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Field measurement of vertical movement and roof moisture performance of the Wood Innovation and Design Centre : instrumentation and first year's performance

https://library.fpinnovations.ca/en/permalink/fpipub44205
Author
Wang, Jieying
Date
March 2015
Material Type
Research report
Field
Sustainable Construction
PDF
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Author
Wang, Jieying
Contributor
Forestry Innovation Investment
Date
March 2015
Material Type
Research report
Physical Description
39 p.
Sector
Wood Products
Field
Sustainable Construction
Research Area
Advanced Wood Materials
Subject
British Columbia
Building construction
Laminate product
Moisture content
Performance
Test methods
Series Number
301008940
Language
English
Abstract
Two of the major topics of interest to those designing taller and larger wood buildings are the susceptibility to differential movement and the likelihood of mass timber components drying slowly after they are wetted during construction. The Wood Innovation and Design Centre in Prince George, British Columbia provides a unique opportunity for non-destructive testing and monitoring to measure the ‘As Built’ performance of a relatively tall mass timber building. Field measurements also provide performance data to support regulatory and market acceptance of wood-based systems in tall and large buildings. This report first describes instrumentation to measure the vertical movement of selected glulam columns and cross-laminated timber (CLT) walls in this building. Three locations of glulam columns and one CLT wall of the core structure were selected for measuring vertical movement along with the environmental conditions (temperature and humidity) in the immediate vicinity. The report then describes instrumentation to measure the moisture changes in the wood roof structure. Six locations in the roof were selected and instrumented for measuring moisture changes in the wood as well as the local environmental conditions. All sensors and instrumentations, with the exception of one, were installed and became operational in the middle of March 2014, after the roof sheathing was installed. The other instrumentation was installed in July 2014. This report presents performance of the building during its first year as measured from topping out of the structure. In the end, the one-year period covers six months of construction and six months of occupancy. This is the first year of a planned five-year monitoring. The first year’s monitoring showed that the wood inside the building had reached moisture content (MC) of about 4-6% in the heating season, from an initial MC of 13% during construction. Glulam columns were extremely dimensionally stable given the changes in MC and loading conditions. With a height of over 5 m and 6 m, respectively, the two glulam columns measured in this study showed very small amounts of vertical movement, each below 2 mm. The cumulative shortening of the six glulam columns along the height of the building would be about 8 mm, not taking into account deformation at connection details or effects of reduced loads on upper floors. The CLT wall was found to be also dimensionally stable along the height of the building. The measurements showed that the entire CLT wall, from Floor 1 to Floor 6, would shorten about 14 mm. The CLT floors, however, had considerable shrinkage in the thickness direction, and therefore should be taken into consideration in the design and construction of components, such as curtain walls, which are connected to the floors. In terms of the roof performance, two locations, both with a wet concrete layer poured above the plywood sheathing, showed wetness during construction but dried slowly afterwards. The good drying performance must be attributed to the interior ventilation function designed for the roof assemblies by integrating strapping between the sheathing and the mass timber beams below. Overall this monitoring study shows the differential movement occurring among the glulam columns and the CLT wall is small and the wood roof has good drying performance.
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Field monitoring of hygrothermal performance of a wood-frame house in the Lower Mainland of BC built to the passive house standard

https://library.fpinnovations.ca/en/permalink/fpipub6071
Author
Wang, Jieying
Mistretta, S.
Date
March 2014
Edition
43873
Material Type
Research report
Field
Sustainable Construction
Author
Wang, Jieying
Mistretta, S.
Contributor
Forestry Innovation Investment
Natural Resources Canada. Canadian Forest Service.
Date
March 2014
Edition
43873
Material Type
Research report
Physical Description
30 p.
Sector
Wood Products
Field
Sustainable Construction
Research Area
Building Systems
Subject
Moisture content
Series Number
W-3100
Language
English
Abstract
A single-family wood-frame house in the Lower Mainland of British Columbia built to the German Passivhaus (Passive House) standard was monitored to investigate its thermal performance and durability in this mild climate. Two double-stud walls, south- and north-facing, were instrumented during construction to measure moisture and thermal performance. A limited amount of thermal modelling was conducted to compare with the field measurements. Monitoring over the past 20 months showed that:
The double-stud walls, south- and north-facing, were both performing well in terms of durability. The moisture content (MC) measured at the bottom of the studs was in general below 15% after the construction was completed. The MC of the south-facing wall dropped from an initial 20%, measured during construction, to about 11% after construction was completed. During the same period of time, the MC of the north-facing wall fell from about 19% to 15%; the slightly higher MC in this wall compared to that in the south-facing wall was a result of lower amounts of solar gain in this orientation.
The relative humidity (RH) measured on the interior side of the medium-density fibreboard (MDF) exterior sheathing in the south-facing wall ranged from 70% to 80%, and occasionally up to 90% during the winter. Being typical of exterior sheathing conditions without exterior insulation in this mild climate, the corresponding RH ranged from 80% up to 100% in the north-facing wall in the winter, indicating potential vapour condensation at this critical location.
Based on vapour pressure analysis, no steep vapour pressure gradients between any specific layers were found in these two walls, indicating the overall vapour permeable nature and good drying performance of the wall design. This could be partially attributed to the use of plywood as structural sheathing located between the double-stud walls as the air barrier and vapour retarding layer, and using MDF as the exterior sheathing.
In the south-facing wall, the vapour pressure analysis showed a vapour drive in the summer from the exterior layers towards the interior layer, primarily due to high temperature outside. The exterior sheathing should have good drying potential if wetting occurred. On the other hand, the partial vapour pressures were largely consistent across the north-facing wall in the winter, not showing a strong vapour drive from interior to exterior in this mild climate. The exterior sheathing would have poor drying performance if wetting occurred in this location.
The simulated temperature distributions based on THERM 6.3 simulations were generally in good agreement with the measured temperatures across the walls, indicating that the thermal simulation was reasonably accurate. The effective R-value of the double-stud walls of this passive house was calculated to be approximately R-50 (hržft2žF/Btu) or RSI-8.8 (m2K)/W) (i.e. with a thermal transmission coefficient of 0.114 W/m2žK). The use of heat flux sensors was not successful in this work, probably due to improper sensor calibration or in-situ installation. Its use needs further exploration to measure heat flow in building envelopes in order to validate calculated effective thermal insulation.
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Vertical movement in wood platform frame structures : basics

https://library.fpinnovations.ca/en/permalink/fpipub6026
Author
Doudak, Ghasan
Lepper, P.
Ni, Chun
Wang, Jasmine
Date
October 2013
Edition
42995
Material Type
Research report
Field
Sustainable Construction
D P L A T F O R M F R A M E S T R U C T U R E S: B a si c s Wood moisture content
Author
Doudak, Ghasan
Lepper, P.
Ni, Chun
Wang, Jasmine
Contributor
Canadian Wood Council
Date
October 2013
Edition
42995
Material Type
Research report
Physical Description
10 p.
Sector
Wood Products
Field
Sustainable Construction
Research Area
Building Systems
Subject
Building construction
Residential construction
Design
Moisture content
Series Number
W-3076
Language
English
Abstract
Movement in structures due to environmental condition changes and loads must be considered in design. Temperature changes will cause movement in concrete, steel and masonry structures. For wood materials, movement is primarily related to shrinkage or swelling caused by moisture loss or gain when the moisture content is below 28% (wood fiber saturation point). Other movement in wood structures may also include: settlement (bedding-in movement) due to closing of gaps between members and deformation due to compression loads, including instantaneous elastic deformation and creep. Differential movement can occur where wood frame is connected to rigid components such as masonry cladding, concrete elevator shafts, mechanical services and plumbing, and where mixed wood products such as lumber, timbers, and engineered wood products are used. Evidence from long-term wood frame construction practices shows that for typical light frame construction up to three storeys high, differential movement can be relatively easily accommodated such as through specifying “S-Dry” lumber. However, differential movement over the height of wood-frame buildings becomes a very important consideration for taller buildings due to its cumulative effect. The APEGBC Technical and Practice Bulletin provides general design guidance and recommends the use of engineered wood products and dimension lumber with 12% moisture content for floor joists to reduce and accommodate differential movement in 5 and 6-storey wood frame buildings. Examples of differential movement concerns and solutions in wood-frame buildings can also be found in the Best Practice Guide published by the Canadian Mortgage and Housing Corporation and the Building Enclosure Design Guide –Wood Frame Multi-Unit Residential Buildings published by the Homeowner Protection Office of BC Housing. This document illustrates the causes and other basic information related to vertical movement in wood platform frame buildings and recommendations on material handling and construction sequencing to protect wood from rain and reduce the vertical movement.
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Vertical movement in wood platform frame structures : design and detailing solutions

https://library.fpinnovations.ca/en/permalink/fpipub6025
Author
Doudak, Ghasan
Lepper, P.
Ni, Chun
Wang, Jasmine
Date
October 2013
Edition
42994
Material Type
Research report
Field
Sustainable Construction
Author
Doudak, Ghasan
Lepper, P.
Ni, Chun
Wang, Jasmine
Contributor
Canadian Wood Council
Date
October 2013
Edition
42994
Material Type
Research report
Physical Description
13 p.
Sector
Wood Products
Field
Sustainable Construction
Research Area
Building Systems
Subject
Building construction
Residential construction
Design
Moisture content
Series Number
W-3075
Language
English
Abstract
Most buildings are designed to accommodate a certain range of movement. In design, it is important for designers to identify locations where potential differential movement could affect structural integrity and serviceability, predict the amount of differential movement and develop proper detailing to accommodate it. To allow non-structural materials to be appropriately constructed, an estimate of anticipated differential movement should be provided in the design drawings. Simply specifying wood materials with lower MC at time of delivery does not guarantee that the wood will not get wet on construction sites and will deliver lower shrinkage amounts as anticipated. It is therefore important to ensure that wood does not experience unexpected wetting during storage, transportation and construction. Good construction sequencing also plays an important role in reducing wetting, the consequent wood shrinkage and other moisture-related issues. Existing documents such as the APEGBC Technical and Practice Bulletin on 5- and 6-Storey Wood Frame Residential Building Projects, the Best Practice Guide published by the Canadian Mortgage and Housing Corporation (CMHC), the Building Enclosure Design Guide –Wood Frame Multi-Unit Residential Buildings published by the BC Housing- Homeowner Protection Office (HPO) provide general design guidance on how to reduce and accommodate differential movement in platform frame construction.
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Vertical movement in wood platform frame structures : movement prediction

https://library.fpinnovations.ca/en/permalink/fpipub6027
Author
Doudak, Ghasan
Lepper, P.
Ni, Chun
Wang, Jasmine
Date
October 2013
Edition
42996
Material Type
Research report
Field
Sustainable Construction
Author
Doudak, Ghasan
Lepper, P.
Ni, Chun
Wang, Jasmine
Contributor
Canadian Wood Council
Date
October 2013
Edition
42996
Material Type
Research report
Physical Description
9 p.
Sector
Wood Products
Field
Sustainable Construction
Research Area
Building Systems
Subject
Building construction
Residential construction
Design
Moisture content
Series Number
W-3077
Language
English
Abstract
It is not possible or practical to precisely predict the vertical movement of wood structures due to the many factors involved in construction. It is, however, possible to obtain a good estimate of the vertical movement to avoid structural, serviceability, and building envelope problems over the life of the structure. Typically “S-Dry” and “S-Grn” lumber will continue to lose moisture during storage, transportation and construction as the wood is kept away from liquid water sources and adapts to different atmospheric conditions. For the purpose of shrinkage prediction, it is usually customary to assume an initial moisture content (MC) of 28% for “S-Green” lumber and 19% for “S-Dry” lumber. “KD” lumber is assumed to have an initial MC of 15% in this series of fact sheets. Different from solid sawn wood products, Engineered Wood Products (EWP) are usually manufactured with MC levels close to or even lower than the equilibrium moisture content (EMC) in service. Plywood, Oriented Strand Board (OSB), Laminated Veneer Lumber (LVL), Laminated Strand Lumber (LSL), and Parallel Strand Lumber (PSL) are usually manufactured at MC levels ranging from 6% to 12%. Engineered wood I-joists are made using kiln dried lumber (usually with moisture content below 15%) or structural composite lumber (such as LVL) flanges and plywood or OSB webs, therefore they are usually drier and have lower shrinkage than typical “S-Dry” lumber floor joists. Glued-laminated timbers (Glulam) are manufactured at MC levels from 11% to 15%, so are the recently-developed Cross-laminated Timbers (CLT). For all these products, low shrinkage can be achieved and sometimes small amounts of swelling can be expected in service if their MC at manufacturing is lower than the service EMC. In order to fully benefit from using these dried products including “S-Dry” lumber and EWP products, care must be taken to prevent them from wetting such as by rain during shipment, storage and construction. EWPs may also have lower shrinkage coefficients than solid wood due to the adhesives used during manufacturing and the more mixed grain orientations in the products, including the use of cross-lamination of veneers (plywood) or lumber (CLT). The APEGBC Technical and Practice Bulletin emphasizes the use of EWP and dimension lumber with 12% moisture content for the critical horizontal members to reduce differential movement in 5 and 6-storey wood frame buildings.
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