1. www.fpinnovations.ca Control of Moisture Content in Wood for Mould Growth Dian-Qing Yang IUFRO All Division 5 Taipei 29 Oct-2 Nov, 2007

2. Wood utilisation in buildings

3. Mould growth in buildings

4. Wood decay in buildings

5. Wood deterioration Soft-rot Internal cellulose and lignin BIODETERIORATIONFUNGIBIODETERIORATIONFUNGI White-rot Brown-rot Deep stain (sapwood)Deep stain (sapwood)

6. Mould and surface stain

7. Problems and economical impact Aesthetic effect Health effect – allergens – airborne mycotoxins Cost for replacement.

8. Toxic mould Stachybotrys chartarum ( S. atra ) Aspergillus spp. Fusarium spp. Paecilomyces variotii

9. Mould growth On virtually any substrate Can be found almost anywhere There is no way to eliminate all moulds The way to control indoor mould growth is to control moisture.

10. Limiting conditions for mould growth Determine water absorption rates of different wood materials in various humidity conditions. Determine minimal water requirement for mould growth on different wood materials. Predict mould growth on wood structures in buildings.

11. Wood materials tested Solid wood: jack pine, black spruce and balsam fir Aspen OSB Spruce plywood Medium density fiberboard (MDF) Gypsum board

12. Test methods Condition wood samples to moisture content 8%. Place samples in environmental chambers at 21°C and relative humidity from 65% to 100%. Determine moisture content of samples and inspect mould growth weekly for 8 weeks.

13. Water absorption from air by jack pine wood at 21°C and various RHs

14. Water absorption from air by black spruce wood at 21°C and various RHs

15. Water absorption from air by balsam fir wood at 21°C and various RHs

16. Water absorption from air by OSB at 21°C and various RHs

17. Water absorption from air by plywood at 21°C and various RHs

18. Water absorption from air by MDF at 21°C and various RHs

19. Water absorption from air by gypsum board at 21°C and various RHs

20. Water absorption from air by various wood materials at 65% RH

21. Water absorption from air by various wood materials at 79% RH

22. Water absorption from air by various wood materials at 86% RH

23. Water absorption from air by various wood materials at 94% RH

24. Water absorption from air by various wood materials at 100% RH

25. MC (%) of wood materials started to be affected by mould Jack pine wood: 19.3 Black spruce wood: 21.5 Balsam fir wood: 19.4 Aspen OSB: 20.2 Spruce plywood: 22.7 Medium density fiberboard: 19.3 Gypsum board: 18.2

26. Time (week) requirement for mould growth on wood materials at 94% RH Jack pine wood: 5 Black spruce wood: 6 Balsam fir wood: 6 Aspen OSB: 5 Spruce plywood: 5 Medium density fiberboard: 5 Gypsum board: 5

27. Time (week) requirement for mould growth on wood materials at 100% RH Jack pine wood: 3 Black spruce wood: 6 Balsam fir wood: 5 Aspen OSB: 2 Spruce plywood: 2 Medium density fiberboard: 2 Gypsum board: 2

28. Mould growth on various wood materials

29. Conclusion and future effort Mould growth on wood materials is generally related to the water absorption rates of the materials, usually a material with a higher water absorption rate is easier to be affected by mould than those materials with lower rates. Studies on water absorption rates of the wood materials by water intrusion from one side and all sides, as well as the drying speed in different environmental conditions are underway.

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