Borate as a potential wood preservative to protect building envelope components from biodegradation NAZMUS SAADAT, PROF. PAUL A. COOPER
Outline Background Durability and environmental issues About borate Experimental procedure Results to date Future work Expected outputs
Background Revised building code in BC, allowing taller(mid rise) wood buildings Introduction of Cross Laminated Timber (CLT) as structural component Unknown issues Fire performance Structural performance Joints and Connections Moisture problem Orientation of wood layers in CLT (Source: FPInnovations) Our goal is to address durability and environmental challenges for mid rise wood buildings
Durability and environmental issues Vulnerability of timber components in buildings to decay and mould growth Concern for areas: Difficult to access after construction Costly to repair Water source: Construction moisture from bad design and bad construction practice Trapped rain water or ice dam Idealized concept of progress of decay (Leicester 2001): Building life can be increased significantly with preservatives The moisture from leaks or condensation from plumbing, exhaust and heating
Trapped moisture Poor in-service maintenance Poor installation Condensation
Issues with common preservatives PMRA regulations for harmful components limit where and how much they can be used Must be applied by pressure treatment Higher cost Not suitable for in situ treatment A safe and environmental friendly wood preservative is necessary for residential uses
About borate Borates (BO 3 3 ) are chemical compounds which contain oxoanions of Boron (B) http://my-bankruptcy-help.com/?b=file:ax3e0-3d-balls.png in oxidation state +3. Examples: Boracol, Timbor/Polybor (Na 2 B 8 O 13.4H 2 O), Boron rod, etc Advantages Inexpensive Colorless and odorless Highly water soluble Proven insecticide & fungicide Safe for human health and environment
More advantages... Corrosion inhibitor, fire & flame retardant (at high loading) Able to diffuse into vulnerable areas even into refractory wood Easy and different treatment procedures as per requirement Can be applied as a primary treatment or applied in service. So, borate is a good system to evaluate
Objectives To investigate variables affecting borate movement To evaluate and develop suitable borate treatment procedures for timber components, joints and other vulnerable areas To investigate the suitability of borate preservatives for cross laminated timber (CLT)
Formulations 40% borate (Polybor ) in Glycerol 40% borate (Polybor ) and 10% coppermea in aqueous solution Species Eastern spruce (Picea glauca or mariana) Douglas fir (Pseudotsuga menziesii)
Experimental procedure Water impregnation to target moisture content Samples treated with borate preservatives and kept for a specified period Extraction by hot water ICP analysis of B (AWPA A21 00)
Results to date Formulations: 14 12 Spruce 12 10 D-fir % BAE 10 8 6 4 2 Glycerol borate Copper borate % BAE 8 6 4 2 Glycerol borate Copper borate 0 0 0.5 1 1.5 2 2.5 3 3.5 0 0 1 2 3 4 Distance from treated surface, cm Distance from treated surface, cm Boron diffusion gradient in longitudinal direction after 7days and at 30% MC Copper borate formulation shows slight better result than glycerol borate More data required Basis: 77.2 mg of material / cm 2 surface area
Results to date Moisture content: 14 12 10 Spruce 7 6 5 D fir % BAE 8 6 4 30% MC 50% MC % BAE 4 3 2 30% MC 50% MC 2 1 0 0 0.5 1 1.5 2 2.5 3 3.5 Distance from treated surface, cm 0 0 0.5 1 1.5 2 2.5 3 3.5 Distance from treated surface, cm Boron diffusion gradient in longitudinal direction treated with glycerol borate and examined after 7 days Deeper boron diffusion at higher moisture content regardless of formulations and species.
Results to date Grain direction: 12 10 Spruce 6 5 D fir 8 4 % BAE 6 4 2 Longitudinal Radial Tangential % BAE 3 2 1 Longitudinal Radial Tangential 0 0 0.5 1 1.5 2 2.5 3 3.5 Distance from treated surface, cm 0 0 0.5 1 1.5 2 2.5 3 3.5 Distance from treated surface, cm Boron diffusion gradient in different directions for samples treated with Glycerol borate and examined after 7 days (30% MC) LONGITUDINAL > RADIAL > TANGENTIAL
Results to date Species: 14 12 MC 30% 9 8 MC 50% % BAE 10 8 6 4 Spruce D fir % BAE 7 6 5 4 3 2 Spruce D fir 2 1 0 0 0.5 1 1.5 2 2.5 3 3.5 Distance from treated surface, cm 0 0 0.5 1 1.5 2 2.5 3 3.5 Distance from treated surface, cm Comparative results for different species treated with glycerol borate in longitudinal direction and examined after 14 days Spruce shows better diffusion extent due to low density
Results to date Exposure to extreme condition Temp: 25 0-27 0 C, R. H. : 90-95%
Results to date Treated & untreated parts of joints after 15 weeks(top left - Copper borate treated & right - Glycerol borate treated)
Results to date Comparison between glycerol borate treated(left) and copper borate treated (right)joints Top- 8 weeks, Bottom- 15weeks
Results to date Treatment to be evaluated: Moulded parts of the untreated joint Treated by glycerol borate and copper borate and enclosed by Tuck tape
Future Works Estimating the diffusion coefficient for boron penetration EGNER S solution: Diffusion Coefficient, cm 2 /s Quantitative measurements of Boron distribution rate for different Variables
Future Works Formulation with DDAC and effectiveness test CLT panel treated with borate preservatives and kept under exposure condition Borate treatment to mouldy CLT panel to evaluate the efficacy of the preservatives
Expected Outputs Quantitative information on factors & variables affecting borate distribution Suitable methods for different treatment procedures Modified and cost effective borate preservative Results and recommendations for CLT
Acknowledgements Dr. Paul Morris and colleagues at FPInnovations NEWBuilds Network
Thank you!
Mid rise Building Project Student Workshop February 3, 2012 Assessing the Moisture Durability of Wall Assemblies for CLT Construction in Canadian Climates Robert Lepage, E.I.T. University of Waterloo
Agenda Determining Moisture Characteristics of Cross Laminated Timber (CLT) Panels Calibration of Hygrothermal Model Defining Durable Wall Assemblies Modelling of CLT Wall Assemblies in WUFI Concluding Results from Modelling Exercise
Moisture Properties of CLT Problem: Moisture performance and properties not fully understood Susceptible to rot, mould, swelling, etc Concerns about construction moisture Approach: Characterize moisture properties of CLT via laboratory tests Simulate wall assemblies with calibrated hygrothermal modelling software
Laboratory Experiment Water uptake test Provides absorption coefficient utilized to calculate liquid water diffusivity via suction Gravimetric drying test Provides drying rates and suggests effective liquid water diffusivity via redistribution
Laboratory Testing Drying Rack Setup Moisture Uptake Test
Laboratory Results
Hygrothermal Software WUFI Wärme und Feuchtentransport instationär Transient heat and moisture simulation software Simulation accuracy verified by numerous full scale field studies Empirically calibrated Produced by Fraunhofer Institut Bauphysiks in Holzkirchen, Germany
WUFI Data Input
Hygrothermal Model Calibration
Durable Wall Assemblies Durability: The ability of a building, or any of its components, assemblies, or materials to perform its required function(s) in its service environment over a period of time without unforeseen cost for maintenance or repair Wall Functions Support Control Finish Distribution
The Perfect Wall Not a new concept Division of Building research, NRC Hutcheon, 1964 Sensitive components are protected: Ultra violet radiation Temperature variation Moisture, etc Hutcheon, 1964
The Perfect Wall Lstiburek, 2008
Wall Assemblies Schedule Cladding Exterior Insulation WRB Int. Cavity Int. V.B. Direction S N X R N P I A B Y N N R
Wall Assemblies Storing Cladding Drainage Cavity Vapour Permeable Exterior Insulation Vapour Permeable Membrane CLT Panel Air Space Gypsum Wall Board
Wall Assemblies Non-Storing cladding Vapour Impermeable Membrane CLT Panel Fibre Glass Batt Insulation Vapour Impermeable Membrane Gypsum Wall Board
Climates Vancouver Edmonton Winnipeg Ottawa Québec St. John
Metrics for Comparison MC for 4mm thick layer on outer and innermost CLT lamina
Modelling Results Code Vancouver Edmonton Winnipeg Ottawa Québec St. John Out In Out In Out In Out In Out In Out In SRPAN NH 13.3 13.2 12.9 13.4 14.3 13.4 13.8 13.2 14.2 13.2 13.5 13.1 SRPAN RH 13.4 13.2 12.9 13.4 14.3 13.4 13.8 13.2 14.2 13.2 13.5 13.1 SXIAN NH 12.4 13.1 12.4 13.3 12.4 13.2 12.4 13.1 12.5 13.1 12.5 13.1 NRPAN NH 13.8 13.2 13.1 13.4 14.7 13.5 14.3 13.3 14.7 13.3 14.0 13.2 SNIBY NH 12.7 12.7 16.3 17.5 16.2 18.0 16.2 17.4 16.5 17.3 16.5 16.8 SNPBY NH 15.3 12.8 14.7 15.3 14.5 15.7 14.5 15.1 15.7 15.1 15.9 14.8
Moisture Management Previous modelling assumes ideal conditions Low starting moisture content No penetration leaks Negligible construction moisture How do wall assemblies accommodate for increased moisture loads?
Construction Moisture Results City/Code Moisture Content (%) 4mm 10mm 30mm 43mm 30mm 10mm 4mm Vancouver 58 57 57 56 49 48 47 NRPAN NH 11 13 18 21 18 14 13 SNIBY NH 49 49 49 49 48 21 16 Environment 14 18 22 24 22 18 15 Ottawa 54 54 37 13 12 13 14 NRPAN NH 9 11 13 14 12 13 13 SNIBY NH 27 27 11 14 17 14 12 Environment 11 14 17 14 12 13 13 St. John 33 46 51 45 24 17 18 NRPAN NH 9 11 27 27 27 20 16 SNIBY NH 33 37 14 20 24 25 23 Environment 14 20 24 25 23 17 16 After 3 years of simulation
Observations CLT panels have capacity to be durable Due to thermal properties, large moisture storage capacity, and vapour flow resistance Vapour impermeable membranes increase moisture risks Specifically on the exterior and with no insulation Vapour permeable membranes, especially coupled with outboard insulation, allow for drying
Conclusions For durability: Exterior insulated Vapour permeable membranes only Failing this: Restrict construction moisture levels (<14%MC) Eliminate leaks from penetrations, details, etc
Field Study of Hygrothermal Performance of Cross Laminated Timber Wall Assemblies with Builtin Moisture Ruth McClung MASc. Building Science Candidate Department of Architectural Science Ryerson University Supervisors: Dr. Hua Ge, Ryerson University Dr. John Straube, University of Waterloo
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
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 hg1 4 wall configurations, with 4 CLT wood species will be tested Wetted panels installed in field testing facility and monitored for at least one year Waterloo BEGhut Test Facility
Slide 3 hg1 change "will be" to "being tested" hua ge, 01/02/2012
Planned Field Testing Layout BEGHut Layout 10420 1 2 3 4 5 6 7 28 Entrance Foyer 8 N 3810 27 26 100 Slab on Grade C L 510 Ø column on 1200 x 1200 footing 9 10 100 25 Heating/ C Cooling L Data 11 acquisition 24 electrical system 12 service panel computer 23 22 Each quadrant is symmetric with the centre lines 21 20 19 18 12.5 Ply clad corner 140/140 P.T. post 140 batt insulation 17 16 15 13 14 CLT Test Wall Location 610 1270 1270 1270 1270
Field Testing Layout CLT Panel Species Type A: European B: Black Spruce A1 Int Dry B1 A2 A3 A4 B2 Int Dry B3 B4 5: Stud Wall 5 All panels wetted on both sides except as indicated C: Western SPF D: Hem fir/ E: Eastern SPF C1 D1 C2 Int Dry E2 C3 D3 Int Dry C4 Ext Dry E4 6: Dry European SPF CLT Panel A6 Wall Assembly Type 1: Low 2: High 3: Medium 4: Low Int ⅜ Gypsum Interior Minimum 3½ Air Space Materials Poly Sheet Blueskin Blueskin VP Exterior 3 Roxul RockBoard 3 Plastifab EPS Materials ½ Fiber Cement Board Built-in Moisture Experiment Stud Wall Materials ¾ Vented Cavity CLT Wall Materials ½ Gypsum + Poly Sheet 2x6 studs @ 16 centres 5½ Roxul ComfortBatt Tyvek ¾ Vented Cavity ½ Fiber Cement Board Same as 2: High Dry/Heat Flux Experiment
Field Testing Layout Wall Configurations: 1. Low Permeability 3 Roxul RockBoard Blueskin Nothing 2. High Permeability 3 Roxul RockBoard BlueskinVP Nothing 3. Medium Permeability 3 Plastifab EPS BlueskinVP Nothing 4. Low Interior Permeability 3 Plastifab EPS BlueskinVP Poly sheet
Sensor Layout Panels 1A to 4D 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
Test Wall Construction Soaking of CLT panels in pool Interior Sensor Leads Panel Installation
Test Wall Construction CLT test wall with insulation, strapping and clading. Interior of wall before drywall installation After installation of water resistive barriers
Preliminary Results Freely Drying to Interior Relatively Uniform Behaviour
Preliminary Results Low Interior Permeance Many Panels still above 26% MC, risk of decay initiation
Preliminary Results High Exterior Permeance Panels dry quickly, react quickly to outdoor RH
Preliminary Results Medium Exterior Permeance Panel Surface RH is high, some risk of mould between insulation and VR WRB
Preliminary Results Medium Exterior Permeance Panel Surface RH is high, causing some panels to increase in MC
Preliminary Results Low Exterior Permeance MC remains high, and likely close to 100% RH on surface
Moisture Content Profiles Low Exterior Permeance Drying towards interior
Moisture Content Profiles High Exterior Permeance Rapid drying across panel
Moisture Content Profiles Medium Exterior Permeance Some drying towards interior
Moisture Content Profiles Low Interior Permeance Drying to Exterior
Preliminary 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.
Next Steps Continue data collection and analysis Compare collected data to WUFI simulations made using material properties developed in labratory testing Potentially examines core samples of CLT panels at the end of winter. hg2
Slide 21 hg2 "..made using material properties" may try "...compare collected data to WUFI simulations using material propoerties derived from laboratory testing" hua ge, 01/02/2012
Key outputs and potential impact of research Refined understanding of assembly level moisture characteristics Guidelines for CLT wall assembly design and construction procedures Calibration of computer hygrothermal simulation models Facilitate market penetration
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.