To achieve suitable indoor thermal conditions, one has two basic options:
either invest heavily in the purchase, installation, operation and maintenance
of HVAC systems;
or reduce energy costs by applying bio climatic principles to building
design.
The operating costs of heating, cooling, ventilation and lighting can be
significant, especially if the design and/or operation of the building is
suboptimal. Considering the fact that operational and maintenance expenses
grow with time and that problems usually get worse unless action is taken, it
makes good sense to place an emphasis on energy conservation right from
the start. In fact, energy savings add up over the years and translate into
cost savings.
Energy conservation has become an important aspect of building design and,
in some countries, a code-mandated requirement. The main objective is to
achieve indoor environmental quality, while balancing the requirements
for energy efficiency and overall energy conservation in an
environmentally acceptable manner.
Building retrofit or renovation costs are much lower than the costs for building
demolition and the construction of a new building. Energy conservation in
existing buildings is a priority, given that the lifetime of buildings is usually
more than 50 years and the existing stock of buildings is much greater than
new construction. Energy conservation measures for new and existing
buildings are already in process within several Member States of the
European Union, in accordance to the new Directives by the European
Commission on “Energy Conservation in Buildings”.
Energy conservation for heating and the reduction of heat losses are mainly
governed by thermal insulation of the building envelope. Thermal insulation
materials have improved significantly over the past decades in terms of
efficiency, safety and functionality. The current average heat loss of new
European buildings is about half of what it used to be for the pre-1945 building
stock. Nevertheless, the majority of existing buildings are poorly insulated,
since in most countries national thermal insulation regulations have been
enforced during the last decades. For example, in Greece, where the national
Thermal Insulation Code became effective in 1981, only 5% of the existing
residential building stock is insulated.
Heat losses through the building envelope are responsible for about 10-
25% of the total energy consumed in buildings, depending on outdoor weather
conditions and building materials. Consequently, a well insulated building
envelope can significantly reduce thermal losses in winter and heat gains in
summer, thus reducing energy consumption and operating costs, and
improving the indoor thermal conditions. The addition of an external cladding
façade, at an appropriate spacing from the main building “body”, on existing
and new buildings, creates an air gap that acts as a thermal buffer zone, thus
reducing heat losses in winter and heat gains in summer. Thermal insulation
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materials should be added on the building “body”, for additional energy
savings. These rules apply to both existing and new buildings
Energy conservation for cooling of buildings is of primary concern in
Mediterranean countries. During the past decades, the use of mechanical air
conditioners (A/C) in southern European countries has increased dramatically.
This is primarily due to an increase of the living standards and the reduction in
price of A/C units. There is a clear trend of increasing sales with gross national
product (GNP) in EU member states. In Greece, sales of A/C units showed an
unprecedented increase of 900% during the late 1980s due to a series of heat
waves over a period of three years. The impact on the electric energy
consumption has been alarming. For the first time peak electric energy loads
occurred in Greece during the summer period. Similar trends have been
observed in most southern European regions, the Middle East, the United
States and Japan.
Solar control (shading) is a key design measure for minimising the heat gain
of indoor building spaces. The use of various shading devices to attenuate the
incident solar radiation can significantly reduce the cooling load and improve
the indoor thermal and visual comfort conditions. External shading is more
effective overall because the main amount of incident solar radiation is
intercepted outside the building and can be dissipated away from internal
spaces.
