A Case-Based Analysis Using the Wilden Living Lab

By Anber Rana and Piyaruwan Perera
PhD Students at UBC Okanagan

Downsizing the carbon footprint by selecting environmental friendly building energy systems can reduce regional carbon emissions and help put a stop to global warming. According to the research in the Wilden Living Lab (WLL), a 97% reduction of operational carbon emissions was estimated from the Home of Tomorrow compared to the Home of Today. 

As concerns associated with climate change become more drastic and frequent, the need to minimize human activities impacting climate has become essential. Carbon dioxide is the largest component of global greenhouse gas (GHG) emissions. GHG emissions are typically expressed as a common unit of global warming potential called Carbon dioxide equivalent (CO₂eq). This is used to represent the total carbon footprint associated with an activity (Brander, 2012).

Buildings are responsible for about 33% of the global GHG emissions according to a report from the United Nations Environment Program (UNEP, 2009). In Canada, 14% of GHG emissions are associated with the residential sector alone (NRCAn, 2016). The carbon footprint of residential buildings can be significantly reduced through the use of energy efficient materials, equipment and long-term use of renewable energy-based upgrades. A residential building’s carbon footprint depends on household characteristics such as the type of residence, energy system performance, vehicle performance, and users’ behavioural patterns (Perera et. al, 2018).

The residential building carbon footprint is associated with activities shown in Figure 1. A recent review on 251 case studies highlights the importance of operation phase related GHG emissions that are approximately 75% of the buildings total emissions (Schwartz et al ,2018).

Calculation of Operational Carbon footprint

Total carbon emissions of a residential building depend on the supply energy mix and the energy consumption of the residential activities. These parameters are used to derive the energy supply emission factors. In Canada, the emissions factors vary with the primary energy sources (Kikuchi, Bristow, & Kennedy, 2009). Unlike other provinces in Canada, British Columbia has low-emissions electricity supply since a major of power generated by the electrical grid comes from hydro-electric dams. Electricity emission factor is 2.80 kgCO₂eq./GJ whereas the emission factor of natural gas is 65.75 kgCO₂eq./GJ (BC Ministry of Environment, 2014).

Equations (1) and (2) are used to calculate carbon emissions associated with the use of electricity and natural gas respectively,

Operational carbon emissions for building systems in the Wilden Living Lab

Since the operational phase of a dwelling is considered as a major contributor to the life cycle carbon footprint, the operational carbon footprint of both houses within the Wilden Living Lab were evaluated in this study. An energy simulation model developed on HOT2000 was calibrated using actual data obtained from both homes. The human behaviours were nullified using fixed parameters in both home of today (HOD) and home of tomorrow (HOM) models. The natural gas and electricity use determined through the software was used to evaluate the carbon footprints of individual energy systems. Figure 2 shows the building system-based results on the carbon footprint.

Table 1 shows the energy savings and emission reductions for different building systems in both homes. The highest carbon emission in HOD is from space heating and cooling activities using the natural gas (NG)-based heating, ventilation, and air conditioning (HVAC) system, while for HOM the highest carbon emissions are from lighting and appliances. It has been observed that upgrading HVAC systems using a state-of-the-art geo-source heat pump-based HVAC system will reduce a major percentage of the existing environmental impacts (reduce by 96.7%). However, the capital and operational costs of geo-source heat pump-based HVAC system could be higher than the conventional NG-based HVAC system. Moreover, replacing the existing HVAC system with new geo-source heat pump-based HVAC system may not practical for conventional households with conventional HVAC systems. Therefore, it is vital to check the practicability of installation and determine the eco-efficiency of alternative building energy system upgrades at the upgrade selection process (Eco efficiency can be defined as units of value generation per unit of environmental impacts (Brattebø 2005)). The total operational carbon footprint of HOD during the use phase is 5,746 kgCO₂eq/year and for HOM it is 157 kgCO₂eq/year (which is a 97% reduction in environmental impacts).

Be advised the carbon footprint calculated for use-phase does not include the carbon attributed by other household activities (building-related transportation, embodiment energies for replacement and maintenance, etc.), but this result can help in determining the relative carbon footprint impacts of different energy systems.

Stay posted for more real-life data results in the future. In next month’s issue, we’ll talk about energy efficiency changes based on indoor temperature set-points!

References:

• BC Ministry of Environment. (2014). BC Best Practices Methodology for Quantifying Greenhouse Gas Emissions. Victoria.

• Brander, M., (2012). Greenhouse Gases, CO₂, CO₂e, and Carbon:What Do All These Terms Mean? Retrieved December 11, 2018, from https://ecometrica.com/assets/GHGs-CO2-CO2e-and-Carbon-What-Do-These-Mean-v2.1.pdf

• Brattebø, Helge. 2005. “Toward a Methods. Framework for Eco-Efficiency Analysis?” Journal of Industrial Ecology 9 (4): 9–11. https://onlinelibrary.wiley.com/doi/abs/10.1162/108819805775247837.

• Kikuchi, E., Bristow, D., & Kennedy, C. A. (2009). Evaluation of region-specific residential energy systems for GHG reductions: Case studies in Canadian cities. Energy Policy, 37(4), 1257–1266. https://doi.org/10.1016/j.enpol.2008.11.004

• Perera, Piyaruwan, Kasun Hewage, M. Shahria Alam, Walter Mèrida, and Rehan Sadiq. Scenario-based economic and environmental analysis of clean energy incentives for households in Canada: Multi criteria decision making approach. Journal of cleaner production 198 (2018): 170-186. https://doi.org/10.1016/j.jclepro.2018.07.014

• NRCan, 2016. Improving energy performance in Canada
  Retrieved March 12, 2019, from https://www.nrcan.gc.ca/sites/www.nrcan.gc.ca/files/energy/pdf/trends2013.pdf

• Retrieved December 11, 2018, from https://ecometrica.com/assets/GHGs-CO2-CO2e-and-Carbon- What-Do-These-Mean-v2.1.pdf

• Schwartz, Y., Raslan, R. and Mumovic, D., 2018. The life cycle carbon footprint of refurbished and new buildings–A systematic review of case studies. Renewable and Sustainable Energy Reviews, 81, pp.231-241. https://doi.org/10.1016/j.rser.2017.07.061

• UNEP-SBCI, “Buildings and Climate Change: Summary for Decision Makers,” Buildings and Climate Change: Summary for Decision-Makers, pp. 1–62, 2009.