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  1. Field Study of Hygrothermal Performance of Cross-Laminated Timber Wall Assemblies with Built-in MoistureRuth McClungMASc. Building Science CandidateDepartment of Architectural ScienceRyerson UniversityCo-authors: Dr. John Straube, University of Waterloo Dr. Hua Ge, Ryerson University Jieying Wang, FPInnovations

  2. Problem • Moisture performance and properties are not fully understood • Susceptible to the same moisture problems as wood (rot, mould, swelling, etc) • Construction moisture may pose an issue

  3. Field Testing Layout • CLT samples wetted on both faces by immersion in water • Instrumented to monitor moisture content, temperature, and relative humidity within the wall assemblies • 4 wall configurations, with 4 CLT wood species are being tested • Wetted panels installed in field testing facility and monitored for at least one year Waterloo BEGhut Test Facility

  4. 10420 4 1 2 3 5 6 7 Entrance 28 8 Foyer N 3810 27 9 100 Slab on Grade 510 Ø column on 1200 x 1200 C L 26 footing 10 Heating/ C 11 25 L Cooling Data acquisition system 24 12 electrical computer service panel 23 13 Each quadrant is 12.5 Ply clad corner symmetric with 140/140 P.T. post the centre lines 140 batt insulation 22 14 18 100 20 17 16 15 21 19 1270 610 1270 1270 1270 Planned Field Testing Layout • BEGHut Layout CLT Test Wall Location

  5. Field Testing Layout Built-in Moisture Experiment

  6. Field Testing Layout Wall Configurations: 1. Low Permeability 3” RoxulRockBoard Blueskin Nothing 2. High Permeability 3” RoxulRockBoard BlueskinVP Nothing 3. Medium Permeability 3” Plastifab EPS BlueskinVP Nothing 4. Low Interior Permeability 3” Plastifab EPS BlueskinVP Poly sheet

  7. Sensor Layout With most panels drying freely to the interior, an estimate of the variability in drying behaviour between samples of the same wood species may be obtained. Typical Sensor Layout

  8. Test Wall Construction Condensation on polyethylene sheeting Soaking of CLT panels in pool Panel Installation

  9. Test Wall Construction CLT test wall with insulation, strapping and clading. Interior of wall before drywall installation After installation of water resistive barriers

  10. Results Freely Drying to Interior • Relatively Uniform Behaviour

  11. Results Low Interior Permeance • Many Panels still above 26% MC, risk of decay initiation

  12. Results Low Interior Permeance • MC in centre of panels slowly drying or increasing, redistribution

  13. Results High Exterior Permeance • Panels dry quickly, react quickly to outdoor RH

  14. Results Medium Exterior Permeance • Panel Surface RH is high, causing some panels to increase in MC

  15. Results Medium Exterior Permeance • Panel Surface RH is high, some risk of mould between insulation and VR WRB

  16. Results Low Exterior Permeance • MC remains high, and likely close to 100% RH on surface

  17. Conclusions • Wetted panels dried very quickly during construction under typical Southern Ontario Summer conditions. • The drying may be slower under cooler and more humid conditions, such as in the rainy winter conditions in Vancouver, causing higher initial MC • High permeance envelope materials can effectively promote drying of CLT panels • Impact of assemblies with medium permeance, including the use of EPS, should be further investigated before any firm recommendations can be made. • Low permeance materials should not be used • Prolong the time period required for wetted panels to dry to a safe level • CLT panel itself is a good vapour retarder, and any additional vapour barrier should not be used in a CLT assembly. • Wood species does not appear to have a significant effect on the drying behaviour of the CLT panels.

  18. Acknowledgments • Thanks to • NSERC for funding this research project as a part of the NEWBuildS strategic research network • FPInnovations, Nordic Engineered Wood, and Henry for building materials • Robert Lepage, Emily Vance, and Sam Siassi for their generous donations of time, effort, and knowledge in commissioning the test wall.

  19. References • Gagnon S., Pirvu C., 2011. CLT Handbook: Cross-Laminated Timber. Vancouver: Forintek Canada Corporation. • Garrahan P., 1988. Moisture Meter Correction Factors. In: USDA Forest Products Laboratory, Proceedings of a seminar on In-grade Testing of Structural Lumber. Madison, WI, USA 25-26 April 1988. Vancouver:Forintek. • Straube J., Onysko D., Schumacher C., 2002. Methodology and Design of Field Experiments for Monitoring the Hygrothermal Performance of Wood Frame Enclosures. Journal of Thermal Environment and Building Science, 26(2), pp.123-151. • Wang, J., Morris P.I., 2011. Decay Initiation in Plywood, OSB and Solid Wood Under Marginal Moisture Conditions. International Research Group on Wood Protection, Document No. IRG/WP/11-20469. IRG, Stockholm, Sweden. 12pp.

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