One of the main causes of energy loss in our home is the old windows. Old windows and doors are the main sources responsible for heat loss during the winter and cooling loss during the summer, which according to studies can reach 35%. Losses can be significantly reduced, and we can save money on energy bills if we replace the old windows with new energy-efficient ones. Replacing old windows, in addition to significant energy savings, offers:
• Thermal insulation.
• Sound insulation.
• Reduction of the energy footprint of the building.
• Improving the quality of accommodation.
• Increase in the resale or rental price.

For the selection of new High-Performance windows, we pay attention to the following coefficients:

Window thermal permeability coefficient Uw

Uw is the energy indicator of the whole window that shows what energy we need to spend to replace the heat loss in the window. The unit of measurement is W/m2K which means how many Watts of energy are required for each m2 of window with a temperature difference between indoor and outdoor space of 1 degree Kelvin, or 1οC. Achieving low Uw requires a thermal break frame and two or more low emission glazing. In Nearly Zero Buildings (nZEBs) the Uw factor must be less than 1.4 W/m2K to reduce heat loss.

Solar heat gain coefficient/ g value

The solar thermal gain coefficient of the window gw expresses the average value of the ratio of the solar radiation that passes from the surface of the window to the solar radiation that falls on it. When the requirement for cooling is low, we want the glass to let more sunlight pass through the space, to reduce the heating loads in winter and to increase the level of natural light. In places that have direct and long exposure to sunlight, a low rate (<40%) of solar gains is required to avoid overheating.

Degree of airtightness

The airtightness indicator shows how many m³ of air enters from the opening. Participates in the calculation of the supply of fresh air that enters the building unintentionally and therefore, in the calculation of thermal losses due to ventilation. Category 4 implies high airtightness and reduced air intakes and escapes and therefore reduced heat loss.

Heat Pumps are so named because they "pump" heat from a cold source (outdoor environment in winter or cooled space in summer) and with the help of a refrigerant, discharge it to a hot source (heated space in winter or outdoor environment in summer). Because they "impose" a heat flow from the coldest to the hottest environment, which is opposite to the "natural flow" of heat (which is from the warmest to the coldest), they require the consumption of an amount of energy (usually electricity) to maintain their operation.

They are characterized by the coefficient of performance (COP) and cooling (EER), which express the ratio of the energy we "get or benefit" to the energy we "consume". In heat pumps, the energy we "get" comes 70% from the external environment and 30% from the energy we "consume". This is the element that brings heat pumps to the top positions of choice as a heating system.

However, heat pumps are the most economical solution when there is a need for continuous heating (eg 24 hours a day). The (significant) increase in electricity consumption from the operation of the heat pump raises the scale in PPC tariffs. An apartment using a heat pump can see electricity consumption doubled. However, if you install a heat pump and combine it with a photovoltaic system to generate the electricity consumed by the heat pump, you can get rid of the extra cost of electricity and be protected from future increases. In other words, you can even have free heating!

Combining heat pumps with small RES applications to generate clean electricity is an excellent way - economical and environmentally sound - to meet your heating needs and eliminate heating costs.

DHW is the water that we heat for various daily uses, either household (washing, cleaning, cooking, etc.) or for large buildings e.g., hospitals, hotels etc.

Thermal solar systems for space heating and domestic hot water production (Solar Thermal Systems) are particularly well known in several European countries and in recent years in Greece. Solar thermal systems collect solar radiation and convert it into thermal energy, which heats the water to meet the daily needs for domestic hot water and heating.

There are different types of solar thermal systems, and the difference lies in the amount of heat they can produce. The simplest form of solar system is the solar water heater, which heats the tap water directly and has a built-in water tank.

Due to the large increase in the prices of heating oil, the need for energy savings, as well as the introduction of the Energy Efficiency Regulation of Buildings, the use of solar systems is increasing.

1. Hot water almost free. A typical home installation saves about 1400 kWh of electricity per year. This amount of energy corresponds to at least 70% of the annual needs of a family of four in hot water.

2. Direct supply of hot water to the tap (especially in the installations connected to the heating system)

3. Financial benefit for the user. During the life of the system the user not only gets his money back but also has a significant financial benefit.

4. In combination with washing machines (dishes and clothes) of Hot Fill technology (connection to the hot water supply) the saving of electricity and money is significant.

5. Environmental protection (using "green" solar energy).

Heat loss in a building is caused by the transfer of indoor air heat to the atmosphere or to cooler areas nearby and / or vice versa. It is known that, between two bodies with different temperatures, a continuous flow of heat is caused from the warmest to the coldest, something that happens in winter from the inside of the building to the outside cold air, but also in summer from the outside hot air to the coolest interior of the building. This heat flow is impossible to block completely and can only be reduced in intensity and duration. This is achieved by the thermal insulation of the building, which reduces the heat exchange through the surfaces (walls, roofs, floors, frames) that separate areas of different temperature.

Today, where building constructions are more complex and lighter than the traditional stone buildings of the past, the solution to thermal changes is offered by the various heating and air conditioning control systems. Energy consumption for their operation was not a problem until the Energy Crisis. Energy sources - especially oil - are no longer cheap and we all now realize the great importance of thermal insulation in saving energy.

All buildings constructed in Greece after 1980 are insulated under the Thermal Insulation Regulation, but almost all buildings constructed before 1980 (almost 82% of buildings in Greece) are not insulated.

The materials that make thermal insulation are always light materials that have trapped air in their mass. Air is the most insulating element in nature, and this is exploited by all these materials.
Thermal insulation must be installed on the following surfaces:

1. In the basement walls.

2. On pilotis, so that the floor of the first floor does not get cold (mainly).

3. On the roof. The thermal insulation of the roof protects both from the heat of summer and the burning of the slab from the sun, as well as from the cold of winter. It should be noted that the hot air rises upwards and an apartment on the top floor or a roof without thermal insulation, is a significant energy loss. No matter how much we heat the space, the heat escapes from our non-insulated roof.

4. On the exterior walls. It is important to insulate our walls as well as to use high energy efficiency systems in the window frames of the building.

It is worth mentioning that the installation of thermal insulation in buildings helps to reduce thousands of tons of emissions of gaseous pollutants into the environment each year, as it leads to a dramatic reduction in fuel consumption for heating or cooling.

The central air-conditioning units are units to meet the requirements of cooling and heating in large spaces, such as large houses or business premises (e.g., event halls, cafeterias, supermarkets, hotels etc.)

Such a unit can save a significant amount of money for the business, as only one machine will operate to provide the corresponding heating or cooling.

For example, if in a hotel we used air conditioners, the cost of each one and the installation cost would be much higher than if we used a central air conditioning unit. From the unit management panel, we could turn off the air conditioner of a room if the customer is not inside and has left it on or set all the air conditioners to operate in a specific temperature (degrees).

The central air-conditioning units control temperature, humidity and air purity. They are connected by a central air duct network which distributes the air to the air-conditioned areas. They have the ability to control them remotely (from remote points) or locally in each air-conditioned space. Central air conditioning has the advantage of the ventilation function.

Aeration & Ventilation with Recovery or otherwise the Aeration & Ventilation Systems with Heat Recovery are an innovative and autonomous space ventilation system, which filters the incoming air and at the same time preheats it in order to completely eliminate the heat losses (respectively, during summer precools the air). The balance achieved between the internal and external environment allows a significant reduction of the required cooling or heating load.

Heat recovery in central air conditioning systems is mandatory
by the European Commission’s Regulation 1253/2014.

Natural gas is a natural product which lies in underground deposits of the earth and is found either alone or in coexistence with oil deposits. It is a gaseous hydrocarbon blend, composed primarily of methane (in a percentage of more than 85%), which is the lightest hydrocarbon, it is very clean, with no impurities and sulfide components.

Natural gas burning presents significant benefits compared to oil burning as it represents a very clean source of energy. During the burning process it produces significantly less pollutants and releases a much smaller proportion of carbon dioxide responsible for the greenhouse effect. Therefore, the use of natural gas helps protect the environment and reduces air pollution.

Natural gas is used by both households and industries, as well as large heating building facilities such as hotels, hospitals, office buildings etc. One of the ways we widely use it is for heating. The calorific value of natural gas is greater than that of oil. This simply means that in order to heat our space with natural gas we will need to consume less energy per square meter compared to oil. Hence, the use of natural gas in heating results in energy savings as well as monetary savings for the consumer.

Heating with the use of natural gas can be conducted in new buildings and in existing apartment buildings by replacing the oil burner with a gas burner, without the need for other interventions in the system. The measurement of consumption is done by the meter readings, as in the cases of electricity and water.

In addition, natural gas does not require a tank installation, as it is available through the distribution network. However, at the moment the network is limited to the three major areas of Attica, Thessaloniki and Thessaly. Yet, investments for the network’s expansion have already started in other urban centers.

The most significant energy savings in lighting can be achieved by utilizing daylight in a room. The less artificial lighting is used, the greater the energy savings and the lower the CO2 emissions. In this respect, lighting management systems are in general a method for saving energy and resources. These include:

Light sensors: Light sensors are used to automatically turn off the lightbulb when natural lighting is sufficient.

Presence sensors: Presence sensors can perceive when there is human presence in a space, so that they are automatically deactivated when no movement is detected for a certain time period. They are easily combined with timers, both to save energy and to facilitate the user.

Timers:Timers are used for spaces where human presence is required for a specific period, such as staircases.

Dimmers:The dimmer changes the lightbulb's power consumption with your own handling, by saving energy.

At the same time, modern lightbulbs offer significant potential for energy saving and environmental protection. Today, the main categories of lightbulbs on the market are divided into 3 large categories, xenon/halogen, savings (small-sized fluorescence) and LED (light-emitting diode).

Xenon/halogen lightbulbs: Xenon lightbulbs (also known as improved incandescent lightbulbs) consume 20 to 25% less energy by producing the same light as the best conventional incandescent lightbulbs. They can be found on the market in two cases, either as lightbulbs for lamps with a special connector or as replacements for conventional incandescent lightbulbs. In improved halogen-technology filament lightbulbs, the halogen capsule shall be placed in a glass envelope so that the final result looks like a conventional calyx filament lightbulb. Both types produce light of equivalent quality to conventional incandescent lightbulbs, but with regular use, they have the double estimated life (2.000 hours). However, their energy savings are not as great as those of other types of lightbulbs. Their energy class is B or C, depending on the model.

Fluorescent lightbulbs: This category includes lightbulbs that capitalize on the fluorescence phenomenon. They are highly efficient and are named after the fact that to produce the same light they consume about 65-80% less energy than incandescent lightbulbs. Their estimated life is much longer than that of single incandescent lightbulbs and can reach up to 6.000-15.000 hours. The main disadvantage of this category of lightbulbs is that they cannot instantly produce the maximum of their brightness. It usually takes a few minutes to reach the final brightness they produce. In addition, due to the presence of mercury in their interior, specific steps must be followed in case the lightbulb burns or breaks. In particular, if the lightbulb burns, it must be returned to the point of sale or another collection point, while in case it breaks, air must circulate in the space and then the fragments should be collected with a wet cloth. You should avoid contact of the fragments with the skin and you should not use a vacuum cleaner to clean the area. The energy classification of these lightbulbs is A.

LED lightbulbs: LED lightbulbs consume up to 80% less energy than standard incandescent bulbs and are more environmentally friendly, as they do not contain mercury. Their estimated life is even longer than that of fluorescent lightbulbs (usually over 30.000 hours), while their performance is equivalent. In the near future this type of lightbulb can replace the entire range of lightbulbs. When a LED lightbulb is no longer in operation, it must be returned to the point of purchase or to specific collection points, so that various parts of it are then recycled. In addition, LED lightbulbs gather a number of advantages, such as the fact that they do not heat up and consequently, do not increase the room temperature in which they are located, they are not sensitive to vibrations and bumps, they do not flicker and they immediately
reach the maximum of its brightness. The energy classification of LED lightbulbs is A.

Photovoltaics belong to the category of Renewable Energy Sources (RES). In the solar renewable energy sources category, solar thermal systems are more efficient than photovoltaics. The difference between solar thermal systems and photovoltaics is that solar thermal convert solar energy first into thermal energy and then into electricity, while photovoltaics converts solar energy directly into electricity. Another important difference between the two is that photovoltaics do not need sunshine to generate electricity.

There are two main categories of PV systems, the interconnected to the network and the autonomous. The autonomous photovoltaics (off-grid) differ from grid-tied or on-grid systems in that no interconnection with the public network is required (e.g. PPC) to operate. The autonomous systems beyond solar energy can also exploit wind energy, so they are called autonomous hybrid systems. Usually, stand-alone systems include batteries (accumulators) and are called stand-alone storage systems.

Interconnected PV: By Interconnected Photovoltaic Systems we refer to those systems that are interconnected to the PPC network and with which the investor generates electricity which is sold directly to PPC for a specific price set by the state.Net Metering (Self-Production) is a new program by PPC, with which consumers by installing a photovoltaic’s unit can set off the energy they generate with the energy they consume for their home or business. If, within a certain time period, more energy is produced by the consumer than was consumed, then the surplus is provided free of charge to the electricity grid. Inversely, if less energy is produced than consumed, then the consumer only pays the difference. The installation of an interconnected photovoltaic system for self-production and energy netting through the Net Metering system is in the interest of all businesses as well as households that have significant electricity consumption, since its depreciation can be achieved in a very short period of time and from there on there is a significant permanent benefit.

Standalone PV:Autonomous power systems are used in buildings that are remote and therefore, cost-intensive or impossible to connect to the public network, in floating boats, country houses, caravans etc. More than a few settlements on the African continent are fully powered by autonomous photovoltaic systems. Moreover, they are used as a back-up solution in cases of increased frequency of power outages mainly for businesses with sensitive products (for example a butcher shop on a tourist island after the black-out of 2013 in Santorini). In Greece, the use of electricity-free holiday homes has significantly increased. In recent years the increase in electricity costs has sharply increased the demand for such systems in businesses mainly touristic (small remote hotels, canteens etc.), but also in main residences.

Geothermal energy is called the natural thermal energy of the Earth, which flows from the warm interior of the planet towards the surface. Of great importance to humans is the utilization of geothermal energy to meet its needs, as it is a practically inexhaustible source of energy. Depending on its temperature level it can have various uses.

• The high enthalpy (>150°C) is commonly used for power generation.

• The average enthalpy (80 to 150°C) is used for heating and/or drying timber and agricultural products as well as sometimes for the production of electricity.

• The low enthalpy (25 to 80°C) is used for space heating, greenhouse heating, fish farming, fresh water production.

The spread of geothermal energy was delayed until now, mainly due to the costs of the relevant installations. Today, however, geothermal energy, like other technologies utilizing renewable energy sources (photovoltaics, thermal solar etc.), are in very high demand in Europe, while the relative trend in Greece is increasing.

Shallow geothermal energy is available and exploitable everywhere, regardless of the existence of geothermal potential. During the summer, the earth's temperature is colder than the atmospheric, while in winter it is warmer. This fact allows us to transfer heat from a warm space to the earth during summer, while during winter to absorb heat from the ground transferring it to the coolest space. The heat transfer is conducted with geothermal heat pumps.

Geothermal heat pumps follow the basic structure of ordinary heat pumps. Everyone with a refrigerator or an air conditioner has been a witness to the operation of a heat pump, even if the term heat pump might be unknown. All of these machines, instead of producing heat, transfer existing heat from a lower-temperature space to a higher-temperature space. So, a heat pump with a heat source of the external air, receives the heat from the outdoor space and pumps it inside the building. A geothermal heat pump operates in the same way, except that its heat source is the warmest land instead of cold air.

Geothermal heat pumps, take advantage of the constant temperature of the subsoil, to provide heating, cooling and hot water use. By utilizing electricity, they ensure heat transfer from the subsoil to the building, during the heating period and vice versa from the building to the subsoil, during the cooling period. The heat source of geothermal heat pumps can be either surface water (lakes, rivers) or the underground aquifer, or fluid which circulates within geoalternatives in a closed circuit.

Geothermal heat pumps are characterized by a higher efficiency factor compared to air heat pumps, as they use as a source of heat the subsoil or subsoil water, which has a temperature stability throughout the year, with a temperature approaching the average temperature of the atmosphere.

Some of the advantages of geothermal pumps are: complete independence from conventional fuels, continuous availability not affected by climate conditions, very satisfactory efficiency level, zero emissions, minimum maintenance costs and long estimated life due to low number of mechanical parts.

KNX technology is a global standard for home and building control and automation. The open platform of KNX has been enshrined in European standards EN 50090 and EN 13321-1, as well as in International standards ISO/IEC 14543.

The large number of manufacturers offers a variety of certified and compatible-KNX products, according to the latest technical standards. KNX-certified control devices (switches, sensors, etc.) are fitted to household or electrical appliances (lighting, heat pumps, air conditioners, etc.) and have a huge potential to control the energy consumed. For instance, space/room lighting can be controlled by the space/room switch, but in combination with a brightness sensor – in case the brightness level during the day is required in the space/room, the lighting will not be allowed to start, for obvious energy saving purposes.

On top of its potential for lighting, heating/ventilation/air conditioning control, engines (tents, rolls, blinds, windows, garage doors), alarm systems, automation, etc., a home KNX installation, can interact with electric KXN vehicle charging controllers, with a photovoltaic KNX installation and with KNX digital meters, in order to turn the household consumer into “home virtual power production unit” or self-producer.

KNX is the basis for all home automation applications.

Combined Heat and Power (CHP – known as Cogeneration) systems produce simultaneously both electrical (and/or mechanical) and thermal energy from the same original energy source. Thermal energy, which is recovered in a CHP system can be used for heating or cooling in industry or buildings.

Cogeneration has a vast range of applications. It can be used in industries, sports facilities, shopping centers, greenhouses, residential complexes etc. Natural gas is mainly used as a fuel, but in specific applications, such as in agricultural businesses, biomass is also successfully used.

The electricity generated can either be used for own use (self-production) i.e. to meet the energy needs of the producer (individual or business) or for sale on the network.

The thermal energy produced has multiple uses depending on the user's needs. Some of the main ones are:

• Hot water production for heating circuits.

• Domestic Hot Water Production.

• Steam production (mainly for industries and crafts).

• Production of hot water for use in refrigeration complexes with the ultimate purpose of producing cooling.

Cogeneration is a mature technology and widely applied, while included in the European Union's list of best available techniques (BAT).

The denomination BMS comes from Building Management System. It is a control system installed in buildings, to supervise and control all electromechanical building systems, such as: Cooling, Heating, Ventilation, Lighting, Energy Systems.

BMS is commonly used in large buildings. Its main function is to manage the temperature, CO2 level and humidity of a building. Most BMS systems control heating and cooling production, manage systems that distribute air throughout the building and locally control the mixture of hot and cold air to achieve the appropriate temperature of each space. They also control the level of human CO2 production by mixing external fresh air with the inside of the building and raising the level O2 without serious Heating/Cooling losses.

By installing a BMS management system in a large building (e.g. Hospital, Ministry, School, Social Service, etc.) we have a graphic display of all of its facilities on a computer screen, regardless of the size of the building. This automatically provides us with immediate information, giving us the opportunity to have the supervision of the building and intervene in case of failure or need to change the operating parameters.

The most important reason for installing a BMS system is to reduce the operational cost of large buildings. Energy and cost savings are achieved by the strict time scheduling of the controlled installations. Systems are planned to function during the building’s operation, while during times when there are no employees and visitors in the premises, their deactivation is ordered. Such systems are lighting, cooling, heating, lifts etc.

A building controlled by BMS systems is often referred to as a “smart building” or “smart house”. A Smart Building is the next generation of conventional buildings.

Fan Coils are units connected to the hydraulic network and through the fan they possess, offer heating and cooling in the space they are installed.

Their main use is like cooling-heating bodies, as they operate extremely well with heat pumps. They can also be connected to a geothermal system.

The main advantages of using fan coil over other conventional bodies are the following:

• They have an increased efficiency in heating and cooling due to the forced circulation of air generated by their fan.

• They can be connected in visible and hidden areas of a space.

• They are the most suitable for business spaces.

It is worth mentioning that there is a possibility of programming fan coils through the global KNX standard, providing energy-saving solutions and thermal comfort. By integrating a fan coil system into a KNX installation a control of space thermostat and system operation adjustment is carried out, according to the room temperature, but also the temperature chosen by the user.