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.
Methods for the analysis of boron in wood were reviewed and one, a method in which base titration of a mannitol/boron complex is done, was chosen for possible routine use. Method parameters were tested and the stages were modified to arrive at a routine which can determine boron content in wood within 5% accuracy. Hot water leaching of chip samples, 2.54 x 2.54 cm x 2 to 3 mm thick, of wood which has been given borate/antisapstain treatment is better than 95% efficient within four hours; this is as efficient as a ten-cycle extraction on a soxhlet apparatus. Using an automatic titrator, analysis for boron is done by titrating a mannitol complex of the boron in the extract. The simplicity, low expense, speed, and accuracy of this routine give it the advantage over several other methods. The aqueous extracts of wood, the mannitol reagent, and secondary components of boron treating formulations can all add to the apparent boron content of the wood sample; these factors are variable but generally total about 8 *g boric acid equivalent per cm2 of wood surface. The method is also suitable for the analysis of boron in heavily (preservative) treated wood.
Several problem areas exist for lumber manufacturers such as, application of antisapstain chemicals, hemlock brownstain and disposal of PRF resin used by wood lamination plants. The ability to monitor the application of antisapstain chemicals can prevent monetary claims against the industry and improve our credibility as a supplier. The mechanism by which hemlock brownstain occurs must be fully understood in order to control it. Lumber lamination plants must have a way of monitoring their waste PRF resin in order to meet provincial environmental regulations.
In an effort to ensure that all materials, products and assemblies are treated in an equitable manner, a very simplistic form of a risk assessment methodology was employed to determine the cost benefit of a three-storey business occupancy - combustible versus non-combustible construction (designed in compliance with BOCA requirements). Statistical data was used to determine the number of fire fatalities in both construction types and to provide the probabilistic values required as input for the decision tree. The number of fire fatalities was then multiplied by the dollar value assigned to demonstrate that the combustible office building does not pose a more serious threat to occupant safety than does the non-combustible office building. Further, in the event of a fire, since the combustible office building is less expensive to construct, it is more cost-effective than the non-combustible office building.
Didecyldimethylammonium chloride (DDAC) is a chemical commonly used in wood protection applications. The penetration of DDAC into wood has implications for efficacy as well as the development of surface analysis techniques such as Fourier transform infrared spectroscopy (FTIR). In order to gain a better understanding of the factors which affect the penetration of DDAC into wood, we saw a need for a technique which can be used to better define the distribution of DDAC within the wood. The technique developed in this project combines a microtome wood sampling procedure with a suitably modified version of Forintek's HPLC method for DDAC analysis. The detection limit was 500ng DDAC per sample vial, or 250ng per 32mm x 7mm x 100µm wood slice. The method was used to profile DDAC distribution in dip-treated wet and dry amabilis fir, Douglas fir, lodgepole pine and western hemlock sapwoods. For all samples tested, detectible DDAC penetration was found to be limited to less than 1mm below the surface. Dry samples were found to retain approximately twice as much DDAC as wet samples, and wet samples were found to retain a higher percentage of their total DDAC near the surface than dry samples. A follow-up study should be done using the techniques described in this paper to analyze DDAC penetration in a larger sample set. The study should compare DDAC penetration in dip, spray and pressure treatments, and should examine the relationship between the penetration of DDAC and other relevant chemicals such as borates and iodopropynylbutyl carbamate (IPBC).
Fourier Transform Infrared spectroscopy (FTIR) has been identified as a potential analytical method that might improve monitoring of sapstain control chemicals application in sawmills. The main benefit from use of this technique would be the ability to respond immediately to application problems identified. Based on preliminary laboratory data Bomem Inc., Forintek Canada Corp. (FCC) and the Pacific Forestry Centre (PFC) agreed to undertake research aimed at the development of FTIR for commercial application in sawmills. The first stage in this project was to validate the FTIR method in the laboratory. A protocol was agreed upon for a test which would determine the precision of the FTIR retention predictions on a variety of wood surfaces. Wood strips of rough, planed and intermediate surface texture were prepared. At FCC a technique was devised by which the wood strips were treated with known amounts of DDAC. Intermediate textured replicate samples were treated to known retentions of DDAC and sent to PFC to use in calibrating the FTIR instrument. Additionally, 20 replicates of each surface texture were treated with random amounts of DDAC over the range 0 - 200ug/cm squared. These "unknowns" were also sent to PFC for analyses by FTIR and prediction of DDAC retentions. Although correlation between actual and predicted DDAC retentions was linear within a particular surface texture, results show a mean difference or error between the actual (weight uptake) and FTIR determinations of DDAC retentions of 46% (standard deviation 28%). Therefore, overall, the FTIR analytical method gave unsatisfactory results. Our conclusion is that, based on the current calibration, the FTIR analytical method is not sufficiently accurate for general sawmill application. The surface texture of the wood being scanned significantly affected the retention of DDAC as determined by FTIR and corrections for surface texture would need to be incorporated into the software if further development was to be considered. Additionally, other variables than surface texture (e.g. formulation additives) may influence analytical results and were not considered in this study.