106
S. M. Kalinovi´ c et al.
cities grow, more and more heat is trapped in them, resulting in an increase in air
temperature of 6–8 °C compared to the suburbs [1]. Buildings and sidewalks are
made mostly of the non-reflective and waterproof building materials, which accumulate solar radiation during the day and then release the heat at night. Heat is also
trapped due to reduction of the green spaces in cities, which leads to a decrease
in radiation cover, limited air circulation through the city streets between buildings
and high production of waste heat from cooling systems, motor traffic, industrial
processes, etc. In order to mitigate the effect of urban heat islands and improve the
energy efficiency of buildings, use of the green infrastructure on the roofs and facades
of buildings has been increased [2].
Since building envelopes generally remain bare, while surrounding areas around
buildings are paved or occupied by other structures and parts of roofs are occupied by
some form of construction services, the vertical green systems represent the simplest
solution.
The green vertical facade systems have several advantages, such as extending
the life of the wall, thermal insulation and reducing the sun absorption. Vertical
gardens protect the exterior of buildings and homes from ultraviolet radiation, rain,
extreme temperature fluctuations and presence of moisture. Their advantages are
reduction of heat load and energy consumption, mitigation of the effect of urban
heat islands, reduction of air pollution, sound absorption, improvement and preservation of urban biodiversity and aesthetic contribution to the city landscape. The
green vertical systems are divided, according to their structural design and characteristics, into green facades and living walls [3]. The green facades are characterized
by climbing plants rooted in soil or pots up to a certain height of the wall. Plants
climb onto the facade directly against the wall or indirectly, on a support (wire, mesh,
or grille) that is located a short distance from the wall. The living walls are made of
panels or geotextile felt, which are fixed to a vertical support or wall construction
and which provide support to vegetation formed by different plants. The panels can
be of different sizes and types, fixed to the wall, with openings containing substrates
and plants. Geotextile felt systems use geotextile felt as a substrate for plants or moss
and are fixed directly to the wall [4].
The importance of green facades has been recognized by a large number of
researchers. In [5] was shown that vegetation on the outer walls stabilized the indoor
air temperature in buildings and reduced heat losses and gains through the outer walls
as well, resulting in a decrease in the building energy load. In the work [6], a mathematical model of an outer wall, covered with vegetation, was derived to evaluate
the thermal effects of plants on the heat transfer through the facades of buildings.
This model allows an analysis of how different physiological parameters of plants,
such as leaf surface index, average leaf size and leaf absorption, can improve the
thermal characteristics of the facade by reducing the external wall surface temperature and heat flux through the facade. Authors of [7] presented results of a series of
experiments performed on ivy overgrown walls and on walls without the ivy. They
examined four pairs of walls of different orientations at existing university buildings, during the summer in Chicago, Illinois, USA. The results of the experiment
showed that the ivy layers reduced the outside surface temperature by an average of
S. M. Kalinovi´ c et al.
cities grow, more and more heat is trapped in them, resulting in an increase in air
temperature of 6–8 °C compared to the suburbs [1]. Buildings and sidewalks are
made mostly of the non-reflective and waterproof building materials, which accumulate solar radiation during the day and then release the heat at night. Heat is also
trapped due to reduction of the green spaces in cities, which leads to a decrease
in radiation cover, limited air circulation through the city streets between buildings
and high production of waste heat from cooling systems, motor traffic, industrial
processes, etc. In order to mitigate the effect of urban heat islands and improve the
energy efficiency of buildings, use of the green infrastructure on the roofs and facades
of buildings has been increased [2].
Since building envelopes generally remain bare, while surrounding areas around
buildings are paved or occupied by other structures and parts of roofs are occupied by
some form of construction services, the vertical green systems represent the simplest
solution.
The green vertical facade systems have several advantages, such as extending
the life of the wall, thermal insulation and reducing the sun absorption. Vertical
gardens protect the exterior of buildings and homes from ultraviolet radiation, rain,
extreme temperature fluctuations and presence of moisture. Their advantages are
reduction of heat load and energy consumption, mitigation of the effect of urban
heat islands, reduction of air pollution, sound absorption, improvement and preservation of urban biodiversity and aesthetic contribution to the city landscape. The
green vertical systems are divided, according to their structural design and characteristics, into green facades and living walls [3]. The green facades are characterized
by climbing plants rooted in soil or pots up to a certain height of the wall. Plants
climb onto the facade directly against the wall or indirectly, on a support (wire, mesh,
or grille) that is located a short distance from the wall. The living walls are made of
panels or geotextile felt, which are fixed to a vertical support or wall construction
and which provide support to vegetation formed by different plants. The panels can
be of different sizes and types, fixed to the wall, with openings containing substrates
and plants. Geotextile felt systems use geotextile felt as a substrate for plants or moss
and are fixed directly to the wall [4].
The importance of green facades has been recognized by a large number of
researchers. In [5] was shown that vegetation on the outer walls stabilized the indoor
air temperature in buildings and reduced heat losses and gains through the outer walls
as well, resulting in a decrease in the building energy load. In the work [6], a mathematical model of an outer wall, covered with vegetation, was derived to evaluate
the thermal effects of plants on the heat transfer through the facades of buildings.
This model allows an analysis of how different physiological parameters of plants,
such as leaf surface index, average leaf size and leaf absorption, can improve the
thermal characteristics of the facade by reducing the external wall surface temperature and heat flux through the facade. Authors of [7] presented results of a series of
experiments performed on ivy overgrown walls and on walls without the ivy. They
examined four pairs of walls of different orientations at existing university buildings, during the summer in Chicago, Illinois, USA. The results of the experiment
showed that the ivy layers reduced the outside surface temperature by an average of