Build greener buildings | University of Nevada, Reno


An assistant professor in the Department of Mining and Metallurgical Engineering has been busy collecting and analyzing data for the past two years. Ehsan Vahidi, John N. Butler Endowed Professor of Extractive Metallurgy, wants to find ways to build a greener country.

Reducing greenhouse gas emissions is largely about determining where mitigation will have the greatest impact. This requires a staggering amount of data, as Vahidi needed to understand the amount of emissions from different types of buildings in different industries in different states with different building codes in different climates using projected and ambitious mitigation strategies for buildings that have been built and that have not yet been built. to build. All of these variables add up.

“I worked almost twelve hours a day for two years,” Vahidi said. But the results suggest that by implementing tailored mitigation strategies, projected emissions could be reduced by up to 9.4 gigatonnes of carbon dioxide through 2050.

The International Code Council (ICC) develops building codes and US states adhere to 2009 codes or 2015 codes. Nevada has adopted the most recent 2015 codes for commercial and residential building types. The 2015 codes prescribe more energy-efficient materials, and if these codes are adopted nationwide for both building types, it would bring reductions closer to the ambitious projections identified in Vahidi’s work.

The before and after of the impacts on emissions

Buildings have two types of impacts: embodied and exploitative. Embodied impacts are composed of greenhouse gas emissions generated during construction (including the development of materials such as concrete). Operational impacts, which are made up of the emissions produced by living or operating the building for 50 years, consist largely of energy costs.

Embedded emissions mitigation efforts have great potential, and one of the major contributors to embodied emissions is the production of concrete. Vahidi details the potential for reducing emissions from concrete production and approaching net zero goals, using new technologies such as carbon capture and sequestration (CCS) and carbon capture and utilization (CCU) . CCS is made of concrete which collects carbon from the atmosphere and stores it, while CCU technology collects carbon from the atmosphere and uses this carbon to reinforce the concrete. Several cement plants in the United States and Canada have implemented CCU technology in combination with synthetic aggregates and found that it could be a solution to achieving net zero concrete mixes by 2050.

Supplemental Concrete Materials (SCM) contain waste from other industries such as steelmaking slag and fly ash generated in power plant boilers, simultaneously reducing landfill waste and the need for extract materials. Recent work by Vahidi concluded that changes to concrete production and concrete construction and pavement systems could reduce embodied emissions by 50% by 2050.

“Each region, each state and even each county has its own way of going down the path of decarbonization,” Vahidi said. “The first step was to model individual buildings in different areas. Building types have been grouped based on energy use and design. »

Ehsan Vahidi spent two years collecting data to analyze greenhouse gas emissions in the construction industry.

To better model current and future building emissions, Vahidi and his colleagues determined four main types of buildings they would analyze: single-family residential, multi-family residential, mid-rise offices, and ambulatory care buildings. Each region has different growth rates for different building types. The West has more single-family homes being built, and the East and South have more industrial buildings in the pipeline. Consideration of these regional differences is important for projections of incorporated impacts.

Vahidi’s research focused on 14 different subclimatic zones in the United States defined by the ICC. Each area requires different building materials and thermal insulation, with climates ranging from the heat and humidity of Miami, Florida, to the winter cold of Duluth, Minnesota. He then looked at what construction materials are used for different types of buildings in this area. For example, a single-family home in Minnesota might be built with a wood frame with specific insulation requirements for wall, roof, and foundation materials, while a single-family home in Florida would likely be made of a concrete frame to withstand hurricanes. – high winds. Using this data, Vahidi and his colleagues were able to estimate the environmental cost of each type of building, right down to nails and paint.

One of the main emission reduction targets identified in the document was the power grid. In the western United States, emissions reductions are expected to be lower than in other parts of the United States because emissions in the west are already relatively low, so there is less room for reduction. improvement. This is due to the generalization of renewable energies to supply the electrical networks. Nevada, for example, has access to geothermal energy. Greening the grid in the central United States would lead to significant reductions in greenhouse gas emissions. Projections from the US Energy Information Administration show that as central US states move away from coal-fired power plants, they have the greatest potential for reducing carbon emissions.

Green mining efforts

Vahidi’s research has shown that by mitigating carbon emissions in the building industry, 26-30% of the total emissions reduction predicted for the United States in the Paris Agreement can be achieved by 2050. .

“It’s promising for the construction industry,” Vahidi said.

Vahidi also mentioned that the centralization of emissions is important. As more and more vehicles on the road become hybrid or fully electric cars, this energy will come from the electrical grid, so decarbonizing the energy grid becomes important for non-building sectors as well. Additionally, energy can be imported from one region to another so that cleaner energy can be moved from a grid powered by wind turbines to a coal-powered grid.

Another project Vahidi is pursuing directly involves the mining industry. He is working with several mining operations to determine the environmental impacts of switching to electric mining trucks, taking into account the number of trucks mining operations have in their fleets, the distances the trucks travel daily and the lifespan of a mine, among other variables. Preliminary results of his research show a 6.2 gigatonne reduction in greenhouse gas emissions over 12 years at a single gold mine.

Further highlighting his efforts to decarbonize the mining and construction industries, Vahidi served as session chair on sustainable mining for the 127th meeting of the American Exploration and Mining Association (AEMA), where several other faculty members, alumni pupils and students presented their work.

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