Preliminary simulation was carried out using hygIRC and WUFI, both 1-D hygrothermal models, to analyze moisture performance of rainscreened wood-frame walls and cross-laminated timber (CLT) walls for the climates in Vancouver and Calgary. The major results are as follows.
In order to provide baseline knowledge, preliminary comparisons between hygIRC and WUFI were conducted to investigate the effects of climate data, wall orientations and rain intrusion on the performance of the rainscreened wood-frame walls based on Vancouver’s climate. hygIRC tended to produce almost constant moisture content (MC) of the plywood sheathing throughout a year but WUFI showed greater variations, particularly when the ventilation of the rainscreen cavity was neglected. Rainscreen cavity ventilation provided dramatic drying potentials for wall assemblies based on the WUFI simulation. hygIRC indicated that east-facing walls had the highest moisture load, but the differences between orientations seemed negligible in WUFI when the rainscreen cavity ventilation was taken into account. When 1% of wind-driven rain was simulated as an additional moisture load, hygIRC suggested that the rainscreen walls could not dry out in Vancouver, WUFI, however, indicated that they could dry to a safe MC level in the summer.
The discrepancies in material property data between the two models and between different databases in WUFI (even for the same wood species) were found to be very large. In terms of wood sorption data, large differences existed at near-saturated RH levels. This is a result of using pressure-plate/membrane methods for measuring material equilibrium moisture content (EMC) under high RH conditions. The EMC of wood at near-100% RH conditions measured with these methods can be higher than 200%, suggesting wood in construction would decay without liquid water intrusion or severe vapour condensation. The pressure-plate/membrane methods also appeared to be highly species-dependent, and have higher EMC at a certain RH level for less permeable species, from which it is relatively difficult to remove water during the measurement. The hygrothermal simulation in this work suggested that such a species bias caused by testing methods could put impermeable species (most Canadian species) at a disadvantage to permeable species like southern pine during related durability design of building assemblies.
In terms of using CLT for construction in Vancouver and Calgary, the WUFI simulations suggested that the use of less permeable materials such as EPS (expanded polystyrene insulation), XPS (extruded polystyrene insulation), self-adhered bituminous membrane and polyethylene in wall assemblies reduced the ability of the walls to dry. On the other hand, permeable assemblies such as those using relatively permeable insulation like semi-rigid mineral wool (rock wool) as exterior insulation, instead of less permeable exterior insulation materials, would help walls dry. The simulation also suggested that using CLT products with initially low MC would significantly reduce moisture-related risks, which indicated the importance of protecting CLT and avoiding wetting during transportation and construction.
In addition, the simulation found that indoor relative humidity (RH) conditions generated by the indoor RH prediction models included in hygIRC and WUFI varied greatly under the same basic climate and building conditions. The intermediate method specified in ASHRAE Standard 160 P resulted in long periods of saturated RH conditions throughout a year for the Vancouver climate, which may not be representative of ordinary residential buildings in Vancouver.
The simulation in this study is preliminary and exploratory. It would be arbitrary to recommend one model over the other based on this report or use the simulation results directly for CLT wall assembly design without consultation with building science specialists. However, this work revealed more opportunities for close collaborations between the wood science and the building science communities. More work should be carried out to develop appropriate testing methods and assemble material property data for hygrothermal simulation of wood-based building assemblies. Model improvement and field verification are also strongly recommended, particularly for new building systems such as CLT constructions.
Dovetail connections were applied for connecting column to column, and beam to beam in traditional timber framed buildings. Previous studies were mainly focused on mechanical behaviour of the connection. However, there was a lack of study on the structural behaviour of the connection under different moisture contents. The goal of this study was to analyse the effects of moisture content on swelling behaviour and structural performance of dovetail connection. Different sizes of 120×120, 180×180, 180×240 mm from larix kaempferi and pinus koraiensis were used. Dimensional changes of dovetail connection made from different species showed different trends with an increment of size. The dimensional changes of member of dovetail connection from larix kaempferi were higher than those of dovetail connection made from pinus koraiensis, whereas the dimensional changes of geometric variables of dovetail connection from pinus koraiensis were higher than those of dovetail connection made from larix kaempferi.
Cross-laminated timber (CLT) panels have potential market in North America for building mid-rise structures due to their good structural and seismic performance, lightweight, and prefabricated nature. However, to ensure long-term durability, the hygrothermal performance of CLT wall assemblies needs to be evaluated in terms of drying and wetting potential before their widespread adoption in North America. A test wall was constructed with initially wetted CLT panels, and monitored over a year. The drying behaviour of the panels was analysed, and results were compared to hygrothermal simulations. It was found from the field data that no tested wall assemblies in the given climate prevented the panels from drying in enough time to prevent decay initiation. The hygrothermal simulation program is capable of predicting general trends, and can predict if a wall be safe, but tends to be overly conservative. Further refinement of the model for wood is needed.
Wood is a highly versatile renewable material (with carbon sequestering properties), that is light in weight, has good strength properties in both tension and compression while providing good rigidity and toughness, and good insulating properties (relative to typical structural materials). Engineered wood products combine the benefits of wood with engineering knowledge to create optimized structural elements. Cross-laminated timber (CLT), as one such engineered wood product, is an emerging engineering material which provides great opportunities for the building industry. While building with wood has many benefits, there are also some concerns, particularly decay. Should wood be exposed to elevated amounts of moisture, rots and moulds may damage the product or even risk the health of the occupants. As CLT panels are a relatively new engineered wood product, the moisture characteristics have yet to be properly assessed.
A long term laboratory investigation on two six-meter-span timber composite beams was started from March 2012 at the University of Technology Sydney. These timber composites were made of laminated veneer lumber (LVL). The web and the flanges of the composite timber section were connected using screw-gluing technique. The specimens have been under sustained loads of (2.1kPa) and the environmental conditions was cyclically alternated between normal and very humid conditions whilst the temperature remained quasi constant (22 °C) –typical cycle duration was six to eight weeks. With regard to EC 5, the environmental conditions can be classified as service class 3 where the relative humidity of the air exceeds 85% and the moisture content of the timber samples reaches 20%. During the test, the mid-span deflection, moisture content of the timber beams and relative humidity of the air were continuously monitored. The paper presents the results and observations of the long-term test to-date and the test is continuing.
Cross-laminated timber (CLT) panels have potential market in North America for building mid-rise or even taller structures due to their good structural and fire safety performance, light weight, and prefabricated nature. However, to ensure long-term durability when used in building enclosures, the hygrothermal performance of CLT wall assemblies needs to be evaluated in terms of wetting and drying potential. A test wall consisting of sixteen 0.6 m by 0.6 m CLT panels made of five different wood species (or species groups) and four different wall assemblies was constructed. The CLT panels were initially wetted with the moisture content (MC) in the surface layers approaching or exceeding 30%, and monitored for MCs and temperatures at different depths over one year in a building envelope test facility located in Waterloo, Ontario. The drying behaviour of these panels was analysed and the measured MCs over time were compared to simulation results using a commercial hygrothermal program. This field study showed that most of the CLT panels dried to below 26% within one month except for CLT walls with a low-permeance interior membrane, which indicated that none of the CLT walls would likely remain at a high MC level long enough to initiate decay under the conditions tested. The simulation results generally agree well with the field data at MCs below 26%. However, it was found that the hygrothermal simulation program tended to overestimate the MC in the centre of the panels by up to 5e10%, and simulated MCs at locations deep into the CLT panels were not as responsive to changes in ambient conditions, as the measurements indicated for assemblies with high exterior permeance.
This document aims to emphasize the importance of an appropriate level of on-site moisture management for wood construction, depending on weather conditions, construction methods, and assemblies used. It covers three different but related research projects. It first describes baseline moisture contents (MCs) measured from...
Nationwide, bridges are deteriorating at a rate faster than they can be rehabilitated and maintained. This has resulted in a search for new methods to rehabilitate, repair, manage, and construct bridges. As a result, structural health monitoring and smart structure concepts have emerged to help improve bridge management. In the case of timber bridges, however, a limited amount of research as been conducted on long-term structural health monitoring solutions, and this is especially true in regards to historic covered timber bridges. To date, evaluation efforts of timber bridges have focused primarily on visual inspection data to determine the structural integrity of timber structures. To fill this research need and help improve timber bridge inspection and management strategies, a 5-year research plan to develop a smart timber bridge structure was undertaken. The overall goal of the 5-year plan was to develop a turnkey system to analyze, monitor, and report on the performance and condition of timber bridges. This report outlines one phase of the 5-year research plan and focuses on developing and attaching moisture sensors onto timber bridge components. The goal was to investigate the potential for sensor technologies to reliably monitor the in situ moisture content of the timber members in historic covered bridges, especially those recently rehabilitated with glulam materials. The timber-specific moisture sensors detailed in this report and the data collected from them will assist in advancing the smart timber bridge.
The objectives of this work include the following:
· Conduct a series of water entry tests over a wide range of simulated wind pressure and WDR loads to measure the water entry rate passing the cladding through deficiencies located in a fibre cement cladding system; A1-100035-03.3 2
· Use the test results to develop correlations for determining the percentage of water entry rate through deficiencies as a function of pressure difference across the assembly and water spray rate onto the cladding surface;
· Analyze the water entry data for the NBC stucco cladding for high wind pressures obtained in a previous study (see  for more details) and applicable for mid-rise and taller buildings and thereafter develop a correlation to determine the percentage of water entry rate as a function of wind pressure and WDR for absorptive claddings.