Construction Industry 2

This session looks at innovative approaches to assess building construction impacts that are typically overlooked in LCA.  Three of the presentations address the inclusion of use phase impacts; topics include the atmospheric NOx removal properties of titanium dioxide in concrete blocks, the inclusion of thermal performance of curtainwall systems, and the emission of VOC’s and semi VOC’s in flooring materials. A web-based platform for incorporating construction and embodied material impact data will also be presented.

Key Discussion Points:

1. Methods used to assess the net NOx emission associated with concrete paving blocks and eco-blocks (with and without TiO2).

2. The environmental performance and thermal behavior of two different curtain wall (CW) systems.

3. Web-based data collection and its use in whole building LCA.

4. The use-phase impact of chemicals encapsulated in flooring materials.

10:30 Md. Uzzal HossainMing-Zhi Guo and Chi Sun Poon

Comprehensive evaluation of NOx emissions associated with the manufacturing and use of TiO2 based eco-product by lifecycle assessment approach

ABSTRACT. Worldwide, the use of photocatalyst in the construction field has gained increasing attention recently. This is mainly due to the air-purification, self-cleaning, and bacteria inactivation potential of the photocatalytic process. The most common photocatalyst used with construction materials is nano titanium dioxide (TiO2) which can degrade organic and inorganic air pollutants by the photocatalytic process, especially nitrogen oxides (NOx) associated with combustion processes and vehicular emissions. By utilizing locally generated construction and demolition (C&D) wastes and waste glass and with the incorporation of a small quantity of nano TiO2, the authors’ research team has successfully developed eco paving blocks with self-cleaning and air purifying functions. However, there is lack of research on the comprehensive evaluation of the effectiveness of the TiO2 based concrete products by taking into consideration both the manufacturing and use phases of the photocatalytic products by lifecycle assessment (LCA) techniques. The present study was conducted to assess and compare the net NOx emission associated with the concrete paving normal blocks and eco-blocks (with and without TiO2) through a comprehensive LCA. The study results demonstrated that, within the ‘cradle-to-site’ system boundary (which includes raw material extraction/production, raw material collection and transport to blocks manufacturing site, blocks manufacturing, and transport of the produced blocks to use sites), eco-blocks had about 18% lower emission of NOx in comparison with normal blocks due to the use of recycled materials. The net NOx emission of eco-blocks with and without TiO2 was almost similar, as TiO2 contributes to the total NOx emission insignificantly (less than 0.5%).

In addition, for eco-blocks with a NOx degradation rate of 0.045 mg/h/kg eco-blocks (during its use phase), it was estimated that about 8 years of service life would be required to compensate for the total amount of manufacturing and transport related NOx emission. In contrary, no NOx removal function was observed for the normal blocks and eco-blocks without TiO2. The overall findings indicate that TiO2 based eco-blocks are more environmentally friendly both by reducing and removing significant amounts of NOx and re-utilizing a significant amount of C&D waste and waste glass to alleviate the burden on landfilling of the wastes.

10:45 Negar BadriGetachew Assefa and Caroline Hachem-Vermette

Energy and Environmental Performance of High-rise Office Facades: a life cycle study of Curtain wall systems for cold-climate region
SPEAKER: Negar Badri

ABSTRACT. Negar Badri (PhD Student in Faculty of Environmental Design, Calgary University, Canada) Getachew Assefa (Associate Professor in Faculty of Environmental Design, Calgary University, Canada)

Abstract: Due to global energy challenges, construction industry has improved a broad range of both practices and studies on energy efficiency of building envelope. Depending on thermal characteristics of building components, building envelope plays a major role in energy performance and thermal behavior of a building [1]. In addition to energy consumed by building in its operational phase, assembly of building envelope itself requires energy, materials, labor and equipment [2] in construction phase. This results in not only energy concerns but it also raises environmental issues such as emissions of air, water, soil pollutants. Notably, fewer studies in construction industry, have applied an integrated framework of energy and environmental analysis.

According to above-mentioned issue, this research aims to examine the life cycle environmental performance and thermal behavior of two different curtain wall (CW) systems, a typical aluminum frame CW and an integrated photovoltaic CW, applied to a hypothetical high-rise office in Canada. The paper applies a LCA method to evaluate the environmental impacts of CW systems in four different impact categories: Global Warming, Acidification, Eutrophication and Ozone depletion. Sima-pro 8.0.1 software (using Ecoinvent 3.0 Data base) is employed to develop life cycle inventory (LCI) of two models during a cradle to grave assessment. In addition, the study applies simulation method to feed the energy input of LCI software and to evaluate the energy performance of two façade systems.

The result from the modeling of two systems will help to identify the curtain wall system with more energy efficient performance and reduced environmental impacts. This provides a framework to identify the components of building envelope that result in improved thermal and environmental performance during the early stages of the design phase.

[1] IEA, Technology Roadmap: Energy-efficient Building Envelopes, International Energy Agency, 2013. [2] R. Azari, Integrated energy and environmental life cycle assessment of office envelopes, Energy and Buildings 82 (2014) 156-162.

11:00 Maggie Wildnauer and Christoph Koffler

Leveraging Web-Based Data Collection for Whole Building Life Cycle Assessments in the Design of Single Family Houses

ABSTRACT. Landmark Group of Companies first utilized LCA with a screening-level assessment to identify the hotspots within the Cradle-to-Gate construction of a single house. This informed the subsequent comparative Cradle-to-Grave assessment, which included supplier-specific data for some of the largest material contributors. Through the LCA model built from these projects, Landmark has positioned themselves to scale up their ability to quickly conduct LCAs on their houses. The initial screening level LCA showed that cement, engineered lumber, and insulation were the largest single contributors to the potential environmental impacts of a typical Landmark house. Supplier-specific data was collected using a web-based software tool and subsequently modeled in the LCA software. This fed into the comparative LCA, which quantified the environmental benefits of Landmark’s panelized construction system and ‘Net-Zero’ house design as compared to a conventional stick-built home. While a typical Landmark house and a traditional stick-built house were comparable over a 60 year operating period, improvements were seen both in the construction of the house and in the lifetime impact of the Net-Zero house. Using the developed LCA model, Landmark is now able to identify significant building materials with respect to environmental impact, quantify benefits of new building systems, and improve environmental footprint of their homes during the design phase. Additionally, Landmark uses web-based tool to collect and calculate the environmental impact of the 700 – 1000 construction sites under their control. For supply chain sustainability, Landmark leverages the same tool to collect product level data from suppliers in terms of energy, materials, emissions, etc. The data can then be used in the LCA software to perform a Cradle-to-Gate LCA of the product. Landmark required a solution to capture both the environmental impacts of the construction of their homes and the upstream supply chain impacts. Using the described combination of web-based data collection and LCA software, Landmark is able to understand the potential environmental impacts of all aspects related to the construction of its houses. This includes site-by-site capture of construction impacts as well as supply chain-specific environmental information, and ultimately allows for the continued environmental improvement of the houses constructed by Landmark.

11:15 Lei Huang and Olivier Jolliet

Quantifying the use-phase impact of chemicals in flooring materials

ABSTRACT. Traditional practices of life cycle assessment (LCA) have primarily focused on the impacts of outdoor emissions or emissions during the raw material extraction, manufacturing and disposal stage. However, studies have demonstrated that near-field chemical intakes during use phase may exceed environmentally mediated exposures and are therefore essential to be considered when assessing the impact across a product’s life cycle.

The present study characterized the use-phase impact of chemicals encapsulated in flooring materials, which is expected to be a major emission source in the indoor environment. A parsimonious model which describes the diffusive emissions of chemicals from materials and the subsequent loss by ventilation has been developed to calculate the chemical emissions from vinyl flooring. This model greatly simplifies previous models and is based solely on explicit equations, which is suitable for high-throughput calculations. The predicted emissions are then multiplied by an indoor inhalation intake factor to calculate the product intake fraction (PiF), which determines the fraction of a chemical in a product that is taken up by humans during its use phase. Inventory emission factors and human health impacts expressed in DALYs per functional unit were also calculated by incorporating the PiF and the initial chemical mass in the flooring material per functional unit.

Chemicals tested include 5 SVOCs (semi-volatile organic compounds) and 6 VOCs. For 1.5mm-thick vinyl flooring, the PiF via inhalation over 15 years ranges from 2·10-7 to 4·10-3. Average daily intakes are in the range of 10-5 to 10-3 mg/kg·day, which are close to the inhalation intakes from secondhand smoke for 4 of the 6 tested VOCs (10-4 to 10-2 mg/kg·day for formaldehyde, acetaldehyde, benzaldehyde and ethylbenzene). Moreover, the impacts of these indoor inhalation intakes are of the same order of magnitude as the respiratory effects of outdoor emissions. The PiF and daily intakes would be even higher if additional exposure pathways such as dermal absorption and hand-to-mouth ingestion are considered.

This study quantitatively evaluates the importance of indoor air emissions of chemicals encapsulated in flooring materials, which has been overlooked in LCA. The parsimonious emission model employed in this study can be easily used in high-throughput screening of the large amount of chemicals encapsulated in building materials and consumer products, which can enable LCA practitioners to identify the product ingredients contributing the most impact and to subsequently target them for improvement of product sustainability.