Cross Laminated Timber (CLT) is an extremely strong engineered wood panel intended for roof, floor, or wall applications. Currently there is little research comparing CLT to steel and concrete, materials CLT hopes to replace This research uses a detailed literary analysis on CLT and case study on Carbon12, a recently constructed CLT structure in Portland, Oregon, to compare the cost and schedule requirements of CLT with a cast-in-place concrete slab. The case study consisted of a detailed analysis of Carbon12, interview with Scott Noble, senior project manager for Carbon12, and a detailed schedule and cost analysis. Results showed that for a concrete floor system used on Carbon12, material costs were far less than costs for a CLT floor system and labor costs were far greater than costs for a CLT floor system. For the schedule analysis, results showed that a concrete floor system would add an additional 10 weeks to the construction schedule of Carbon12. These results led to the conclusion that CLT is a feasible building material for dense, urban, mid-rise structures similar to Carbon12. The quick installation time, small crew, and environmental benefits of CLT outweigh the added costs of the material.
Cross-laminated timbers (CLTs) are strong and lightweight structural building materials. CLTs are made from renewable wood resources and have significant economic potential as a new value-added product for the United States. However, market penetration has been obstructed by product affordability and lack of availability for use. Previous studies and projects have surveyed opinions of designers and contractors about the adoption of CLTs. No previous study was found that surveyed cost estimators, who serve the essential function of creating economic comparisons of alternative materials in commercial construction. CLTs are not included in these current cost estimation tools and software packages which may be limiting the potential use of CLT in construction.
The purpose of this study was to discover if cost estimation is being used to make structural decisions potentially affecting the marketability of CLT use in construction and building design because of the ability to estimate CLTs adequately. Through the use of a survey, the re-designing of a building, and discussions with subject matter experts, this study examined the knowledge level of cross-laminated timbers of under-surveyed building construction professions and the relationship between cost estimation and structural material choices. Their responses are demonstrating the need for better cost estimation tools for cross-laminated timbers such as inclusion in the Construction Specifications Institute's classification systems in order for CLTs to become a more competitive product. The study concluded that cost estimation is important for CLT market development, because it is being used extensively in the construction industry.
Traditionally, mid-rise buildings, typically 6-12 stories in height, have used concrete and steel as
structural materials. Recent advancements in engineered wood products, as well as increased concerns for environmental impacts, such as carbon emissions, are driving interest in utilizing mass timber as the primary structural system for mid-rise buildings, particularly residential projects in British Columbia. Demonstration projects like UBC Brock Commons Tallwood Building have showcased the feasibility and opportunities of mass timber structural systems, and anticipated changes to the national and provincial building codes could facilitate the development of mass timber buildings up to twelve stories in the near future.
The City of Vancouver is the regulating body for the building construction in Vancouver and as such, is developing policies that could incorporate considerations for building mid-rise mass timber buildings. While there has been a significant amount of well-documented research on the characteristics and performance of mass timber products and structural systems, there has been less on the cost implications and affordability factors of mass timber buildings above six stories. Cost is a major driver and constraint for decisions at every stage of building projects, from planning through operations, and the lack of information is an area of uncertainty in the widespread adoption of mass timber as a primary building construction material.
This study, Literature review of cost information on mid-rise, mass-timber building projects, was initiated by the City of Vancouver’s Sustainability Department, and was undertaken in the summer of 2019 by the University of British Columbia’s Sustainability Initiative. The study aims to develop an understanding of various cost indicators and the data available in the literature to identify evidential support for the benefits of mass timber construction. The results may inform the City of Vancouver on the current trends, knowledge gaps and future research identified in the literature, and serve as a starting point in collecting cost relevant information for policy and regulations.
The research presents a Carbon Value Engineering framework. This is a quantitative value analysis method, which not only estimates cost but also considers the carbon impact of alternative design solutions. It is primarily concerned with reducing cost and carbon impacts of developed design projects; that is, projects where the design is already a completed to a stage where a Bill of Quantity (BoQ) is available, material quantities are known, and technical understanding of the building is developed.
This research demonstrates that adopting this integrated carbon and cost method was able to reduce embodied carbon emissions by 63-267 kgCO2-e/m2 (8-36%) when maintaining a concrete frame, and 72-427 kgCO2-e/m2 (10-57%) when switching to a more novel whole timber frame. With a GFA of 43,229 m2 these savings equate to an overall reduction of embodied carbon in the order of 2,723 – 18,459 tonnes of CO2-e. Costs savings for both alternatives were in the order of $127/m2 which equates to a 10% reduction in capital cost.
For comparison purposes the case study was also tested with a high-performance façade. This reduced lifecycle carbon emissions in the order of 255 kgCO2-e/m2, over 50 years, but at an additional capital cost, due to the extra materials. What this means is strategies to reduce embodied carbon even late in the design stage can provide carbon savings comparable, and even greater than, more traditional strategies to reduce operational emissions over a building’s effective life.
This paper aims to develop an artificial neural network (ANN) to predict the energy consumption and cost of cross laminated timber (CLT) office buildings in severe cold regions during the early stage of architectural design. Eleven variables were selected as input variables including...
The Task Group on Combustible Construction is in the process of evaluating a proposed code change request related to buildings of encapsulated mass timber construction (EMTC). As part of the analysis of the code change request, an impact analysis is required that includes a cost-benefit analysis.
Hanscomb was hired to provide a cost-benefit analysis and to compare the estimated value of the following:
1. The cost of constructing a building of mass timber (unprotected) versus a building constructed of encapsulated mass timber (e.g. mass timber protected with a double layer of Type X gypsum board) versus a traditional concrete and steel building.
2. The time to build a building of mass timber construction (unprotected) versus a building of encapsulated mass timber construction versus a traditional concrete and steel building.
3. The annual maintenance costs of building of mass timber construction versus a building of encapsulated mass timber construction versus a traditional concrete and steel building.
For the purposes of this study two sets of conceptual floor plans and elevations have been created:
1. A 12 storey building with a Group C major occupancy (residential) where each storey is 6,000 m2 in floor area.
2. A 12 storey building with a Group D major occupancy (office) where each storey is 7,200 m2 in floor area.
Recent changes to the National Building Code of Canada (NBC), and a trend towards more diversified housing options, have meant that many Canadian jurisdictions are acting quickly to capture the environmental, economic and social benefits of higher wood buildings. The 2015 NBC now permits wood frame construction to be 6 storeys high. Today, already 75% of Canadians live in jurisdictions that allow 6 storey wood frame construction. With the overall benefits of using wood as a building material well documented, Atlantic WoodWORKS!
studied the opportunities for 6 storey wood construction in Atlantic Canadian Centres. The research included a comprehensive market study and projections for mid-rise demand in
four major centres in Atlantic Canada, a review of recent and upcoming planning changes in major Atlantic Canadian cities and a full cost analysis, comparing wood construction to three
other construction methods in use in the Atlantic market using a real-life wood mid-rise structure built by an experienced builder.