Hygrothermal properties of cross laminated timber and moisture response of wood at high relative humidity

Alsayegh, George

doi:10.22215/etd/2013-07273

Cited by 5 publications

(5 citation statements)

References 23 publications

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“…The adhesive layer (assumed to extend 2 mm deep in the plank) was modeled with the same material properties as spruce, with the exception that the water vapor permeability and liquid water diffusivity were decreased by 50%. This was in line with the results obtained in [16] which showed that CLT's vapor permeability and moisture diffusivity are substantially reduced in comparison with those of solid wood.…”

Section: Wall Assembliessupporting

confidence: 92%

“…Figure 2 shows the schematic of the wood frame and massive timber walls. Material properties of wall components were obtained from [15] and [16]. CLT panel is composed of wood (spruce) layers glued together with an adhesive.…”

Section: Wall Assembliesmentioning

confidence: 99%

“…The initial conditions for relative humidity (RH) and temperature (T) were set to 80% and 21°C, respectively, for all components. Indoor ambient T and RH were set as constant Material properties of wall components were obtained from [15] and [16]. CLT panel is composed of wood (spruce) layers glued together with an adhesive.…”

Section: Simulation Setupmentioning

confidence: 99%

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Application of Support Vector Regression to the Prediction of the Long-Term Impacts of Climate Change on the Moisture Performance of Wood Frame and Massive Timber Walls

2021

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The objective of this study was to explore the potential of a machine learning algorithm, the Support Vector Machine Regression (SVR), to forecast long-term hygrothermal responses and the moisture performance of light wood frame and massive timber walls. Hygrothermal simulations were performed using a 31-year long series of climate data in three cities across Canada. Then, the first 5 years of the series were used in each case to train the model, which was then used to forecast the hygrothermal responses (temperature and relative humidity) and moisture performance indicator (mold growth index) for the remaining years of the series. The location of interest was the exterior layer of the OSB and cross-laminated timber in the case of the wood frame wall and massive timber wall, respectively. A sliding window approach was used to incorporate the dependence of the hygrothermal response on the past climatic conditions, which allowed SVR to capture time, implicitly. The variable selection was performed using the Least Absolute Shrinkage and Selection Operator, which revealed wind-driven rain, relative humidity, temperature, and direct radiation as the most contributing climate variables. The results show that SVR can be effectively used to forecast hygrothermal responses and moisture performance on a long climate data series for most of the cases studied. In some cases, discrepancies were observed due to the lack of capturing the full range of variability of climate variables during the first 5 years.

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Section: Wall Assembliessupporting

confidence: 92%

Section: Wall Assembliesmentioning

confidence: 99%

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Application of Support Vector Regression to the Prediction of the Long-Term Impacts of Climate Change on the Moisture Performance of Wood Frame and Massive Timber Walls

2021

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“…The CLT adhesive layer (assumed to extend 2 mm deep in the plank) was modeled with the same material properties as spruce, with the exception that the water vapor permeability and liquid water diffusivity were decreased by 50%. In fact, previous studies on the characterization of the hygrothermal properties of CLT have shown that its vapor permeability and moisture diffusivity are substantially reduced in comparison with those of solid wood [26].…”

Section: Building and Wall Componentsmentioning

confidence: 98%

Effects of Climate Change on the Moisture Performance of Tallwood Building Envelope

Defo

Lacasse

2021

Buildings

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The objective of this study was to assess the potential effects of climate change on the moisture performance and durability of massive timber walls on the basis of results derived from hygrothermal simulations. One-dimensional simulations were run using DELPHIN 5.9.4 for 31 consecutive years of the 15 realizations of the modeled historical (1986–2016) and future (2062–2092) climates of five cities located across Canada. For all cities, water penetration in the wall assembly was assumed to be 1% wind-driven rain, and the air changes per hour in the drainage cavity was assumed to be 10. The mold growth index on the outer layer of the cross-laminated timber panel was used to compare the moisture performance for the historical and future periods. The simulation results showed that the risk of mold growth would increase in all the cities considered. However, the relative change varied from city to city. In the cities of Ottawa, Calgary and Winnipeg, the relative change in the mold growth index was higher than in the cities of Vancouver and St. John’s. For Vancouver and St. John’s, and under the assumptions used for these simulations, the risk was already higher under the historical period. This means that the mass timber walls in these two cities could not withstand a water penetration rate of 1% wind-driven rain, as used in the simulations, with a drainage cavity of 19 mm and an air changes per hour value of 10. Additional wall designs will be explored in respect to the moisture performance, and the results of these studies will be reported in a future publication.

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“…There are different building systems used across the world and even if wood is a common material; it is used under various forms made from various species. Al Sayegh (2012) and Lepage (2012) showed that differences between CLTs from various origins (Europe and Canada) and the differences mainly came from the cracks in the wood and the way boards were glued together, this having an effect on the permeability of the panels. Ozolins et al (2013) evaluated hygrothermal properties of multi-layered walls in cold climate using COMSOL and WUFI and confirmed the results with in-situ measurements.…”

Section: Model Validationmentioning

confidence: 99%

Modeling the impact of assembly tolerances regarding air leaks on the energy efficiency and durability of a cross-laminated timber structure

Martin

Blanchet

Potvin

2018

BioRes

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Air leaks have a considerable impact on the energy load and durability of buildings, particularly in cold climates. In wood construction using cross-laminated timber (CLT), air leaks are most likely to be concentrated at the joints between panels and other elements. This study used simulations of heat, air, and moisture transfers through a gap between two CLT panels causing air leakage in winter conditions under a cold climate. A real leakage occurrence was sized to validate the simulations. The aim of this work was to assess the impact on the energy loads and the durability of an air leak, as either infiltration or exfiltration, for different gap widths and relative humidity levels. The results showed that infiltrations had a greater impact on the energy load than exfiltrations but did not pose a threat to the durability, as opposed to exfiltrations. Gap sizes in CLT may vary, but the effect on the energy load was sensitive to the leakage path in the rest of the wall. As expected, a combination of winter exfiltration and a high level of interior relative humidity was particularly detrimental.

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Hygrothermal properties of cross laminated timber and moisture response of wood at high relative humidity

Abstract: A Thesis submitted to the Faculty o f Graduate and Postdoctoral Affairs in partial fulfillment o f the requirements for the degree o f Master o f Applied Science in Civil and Environmental Engineering

Cited by 5 publications

References 23 publications

Application of Support Vector Regression to the Prediction of the Long-Term Impacts of Climate Change on the Moisture Performance of Wood Frame and Massive Timber Walls

Application of Support Vector Regression to the Prediction of the Long-Term Impacts of Climate Change on the Moisture Performance of Wood Frame and Massive Timber Walls

Effects of Climate Change on the Moisture Performance of Tallwood Building Envelope

Modeling the impact of assembly tolerances regarding air leaks on the energy efficiency and durability of a cross-laminated timber structure

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