 29. Roof and Sensor Installation
  30. 30. Roof and Sensor Installation
  31. 31. Roof and Sensor Installation
  32. 32. Measured Insulation Performance
  33. 33. My Most Common Designer Question Lately: What R-value is My Insulation?
  34. 34. Laboratory Testing of Insulation R-values  3rd Party ASTM C518 thermal transmission material testing performed as part of monitoring study  Polyiso and stone wool insulation removed from site + aged 4 year old polyiso samples from prior research study  Wanted to know actual R-value as installed and temperature impacts to calibrate sensors  Testing performed at mean insulation temperatures from 25, 40, 75, and 110°F to develop R-value vs temperature
  35. 35. Laboratory Testing of Project Insulation 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 20 40 60 80 100 120 R-valueperinch-IPUnits Mean Temperature of Insulation - °F Installed & Aged Insulation R-values per Inch - Based on Mean Temperature (°F) Polyiso - Maximum Polyiso - Average Polyiso - Minimum Polyiso - Aged (4 years) Stone Wool - Average
  36. 36. Applying Laboratory Testing to the Field  Design R-values for each assembly ~R-21.5 Stone Wool -2.5” + 3.25”, Weight 26.7 kg/m2 , Heat Capacity – 22.7 kJ/K/m2 Polyiso - 2.0” + 1.5”, Weight 4.6 kg/m Heat Capacity – 6.8 kJ/K/m2 Hybrid – 2.5” Stone wool over 2.0” Polyiso, Weight 14.3 kg/m2 , Heat Capacity – 13.7 kJ/K/m2
  37. 37. Varying R-value of Field Roof Assemblies 14 15 16 17 18 19 20 21 22 23 24 10 20 30 40 50 60 70 80 90 100 110 120 130 140 EffectiveAssemblyR-value-IPUnits Outdoor Membrane Surface Temperature (Indoor, 72°F) Effective Roof Insulation R-value - Based on Roof Membrane Temperature Stone Wool (Initial or Aged) Hybrid (Initial Average) Hybrid (Aged) Polyiso (Initial Average) Polyiso (Aged)
  38. 38. Field Monitoring Findings
  39. 39. Field Monitoring Results  Monitoring from first 2 years shown today  Plan to monitor for 5 years for long-term trends and aging effects  Data shown here to demonstrate: 1. Impact of Membrane Color 2. Impact of Insulation Strategy 3. Combined Impacts SENSOR CODING: W – white G – grey B – black SW - stone wool ISO – polyiso ISO-SW – hybrid
  40. 40. Study Findings: How Big of a Difference does Membrane Color Have?
  41. 41. White Membrane Soiling & Reflectance 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual Rated Reflectance Reflectance of Membranes White (high) White (low) Grey * *Rated reflectance was measured using a different method than was used in the field study.
  42. 42. 32 50 68 86 104 122 140 158 176 194 0 10 20 30 40 50 60 70 80 90 May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Temperature[°F] Temperature[°C] Monthly Average of Daily Maximum Membrane Temperatures and Maximum Membrane Temperature for Each Month by Membrane Colour White Grey Black White - Maximum Grey - Maximum Black - Maximum * * *W-ISO-SW had significant data loss in August and September and is removed from the average for those months. Color – Impact on Surface Temperatures
  43. 43. Color - Differences in Net Heat Flow -200 -150 -100 -50 0 50 100 May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual DailyEnergyTransfer[W·hr/m²perday] Monthly Average Daily Energy Transfer by Membrane Colour White Grey Black Outward HeatFlow Inward HeatFlow Monthly Average Daily Energy Transfer by Membrane Color
  44. 44. Color & Calculated Degradation  Relative degradation rate calculated from measured cap sheet temperatures  Further study needed to quantify age and physical property effects Black roof with stone wool directly below the membrane doesn’t get as hot
  45. 45. Study Findings: How Big of a Difference does the Insulation Strategy Have?
  46. 46. Insulation Impact on Peak & Lagging Membrane & Metal Deck Temperatures RoofMembraneMetalDeck 0 10 20 30 40 50 60 70 80 90 Jun 30 0:00 Jun 30 6:00 Jun 30 12:00 Jun 30 18:00 Jul 1 0:00 Temperature[°C] Roof Membrane Cap Sheet Temperatures W-ISO T-CAP W-ISO-SW T-CAP W-SW T-CAP G-ISO T-CAP G-ISO-SW T-CAP G-SW T-CAP B-ISO T-CAP B-ISO-SW T-CAP B-SW T-CAP Outdoor-T 24 26 28 30 32 34 36 Jun 30 0:00 Jun 30 6:00 Jun 30 12:00 Jun 30 18:00 Jul 1 0:00 Temperature[°C] Metal Deck Temperatures W-ISO TEMP-DECK W-ISO-SW TEMP-DECK W-SW TEMP-DECK G-ISO TEMP-DECK G-ISO-SW TEMP-DECK G-SW TEMP-DECK B-ISO TEMP-DECK B-ISO-SW TEMP-DECK B-SW TEMP-DECK 176°F 140°F 104°F 68°F 97°F 75°F 86°F
  47. 47. Heat Flux Data – Heat Loss vs Gain -30 -25 -20 -15 -10 -5 0 5 10 15 Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar HeatFlux[W/m²] Heat Flux Sensors W-ISO HF W-ISO-SW HF W-SW HF G-ISO HF G-ISO-SW HF G-SW HF B-ISO HF B-ISO-SW HF B-SW HF SENSOR CODING: W – white, G – grey, B - black SW - stone wool, ISO – polyiso, ISO-SW - hybrid Heat Loss Heat Gain 1 W/m2 = 0.32 Btu/hr/ft2
  48. 48. Heat Flow – Heat Loss vs Heat Gain Winter vs. Summer -25 -20 -15 -10 -5 0 5 10 Feb 21 Feb 22 Feb 23 HeatFlux[W/m²] Heat Flux Sensors W-ISO HF W-ISO-SW HF W-SW HF G-ISO HF G-ISO-SW HF G-SW HF B-ISO HF B-ISO-SW HF B-SW HF -25 -20 -15 -10 -5 0 5 10 Jun 30 Jul 1 Jul 2 HeatFlux[W/m²] Heat Flux l 2 Flux Sensors W-ISO HF W-ISO-SW HF W-SW HF G-ISO HF G-ISO-SW HF G-SW HF B-ISO HF B-ISO-SW HF B-SW HF W- white, G-grey, B-black, SW-stone wool, ISO - polyiso Heat Loss Heat Gain
  49. 49. Heat Flow – Variation with Insulation Strategy -25 -20 -15 -10 -5 0 5 10 Jun 30 0:00 Jun 30 6:00 Jun 30 12:00 Jun 30 18:00 Jul 1 0:00 HeatFlux[W/m²] Heat Flux Sensors W-ISO HF W-ISO-SW HF W-SW HF B-ISO HF B-ISO-SW HF B-SW HF Heat Loss Heat Gain SENSOR CODING: W – white, B - black SW - stone wool, ISO – polyiso, ISO-SW - hybrid
  50. 50. Heat Flow – Variation with Insulation Strategy SENSOR CODING: SW - stone wool, ISO – polyiso, ISO-SW - hybrid -25 -20 -15 -10 -5 0 5 10 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec HeatFlux[W/m²] Heat Flux Sensors G-ISO HF G-ISO-SW HF G-SW HF
  51. 51. Net Annual Impact of Insulation Strategy 0 100 200 300 400 500 600 -150 -100 -50 0 50 100 May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr Annual DegreeDays[°C·days] DailyEnergyTransfer[W·hr/m²perday] Monthly Average Daily Energy Transfer by Insulation Arrangement ISO ISO-SW SW Heating Degree Days (18°C) OutwardHeatFlowInwardHeatFlow 1 W/m2 = 0.32 Btu/hr∙ft2
  52. 52. Other Findings to Date  Insulation Movement monitoring ongoing  Observing daily insulation swings  Seeing some long-term movement of insulation, but also movement of metal deck structure interfering with long-term data  Relative Humidity and moisture movement ongoing  Seeing harmless seasonal movement of built- in water vapor through insulation  Water vapor also moves energy – latent heat  Cut-tests confirm roofs all dry and no issues
  53. 53. Optimizing Membrane Color and Insulation Strategy for Energy Efficiency
  54. 54. Energy Consumption and Membrane/ Insulation Design  Calibrated energy modeling used to compare roof membrane color/solar absorptivity & insulation strategy  White, Grey or Black Roof Membrane  Polyiso, Stone wool, or Hybrid insulation approach • Stone wool has lower R-value/inch but higher heat capacity and higher mass • Polyiso has a higher R-value/inch (varies with temperature) and has a lower heat capacity and lower mass • Hybrid approach has stone wool over top of polyiso which moderates temperature extremes of polyiso insulation – makes polyiso perform better
  55. 55. Energy Consumption and Membrane/Insulation Design  Energy modeling performed for a commercial retail building (ASHRAE building prototype template)  Results calibrated with temperature/heat-flux data from monitoring study  Input temperature dependant & aged R-values into energy model – base R-20 roofs  Help to select the optimum insulation and membrane color combination for energy efficiency
  56. 56. Energy Modeling of Temperature Dependant Insulation R-values  Input lab measured temperature dependant insulation R-value for polyiso and stone wool into energy model  Heating energy for Climate Zone 4 (Vancouver) shown here, R-20 insulation  Impact is significant enough that should be accounted for  Results in different design rankings of lowest to highest energy consumption 36 37 38 39 40 41 42 43 44 Dark Roof Gray Roof White Roof AnnualHeatingEnergyConsumption, kWh/m2 Model Default - Constant Conductivity Polyiso Stone wool Hybrid 36 37 38 39 40 41 42 43 44 Dark Roof Gray Roof White Roof AnnualHeatingEnergyConsumption, kWh/m2 Revised Model - Temperature Dependent Conductivity Polyiso Stone Wool Hybrid Total Energy Consumption includes walls, windows, air leakage, slab on grade, +roof
  57. 57. 0 10 20 30 40 Black Roof Gray Roof White Roof AnnualHeatingEnergyConsumption, kWh/m2 Polyiso Stone Wool Hybrid Aged Polyiso Aged Hybrid Most Energy Efficient Roofing Combination in Philadelphia Region – Climate Zone 4 0 10 20 30 40 Black Roof Gray Roof White Roof AnnualCoolingEnergyConsumption, kWh/m2 Polyiso Stone Wool Hybrid Aged Polyiso Aged Hybrid 0 10 20 30 40 Black Roof Gray Roof White Roof AnnualSpace-ConditioningConsumption, kWh/m2 Polyiso Stone Wool Hybrid Aged Polyiso Aged Hybrid Lower is Better – Total Energy Includes Loss through Roofs + Walls, Floor, Windows, Air Leakage etc. 12 kBtu/ft2 /yr
  58. 58. Most Energy Efficient Roofing Combination? 0 20 40 60 80 100 120 1 - Miami 2 - Houston 3 - San Francisco 4 - Baltimore 5 - Vancouver 6 - Burlington VT 7 - Duluth 8 - Fairbanks AnnualHeatingEnergy,kWh/m2 Climate Zone Black - Aged Polyiso Black - Stonewool Black - Aged Hybrid White - Aged Polyiso White - Stonewool White - Aged Hybrid 0 20 40 60 80 100 120 1 - Miami 2 - Houston 3 - San Francisco 4 - Baltimore 5 - Vancouver 6 - Burlington VT 7 - Duluth 8 - Fairbanks AnnualCoolingEnergy,kWh/m2 Climate Zone Black - Aged Polyiso Black - Stonewool Black - Aged Hybrid White - Aged Polyiso White - Stonewool White - Aged Hybrid Commercial Retail Building Heating Energy – kWh/m2 /yr Commercial Retail Building Cooling Energy – kWh/m2 /yr
  59. 59. Most Energy Efficient Roofing Combination? Lighter membrane, stone wool or hybrid is better for same design R-value Darker membrane, stone wool or hybrid is better for same design R-value
  60. 60. Summary – Key Points  Research and Field Monitoring Study Findings  Design R-value may change in service – all types of insulation are affected to varying degrees – Is not Static  In addition to design R-value - heat capacity and latent moisture transfer within insulation has an impact on temperatures and energy transfer  Optimization of heating and cooling based on roof membrane color and insulation strategy suggested  Careful selection of insulation strategy and membrane color will have a positive impact on roof assembly performance
  61. 61. Case Studies
  62. 62. Stone Wool Insulation in Conventional Roofing  R-value of stone wool is R-3.7/inch compared to a R-4 to R-6/inch for polyiso and R-4/inch for EPS  Need thicker stone wool to achieve same R-value as polyiso in design  If polyiso kept closer to indoor temperatures, then it has a higher effective R/inch (closer to LTTR)  Insulate the Polyiso!  Hybrid insulation provides good blend of material properties and economics  Tapered insulation packages available: EPS, Polyiso, or Stone wool
  63. 63. Case Study 1 - High-rise Re-Roof Assembly: 2-ply SBS torched to 2” asphalt impregnated stone wool over 2” polyiso (adhered)
  64. 64. Case Study 2 – Residential Re-Roof Assembly: 2-ply SBS torched to 2” asphalt impregnated stone wool, over 2” polyiso, over polyiso tapered package (mechanically attached)
  65. 65. Case Study 3 – Heritage Re-Roof Assembly: 2-ply SBS torched to 1” stone wool asphalt impregnated cover board adhered to 2” stone wool, mechanically fastened through EPS taper package
  66. 66. Case Study 4 – New Roof over First Tallest Wood Structure in North America Design & Architectural Renders: Michael Green Architecture (MGA)
  67. 67. Case Study 4 – New Roof over First Tallest Wood Structure in North America R-40+ Conventional Roof Assembly – 2 ply SBS, 4” Stonewool, 4” Polyiso, Protection board, Tapered EPS (0-8”), Torch applied Air/Vapor Barrier(Temporary Roof), ¾” Plywood, Ventilated Space (To Indoors), CLT Roof Panel Structure (Intermittent)
  68. 68. Case Study 4 – New Roof over First Tallest Wood Structure in North America
  69. 69. Case Study 5 – What Would RDH Do?
  70. 70. Designer and Roofing Contractor Feedback  Stone wool insulation relatively easy and fast to install. Heavier than EPS/polyiso boards, but doesn’t blow away  Stone wool insulation lays flat and takes up uneven surfaces, tight board installation, very few gaps compared to more rigid foam boards  Stone wool is softer than polyiso and potentially softens during construction from foot traffic – not issue in open field areas, but compression can occur in high traffic areas prior to covering  Typically address with extra asphalt protection board overlay.  Thicker insulation build-up for stone wool compared to polyiso due to R-value differences, may be an issue where thickness is at a premium or could be issue during re-roof around existing doors and curbs etc.  Watch mechanical fasteners without a protection board.  Adhesive with stone wool must be applied and set-in quickly before foam expands. Slightly different process than with EPS/polyiso.
  71. 71. Recommended Conventional Roofing Strategies for Energy & Durability  Design to provide good balance of cost, thickness, & performance (energy, durability, membrane life)  Roof Membrane – grey or other neutral color for northern climates, light in south  Adhered system with stone wool insulation as top layer / cover board (30- 50% of total insulation R-value)  Layer of polyiso (below staggered) joints with taper package  Self adhered/torched sheet air/vapour barrier membrane (temporary roof) over substrate  Adhered layers preferred instead of mechanically attached, where possible to balance cost
  72. 72. This concludes The American Institute of Architects Continuing Education Systems Course Graham Finch Dipl.T, MASc, P.Eng RDH Building Sciences Inc. gfinch@rdhbe.com
  73. 73.  rdhbe.com Discussion + Questions Graham Finch – gfinch@rdhbe.com – 604 873 1181

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