The construction sector is one of the fastest growing sectors worldwide. An important objective for the construction sector is the construction of buildings with minimal environmental impact and energy consumption, which is one of the most important issues in the life of a building and for this reason the low-consumption buildings have become an important field of research.
The rapid increase in energy consumption observed in buildings is both quantitative having increased energy consumption and quality, using more electricity. The main cause of energy consumption growth is the change in quality of life for the better, using automated devices with higher power requirements, the generally fair condition heating systems resulting in reduced efficiencies. Also very important is that the majority of the buildings date back to 1980, which have no heat and require large amounts of energy to obtain the desired thermal comfort conditions.
The actions that we can do to achieve better results, divided into 3 stages.
Small interventions include procedures at low cost, such as replacing incandescent light bulbs with low energy consumption, use of vegetation, awning, blinds shading, closing cracks / joints etc.
Major interventions predisposing costly but is much more effective, such as replacing windows and doors and windows, adding insulation materials, changing burner with a new type etc.
Finally, non-technical procedures, which have no cost simply require proper functioning of the existing systems of the building, such as the use of windows for ventilation, shutters for shading and generally rational use of appliances. O energy building design aims to ensure the best conditions esoklimatikes with the correct thermal performance of the building and the reduction of energy consumption, with all the benefits that entails, economic, environmental, reduce CO2 emissions, quality of life, etc. Then, we will describe the main areas and actions to be undertaken to achieve these objectives, starting from the original building construction.
The greatest energy savings in buildings resulting from the correct and rational design, with regard to the location and orientation of the building.
The location of the building and the orientation of the building must be such that:
- To ensure good lighting during the day
- there are solar gains from the incidence of the rays of the sun inside during the winter months
- to ensure shade in the summer season
In all, therefore the cases not ensured the southern exposure with acceptable maximum deviation ± 25 ° east or west, the designer could instead choose conventional solutions, propose correspondingly other, so that all buildings be iliazontai and adequately lit naturally while not create secondary problems such as a decrease in thermal and visual comfort. The buildings are designed to deal with friendly environment, follow the basic principles of bioclimatic architecture and energy saving, therefore, a house should have smaller openings to the north and smaller in the south. If possible on the north side we would be put spaces parking, warehouses or tall trees in order to protect from cold winds. It is also important to have the possibility of summer ventilation.
Functional organization of the interior of the building
When designing the floor plan the interiors should be organized and grouped so that those with long use and desired high internal temperatures (living room, dining room, office) be sited on the south side of the building. Instead spaces with limited use and require comparatively lower temperatures (W.C., bedrooms) should be located in an intermediate thermal zone. The other auxiliary rooms, if there are to study, garages, warehouses, etc., should be provided on the north side, to act as a thermal buffer zone between the heated space and the external environment. Thereby decreasing actually the heat loss of the key main areas.
Thermal insulation is one of the basic steps for reducing the thermal losses, and thereby to prevent the transfer of heat from the interior of the building to the outside and vice versa in winter the summer. Typical insulating materials are glass wool, polystyrene and insulation Heraklith sheets. In frames must choose thermal break, so that the outer surface contacts the inner and not to create thermal bridges. Particular importance has the appropriate choice of glass, with the choice of double glazing, where losses of up to 50% or reinforced insulation may be reduced where necessary.
Also seeking the use of materials with high heat capacity. This measure aims to delay transmission of heat indoors, at times can be calculated so as to coincide with the reduction of the external temperature in the evening. If the above combined with nocturnal ventilation of rooms, then indeed achieved
and the cooling of spaces naturally. Significant measures are the sealing of joints and replacement windows. They recommended opening frames, because it is more airtight than sliding and for their ventilation during the summer months. The insulation may be internal or external, with the first having a higher yield and a more complete solution, because it protects the outer shell of the building and provides less variation in the internal temperature. Also important is the building's color, that dark colors outside tend to absorb energy, which transmit to the interior of the building as opposed to the light colors that reflect a large portion of the solar radiation back into the environment and helping to prevent overheating building.
The use of solar energy is a critical factor for energy savings not only for the most advanced solar heating systems or freeze-for photovoltaics, but also for the simple use of the sun. The existence of the necessary openings in the correct orientation is the first condition. West and east exposures are very unfavorable and must only provided to meet the needs of ventilation and lighting, while the north should be avoided. Furthermore, there are various techniques for the thermal utilization of the solar energy, such as the wall trombe, storing heat as the atria.
Of course, the use of the sun in Greece, everything must be done with the understanding that the warm summer months we need protection from radiation. In addition, the selection of appropriate sun-protective devices depending on the orientation of the faces, ie horizontal provisions in the south, vertical in the East and West with the right angle to the path of solar rays, so as to remove the solar radiation from the housing building. For the same purpose could be used special crystals in the windows and doors, which can particularly reduce the transmittance of sunlight through the transparent sensitive elements. Also, a natural way of shading the deciduous planting trees and evergreen in the South to North wind if possible. To avoid excessive heat inside the building during the summer months, take care of the appropriate shade of pergolas and awnings. Very effective method is the perforated rolls, a technique suitable for all orientations, which are installed internally or externally and consisting of glass fibers, plastic or aluminum, but are particularly costly.
The natural cooling in conjunction with the use of air especially in the summer can bring significant results. In cooperation with several methods such as sun protection, the shading, proper insulation and orientation, can ensure a satisfactory temperature significantly reducing the use of air conditioning. Additionally important would be the existence of cross-ventilation of premises, especially in the provision or strengthening their nocturnal ventilation for the discharge of components from the heat that builds up during peak hours. If this measure can not be satisfied by existing
openings in the sides of the building, then the use of apertures in the roof of the building or the construction of solar chimney for accelerating the hot exhaust air from the building, or anemopyrgou for forced air movement, would be effective techniques.
Electrical appliances and equipment
An important step is to save energy by electrical devices. This will be achieved by buying more energy efficient appliances (marker A or B), avoiding the waiting position ( «stand by») which consumes a significant amount of energy unnecessarily and use photocells for lighting and thermostat for heating . Corrective actions and upgrading equipment is also necessary, such as replacing aging boilers with new high efficiency and low exhaust gas outlet temperature, replacement of old diesel boilers with new dual fuel multistage, replace any worn hot water supply heat insulation, installation of thermostatic valves, timers, flow switches, thermostats sites to correlation of climatic conditions.
With proper use of natural lighting can reduce power consumption enough artificial light. Suitable openings and skylights, can offer a good alternative. Today the market move savers, lighting systems with energy efficiency index A and low consumption lamps. CRES estimates that a set of measures can be achieved reducing energy consumption for artificial lighting by 30% - 50%. Also appropriate it is to use task lights for work and office and suitable local manual control or centrally driven automatic control, which is achieved by using switches, grading, timers and light sensors.
In addition, the north-facing openings help in a good light quality of the premises, because receiving diffused light, not direct. In any case, the use of thermal insulation glazing with a low U-value or even better use of advanced glass (Low «Low-E») is considered one of the most efficient measures.
Passive solar systems for the exploitation of solar thermal gains
Provided that they ensure all the above measures to reduce heat loss in buildings, such as the southern exposure and strong insulation in the building envelope can be done using more sophisticated measures for greater exploitation of solar gain.
Such systems are:
- Direct solar gain from the south oriented openings
- The attached conservatory
- The mass wall or thermal storage
- The ventilated wall Trombe
- The solar patio
- the heater panel
- The air collectors
An energy management in buildings (Building Management Systems-BMS) consists of a set of electronic equipment, including sensors, actuators, and a
information processing system that controls and monitors the environmental services in the building. The BMS may take into account while all systems and parameters. Such as heating, lighting, air conditioning, etc., unlike conventional systems, and simultaneously calculates the energy consumed each time so that it can easily be calculated and the cost. An example that the use of BMS may decrease up to 40% of the total consumption and thus the costs.
- Automatic activation / deactivation of heating, lighting, etc. or switches e.g. heater or thermostat
- Optimization of the facilities and services
- Optimization of the fuel / air for boilers
- Maximum use of outside air for air conditioning and ventilation. Monitoring the situation of facilities and environmental conditions
- Flow temperature
- Assess condition of the filters. Provision of information for energy management
- About the streams and energy consumption
- Evaluate the effectiveness of the measures
- Display indications. How energy management systems help save energy?
- Minimize unnecessary use of lighting, heating, etc.
- Optimizing the performance of facilities
- operational maintenance level Optimization
- Enable improved standard of overall energy management
- they can encourage higher levels of awareness about energy consumption.
Energy saving in buildings is a very important piece in the green field development. Using existing technologies can achieve high energy efficiency and thermal comfort, while reducing costs and environmental impact. In which sector will decide the designer to give more weight obviously depends on the climatic characteristics of the region and of course the use of the building. The construction cost of a building energy efficient does not exceed 10% of creating a conventional building and the money depreciated over the lifetime of the building, as the economy in energy can reduce operating costs by 60%. Beside the above relatively simple interventions can be added to systems that utilize solar energy not only for the solar water heater, but to enhance the heating and even cooling in the summer, such as photovoltaic panels to produce electricity, and even use the geothermal. All these systems are no longer inaccessible and can be treated as an investment for the future as well, increase the value of the building.
Seraphim Georgakopoulos - Civil Engineer TE , MSc in Energy