The objective of this project was to quantify and compare the environmental impacts associated with alternative designs for a typical North American mid-rise office building. Two scenarios were considered; a traditional cast-in-place, reinforced concrete frame and a laminated timber hybrid design, which utilized engineered wood products (cross-laminated timber (CLT) and glulam). The boundary of the quantitative analysis was cradle-to-construction site gate and encompassed the structural support system and the building enclosure. Floor plans, elevations, material quantities, and structural loads associated with a five-storey concrete-framed building design were obtained from issued-for-construction drawings. A functionally equivalent, laminated timber hybrid design was conceived, based on Canadian Building Code requirements. Design values for locally produced CLT panels were established from in-house material testing. Primary data collected from a pilot-scale manufacturing facility was used to develop the life cycle inventory for CLT, whereas secondary sources were referenced for other construction materials. The TRACI characterization methodology was employed to translate inventory flows into impact indicators. The results indicated that the laminated timber building design offered a lower environmental impact in 10 of 11 assessment categories. The cradle-to-gate process energy was found to be nearly identical in both design scenarios (3.5 GJ/m2), whereas the cumulative embodied energy (feedstock plus process) of construction materials was estimated to be 8.2 and 4.6 GJ/m2 for the timber and concrete designs, respectively; which indicated an increased availability of readily accessible potential energy stored within the building materials of the timber alternative.
Many actions have been taken to decrease the operational energy use in buildings. However, with higher energy efficiency standards, the focus is increasingly shifting to energy demand for the production of building materials and the related greenhouse gas emissions. When moving towards zero emission buildings, the developments of more sustainable bearing structure are of interest. A six story housing complex was constructed in Gothenburg, Sweden in 2012 with a structure made of laminated veneer lumber floor elements and glue laminated beams and columns. The use of laminated veneer lumber has the advantage of being a light weight solution.
Building with wood in Norway is generally regarded as a carbon efficient solution, but the impact of additional materials such as glue and insulation can influence the overall results is of interest. Life cycle assessment is used as a tool to calculate the carbon footprint in the production of the main building materials of the structure. The goal of the assessment is to compare the wood structure as built with an equivalent steel and concrete structure and to optimise the use of materials. The scope of the assessment includes the foundation and elevator shaft, structural beams and columns and the floor elements. The results indicate that the steel and concrete alternative have about 35% higher greenhouse gas (GHG) emissions than the as built wood solution, but that almost half of the total emissions are related to the foundation and elevator shaft.
FP Innovations engaged the Athena Institute to complete a cradle-to-gate life cycle assessment of Canadian average cross-laminated timber (CLT) manufacture. The cradle-to-gate analysis included primary LCI data collection for the CLT production process that included all material resources, ancillary and energy input flows entering the CLT production facility as well as all emissions to air, water and land associated with the production of the finished product.
Australian Life Cycle Assessment Society conference
Research Status
Complete
Summary
The use of timber construction products and their environmental impacts is growing in Europe. This paper examines the LCA approach adopted in the European CEN/TC350 standards, which are expected to improve the comparability and availability of Environmental Product Declarations (EPDs). The embodied energy and carbon (EE and EC) of timber products is discussed quantitatively, with a case study of the Forte building illustrating the significance of End-of-Life (EoL) impacts. The relative importance of timber in the context of all construction materials is analysed using a new LCA tool, Butterfly. The tool calculates EE and EC at each life cycle stage, and results show that timber products are likely to account for the bulk of the EoL impacts for a typical UK domestic building.
The building sector is increasingly identified as being energy and carbon intensive. Although the majority of emissions are linked to energy usage during the operation part of a building's life cycle, choice of construction materials could play a significant role in reducing greenhouse gas emissions and other environmental end-point damages. Increasing the use of wood products in buildings may contribute to the solution, but their environmental impacts are difficult to assess and quantify because they depend on a variety of uncertain parameters. The present cradle-to-gate life-cycle analysis (LCA) focuses exclusively on a glued-laminated wood product (glulam) produced from North American boreal forests located in the province of Quebec, Canada. This study uses primary data to quantify the environmental impacts of all necessary stages of products' life cycle, from harvesting the primary resources, to manufacturing the transformed product into glulam. The functional unit is 1 m3 of glulam. This is the first study based on primary data pertaining to Quebec's boreal forest. Quebec's boreal glulam manufacturing was compared with two other LCAs on glulam in Europe and the United States. Our results show that Quebec's glulam has a significantly smaller environmental footprint than what is reported in the literature. From an LCA perspective, there is a significant advantage to producing glulam in Quebec, compared with the European and American contexts. The same holds true in regard to the four end-point damage categories.
Report Summary: A Comparative Life Cycle Assessment of Two Multistory Residential Buildings: Cross-Laminated Timber vs. Concrete Slab and Column with Light Gauge Steel Walls
This short report summarizes a life cycle assessment (LCA) study comparing a cross-laminated timber mid-rise building to the same building in concrete1. For more detail, refer to the original report which was the product of a rigorous, comparative LCA research project that complied with the international LCA standard ISO 14040:2006. In that study an apartment building in Quebec City, Canada was analyzed using two different building systems in order to understand the environmental footprint of each relative to the other. A LCA model was developed for a real, 4060 m2, 4-storey, cross-laminated timber (CLT) apartment building. The same building was then designed using reinforced concrete slabs and columns with light gauge steel stud walls. That design was intended as a building system that CLT would likely be compared with in the midrise construction market where CLT is likely to compete.
Report Summary: A Comparative Life Cycle Assessment of Two Multistory Residential Buildings: Cross-Laminated Timber vs. Concrete Slab and Column with Light Gauge Steel Walls
This short report summarizes a life cycle assessment (LCA) study comparing a cross-laminated timber mid-rise building to the same building in concrete1. For more detail, refer to the original report which was the product of a rigorous, comparative LCA research project that complied with the international LCA standard ISO 14040:2006. In that study an apartment building in Quebec City, Canada was analyzed using two different building systems in order to understand the environmental footprint of each relative to the other. A LCA model was developed for a real, 4060 m2, 4-storey, cross-laminated timber (CLT) apartment building. The same building was then designed using reinforced concrete slabs and columns with light gauge steel stud walls. That design was intended as a building system that CLT would likely be compared with in the midrise construction market where CLT is likely to compete.
Lend Lease is constructing a new residential building using cross laminated timber (CLT). This material is a relatively new building material in Australia, which has found increased use in multi-story residential and commercial buildings, particularly in Europe. The Centre for Design (CfD), School of Architecture and Design, RMIT University was commissioned by Lend Lease through Forest and Wood Products Australia (FWPA), to investigate the environmental performance associated with the production of the materials, along with HVAC and lighting systems, and associated operation and end-of-life of this novel building, using a life cycle approach.
Life Cycle Assessment (LCA) has been used as the core method for determining the potential environmental impacts of the products considered. LCA has been applied in accordance with ISO 14040:2006. Data on the building materials quantities and construction details were supplied by Lend Lease, background life cycle inventory data was gathered from Australian (AUPLCI) and European (Ecoinvent) databases. Data on cross laminated timber was provided by the manufacturer in an Environmental Product Declaration (EPD). Annual operational energy use for the Forté and the reference buildings were calculated using the dynamic building energy simulation software tool ApacheSim. The simulation results for residential spaces were validated against results from an Accurate assessment.
A Comparative Life Cycle Assessment of Two Multistory Residential Buildings: Cross-Laminated Timber Vs. Concrete Slab and Column with Light Gauge Steel Walls
This study provides a comparative life cycle assessment (LCA) of a 4060 m2, 4-storey cross laminated timber (CLT) apartment building located in Quebec City, Canada and an equivalently designed building consisting of reinforced concrete slabs and columns with light gauge steel studded walls (CSSW). The emergence of CLT as a structural material that can be used in mid-rise building structures combined with limited work investigating the environmental performance of CLT in building applications provides the motivation for this comparative study.
International Design Engineering Technical Conferences and Computers and Information in Engineering Conference
Research Status
Complete
Notes
August 4–7, 2013, Portland, Oregon, USA
Summary
As sustainable building design practices become more prevalent in today’s construction market, designers are looking to alternative materials for novel design strategies. This paper presents a case study comparing the sustainability performance of cross laminated timber (CLT) and reinforced concrete. A comparative sustainability assessment of cross laminated timber and concrete, considering economic, environmental, and social aspects was performed. Environmental impact is measured in terms of CO2 equivalent, economic impact is measured with total sector cost (including sector interdependencies), and qualitative metrics were considered for social impact. In order to conduct an accurate performance comparison, a functional unit of building facade volume was chosen for each product. For this paper, several end-of-life strategies were modeled for CLT and concrete facades. To understand environmental, economic, and social impact, three different scenarios were analyzed to compare performance of both CLT and concrete, including cradle to gate product manufacturing, manufacturing with landfill end-of-life, and manufacturing with recycling end-of-life. Environmental LCA was modeled using GaBi 5.0 Education Edition, which includes its own database for elements including materials, processes, and transportation. To compare the economic impact, Carnegie Mellon’s EIO-LCA online tool is used. Finally, social life cycle impact was considered by identifying process attributes of both products that affect the social domain. Based on this analysis, the use of CLT has a significantly lower environmental impact than concrete, however there are additional costs.
