There was no change to the moisture content of any of the western hemlock log sample sets during the study period between 1 Dec 2014 and 5 mar 2015. It seems that this lack of change is related to stability in environmental humidity experienced by the logs. Whether or not time since cutting influences the ability of Hw logs to change moisture content could not be conclusively determined by the study.
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This study was conducted with the aim of assessing the effects of log storage time and conditions at a BC mill yard on veneer production under mill production conditions. The second objective was to validate the FPInnovations LogdryTM drying model for developed for wood piles in Eastern Canadian mills. The software was used to generate drying rate predictions under the BC mill’s prevailing weather conditions and storage times for comparison with some measured residual moisture contents of Douglas fir logs kept in storage at the mill for six and nine months, sampled and peeled in a laboratory trial in 2016.
The 2016 lab trials suggested little effect of lengthy (winter) storage up to 9 months but mill experience suggests this is excessively long and logs deteriorate in terms of veneer production and quality considerably earlier. Unfortunately due to experimental circumstances the mill peeling trials for the 9 month stored logs were unable to provide an accurate assessment of the true effect on production. Mills trials indicated % heavy sap had remained fairly stable largely within the mill target of 14% to 17% over the storage periods. During the mill trials there were unavoidable heavy confounding effects of different average diameter for log groups and peeler knife condition affecting the expected veneer production variables.
The trials also demonstrated how pile size and height play a major role in protecting logs from drying; with very dry logs having a deleterious effect on veneer production. Logs held in small piles for 12 months or more, even with artificial ‘drying retardants’ such as end sealant and tarping were too dry for reliable peeling, causing very rapid knife wear, spinouts, veneer break-up and line blockages and significant lost recovery. The % heavy sap offtakes from these trials were just 2% to 4%.
LogDryTM provides a fairly good estimate of likely drying rate trends of mid-sized (35 cm/14” to 41 cm/16” range) Douglas fir under the BC mills historic weather conditions over 6 and 9 months.
LogDryTM (Birch setting) was closest to measured log MC in large diameter (46 cm/18”) logs but the Aspen setting was closer to measured MC in small logs (<30 cm/12”). In the limited sample of logs available from the mill in 2016 the 12” logs were much drier after 9 months storage than the model predicted, even on the Aspen setting. Further sampling of piled logs in the small diameter range is needed to verify this observation.
LogDryTM was used to estimate drying rates of logs stored before or after Summer. Modelling indicated a shorter viable storage window for logs delivered before Summer compared to just before Winter, especially in the 6-month range. Residual log MCs were very similar after 12 months regardless of start time.
Further work is required to better calibrate LogdryTM for major Western Canadian species, particularly Douglas fir, Spruce and Lodgepole pine, and reduce the calculation time for simulations. Further adjustment may be needed for simulating real drying rates in very small logs. The model assumption of similar residual MC after 12 months regardless of start time also needs to be verified.
The problem of second-growth western hemlock (Tsuga heterophylla) sinking when watered continues to plague the coastal logging industry of British Columbia. A study conducted by FPInnovations in 2015-16 concluded that felled hemlock logs took two distinct trajectories in their drying patterns through time, depending on whether they were felled before or after May.
This report documents the instrumentation installed for monitoring moisture, indoor air quality and differential movement performance in a six-storey building located in the City of Vancouver. The building has five storeys of wood-frame construction above a concrete podium, providing 85 rental units for residential and commercial use. It was designed and built to meet the Passive House standard and, once certified, will be the largest building in Canada that meets this rigorous energy standard. Although the design and construction focused on integrating a number of innovative measures to improve energy efficiency, much effort was also made to reduce construction costs. One example of the design measures is the use of a highly insulating exterior wall assembly that integrates rigid insulation between two rows of wall studs as interior air and vapour barriers.
This monitoring study aims to generate data on long-term performance as part of FPInnovations’ effort to assist the building sector in developing durable and energy efficient wood-based buildings, which is expected to translate into reduced energy consumption and carbon emissions from the built environment. The monitoring focuses on measuring moisture performance of the building envelope (i.e., exterior walls, roof, and sill plates); indoor environmental quality including temperature, humidity, and CO2; and vertical differential movement between exterior walls and interior walls below roof/roof decks. In total, 79 instruments were installed during the construction.
The next steps of this study will focus on collecting and analysing data from the sensors installed, and assessing performance related to the building envelope and vertical differential movement. FPInnovations will also collaborate with CanmetENERGY of Natural Resources Canada to monitor heat recovery ventilators and to assess whole-building energy efficiency and occupant comfort. This is expected to start after the mechanical systems are fully commissioned during occupancy. Results of these upcoming phases of work will be published in future reports.
The idea that a wicking treatment – leaving tops, branches, and needles attached to the stem after felling – would reduce stem moisture content and lead to reduced loss of western hemlock logs from sinking during watering was tested. This study did not show that wicking produces a different result from normal bucking in average stem moisture content if both groups are treated equally. Further, after curing for two months logs did not increase in moisture content during watering.
Based on the data from this study and a literature review, there are two distinct trajectories for hemlock wood moisture content, depending on if the tree was felled before or after May. Hemlock trees felled before May gain the full benefit of spring drying according to the ambient conditions of their local micro-climate. Trees felled after May suffer from a physiological spike in moisture content that the tree generates to promote its growth and survive the summer soil drought.
Ce manuel assemble les renseignements existants sur la technologie du séchage des placages. Il est destiné aux opérateurs de séchoirs, aux contremaîtres et aux gérants. Il est conçu spécialement pour les usines de l'Est du Canada mais contient des références aux essences et aux méthodes de séchage couramment utilisées dans l'Ouest canadien. Les sujets suivants sont abordés dans ce manuel: humidité du placage, hydromètres, processus de séchage, types de séchoirs, opération et entretien des séchoirs, incendies, pollution et défauts des placages causés par le séchage.
Correction factors are provided for the Delmhorst resistance-type moisture meters equipped with 2-pin insulated electrodes. These factors allow the operator to adjust the meter reading for a wood temperature range of -40 degree centigrade to 50 degree centigrade. Factors are provided for 12 softwood species and 14 hardwood species.