Skip to main content
  • English (en)
  • Accessibility
  • Sitemap
  • About this site
  • FAQ
  • Legal notice
  • Cookies
  • Contact
  • Search
SETIS

SETIS

Strategic Energy Technologies Information System
Home
Menu

You are here

European CommissionSETISPublicationsSETIS MagazineEnergy Efficiency in BuildingsOccupant behaviour and the energy savings gap...

Header menu

  • Home
  • Search
  • Home
  • About SETIS
    • SET Plan community
    • A European Green Deal
  • Actions towards implementing the Integrated SET Plan
    • No 1 in Renewables
    • Smart Solutions for Consumer
    • Smart Resilience and Secure Energy System
    • Energy Efficiency in Buildings
    • Energy Efficiency in Industry
    • Batteries and e-Mobility
    • Renewable Fuels and Bioenergy
    • Carbon Capture Utilisation and Storage
    • Nuclear Safety
    • Towards an Integrated Roadmap
    • Implementation plans
  • Low Carbon Energy Technologies
    • No1 in Renewables
    • Smart Systems and Consumers
    • Efficient Energy Systems
    • Sustainable Transport
    • Carbon Capture Utilisation and Storage
    • Nuclear Safety
  • Publications
    • SET Plan Implementation Progress Reports
    • SETIS Research & Innovation data
    • SETIS Magazine
    • Relevant reports
    • Integrated SET Plan infographics
  • Calendar

Search form

Recent news

Recent News

Energy Efficiency in Buildings

SETIS Magazine, October 2019

Subscribe

Index

Editorial
Foreword: The role of buildings in the 2050 long-term strategy
Dimitrios Athanasiou talking to SETIS
The role of buildings in the heating sector transition
Cost-effective transformation of Italian building stock
Laure Itard talking to SETIS
Smart buildings and the role of digitalisation
Building energy epidemiology as a tool to support European building energy performance improvement
A Swedish perspective on energy communities and districts
Andreas Hermelink talking to SETIS
EPBD19a feasibility study on building renovation passport – definition and first results
Occupant behaviour and the energy savings gap in Hellenic residential buildings
Epilogue: Implementation of the SET Plan Action on energy efficiency solutions for buildings
SET Plan news

Publications

  • SET Plan Implementation Progress Reports
  • SETIS Research & Innovation data
  • SETIS Magazine
  • Relevant reports
  • Integrated SET Plan infographics

Occupant behaviour and the energy savings gap in Hellenic residential buildings

LinkedIn Twitter Facebook Google Plus 


COSTAS BALARAS

Costas Balaras is a mechanical engineer and holds a PhD from Georgia Tech. He is a research director at the Institute for Environmental Research & Sustainable Development (IERSD) at NOA in Athens, Greece. He is active in energy conservation, high performing buildings, sustainable cities, thermal and solar applications, building energy audits diagnosis and environmental impact assessments. He has participated in around 50 R&D and demonstration projects and was instrumental in the national adaptation of EPBD in Greece. He has published over 250 articles in journals, books and conference proceedings. He is a chartered engineer in Greece, an ASME Fellow and ASHRAE Fellow.


ELENA DASCALAKI

Elena Dascalaki is a building physicist and holds a PhD from the University of Athens. She is a senior researcher at the Institute for Environmental Research & Sustainable Development (IERSD) at NOA in Athens, Greece. She currently works on building typologies and building stock modelling, lifecycle analysis, building thermal simulations, and computational fluid dynamics. She has participated in over 35 R&D and demonstration projects and published over 130 articles in journals, books and conference proceedings.

© Dimitris Vetsikas - Pixabay

Residential buildings in Greece account for 27.5% of the country’s total final energy use (Figure 1), and are responsible for 21.7% of total carbon dioxide emissions[1]. Space heating (56.2%) and domestic hot water (DHW) (13.5%) are the most important end-uses[2] . According to the latest national Buildings Census, there are ~3 million exclusive residential use buildings, representing ~79% of the building stock[3]. The grim reality is that the vast majority lack proper thermal protection and have ageing heating, ventilation and air conditioning (HVAC) installations, failing to meet the new energy efficiency standards according to the national transposition of the EPBD[4] mandates, KENAK[5].

A bottom-up building stock model has been developed for Hellenic residential buildings, based on the national TABULA typologies for assessing energy conservation measures and quantifying savings from renovation scenarios6. However, the gap between calculated and actual energy use has long been recognised as a major hurdle for realistic assessments of building performance[7].

'Residential buildings in Greece account for 27.5% of the country's total final energy use in 2017, and are responsible for 21.7% of the total carbon dioxide emissions'

To make more realistic estimates of actual energy use, heating energy consumption calculated by KENAK can be adapted using empirical factors derived from data included in energy performance certificates (EPC) or collected from simple behavioural occupant surveys.

Figure 1 - Evolution of total final energy consumption in Greece. The doughnut chart summarises the final energy consumption by sector and the pie chart illustrates the breakdown of exclusive-use buildings in Greece. Source: EUROSTAT and ELSTAT
Figure 2 - Scatter plots and power regression curve of data for the calculated and actual space heating & DHW final EUI (kWh/ m2) from 1899 residential buildings in Greece. The 45-degree line (x = y) represents scenarios where the calculated and actual energy consumption values match. Source: Buildingcert

Data from the Hellenic EPC repository[8] was used to derive empirical adaptation factors, defined as the ratio of the specific actual (operational) energy use to the normative calculated (asset) final energy consumption from each building. Figure 2 illustrates the final energy use intensities (EUIs) for space heating and DHW derived from 1899 EPCs issued in 2011-2018. The large variations can be attributed in part to unique building characteristics, prevailing weather conditions, occupant behaviour and the deviation of actual operating conditions from the default values used in calculations.

'Moving forward, the big challenge is to improve the energy performance of our buildings while securing proper indoor environmental quality'

The average adaptation factor is 0.584 (i.e. 41.6% lower actual energy use than calculated). In general, higher calculated EUIs correspond to lower actual energy use, known as the ‘prebound’ effect. This is more evident for dwellings with a high calculated EUI (i.e. poor energy performance). This corresponds with published results of actual energy use ranging from 30% to 47% less than calculated space heating[9].

© Kookay - Pixabay

'On the more important end of indoor comfort conditions, only half of the occupants manage to feel comfortable in their dwellings'

The opposite phenomenon is known as the ‘rebound’ effect, when actual energy use is higher than calculated, most notable in low-EUI dwellings (i.e. good energy performance). The values reported range from 36 % to 51 %. Periodically updated field surveys of homeowners in 278 dwellings reveal additional insights into behavioural changes and trends in the use of heating systems (Figure 3).

Figure 3 - Actual operating characteristics in single-family (SFH) and multi-family (MFH) houses from field surveys. (a) Average daily operating periods of space heating systems; (b) Percentage of isolated non-heated floor areas; (c) Percentage of average indoor day and night set-point temperatures. The grey shaded areas identify the assumed values used in the normative calculations. Source: Own datasets.

According to field data, only about 14.3% of singlefamily houses (SFHs) and 9.3% of multi-family houses (MFHs) have operating hours close to the assumed continuous heating (Fig. 3a). Distribution peaks around 3-4 and 5-6 hours per day in SFHs and MFHs respectively. About 69% of SFHs and 78% of MFHs operate their central heating for less than eight hours. Isolating some rooms is another common practice by homeowners for reducing energy costs (Fig. 3b). Only 38% of SFHs and 44% of MFHs heat their entire dwelling. A notable trend revealing the impact of the recent recession in Greece and of high heating oil prices (through taxes) is that 26% of MFHs have turned off their central heating systems, and over 16% of SFHs. Lowering the temperature is another common way to reduce heating costs, even at the expense of thermal comfort. Only 25% of the occupants of SFHs and 19% in MFHs reported an average temperature setting of 20 oC (Fig. 3c), the indoor set-point used in normative calculations. The derived adaptation factors that address these deviations are 0.40 for heating operating hours, 0.89 for reduced heated floor areas and 0.86 for indoor temperature. These factors can be used as multipliers to obtain more realistic estimates of actual energy use. The unfortunate impact of these behavioural trends is that only half of occupants (52% of SFHs and 45% of MFHs) feel comfortable in their dwellings, while 6% of SFHs and 10% of MFHs are forced to live in severely adverse conditions.


[1] Energy statistical country datasheets, European Commission, DG Energy, Unit A4, July 2019.

[2]Energy consumption in households, Eurostat, May 2019.

[3]Buildings Census 2011, Hellenic Statistical Authority (ELSTAT), Athens, 2015.

[4]Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings

[5]Dascalaki E.G., Balaras C.A., Gaglia A.G., Droutsa K.G., Kontoyiannidis S., Energy Performance of Buildings - EPBD in Greece, Energy Policy, Vol. 45, 2012, pp. 469–477.

[6]Dascalaki E.G., Balaras C.A., Kontoyiannidis S., Droutsa K.G., Modeling Energy Refurbishment Scenarios for the Hellenic Residential Building Stock Towards the 2020 & 2030 Targets, Energy & Buildings, Vol. 132, 2016, pp. 74-90.

[7]Balaras C.A., Dascalaki E.G., Droutsa K.G., Kontoyiannidis S., Empirical Assessment of Calculated and Actual Heating Energy Use in Hellenic Residential Buildings, Applied Energy, Vol. 164, 2016, pp. 115-132.

[8]Buildingcert - National EPC repository, Hellenic Ministry of Environment & Energy in collaboration with CRES.

[9]Galvin R., Sunikka-Blank M., Quantification of (p)rebound

  • Archive
  • Newsroom
  • Toolbox
  • Last update: 25/02/2021
    • Accessibility
    • Sitemap
    • About this site
    • FAQ
    • Legal notice
    • Cookies
    • Contact
    • Search
    | Top