This Report presents the results from experimental studies of the airborne sound transmission of mass timber assemblies, together with an explanation of the calculation procedures to predict the apparent sound transmission class (ASTC) rating between adjacent spaces in a building constructed of mass timber assemblies.
The experimental data which is the foundation for this Report includes the laboratory measured sound transmission loss of wall and floor assemblies constructed of Cross Laminated Timber (CLT), Nail-Laminated Timber (NLT) and Dowel-Laminated Timber (DLT), and the laboratory measured vibration reduction index between assemblies of junctions between CLT assemblies. The presentation of the measured data is combined with the presentation of the appropriate calculation procedures to determine the ASTC rating in buildings comprised of such assemblies along with numerous worked examples.
Several types of CLT constructions are commercially available in Canada, but this study focused on CLT assemblies with an adhesive applied between the faces of the timber elements in adjacent layers, but no adhesive bonding between the adjacent timber elements within a given layer. These CLT assemblies could be called “Face-Laminated CLT Assemblies” but are simply referred to as CLT assemblies in this Report. Another form of CLT assemblies does have adhesive applied between the faces of the timber elements in adjacent layers as well as adhesive to bond the adjacent timber elements within a given layer. These assemblies are referred to as “Fully-Bonded CLT Assemblies” in this Report. Because fully-bonded CLT assemblies have different properties than face-laminated CLT assemblies, the sound transmission data and predictions in this Report do not apply to fully-bonded CLT assemblies.
The 2015 edition of the National Building Code of Canada (NBCC) includes significant changes to the acoustic requirements for residential constructions. The 2015 edition defines the acoustic requirements in terms of the Apparent Sound Transmission Class (ASTC) rating which includes contributions from flanking transmission and therefore is a better descriptor of how well the sound insulation of a building will actually protect the inhabitants of the building from unwanted noise than the STC rating which was used in earlier editions of the NBCC. The 2015 NBCC requires an ASTC rating = 47 for constructions between dwelling units.
The ASTC rating that a construction will achieve depends on the design of the building elements including the gypsum board, the framing and the thermal insulation as well as the design of the junctions between the building elements. Changes to the building elements or the junctions will change the ASTC rating.
Fifty five examples of the calculation of the ASTC rating for typical mid-rise wood constructions (single and triple staggered wood stud walls and floors constructed of I-joists) with 15.9 mm (5/8”) SilentFX® QuickCut gypsum board, 15.9 mm CertainTeed Type X gypsum board and CertainTeed Sustainable fiberglass insulation are presented. All of the constructions shown in the examples have an ASTC rating which is greater than 47.
In addition to the examples for mid-rise wood framing, an example using 15.9 mm SilentFX® QuickCut gypsum board as a lining on a cross laminated timber (CLT) construction is also presented.
In recent years, the science and engineering for controlling sound transmission in buildings have shifted from a focus on individual assemblies such as walls or floors, to a focus on performance of the complete system. Standardized procedures for calculating the overall transmission, combined with standardized measurements to characterize sub-assemblies, provide much better prediction of sound transmission between adjacent indoor spaces. The International Standards Organization (ISO) has published a calculation method, ISO 15712-1 that uses laboratory test data for sub-assemblies such as walls and floors as inputs for a detailed procedure to calculate the expected sound transmission between adjacent rooms in a building. This standard works very well for some types of construction, but to use it in a North American context one must overcome two obstacles – incompatibility with the ASTM standards used by our construction industry, and low accuracy of its predictions for lightweight wood or steel frame construction. To bypass limitations of ISO 15712-1, this Guide explains how to merge ASTM and ISO test data in the ISO calculation procedure, and provides recommendations for applying extended measurement and calculation procedures for specific common types of construction. This Guide was developed in a project established by the National Research Council of Canada to support the transition of construction industry practice to using apparent sound transmission class (ASTC) for sound control objectives in the National Building Code of Canada (NBCC). However, the potential range of application goes beyond the minimum requirements of the NBCC – the Guide also facilitates design to provide enhanced sound insulation, and should be generally applicable to construction in both Canada and the USA. This publication contains a limited set of examples for several types of construction, to provide an introduction and overview of the ASTC calculation procedure. Additional examples and measurement data can be found in the companion documents to this Guide, namely NRC Research Reports RR-333 to RR-337. Furthermore, the calculation procedure outlined and illustrated in this Guide is also used by the software web application soundPATHS, which is available for free on the website of the National Research Council of Canada (see the references in Section 7 of this Guide for access details).
This article provides an overview of the code requirements pertinent to large cross-laminated timber (CLT) buildings and the methods for meeting the requirements in Canada. Canadian building codes are objective-based. Compliance with the code is achieved by directly applying the acceptable solutions up to certain prescriptive building sizes (height and area) or by developing alternative solutions beyond the height and area limits. The fire safety design for a CLT building larger than the prescriptive limit must demonstrate that the building will achieve at least the minimum level of performance afforded by noncombustible construction in limiting the structural involvement in fire and contribution to the growth and spread of fire during the time required for occupant evacuation and emergency responses.
This report is published as an addendum to NRC Research Report RR-335 “Apparent Sound Insulation in Cross-Laminated Timber Buildings." It is intended that this addendum will be merged with RR-335 in the future as a report for predicting the sound insulation in buildings using mass-timber constructions including NLT assemblies. This report presents the results from experimental studies of airborne sound transmission through assemblies of nail-laminated timber (NLT) with various linings. To put the data presented in this report in the proper context, this report begins with a brief explanation of calculation procedures to predict the apparent sound transmission class (ASTC) between adjacent spaces in a building whose structure is a combination of mass-timber assemblies such as nail-laminated timber (NLT) or cross-laminated timber (CLT) panels.
Recent architectural trends include the design and construction of increasingly tall buildings with structural components comprised of engineered wood referred to by names including; cross laminated timber (CLT), laminated veneer lumber (LVL), or glued laminated timber (Glulam). These buildings are cited for their advantages in sustainability resulting from the use of wood as a renewable construction material. Previous research has shown that timber elements contribute to the fuel load in buildings and can increase the initial fire growth rate – potentially overwhelming fire protection system and creating more severe conditions for occupants, emergency responders, and nearby properties.
The overarching goal of this project Fire Safety Challenges of Tall Wood Buildings Phase 2 (involving five tasks) is to quantify the contribution of CLT building elements (wall and/or floor-ceiling assemblies) in compartment fires and provide data to allow comparison of the performance of CLT systems against other building systems commonly used in tall buildings.
Client Report (National Research Council Canada. Construction)
In early 2018, with funding support from Natural Resources Canada and the Province of Ontario, the National Research Council of Canada conducted a series of room scale fire tests of Encapsulated Mass Timber Construction (EMTC). The goal of this test series is to further quantify the contribution of mass timber elements to fires and provide additional data for forming the technical basis for exposed mass timber elements in EMTC buildings without significantly increasing fire risks to life and property. The goal includes studying the fire performance of the 2nd generation cross-laminated timber (CLT) in resisting char layer fall-off, which could cause fire regrowth in the cooling phase of fully developed fires. The issues of char layer fall-off for the 1st generation CLT panels resulting in fire regrowth during the cooling phase of the fire were clearly revealed in the previous large scale CLT compartment fire tests under the auspices of the Fire Protection Research Foundation.
This Report presents the results from substantial experimental studies of sound transmission, together with an explanation of calculation procedures to predict the sound transmission between adjacent spaces in a building with wood-framed walls and floors. This Report presents two types of experimental data for wood-framed constructions:
- Test data for direct sound transmission through typical wood-framed wall assemblies and wood-framed floor assemblies, plus a summary of trends for such constructions and references to compilations of additional data
- Test data for flanking sound transmission measured following the procedures of ISO 10848 for coupled wall/floor junctions and wall/wall junctions
Worked examples for calculating the apparent sound transmission class (ASTC) rating between adjacent dwelling units are presented to illustrate how the experimental data can be applied.
This Report presents the results from experimental studies of airborne sound transmission, together with an explanation of calculation procedures to predict the apparent airborne sound transmission between adjacent spaces in a building whose construction is based on cross-laminated timber (CLT) panels.
There are several types of CLT constructions which are commercially available in Canada, but this study only focused on CLT panels that have adhesive between the faces of the timber elements in adjacent layers, but no adhesive bonding the adjacent timber elements within a given layer. There were noticeable gaps (up to 3 mm wide) between some of the timber elements comprising each layer of the CLT assembly. These CLT panels could be called "Face-Laminated CLT PAnels" but are simply referred to as CLT panels in this Report.
Another form of CLT panels has adhesive between the faces of the timber elements in adjacent layers as well as adhesive to bond the adjacent timber elements within a given layer. These are referred to as "Fully-Bonded CLT Panels" in this Report.
This report contains the transmission loss (TL) results measured in accordance with ASTM E90-09 and the normalized impact sound pressure level (NISPL) results measured in accordance with ASTM E492-09 of 13 cross-laminated timber (CLT) floor assemblies and 5 glulam floor assemblies. The report also contains the nonstandard impact sound pressure level results measured on 6 different small patch specimens.
Summary tables containing the specimen number, sketch, short description, the sound transmission class (STC) and impact isolation class (IIC) ratings, as well as, the page number of the detailed test reports are provided starting on page 5.
A brief analysis of the floors tested as part of this test series is provided after the summary tables on page 9. The standard test reports of the tested floor assemblies begin on page 16. The floor assemblies were built and tested between January and April 2016.