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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).

Carbon footprint residential building figure

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,

carbon emissions associated with the use of electricity equation
carbon emissions associated with the use of natural gas equation

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.

building system-based results on the carbon footprint figure

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).

Possible upgrades to reduce emission table

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!


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