In the face of the most serious international energy crisis of the last 40 years and with the daily increase in energy costs, interventions to improve the energy efficiency of buildings are now the main factor in saving energy in households.
According to published European Commission data, the distribution of energy costs in domestic buildings is as follows:
- 65% of total energy consumption is for heating needs.
- 10% of the total energy consumption is for hot water production needs.
- 5% of total energy consumption is for air conditioning needs.
- 10% of total energy consumption is for lighting.
- Only 10% of energy consumption is for other household appliances.
Nowadays, both European and Greece legislation for Regulation of Energy Performance of Buildings (greek:KENAK) for the construction of new buildings set strict conditions for their energy efficiency. Specifically, all newly constructed buildings, after 1/1/2022, must be necessarily classified at least in Energy Class A, i.e. their energy consumption must not be higher than 60 Kwh/sq.m/year. In order to achieve such energy efficiency in the building, a set of specific interventions is necessary, both in the building shell (thermal insulation, windows and doors) and in the heating, cooling, ventilation and hot water production systems.
Energy classification of a building* based on the total primary energy consumption in KWh/m2.
*According to the Technical Chamber of Greece, this classification method will be adopted in the future. Currently, the classification method is calculated by comparing the building under study with the reference building of the Regulation of Energy Performance of Buildings (greek: KENAK).
The buildings of Greece, which was mostly built before 1980, is uninsulated buildings with energy-intensive heating and cooling systems. In 1980 the regulations were changed and a basic insulation was required in new constructions. Such buildings, in addition to their general age, are classified in the lowest energy class H, and actually in the lowest levels of it.
As mentioned above, the building regulation today requires new buildings to be at least energy class A, and old buildings that are being upgraded should also aim towards this energy class.
In practice, a class H building, in climate zone A, with a surface area of 100 m2 spends about 1000€/year on heating (based on last year's 2020/2021 prices, which have doubled or even tripled in 2022), while a class A building, for exactly the same quality of heating, would spend only 100€. Similarly, if we look at the spending in KWh, a class H building typically spends 600KWh/per sqm/per year, while a class A building is under 60KWh/per sqm/per year, as mentioned before.
Which Energy Interventions should be made in both new and existing buildings
The first advice to building owners is that in order to reach the required energy efficiency, a set of interventions must be made in the building and not individual actions such as replacing windows, solar water heater or air conditioner as most people think.
The required interventions for significant energy savings in buildings are outlined in the latest EU funded programmes and include a set of interventions.
The operation of Heat Pump, which is the most advantageous source of heating
The most important of them are the upgrade of the heating-cooling system and the production of domestic hot water, the insulation of the building envelope, i.e. the energy windows and glass panels, as well as the insulation of the walls and the roof.
In addition, the automations offering quality control of the systems, a heat recovery mechanical ventilation or the photovoltaic systems, if they can be installed, are also very important. All these interventions, with an appropriate combination of each other and depending on each case, which is different, enable the building to move up energy classes.
Priority to Efficient Heating, Cooling and Production of Domestic Hot Water systems
It is now clear that in new buildings, a set of interventions should be made, since it is mandatory to achieve at least Energy Class A. On the other hand, what happens in existing buildings, which often cannot afford extensive interventions?
According to the relevant study of the Laboratory of Steam Engines & Boilers of the National Technical University of Athens, which compares the technoeconomic results of various energy interventions in Greek buildings, the energy upgrade of a building is primarily through the replacement of the existing heating and cooling system with new advanced systems with higher energy efficiency, but also in combination with the use of modern automation systems.
The recommended interventions in the heating system primarily include the replacement of the heating source, usually the oil boiler, either with a modern boiler with condensing technology, or even better with a heat pump which results a very low energy consumption and seems to be the only solution for achieving primary energy consumption levels in the nZEB (Nearly zero-energy buildings) area, in which newly constructed buildings should be classified. From 1/1/2030 onwards, newly constructed buildings will have to be ZEBs.
Solar thermal systems are an excellent choice for additional energy savings
One more intervention, with a particularly high contribution to energy efficiency, is the use of solar thermal systems to support heating, as well as production of domestic hot water. An intervention that allows a building to be classified in Energy Class A+, without the use of a photovoltaic system.
Building automation and Smart Home offer efficient control of systems
The control and automation devices of the heating installation have an important impact on the energy efficiency of the building. From the thermostat, which must be modern with intelligent self-learning algorithms, to Smart Home systems and their extended capabilities, both functional and energy-saving, are solutions that consumers should consider, as they can increase the energy rating up to two categories.
Finally, another investment with a fast payback time is adding ventilation systems with heat recovery, since they almost eliminate ventilation losses and result in extra savings of up to 30% on heating costs.
Heat Recovery Ventilation Systems reduce ventilation losses in heating by up to 93% while creating a healthy atmosphere
Thus, it is obvious that the replacement of the heating system must precede the other interventions. In cases of limited financial resources, which require priority setting and scheduling of actions, upgrading the heating system at the first stage will both maximise the financial benefits and returns per euro invested, and will not cancel any future upgrade projects.
Case Study: Villa Vesta building in Kalamata where it was upgraded in 2021 and from category H: 221 kwh/m2 it was raised to category A+: 39 kwh/m2
*The article of George Char. Andrianos, Dipl. Electrical Engineer MBA, founder and CEO of "ANDRIANOS", as published in the special edition "Residence" of the daily newspaper of Kalamata "Eleftheria", July 2022.