ENERGY EFFICIENCY OF BUILDINGS

1. Need for thermal insulation of buildings

In its thousand-year history, the humanity has always understood the buildings it built as a means of protection from the adverse effects of the natural environment. The surrounding elements of the building (roof, walls, floor, windows) create conditions in its premises to create a certain microclimate, the parameters of which correspond to the sanitary-hygienic and technological requirements.

The main functions that the thermal insulation of the surrounding elements of the building must perform can be formulated as follows:

• To make the heat exchange between the indoor air and the outside air as difficult as possible.
• To reduce energy losses when heating buildings during the winter season, as well as to protect the premises from overheating the air in them during the summer.
• To help achieve optimal sanitary-hygienic, and in certain cases technological parameters of the microclimate in the premises during the living and intended use of the buildings.

The microclimate in the premises is created by air and radiation regime.

Air mode is the interaction of temperature, humidity and air movement. From the combination of these three components at some point the indoor air regime can have a different physiological effect on humans.

The radiation regime in the premises is on the one hand heat exchange by radiation between the person and the surrounding elements of the building (windows, walls, floor, ceiling), and on the other – between the person and the outside space (with open windows, balcony doors, etc.)

Thermal discomfort for the occupant of a room or building occurs either in very hot weather (summer season), when his body needs to get rid of excess heat through heat exchange, or in cold weather (winter season), when his body cannot compensate for the heat given by the body to the surrounding space. To ensure this balance in the various temperature effects on humans, the measures and methods for regulating the microclimate in the premises are crucial, as well as for their skilful and economically purposeful use in the design of thermal insulation of the enclosing elements of a building.

         2. Modern trends in the design and implementation of energy efficient thermal insulation systems of new buildings

The problem of energy efficiency in heating and air conditioning of residential, public, industrial buildings is also extremely relevant in terms of energy savings. In a number of European countries the normative documents for designing the thermal insulation systems of buildings are aimed at improving their energy efficiency, and this is the goal of the Ordinance №7 on energy efficiency of buildings in force in Bulgaria since 2005.

In order to achieve energy efficiency of a building, it is necessary in the "conceptual design" phase to clarify the main points of the thermal insulation systems of its enclosing elements (facade walls, roofs, windows, floors above unheated rooms). In the "technical design" phase, part "architecture", the adopted solutions of the thermal insulation systems of the enclosing elements of the building must be specified, as well as the materials and the location of their thermal insulation layer must be specified. The working project in the "architecture" part of the thermal insulation systems of the enclosing elements of buildings gives specific solutions to their constructions and details based on the use of certain company materials and products.

When designing energy-efficient buildings, special attention is paid to the windows and glazing of doors and windows on facades, as they generally have higher thermal conductivity than well-insulated facade walls and in this sense represent the so-called "thermal bridge".

In many European countries and in recent years have implementations in Bulgaria, used windows and doors, heat transfer coefficient (u), which does not exceed 1.4, and in some cases even 0.7.

When the so-called "low-emission glass" is used in the glazing of doors and windows, energy savings in the heating of buildings can be achieved by not less than 25%, compared to those that have glazing units of traditional window glass.

An essential moment for achieving energy efficient buildings is during the construction the control bodies to help for the strict implementation of the decisions adopted in the project of the thermal insulation systems of the facade walls, roofs, etc.

3. Improving the energy efficiency of existing buildings

1. Preparation of a special part of the project for renovation of the building, related to the improvement of the thermal insulation of its enclosing elements, on the basis of the Ordinance №7 for heat storage and energy saving in buildings, effective in our country since 2005.

This project is developed on the basis of an energy audit of the building, made by legal entities accredited by the Energy Efficiency Agency.

2. Use of modern effective thermal insulation materials, such as mineral wool products, expanded polystyrene, polyurethane foam, foam glass, etc. for implementation of the additional thermal insulation system of the enclosing elements of the building.

This thermal insulation system is located on the outer surfaces of the enclosing structures of the building.

3. It is possible for the additional thermal insulation of the facade enclosing elements of the building to be in the version of panels, type "sandwich", which have a middle layer of foam, or of mineral wool boards.

These panels must be anchored securely to the facade walls by means of dowels.

4. Replacement of existing windows and balcony doors with aluminium, plastic or wooden windows, using "low-emission" glass.
5. The implementation of the works on the energy rehabilitation of buildings must be performed by specialized companies in this field, which have competent specialists and workers, as well as the necessary tools and machines for this purpose.

Why is energy efficiency of buildings important?

Energy efficiency has a goal of reducing energy costs not through saving, like the methods of energy saving but through the use of new technologies and methods, while reducing energy losses and the human footprint on the environment as much as possible.

The buildings which represent one of the biggest consumers of energy have an important role in the transit towards a greener economy. Therefore, the energy efficiency of buildings, which is reflected in modern trends in the design and implementation of energy efficient thermal insulation systems of new buildings, is one of the key goals of the European Union for energy efficiency and the reducing of energy losses and gas emissions with at least 55% in 2030, in comparison to these of 1990.

Renovation of buildings is promoted through the European Comission’ strategy – “A renovation wave of Europe – greening our buildings, creating jobs, improving lives” which aims towards increasing the pace of renovation of buildings in Europe and guaranteeing the better energy and resource efficiency. The initiative is based on the already agreed measures and conditions towards each member state for the preparation of national strategies in the field of energy and climate.

The legislation governing the Union’s objectives and each member state’s obligations, consists of the 2010 Energy performance of buildings directive, as amended in 2018 and 2018 Energy efficiency directive. These two directives aim to ensure “high energy efficiency and decarbonisation of the building stock in each Member State by 2050, in order to achieve the energy efficiency targets for Europe, such as reducing CO2 emissions in the EU by 80-95% compared to 1990” while supporting the modernization of all buildings trough intelligent technologies.

Energy efficiency challenges?

Of course, there are existing challenges in the improving and use of technologies and methods in energy efficiency.

The International Energy Agency reports that some of these challenges can be: high costs in the transit towards energy efficient methods, problems such as gathering reliable information on the subject, lack of the technological expertise for design, building and maintenance of buildings and equipment, lack of investments, limited access to financing and difficulties in the coordination of construction industry stakeholders.