Creation of Net Zero Carbon Emissions Residential Buildings due to Energy use in the Mediterranean Region: Are they Feasible?
Mediterranean Agronomic Institute of Chania, Greece
Submission: February 17, 2020; Published: March 03, 2020
*Corresponding Author: John Vourdoubas, Mediterranean Agronomic Institute of Chania, Greece
How to cite this article: John Vourdoubas. Creation of Net Zero Carbon Emissions Residential Buildings due to Energy use in the Mediterranean Region: Are they Feasible?. Civil Eng Res J. 2020; 10(1): 555777.DOI:10.19080/CERJ.2019.09.555777
Creation of buildings with zero carbon footprint due to energy use is of primary importance for mitigation of climate change. The technical and economic feasibility of constructing carbon neutral residential buildings in the Mediterranean region has been investigated and the required sustainable energy technologies which can be used have been identified. A study of a carbon neutral residential building with a covered area of 120 m2 has been implemented and the required renewable energy systems have been sized. They include a solar thermal system, a solar photovoltaic system and a ground source heat pump. It is indicated that the use of endogenous renewable energy resources in this region can zero the net carbon emissions of residential buildings while the required technologies are mature, reliable and cost-effective. The installation cost of the required solar photovoltaic system for achieving carbon neutrality in the residential building due to life cycle energy consumption has been estimated at 5-10% of the initial construction cost which corresponds to between 59.84 €/m2 and 123.84 €/m2. The annual CO2 savings in the residential building have been estimated from 74 kgCO2/m2 to 134 kgCO2/m2. It is concluded that the creation of net zero carbon emissions buildings due to life cycle energy use in the Mediterranean region is technically and economically feasible and it should be promoted in the future with appropriate policies and incentives as well as with the removal of the existing barriers..
Buildings consume large amounts of energy and contribute to greenhouse gas (GHG) emissions into the atmosphere. The necessity to mitigate climate change requires the sharp decrease of their electricity and fossil fuel consumption. New EU regulations promoting nearly-zero energy buildings (NzEBs) have made the decrease of energy consumption obligatory in new buildings and the increase of energy efficiency in old buildings which should be refurbished. Additionally, to the operational energy usage, buildings consume energy during their construction, refurbishment and demolition, defined as embodied energy. When buildings’ operational energy consumption is reduced, the share of embodied energy in their total life cycle energy use is increased. Apart from the building sector, the challenge to reduce fossil fuel consumption in the transport sector necessitates the replacement of conventional vehicles, having internal combustion engines, with electric vehicles (EVs). The electric batteries of these vehicles can be recharged with solar electricity generated with solar photovoltaic (solar-PV) systems installed in residential buildings.
Solar energy is abundant in the Mediterranean region and it can
be used for heat and electricity generation with solar thermal and solar-PV systems. The required solar energy technologies are mature, reliable, cost-effective, and they are already used commercially in buildings and other applications. Promotion of net zero carbon emissions (NZCE) residential buildings in the Mediterranean basin, using locally available benign energy sources, for covering their embodied and operational energy needs as well as the energy required in residents’ electric cars could assist in the achievement of the global targets regarding carbon emissions reductions. Various existing barriers should be overcome for future promotion of NZCE buildings. The required sustainable energy technologies are cost-effective while the necessary legislative framework is favorable in many countries.
A calculation of the energy consumption and the carbon emissions in housing construction in Japan has been presented . The authors stated that the embodied energy of residential buildings depends on the type of construction and the materials
used. They estimated that their embodied energy varied between
833-8,777 KWh/m2 while their carbon emissions due to embodied
energy was at 250-850 kgCO2/m2. Energy consumption in
EU and Hellenic buildings has been reported . The authors
mentioned that total annual energy consumption in EU buildings
varied between 150-230 KWh/m2. They also stated that annual
residential energy uses per capita varied from 1,500-5,000 KWh/
capita in Southern Europe up to 8,000 KWh/capita in Northern
Europe. A study on the energy performance of existing dwellings
has been published . The authors mentioned that, in the EU,
the final energy consumption of the building sector corresponds
to 40.3% of the total EU-25 final energy use while the consumed
energy in dwellings corresponds to 25.4% of the total final
energy use. A study on energy consumption in buildings has been
published . The authors stated that energy consumption varies
significantly according to end uses among EU countries while the
largest share of energy consumption corresponds to use for airconditioning.
A report regarding the embodied carbon in buildings has been
released . It mentions that the impacts of embodied energy in
buildings become greater with the decrease of their operational
energy usage while increasing their thermal insulation has
minimal impacts on their embodied emissions. It also mentioned
that the concrete structure has the highest amount of embodied
carbon followed by steel and timber. An analysis on the life cycle
energy consumption of buildings has been published . The
authors mentioned that the life cycle primary energy requirement
of conventional residential buildings falls in the range of 150-400
KWh/m2y which includes both operating and embodied energy.
The operating energy corresponds to 80-90% of the total energy
used and the embodied energy to 10-20%. They also reported
that demolition energy has a negligible effect on the total energy
balance of the building. A report on the operating and embodied
energy of an Italian building has been published . The authors
emphasized the key issue of its embodied energy which is
particularly important in the case of low energy buildings. They
also pinpointed the difficulty in defining the reference area in the
building, including service and unheated zones and the absence
of an internationally accepted protocol for that. A life cycle energy
analysis in buildings has been implemented . With reference
to net zero energy buildings, where on-site renewable energy
generation covers the annual energy load, the authors mentioned
the increase of the share of embodied energy compared with
the operating energy. They stated that: a) in the last decades the
embodied energy in new buildings has slightly decreased and b)
the relative share of embodied energy to life cycle energy use has
significantly increased due to the sharp decrease in operating
energy consumption because of more strict energy regulations.
An investigation on the possibility of creating NZCE buildings
in Crete, Greece due to life cycle energy use has been made .
The author stated that the creation of net zero CO2 emissions
residential buildings due to life cycle energy use in Crete,
Greece does not have major difficulties and it could be achieved
relatively easily with the use of mature and reliable renewable
energy technologies. A review of current operating trends versus
embodied emissions in buildings has been published . The
authors stated that in order to mitigate climate change, buildings
must be designed and constructed with minimum environmental
impact. Total life cycle emissions from buildings are both due to
operating and embodied energy use. Considerable efforts have
been made to reduce operating emissions from buildings, but
little attention has been paid to embodied emissions. Therefore,
a critical review on the relation between operating and embodied
emissions is necessary in order to highlight the importance of
embodied emissions. A report on life cycle energy consumption
in net zero energy buildings has been released . The authors
stated that apart from the operating energy consumed during
the operation of the house, its embodied energy used during its
construction, refurbishment and demolition should be considered.
A comparison of a conventional house with a net zero energy
house has been performed . The authors have proposed the
use of energy saving systems, a solar water heater and solar-PV
panels in net zero energy houses. They indicated that many of
these sustainable energy systems are cost-effective. A presentation
of the myths and facts regarding zero energy and zero carbon
buildings has been made . The author stated that in recent
years these types of buildings have attracted much attention in
many countries although there is a lot of debate as to whether
their construction is feasible. He concluded that energy selfefficiency
in buildings can be achieved and zero energy and zero
carbon emissions buildings will soon become economically and
socially accepted. A report on net-positive energy buildings has
been released . The author stated that net-positive buildings
introduce several new design considerations and possibilities.
He mentioned that net-positive energy buildings involve energy
and economic exchanges and negotiations with power utilities. A
review of the research already published on low or zero carbon
emissions buildings has been published . The authors have
considered the use of renewable energy technologies, the use of
low carbon building materials, and the design and assessment
methods used. Among renewable energy technologies, they
mentioned wind turbines, solar-PVs, solar thermal collectors,
wood heating and high efficiency heat pumps. A holistic study on
the concept of zero energy buildings has been realized . The
author mentioned that firstly energy saving measures should be
considered, and secondly renewable energies should be utilized in
order to supply the required energy in the buildings. It was stated
that it is always easier to save energy than to produce it. It was
also suggested that indoor climate conditions should be defined in order to compare zero energy buildings (ZEBs) in different
locations. A critical look at zero energy buildings has been made
. The authors have defined four types of ZEBs as follows: (a)
Net zero site energy; (b) Net zero source energy; (c) Net zero
energy cost; and (d) Net zero energy emissions. They have also
commented on the advantages and disadvantages of each one of
them. A review on net zero energy buildings has been presented
. The authors stated that net zero energy buildings are the
future target in the design of buildings, and this requires a clear
and consistent definition of them, as well as a commonly agreed
methodology for their calculations.
A report on the feasibility of zero carbon homes in England
by 2016 from the perspective of house builders has been
published . The authors stated that achieving the targets for
carbon emissions in the UK by 2050, all industries, including the
housing sector, must reduce their carbon emissions. They found
that although zero carbon homes are technically feasible in the
long term, clear and concise actions are required from both the
government and the house building industry. A study on the
existing barriers for constructing zero carbon homes in the UK
has been realized . The authors mentioned that, from the
point of view of the construction industry, five barriers have
been identified which are categorized as economic, skills and
knowledge, industry, legislative and cultural. They stated that
although the barriers are more than the drivers in the zero-carbon
homebuilding industry, new policy mechanisms could overcome
them. A study on sustainable design for zero carbon architecture
has been made . The authors mentioned that zero carbon
homes (ZCBs) are expected to decrease their energy requirements
via effective “passive and active design solutions”, and secondly
by means of renewable energy systems to supply the remaining
energy demand. They also stated that the focus would be on the
“building’s envelope”. A study on the cost of carbon reduction
in new buildings has been reported . The study indicated
that an additional capital cost at 5-11% of the initial building’s
construction cost is required in order to achieve the zero carbon
emissions targets. A report concerning net zero carbon emissions
buildings has been published . The report mentioned that,
in new buildings, embodied energy has a share of approximately
50% of their life cycle energy consumption. It also stated that five
steps should be followed in achieving a net zero carbon emissions
building which includes planning, reduction of construction
impacts, reduction of operational impacts, increase in renewable
energy supply and offset of any remaining carbon. The creation
of net zero CO2 emissions residential buildings due to operational
energy use in Crete, Greece has been reported . The author
stated that the use of reliable and cost-effective renewable energy
technologies including solar thermal, solar-PV, solid biomass
combustion and ground-source heat pumps could cover all its
operational energy requirements. A study on zero carbon building
refurbishment has been realized . The authors categorized
a range of technologies in a hierarchical manner. The proposed
hierarchical pathway of sustainable energy technologies included
building insulations, high efficiency equipment and microgeneration
using renewable energy technologies.
An investigation on the possibilities of charging electric
car batteries with solar-PV systems installed in residential
buildings in Sweden has been implemented . The authors
mentioned that home charging of electric batteries increases selfconsumption
of solar electricity. They stated though that due to
climate conditions, this option is not attractive in Sweden while
it would be an interesting solution in countries with high solar
irradiance throughout the year. Research on the possibility of
charging electric vehicle batteries with solar energy in workplaces
in the Netherlands has taken place . The authors mentioned
that due to low solar irradiance in the country, the PV panels can
be oversized with respect to the converter’s power. They also
stated that the solar-PV charger can integrate a storage system
in order to be independent from the grid. A report on smart EV
charging systems in Norway has been published . The report
investigates the interaction of charging stations with the energy
needs in buildings and the local generation. Solar-PV systems
installed in homes can be used for charging since they increase the
electricity self-consumption. Power use during charging varies
between 2.3 KW to 3.6 KW while fast charging requires higher
The aims of the current study are:
a) The investigation of the possibility of creating NZCE
residential buildings in the Mediterranean region with
reference to their requirements in operational and embodied
energy as well as the energy consumed for recharging the
batteries of residents’ electric cars.
b) The presentation of the appropriate sustainable energy
technologies which could be used in these buildings, and
c) The cost estimation of the required sustainable energy
systems for achieving this goal.
The methodology followed includes: 1. Estimation of the energy
consumption in a residential building including its operational
energy, embodied energy and energy used in recharging electric
batteries of vehicles, 2. Presentation of the characteristics of the
reliable, mature and cost-effective renewable energy technologies
which could be used, 3. Presentation of a case study for a NZCE
residential building and sizing of the required sustainable energy
systems, and 4. Cost and environmental considerations.
Energy consumed in a residential building over its life span
includes the energy used during its construction, its operation, its refurbishment and its demolition. The energy consumed
during the phases of construction, refurbishment and demolition
is defined as the embodied energy of the building. Operational
energy in a residential building is the energy consumed during its
operation. Embodied energy has a low share in its life cycle energy
consumption while operational energy has the highest share in
the total energy used in the building.
Energy is consumed in various sectors of residential buildings
1. Space heating,
2. Space cooling,
3. Domestic hot water (DHW) production,
4. Lighting, and
5. Operation of various electric appliances and apparatus
The main energy sources used are grid electricity for lighting,
operation of electric devices and air-conditioning, while fossil
fuels, mainly diesel oil and natural gas, are often used for space
heating and DHW production. The typical operational energy
consumption in a residential building, with a covered area of 120
m2, located in the island of Crete, Greece is presented in Table 1.
1 Covered area=120 m2, 2 Use of diesel oil= 0.31 kgCO2/KWh, 3 Use of heat pump with C.O.P.=3.5, 4 Energy consumption by the heat pump = 408 KWh/y, 5 Use of electricity= 0.75 kgCO2/KWh
Assuming that the life span of the residential building is 50
years, then its overall operational energy consumption over this
period is estimated at 1,020,000 KWh or 8,500 KWh/m2 while its
CO2 emissions are 444,000 kgCO2 or 3,700 kgCO2/m2.
The average embodied energy in a typical residential building
varies depending on many factors. It has been estimated in
various published studies at approximately 5-20% of its life cycle
energy requirements. Assuming that in the previously mentioned
residential building, its embodied energy corresponds to 15% of
its specific life cycle energy used, it is calculated at 30 KWh/m2y.
For the abovementioned residential building and for a life span of
50 years,its overall embodied energy consumption is estimated at
180,000 KWh or 1,500 KWh/m2. Therefore, its specific life cycle
energy consumption, including its embodied and operational
energy, is 200 KWh/m2y while its total energy consumption is
Replacement of conventional internal combustion vehicles
with EVs is increasing in many countries for environmental and
other reasons. EVs require frequent recharging of their batteries
which can be done at home. In this case, additional electricity
is needed in the residential building for battery charging. It is
assumed that the residents own two vehicles and each vehicle
travels 15,000 Km annually while their electricity consumption
is 0.2 KWh/Km. In that case the annual electricity requirements
for fueling electric vehicles are estimated at 6,000 KWh/y. This
corresponds to additional specific energy consumption in the
residential building at 50 KWh/m2y.
NzEB is a building which has significantly reduced its
operational energy consumption using various energy saving
techniques and technologies resulting in lower heat, cooling
and electricity needs. The necessity to mitigate climate change
has increased the efforts to improve the energy behavior of
buildings, lowering their energy consumption, their fossil fuels
use and their carbon emissions. New regulations, building codes
and legislation in many countries have made the construction of
new buildings obligatory, with nearly-zero energy consumption,
while the old buildings should be renovated in order to decrease
their energy use. With reference to the previously mentioned
residential building, its energy renovation could decrease
its specific operational energy consumption from 170 KWh/
m2y to 50 KWh/m2y. In this case, its specific life cycle energy
consumption will be at 80 KWh/m2y which is significantly lower
than the initial estimated consumption at 200 KWh/m2y. The
energy requirements of the abovementioned residential building
regarding its embodied energy, operational energy and energy required for recharging the batteries of two EVs are presented in
Various locally available renewable energy sources have been
used for providing heat, cooling and electricity in residential
buildings. Their technologies are mature, reliable and costeffective,
while their use in buildings results in net zero carbon
emissions in the atmosphere due to operational energy use. The
most common renewable energies used in the Mediterranean
region are solar energy, solid biomass and low enthalpy geothermal
energy, while the technologies used include the following:
It is used for DHW production with flat plate solar
collectors, providing hot water at 50-70oC, depending on the
local solar irradiance. These systems are simple in operational
and maintenance requirements, while they have been used
commercially in residential and commercial buildings in the last
Solar-PVs are used commercially during the last 10-12 years
for electricity generation in on-grid and off-grid residential
buildings as well as in other applications. Their use has taken
off due to the sharp decrease in their prices during the last two
decades. Their annual productivity depends on solar irradiance
while their requirements in operation and maintenance are
very low. National legislation in many countries encourages and
facilitates the use of solar-PVs in buildings and other applications.
Locally produced solid biomass can be burnt in appropriate
wood stoves or fireplaces generating heat used in space heating
and for DHW production. It has been used for heat generation for
many years and the burning systems currently used are reliable
and cost-effective. Solid biomass is usually a cheap and renewable
fuel which can replace fossil fuels for heat generation in residential
buildings located in rural areas. However, its use does not result
in net zero carbon emissions, like solar energy, due to the energy
consumed during its processing and transportation.
High efficiency heat pumps including ground source heat
pumps are very efficient energy devices used extensively in
residential buildings for heat and cooling generation. They utilize
the heat stored under the ground while they consume electricity
generating heat and cooling. They are reliable devices having
a high initial installation cost but, in the long run, they are costeffective.
Various other renewable or low carbon energy technologies,
when appropriate, can be used in residential buildings. These
include wind turbines generating electricity, heat and power
co-generation systems generating heat and electricity, district
heating systems providing heat and systems using rejected
industrial heat. Other technologies like solar thermal cooling need
further development in order to be commercialized. The most
often used renewable energy sources in residential buildings in
the Mediterranean region are presented in Table 3.
Buildings consume fossil fuels and grid electricity for covering
their energy requirements and they emit CO2 into the atmosphere. A net zero carbon emissions (NZCE) building is considered the
building which either does not emit CO2 due to its operational
energy use or it compensates all its operational energy
consumption related to carbon emissions with carbon emissionsfree
energy generated by renewable energy sources in-situ or
off-situ. It can be assumed that a typical residential building uses
grid electricity which is generated by fossil fuels. It also uses fossil
fuels including diesel oil or natural gas for heat generation. In that
case, a NZCE residential building should:
a) Replace all fossil fuels used with renewable energies, and
b) Offset all the grid electricity used annually with
electricity generated by renewable energies like solar-PV
electricity, generated in-situ or off-situ. If solar electricity,
when generated, is not consumed in the building, it will be
fed into the grid. Its embodied energy, additionally to its
operational energy, can be offset with green solar electricity.
Grid electricity consumption can be offset with green
electricity generated with renewable energies and fed into the
grid. This is allowed in many countries according to the netmetering
regulations. These regulations allow the compensation
of net annual grid electricity consumption in the building with
solar-PV electricity. Solar-PV panels can be installed on-site or
off-site in the building generating electricity, which is partly
consumed in the building, if needed, while the rest is fed into
the grid. Electricity balance is made on an annual or bi-annual
basis. If the amount of green electricity generation is higher than
the grid electricity consumption, the owner does not usually
get any financial compensation for the surplus energy sent into
the grid. If the solar-PV system has been seized to generate as
much electricity as the building consumes annually, then its net
electricity consumption is zero. In this case, if grid electricity
is generated with fossil fuels, the net carbon emissions in the
building due to electricity use are zero.
A case study for a residential building with NZCEs due to
energy use is presented. The building is in Greece which has high
solar energy resources. The energy requirements of the residential
building are covered with a) A solar thermal system for DHW
production, b) A solar-PV system for electricity generation, and
c) A high efficiency ground source heat pump for air-conditioning.
The building relates to the electric grid and it compensates all its
annual electricity consumption with solar electricity according to
the net-metering regulations. In order to calculate the required
energy systems in the building, the following assumptions have
a. Its covered area is 120 m2 and its specific operational
energy consumption is 170 KWh/m2 y,
b. Its embodied energy is equal to 15% of its life cycle
c. The residents have two EVs and they charge their
batteries at home. Each car travels 15,000 Km/year and
its consumption is 0.2 KWh/Km,
d. A solar thermal system with flat plate collectors is
producing two thirds (2/3) of the annually required
DHW. The rest is produced with an electric heater. The
area of the collectors is 2 m2. Its installation cost is 450€
per m2 of collector area. The cost of an electric heater
producing DHW is 150€,
e. A solar-PV system is generating the required electricity.
The solar-PV system generates 1,500 KWh/KWp
annually while its installation cost is 1,200€/KWp,
f. A ground source heat pump is covering all its airconditioning
requirements. It operates 1,600 hours/
year while its C.O.P. is 3.5. Its installation cost is 2,000
1. The annual energy requirements for DHW in the
building are 1,836 KWh/y. The solar thermal system produces
1,224 KWh/y while the remaining 612 KWh/y are produced
with an electric heater. The solar thermal system has flat plate
collectors with an area of 2m2 and its installation cost is 900€.
The power of the electric heater is 3 KWel and its installation
cost at 150€.
2. The annual energy requirements for air-conditioning
(space heating and cooling) are 14,280 KWh/y. Airconditioning
will be provided by a high efficiency heat pump
with C.O.P. at 3.5. The electricity consumption by the heat
pump is 4,080 KWh/y. Its power will be 2.55 KWel while its
installation cost is 5,100€.
3. The total electricity requirements in the residential
building include needs for lighting, operation of various electric
devices, requirements for the electric heater and the heat
pump. The total amount is 2,448+1,836+612+4,080=8,976
KWh/y. The nominal power of a solar-PV system providing the
required electricity annually is 5,984 KWp and its installation
cost is 7,180.8€.
The size and installation cost of the required energy systems
for covering all the operational energy needs in the residential
building are presented in Table 4.
Additional solar electricity could be generated and fed into
the grid for covering the embodied energy of the residential
building. In that case, the building is considered as a “negative
carbon emissions building” since it generates annually more
solar electricity than it consumes from the grid and therefore it
contributes to atmospheric carbon removal. The construction and
operation of this type of building probably requires negotiations
and agreements with the power utility regarding its financial
compensation. Therefore, the size of the solar-PV system should
be increased. The embodied energy of the residential building is
30 KWh/m2 y (Table 2) or 3,600 KWh/y. The additional size of the
solar-PV system for generating the embodied energy annually is
2.4 KWp and its installation cost is 2,880€.
Additional solar electricity should be generated in order to be
used for recharging the electric batteries of residents’ cars. The
required energy for recharging the batteries of the two EVs is 50
KWh/m2 y (Table 2) or 6,000 KWh/y. The additional size of the
solar-PV system for generating annually the electricity required
for recharging the batteries is 4 KWp and its installation cost is
A conventional grid-connected residential building usually
includes a DHW producing system and an air-conditioning
system. However, a solar-PV system generating all the required
electricity in the building should be additionally installed
according to the net-metering regulations. The size of the solar-
PV system should be, depending on the energy requirements that
it will cover, between 5,984 KWp and 12,384 KWp, while its cost
varies between 7,180.8€ (59.84€/m2) and 14,860.8€ (123.84€/
The use of renewable energy technologies in the residential
building will result in the reduction of carbon emissions due
to energy use. For calculating the environmental benefits, the
following assumptions are made:
1. The building initially used a solar thermal system for
DHW production, electric energy for producing part of the
DHW required, lighting and operation of the electric devices
including space cooling, while it used diesel oil for space
heating. The C.O.P. of the heat pump used in space cooling was
2. CO2 emissions due to energy use are 0.75 kgCO2/KWh,
3. CO2 emissions due to diesel oil use are 0.31 kgCO2/KWh
Assuming that the construction cost of the abovementioned
residential building is at 1,400€/m2 the cost of the required
renewable energy systems for transformation to a NZCE building
is estimated at 4.27% to 8.85% of its initial construction cost.
Decreasing energy consumption and carbon emissions in
buildings is necessary for the achievement of climate change
mitigation targets. The creation of NZCE buildings requires
firstly the reduction of their energy consumption and secondly
the replacement of fossil fuel use with renewable energies. Apart
from the operational energy use in buildings, energy is consumed
during their construction, refurbishment and demolition, defined
as embodied energy. Although in conventional buildings the
share of embodied energy is approximately 15% of their life cycle
energy consumption, it could reach 50% in NzEBs. In our case
study the annual energy consumption in the residential building
is in the same range of values reported in published literature.
Current European policies promote the creation of NzEBs with
low energy consumption and low carbon emissions. Various
reliable, mature and cost-effective renewable energy technologies
which are required for the creation of NZCE buildings are already
broadly used in various applications. Therefore, their technical
feasibility as well as their cost-effectiveness has already been
established. Among them, solar energy technologies used for
heat and electricity generation are very important. Solar energy is
abundant in the Mediterranean region and it is currently used for
energy generation in many applications. The additional cost of the
required solar-PV system for achieving a NZCE building has been
estimated in previous studies as well as in the current study at
5-10% of the initial construction cost of a conventional residential
building. Renewable energy technologies necessary for achieving
a NZCE residential building can be used for recharging the
batteries of the residents’ EVs. In this case, solar electricity selfconsumption
in the buildings will be increased. Creation of NZCE
residential buildings will promote energy democracy, increasing
the independence of their residents from energy providing
utilities. It has been indicated that energy saving is easier and
more desirable than energy generation. However, reduction of the
energy consumption in the residential building studied has not
been considered. If, however the energy consumption is decreased,
then the size of the required sustainable energy systems would be
lower. Different existing barriers hinder the promotion of NZCE
buildings including economic, knowledge and legislative issues.
The definition of NZCE buildings should be clarified while a
commonly agreed calculation methodology should be established.
Coordination of all stakeholders, involved in the creation of
NZCE buildings including governmental organizations, building
designers, construction companies and the general public, is
necessary for their promotion and construction on a large scale.
The creation of NZCE residential buildings in the Mediterranean
region is technically feasible and the required sustainable energy
technologies are cost-effective and already commercialized. The
renewable energy sources which can be used include solar energy,
solid biomass and low enthalpy geothermal energy combined
with heat pumps. Solar energy can be used for DHW production
and electricity generation, solid biomass for heating and ground
source heat pumps for air-conditioning. The availability of solar
energy in the Mediterranean region is high and its use for energy
generation is attractive. The abovementioned renewable energies
can cover all the operational and embodied energy requirements
of a residential building as well as the energy required for
recharging the batteries of residents’ EVs in a cost-effective way,
zeroing its net carbon emissions. The total installation cost of
the required solar-PV system for achieving carbon neutrality
due to life cycle energy consumption in the residential building,
studied in the present work, varies between 5-10% of its initial
construction cost which corresponds to 59.84€/m2 to 123.84€/
m2. The annual CO2 savings in the residential building have been
estimated at 74 kgCO2/m2 to 134 kgCO2/m2. Therefore, creation of
NZCE buildings in the Mediterranean region are technically and
economically feasible using the local benign energy sources which
are mature, reliable and cost-effective. Their promotion will
require the development of appropriate policies and the removal
of various barriers which currently hinder their promotion.
Further research should be oriented towards estimating the
technical and economic feasibility of NZCE buildings with nearly
zero energy consumption according to the current EU regulations.
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