Cross-laminated timber (CLT) modular construction possesses the advantages of wood, such as excellent carbon storage and thermal insulation, and of modular construction, such as considerably reduced construction period and cost as well as high productivity. This study evaluates the hygrothermal performance of CLT walls considering modular construction in future climatic conditions. Firstly, CLT walls with plywood applied to a core layer were manufactured. A mock-up of a CLT building was produced and its construction process was analyzed. Hygrothermal behavior of the CLT walls was simulated using WUFI simulation program, and the predicted results were verified against measurements obtained from the mock-up experiment. Finally, the hygrothermal performance of the CLT wall was evaluated for four types of insulation and future climate in eight cities of USA. The coefficient of variation—root mean square error (CV(RMSE))—of the temperature and relative humidity inside the ply-lam CLT wall from mock-up experiments and simulation evaluation were 6.43% and 7.02%, respectively, which met the validation criteria. Based on the hygrothermal performance, the ply-lam CLT wall with extruded polystyrene insulation was evaluated as safe from moisture problems in all the eight cities considered in this study. However, the risk of mold growth in all regions and insulation types increased under climate change with a rise of average annual temperature.
Cross-laminated timber (CLT) is becoming increasingly adopted into North American construction, yet little is known about the impacts of environmental exposure (e.g., to rain during construction) on its long-term performance. The lack of protocols for on-site moisture protection in North America makes it a pressing matter to determine general moisture responses of this material in order to establish a behavioral baseline for practitioners and future researchers.
A CLT floor panel sample was exposed to cycles of wetting and drying in an environmental chamber. During these cycles, physical and geometrical properties of the panel were monitored. Testing results indicate that discontinuities in the layup CLT affects the hygroscopic behavior of the product. While the panel showed high dimensional stability, it also exhibited checking, cupping, and interfacial shearing after cycling. Bending test results before and after cycling indicated a reduction of the structural capacity due to the weathering.
Unlike other solid wood panel systems, ICLT panels are manufactured without the use of adhesives or fasteners. Wood members are connected with tongue-andgroove joints within a given layer and with dovetail joints across layers. This reduces cost and allows ICLT panels to be disassembled at end of life to be repurposed in the building material supply chain. In addition, ICLT panels provide a means to utilize lumber from trees killed by mountain pine beetle.
Durability is critical for sustainable construction, and avoidance of moisture accumulation in wood structural members is essential for long-term performance. Little work has been done specifically on hygrothermal performance of massive timber construction.
The objective of this research is to identify building envelope design and construction practices for robust hygrothermal performance of ICLT walls in multiple U.S. climates.
A test program was conducted to generate hygrothermal performance data for light-wood-frame exterior walls meeting the R22 effective (RSI 3.85) requirement for buildings up to six storeys in the City of Vancouver. Six types of exterior wall assemblies, with 12 wall panels in total, were tested using a test hut located in the rear yard of FPInnovations’ Vancouver aboratory. This document provides a brief summary of the test and performance of these walls based on the data collected over the 19 months’ period from October 2018 to May 2020
Currently, design of tall wood buildings is generally accomplished in the USA through the so-called alternate means process, with requires extensive testing, engineering analysis, and a stringent peer review process. As it pertains to cross-laminated timber (CLT), it is critical to develop effective performance prediction models, through laboratory testing elaborating on material behaviors (e.g. hygrothermal, vibrational, etc.) as well as monitoring data on the mid- to long-term performance of timber structures in situ. This paper presents the scope and preliminary outcomes of a project aiming to cross reference laboratory research and in-situ monitoring to establish a holistic performance-monitoring protocol for mass timber buildings; this protocol can later serve to define standards for mid- to long-term monitoring as well as to develop guidelines for the design of mass timber structures.
The aim of this work is to examine the hygrothermal performance of timber-based envelopes across Australia. The heat and moisture (HAM) analyses are performed with consideration of various climatic conditions for all major Australian cities including: Darwin (zone 1); Brisbane (zone 2); Sydney (zone 5); Melbourne (zone 6); and Canberra (zone 7). Two main typical wall sections are selected for investigation, a massive CLT wall type with an external insulation layer and a cavity-insulated timber frame wall. The transient hygrothermal behaviour and mould growth risk assessments are simulated with WUFI software. The study shows how emerging construction practices perform poorly with respect to HAM transfer, particularly in hot and humid climatic contexts during the cooling season.Critical configurations are identified and design alternatives suggested so to prevent material damage, guarantee durable wood structures and maintain indoor environment healthiness.
Timber envelopes provide multiple benefits in reducing both operational and embodied energy environmental impacts in construction. However, when poorly designed, they may incur in high risk of mould growth, affecting both building performance and occupant’s wellbeing. This research investigates the risk of mould growth associated with emerging timber envelopes in Australia, particularly looking at mass-timber and timber-framed wall typologies. The study compares the use of two mould growth assessment models: the VTT and the IBP biohygrothermal. Results provide relevant insights on both current design approaches and performance assessment methodologies. Whilst the study is based on Australian practice, conclusions have international relevance and applicability.
The physical input values of buildings were entered into a thermal moisture simulation software called WUFI. The categorized criteria were variables of insulation type, standards of insulation (U-value), climate, and the presence or absence of vapor permeable inside and outside the wall. The simulation results graphically displayed the moisture content of the entire wall and the potential for mold growth. The results showed that a vapor barrier paper needs to be installed inside the wall to produce less mold and that the wool-type insulation materials have more moisture content than that of polyester insulation materials. Next, the actual experiment was conducted in a Facing thermo-hygrostat for evaluating the performance of the hygrothermal behavior of the CLT wall using different types of insulation, namely, XPS, PF board, and glass wool. The direction and amount of water vapor in the wall owing to temperature changes were observed in the external environment. The experimental results showed that the CLT wall containing the glass wool insulation was vulnerable to heat and humidity, whereas the CLT wall containing the PF insulation was excellent in resisting heat and humidity. Finally, CLT building with the previously studied was implemented. In this process, a life cycle cost analysis was performed by calculating the daily heating and cooling values for domestic climates to determine the optimal thickness of the insulation to used for each CLT wall.
Un programme d’essais a été réalisé en vue de générer des données sur le rendement hygrothermique des murs à ossature légère de bois qui répondent à l’exigence R22 (RSI 3,85) pour les bâtiments d'au plus six étages à Vancouver. Six types d’assemblage de mur extérieur, avec un total de 12 murs extérieurs, ont été mis à l’essai à l’aide d’une hutte d’essai située dans la cour arrière du laboratoire de FPInnovations à Vancouver. Le présent document présente un court résumé de l’essai et du rendement de ces murs en se basant sur les données recueillies sur une période de 19 mois, soit d’octobre 2018 à mai 2020 (Wang 2021).
