and time needed in future to make any development in this field will be high (Adedeji & Reuben
& Olatoye, 2014). Buildings consume about 40% of the world’s energy and produce more than a
third of global carbon emissions (Medved, Domjan, & Arkar, 2019). Reducing carbon emissions
and achieving zero emissions in the construction sector are major parts of the road towards
a zero-emissions economy. To achieve this target, many new concepts in the building sector
are becoming more commonplace, such as zero-emission and nearly zero-emission buildings.
Zero-emissions buildings reduce their operational energy by upgrading the building envelope,
using efficient systems, and using renewables to cover the remaining required energy. The target
of achieving zero-emission buildings is achievable but challenging (Zabaneh, 2011). In a similar
definition, Ahmed et al. (2022) state that net-zero-emissions buildings are buildings that have
high operation energy efficiency, and this can be achieved by using a highly insulated envelope,
highly efficient heating and/or cooling systems, and low operation energy to operate the building
equipment as well as using passive techniques, then using renewables to cover the remaining
energy needed.
The EU has accomplished a remarkable reduction in carbon emissions in recent decades. In
2018, the Union’s carbon emissions had decreased by 23% compared to the 1990s emissions.
The EU targets achieving 40% by 2030 and becoming a zero-emissions economy by 2050
(Herold et al., 2019). The EU has published numerous directives across sectors to achieve this
target. In the building sector, the European Energy Performance of Buildings Directive (EPBD)
was adopted in 2010. The EPBD introduces the term nearly zero-emissions buildings (NZEB),
stating that all new builds should be NZEB by 2020 (Medved & Domjan, & Arkar, 2019). The UK
sets an ambitious target to reach zero emissions by 2050. In the UK, buildings account for 26%
of the country’s total GHG emissions, and homes are the major contributor, accounting for 77%
of the total buildings sector direct emissions. Only 15% of the UK residential building stock was
built after 1990. Therefore, the majority of this stock was built to meet low energy-efficiency
requirements. According to this, most UK homes need to be upgraded to improve their energy
efficiency (The House of Commons, 2019).
Specific steps are required to achieve NZEB in existing buildings: upgrade the building
envelope, install highly efficient equipment, and add renewable energy. Reaching NZEB in a new
building is a complicated process, but it is more complex in existing buildings (Torgal, 2013).
Many of the aspects applied in the new build to achieve NZEB could not be applied to existing
buildings because of their existing features, such as site, orientation, and building massing. All
these challenges complicate and problematize the target of achieving NZEB in existing buildings
(Menassa & Ortiz-Vega, 2013). One of the main challenges in refurbishing existing buildings to
achieve NZEB status is the high initial cost and long payback periods (Asadi et al., 2013). The
only way to justify the high cost of the energy-efficiency refurbishment is a reasonable payback
period (Menassa & Ortiz-Vega, 2013).
To reduce the overall environmental impact of the refurbishment, the three sustainability
pillars (environmental, social, and economic) should be considered. Sustainable refurbishment
can generate many benefits, such as reducing energy consumption/emissions, waste, and
water consumption, as well as improving the indoor environment. Moreover, using sustainable
materials during refurbishment is important for reducing the embodied energy of the process
(Chan, 2014). Construction materials should have a low environmental impact to improve the
environmental performance of the construction process. One of the tools used to measure the
product’s environmental performance is the Life Cycle Assessment (LCA), which measures the
product’s environmental impacts throughout the whole life of the product, starting from the
extraction of the raw materials to the production process, and then the use of the product and
ending with the product’s end of life (Passer et al., 2015). The Environmental Product Declaration
(EPD) system provides LCA data for different products, prepared by manufacturers and verified
by a third party (BRE Global, 2020).
This research suggests a process for refurbishing an existing house. It proposes different
sustainable alternatives and scenarios that will achieve nearly zero-emission criteria. These
scenarios will be evaluated by calculating the best payback periods.
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