Commercial and multi-family residential construction represents a growth area for the Canadian wood products industry. To capitalize on this opportunity, a thorough understanding of the necessary products and system attributes will be essential. Adequate levels of noise/sound control in multi-family buildings are mandatory requirements of building codes in Canada, the United States, Europe, and most developed Asian countries. In many jurisdictions, these requirements are as strictly enforced as those for structural sufficiency and fire safety. Much effort has been spent on evaluation of sound transmission class (STC) and impact sound insulation class (IIC) of floor and wall assemblies and on studies of flanking transmission in multi-family dwellings in Canada. However, continuing occupant complaints of poor acoustic performance in wood-frame buildings that appear to have been built according to wall and floor construction practices recommended in building codes suggest the existence of gaps in current noise control techniques.
Forintek initiated this project to investigate the relative importance of noise transmission in wood-frame residential buildings in comparison with other building serviceability issues, and to conduct a pilot study to examine construction designs of wood-frame buildings that exhibit unsatisfactory and satisfactory noise control and to identify existing gaps in current noise control techniques.
A literature review and survey of 123 occupants of wood-framed multi- and single-family residential buildings was conducted to determine the relative importance of noise transmission in comparison with other building serviceability attributes. Case studies were conducted on construction details and designs of six new wood-frame condominiums and one single family-house that were built according to code requirements and recommendations for controlling noise transmission.
We found that the general public had high expectations regarding adequate acoustic privacy. Even single- family house builders considered low sound transmission important. The multi-family building occupants ranked “sound insulation” the most “important” serviceability attribute, while single-family occupants were most concerned with “water penetration and condensation”. The lowest level of “satisfaction” was given by all respondents to “noise transmission” for their current residences, including single-family occupants, who had ranked it as not being so “important”. The case studies revealed that, current construction practices were much more effective in controlling airborne sound transmission than impact noise. The footfall noise transmission from stairs through the walls is still an unresolved issue that is not considered in the current Canadian Building Code. The low frequency footfall noise transmission between vertically-stacked units was the common complaint in some of these buildings. With no requirement for impact sound insulation in the current National Building Code of Canada, and with our existing knowledge gap concerning low frequency footfall noise transmission problems and solutions to control them, builders, acoustics consultants and design engineers have simply tended to blame wood building materials for noise-related complaints.
We concluded that if we are to satisfy the occupants of both single-and multi-family wood-frame buildings and to provide confidence for builders and design engineers in wood-frame construction with satisfactory acoustic performance, a much greater effort is needed to improve sound insulation including development of better sound insulated wood-frame systems and building materials as well as retrofitting techniques. Acoustic performance will be a critical factor for the wood products industry in gaining a greater share of the multi-family construction market and in competing with other building materials.
Hardwood Initiative - Part 5: Development of new processes and technologies in the hardwood industry (Project 16) ; Testing the impacts of tree and stand attributes on the variability of acoustic velocity in standing trees (ST300) and logs (HM200)
Transformative Technologies Program ; Project No. TT5.15
Hardwood Initiative Project is based on two paradigms. First, the end-use potential and value of a wood product basket can be determined by the properties of its wood and should be quantified as much as possible before trees are harvested. Second, as the correlations between site conditions and wood fibre attributes can be changed by silvicultural treatments, it would be possible to optimize the wood production in terms of quantity and quality through a better understanding of silvicultural impacts on changes in wood fibre properties. This document presents the preliminary results of a research component of the project related to acoustic velocity. It focuses on testing the impacts of tree and stand attributes on the variability of non-destructive velocity (ST300 non-destructive measurement in standing tree) and of destructive velocity (HM200 destructive measurement in log). The acoustic measurements were conducted in 30 plots of sugar maple mixed with yellow birch in New Brunswick. Among the trees measured, 64 trees have been subjected to both non-destructive and destructive velocity measurement. Regression analysis by mixed model showed no significant impact of stand attributes (stand basal area and stand height) on the variation of both velocities. In addition, the defects represented by stem deformation, hole, split, wound, and stump swelling, had no significant impact on both velocities. By cons, the test showed a significant correlation between both velocities and dbh and light crown area of the tree. Non-destructive velocity was better explained by dbh and light crown than the destructive velocity. These results open the potential to produce an equation to predict the non-destructive acoustic velocity of the tree using simple tree attributes (e.g., dbh and light crown) as predictors, and to prescribe the thinning intensity for a desired level of velocity and then a desired level of wood density or stiffness.
Full title: Hardwood Initiative - Part 5: Development of new processes and technologies in the hardwood industry (Project 16) : Testing the impacts of tree and stand attributes on the variability of acoustic velocity in standing trees (ST300) and logs (HM200)
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.