New developments in Energy Efficiency

Despite its rapid growth and significant importance to the EU economy, the construction industry accounts for the largest share of total EU final energy consumption (40%), generating about 35% of all greenhouse emissions[1]. Additionally, buildings constitute the third-largest consumer of fossil fuels after industry and agriculture. Thus, energy conservation through the exploitation of buildings’ energy efficiency is becoming of increasing value, not only in Europe but all over the world.

In order to reduce buildings’ energy consumption, and thus their CO2 emissions, the following approaches can be viewed as state-of-the-art:

1.Implementation of passive design, meaning to design buildings in a manner that maximises the use of natural sources of heating, cooling and ventilation. The main passive strategies include:

a) South- or north-facing orientation of buildings: orientating a building to take advantage of how the sun moves across the sky is the easiest and most effective passive design strategy.

b) Daylighting: the practice of dictating the type of windows based on the climate in which a building is located.

c) Natural ventilation: using natural ventilation as a passive design strategy is most effective in climates where there is a comfortable outdoors ambient temperature for several months of the year and less common in climates where a building is not comfortably occupied without being mechanically cooled or heated.

d) Proper insulation: adding extra insulation, in the form of a building envelope above the mere code requirements, is widely acknowledged as a good passive design tactic.

e) Use of metal building construction products: metal building systems and construction products can provide high R-vales on the wools and roof, whilst their reflectivity can increase products’ solar reflectance index (SRI) value, supporting the reduction of cooling loads through passive design.

2. Building-integrated renewable energy technologies. Such technologies include:

a) Flat Plate Thermosyphon Units (FPTU) and Integrated Collector Storage (ICS): these are small size solar water heaters, aiming to cover domestic needs of about 100-200 litres of hot water per day.

b) Solar Collectors with Coloured Absorbers: Solar collectors with coloured (rather than black) absorbers might have lower absorptance and energy efficiency levels, but they enable architects to apply them to a larger extent in modern or traditional buildings.

c) Solar Collectors with Booster Reflectors: horizontal roof and solar collectors can be installed in parallel rows, placed at a proper distance, which is exploited to provide additional solar radiation on the collector aperture surface.

d) Unglazed Solar Collectors: relies on the use of glass coatings that diffuse reflected light.

e) Hybrid Photovoltaic/Thermal (PV/T) systems: hybrid PV/T systems that consist of PV modules coupled with water or air heat extractors can achieve higher energy conversion efficiency.

f) Fresnel Lenses for Building Atria: optical devices for solar radiation concentration.

g) Building Integration of Solar/Wind systems: the combination of solar and wind systems constitutes one of the most interesting renewable energy sources for built environments. Small wind turbines can be mounted on building roofs, while the facades and the horizontal/inclined roofs are appropriate surfaces for the application of solar energy conversion systems.

Check out the technologies that are being developed within RE-COGNITION project: Building-integrated photovoltaics (BIPV) and Vertical Axis Wind Turbine self-adapting to variable winds.

h) Smart air handling units: pre-heating the fresh, ambient air using Earth-water heat exchanger integrated with water-air heat exchanger.

3. Use of low embodied energy materials that reduce energy during building construction. The term ‘embodied energy’ refers to the energy capital that is due to the manufacturing and transportation ‘environmental cost’ of building materials. This type of energy is estimated to be accountable for about 15% to 20% of the energy used by a building over a 50-year period. The use of low embodied energy materials such as stone, soil-cement blocks and hollow concrete blocks can greatly reduce the environmental impact of building construction. Reducing the transportation distance of building materials can also positively affect the environmental imprint of the construction industry.

4. Use energy-efficient domestic appliance to conserve the operational energy of buildings. Domestic appliances include, among others, lighting and home entertainment appliances, white goods, kitchen appliances, EV chargers, washing machines, dryers and dishwashers. In this context, checking the energy labels and ratings (where applicable) of domestic appliances and avoid leaving appliances on standby are recommended practices.

In conclusion, the combination of various solar passive design aspects can be easily integrated into new buildings based on the site, the orientation of the building and local climatic conditions and has shown promising results. Similarly, the use of the proper design of daylighting can lead to a tremendous reduction in the use of artificial lights during daytime and thereby reduces the energy consumption by building for lighting. Hence, the integration of solar passive features into the building leads to a reduction in energy consumption of the building which ultimately reduces the CO2 emissions and helps in sustainable development. The second important aspect is related to the use of low embodied energy and locally available building materials for the construction industry. This practice can lead to a tremendous improvement in terms of energy input required during building construction and thereby to a significant reduction of CO2 emission caused by the building sector. Finally, the move to highly energy-efficient or zero-emission green buildings, meaning buildings that are able to meet all their energy requirements by relying mostly or solely on renewable energy technologies, can be viewed as a feasible alternative to reduce the consumption of energy that derives from fossil fuels.


Chel, A., Janssens, A., & De Paepe, M. (2015). Thermal performance of a nearly zero-energy passive house integrated with the air-air heat exchanger and the earth–water heat exchanger. Energy and Buildings96, 53-63.

Chel, A., & Kaushik, G. (2018). Renewable energy technologies for sustainable development of an energy-efficient building. Alexandria Engineering Journal, 57(2), 655-669.

Thormark, C. (2002). A low energy building in a life cycle—its embodied energy, energy need for operation and recycling potential. Building and Environment, 37(4), 429-435.

Tripanagnostopoulos, Y., & Souliotis, M. (2004). ICS solar systems with horizontal (E–W) and vertical (N–S) cylindrical water storage tank. Renewable Energy, 29(1), 73-96.

Tripanagnostopoulos, Y., Tselepis, S., Souliotis, M., Tonui, J. K., & Christodoulou, A. (2004). Practical aspects of small wind turbine applications. In Proc. in Int. EWEC 2004 Conf., Track (Vol. 7).


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