1. Rainscreen Performance Monitoring: Continuing Research Current Masters Thesis Research Highlights Presented by: Graham Finch, Dipl.T, BASc University of Waterloo, MASc Student

2. May 2006 - BCBEC Symposium2 Introduction  Background  Current Research Highlights Exterior Gypsum Hygrothermal Modeling Building 3 – A Case Study  Monitoring Program Improvements  Still to Come

3. May 2006 - BCBEC Symposium3 Background  Building Monitoring Program RDH Building Engineering (RDH) Canadian Mortgage and Housing Corporation (CMHC) Homeowner Protection Office British Columbia Housing Management Commission  Designed and installed on five buildings in Vancouver, BC being constructed or rehabilitated using a rainscreen wall assembly.  Data collected includes temperature, relative humidity, moisture content, wetness, pressure, wind, rain, and driving rain.

4. May 2006 - BCBEC Symposium4 Background  University of Waterloo MASc Student Rainscreen Performance Monitoring Study part of Graduate Thesis work  Build on initial RDH work  Further work as part of thesis Further data analysis  Trends, Normals, Abnormalities  Wetting and Drying Rates Hygrothermal Modeling Validation Material Testing

5. May 2006 - BCBEC Symposium5 Presentation Outline – Research Highlights  Measuring moisture content of exterior gypsum using electrical resistance  Hygrothermal modeling of ventilated rainscreen walls Seasonal performance of Building 1 Improving performance by design  Building 3: A case study Field validation of monitored results

6. May 2006 - BCBEC Symposium6 Exterior Gypsum Sheathing Properties  Purpose Measure performance of exterior fiberglass faced gypsum exposed to humid conditions Correlate electrical resistance of gypsum with gravimetric moisture content  Well established correlation for wood  More difficult with gypsum Provide approximate sheathing moisture contents for Buildings 3 and 5 to assess performance

7. May 2006 - BCBEC Symposium7 Exterior Gypsum Sheathing Properties  Physical Properties Strength loss with elevated moisture content  As a result of high relative humidity or liquid water exposure  Levelton study results (Later today)  Other Issues Mould Growth Corrosion when in contact with metals ie. Steel studs

8. May 2006 - BCBEC Symposium8 Why does it matter?  Significant strength loss with as little as 1 - 2% moisture content  Saturated = Destroyed Exposed to 100% RH for 1 year

9. May 2006 - BCBEC Symposium9 Mould Growth  Possible under humid conditions and prolonged periods of time 4 years 4 months

10. May 2006 - BCBEC Symposium10 When is it an Issue?

11. May 2006 - BCBEC Symposium11 How Long does it take?  Gypsum boards relatively permeable to water vapour 1000-2000 metric perms  Fast response to moisture  Wetting - 2% moisture content increase (from dry) in 2 days exposed to 100% RH  Even faster drying rates Likely prevent very high MC levels from being achieved in the field

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13. May 2006 - BCBEC Symposium13 Moisture uptake rate much slower than drying rate 10 days to wet, 1 day to dry half

14. May 2006 - BCBEC Symposium14 Moisture Content and Electrical Resistance  Used to correlate measured electrical resistance (ohms) with an approximate gravimetric moisture content for field monitoring studies  Determine “how wet” the gypsum is without destructive testing  Handheld moisture meters give only relative idea of moisture content Different meters, different scales

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16. May 2006 - BCBEC Symposium16 Hygrothermal Modeling  Purpose: To correlate field results with those predicted by hygrothermal simulation  Can we accurately model walls with ventilated claddings? ie Rainscreen Walls Can you accurately model a 2D problem with 1D software? Ventilation cannot be neglected  Current software has limitations

17. May 2006 - BCBEC Symposium17 Modeling Requirements  Modeling ventilated wall assemblies with 1D software Cladding input into model with an “effective permeance” which accounts for an assumed ventilated rate through cladding vent openings Literature available for equivalent permeance values typically in range of 1000 + perms depending on flow rate

18. May 2006 - BCBEC Symposium18 Modeling Requirements  Modeling correlation with field results Effective permeance method works on average however:  Ventilation is a dynamic variable - Wind and temperature differences drive pressures which change on a daily basis Better correlation achieved by using actual temperature/relative humidity values from ventilated cavity/drainage space

19. May 2006 - BCBEC Symposium19 Building 1

20. May 2006 - BCBEC Symposium20 Building 1: Typical Ventilated Rainscreen Wall

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23. May 2006 - BCBEC Symposium23 Discussion of Results  Stucco, Vinyl, and Cement board clad buildings all had similar annual trends and similar moisture levels of the sheathing  High RH (80-100%) and cool temperatures in the ventilated cavity space result in sheathing moisture contents between 20-25% during winter months

24. May 2006 - BCBEC Symposium24 Discussion of Results  Correlation of hygrothermal simulation with field data is good  Material properties are important to correlation Moisture Isotherm for plywood/OSB have direct impact on results

25. May 2006 - BCBEC Symposium25 Uses for Hygrothermal Modeling  How can we improve the performance of ventilated rainscreen walls? Insulated Sheathing Is a polyethylene vapour barrier required? Would painted drywall work instead? What is the impact of the indoor relative humidity and temperature?

26. May 2006 - BCBEC Symposium26 Can Insulated Sheathing Improve Performance?  Base case R-19 (2x6 wall)  Compare to R-12 (2x4 wall)  R-19 stud insulation plus vapour permeable R-8 insulation on exterior (no poly)  R-12 stud insulation plus vapour permeable R-8 insulation on exterior (no poly)  Vapour permeable R-12 on exterior only (no stud space insulation, no poly)

27. May 2006 - BCBEC Symposium27 Impact of Insulated Sheathing More Insulation on Exterior = Drier

28. May 2006 - BCBEC Symposium28 Impact of Insulated Sheathing More Insulation on exterior = Drier

29. May 2006 - BCBEC Symposium29 Role of Vapour Control Strategy  Typical R-19 insulated wall assembly (ventilated rainscreen)  Remove interior polyethylene vapour barrier  Use 50, 250 and 400 metric perm vapour retarding paints on drywall

30. May 2006 - BCBEC Symposium30 Impact of a Paint VR vs. Poly VB Assuming no rain water Leaks!

31. May 2006 - BCBEC Symposium31 Impact of Interior Conditions  250 metric perm paint layer (interior latex paint)  3 indoor cases analyzed using real vapour pressure data for Vancouver Poorly ventilated (avg. winter RH 57%) Building 1 as measured (avg. winter RH 39%) Well ventilated (avg. winter RH 34%)

32. May 2006 - BCBEC Symposium32 Relative Humidity at interior side of Sheathing

33. May 2006 - BCBEC Symposium33 Moisture Content of Sheathing

34. May 2006 - BCBEC Symposium34 Other Simulated Cases  OSB vs. Plywood, negligible difference in RH or MC results Using standard OSB and Plywood properties from WUFI 3.3 database

35. May 2006 - BCBEC Symposium35 Results  Insulated sheathing improves the performance of ventilated rainscreen walls  A paint vapour retarder can be used as a replacement for poly, however exterior insulation and designed ventilation are both required

36. May 2006 - BCBEC Symposium36 Building 3: A Case Study

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39. May 2006 - BCBEC Symposium39 Problems  High relative humidity within stud space 80-100% during winter months (All 8 monitored locations)  Corresponding high moisture content of fiberglass faced exterior gypsum  Interior suites – High relative humidity during winter (50-70%)

40. May 2006 - BCBEC Symposium40 Seasonal Interior Suite Relative Humidity/Temperature July 2002-2003

41. May 2006 - BCBEC Symposium41 Seasonal Relative Humidity and Temperature at Exterior Sheathing

42. May 2006 - BCBEC Symposium42 Seasonal Relative Moisture Level at Exterior Sheathing

43. May 2006 - BCBEC Symposium43 Field Openings  Interior openings made in January 2006 During seasonal period of elevated moisture levels within wall assembly  Confirm presence of moisture within stud cavity  Observe interstitial wall conditions after 4 years of service

44. May 2006 - BCBEC Symposium44 Location of Test Openings

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49. May 2006 - BCBEC Symposium49 Suite Observations  Interior of all suites had high interior relative humidity  Condensation on window frame and glazing surfaces  Mould growth on interior drywall surfaces at corners

50. May 2006 - BCBEC Symposium50 Wall Opening Observations  Openings confirmed fiberglass faced exterior gypsum is getting wet 80-100 relative moisture level (Delmhorst BD- 10) Calculated 1-2% moisture content (up to 6% in some locations)  Surface corrosion on steel studs  Sensors are returning valid data  Problematic details also contributing to moisture problems (thermal bridging)

51. May 2006 - BCBEC Symposium51 Corner Detail Condensation on steel studs and gypsum sheathing observed

52. May 2006 - BCBEC Symposium52 Thermal Modeling Interior 19C, Exterior 5C Interior Dewpoint 10C Temperature Isotherms – THERM 5.2 Failed Air Barrier @ Corner = Condensation

53. May 2006 - BCBEC Symposium53 What went wrong?  High interior relative humidity/dewpoint during the winter – Poor Ventilation  When building was retrofit in 2002, original R-8 insulation was left in stud cavity and polyethylene vapour barrier was removed  Wall Design Flawed?  Morrison Hershfield (next) will talk about potential rehabilitation strategies and improvements to mitigate the high wintertime RH in next presentation

54. May 2006 - BCBEC Symposium54 Prevention by Design?  Use hygrothermal modeling (WUFI) to analyze the impact of modifications on the original design What if the poly was left in? What if the batt insulation were removed? Vapour Permeable Air/Water Resistant Barrier in lieu of peel and stick

55. May 2006 - BCBEC Symposium55 Hygrothermal Results  Leave in Poly – dual vapour barrier, in theory would work (perfect system) however in practice would fail, small leaks  Remove R8 batt Insulation – increases the temperature of the sheathing and improves drying  Trowel or Spray applied Air/Vapour/Moisture membrane (300-600 metric perms) in lieu of peel and stick - improves drying even with high indoor RH  Must improve indoor ventilation – lower RH during the winter

56. May 2006 - BCBEC Symposium56 Monitoring Program Suggestions  Data Collection interval (1 hour vs. 15 minute)  All data collected with loggers No separate Hobos for interior or exterior data  Collect Solar Radiation Data  Monitor all elevations, not just wind-driven rain exposed, ie North

57. May 2006 - BCBEC Symposium57 Research Still to Come  Analyze wetting events and material response  Analyze drying rates  Further hygrothermal modeling  Final report of results and recommendations

58. May 2006 - BCBEC Symposium58 Thank you Building Engineering Ltd. RDH Ontario Graduate Scholarship