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Solution sets for the Cost reduction of new Nearly Zero-Energy Buildings - CoNZEBs

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Innovative solutions lower the investment needed for buildings with better energy efficiency

Global climate change and growing populations are increasing the energy demand of buildings – and fostering initiatives to reduce the impact. Technical solutions that lower the costs of nearly zero-energy buildings (NZEBs) should help countries get on board.


Heating and cooling in response to extreme weather combined with the growing electrical demands of human activities resulted in an all-time high in building-related emissions in 2018. The EU’s Energy Performance of Buildings Directive targets NZEBs. While country guidelines vary, NZEBs focus on enhancing energy efficiency and increasing the use of renewables. Leading national research institutes in the field of high-performance buildings joined forces with innovative housing organisations to lower the investment cost associated with planning and construction of NZEBs. Their EU-funded CoNZEBs project identified multiple solution sets tailored to four countries to enhance each one’s market uptake of energy-efficient technologies for buildings.

Four countries and a focus on energy, time and money

CoNZEBs began by conducting research in the partner countries of Denmark, Germany, Italy and Slovenia to compare the investment costs of multifamily housing for conventional buildings, NZEBs and buildings exceeding the NZEB requirements. NZEBs cost more than conventional buildings by EUR 45/m2 in Germany and up to EUR 229/m2 in Italy due to factors including each country’s energy performance requirements, NZEB definitions and technology costs. Project coordinator Heike Erhorn-Kluttig of the Fraunhofer Institute for Building Physics explains: “We then analysed statistical cost information and a survey of planners and construction companies to find technologies or methods that reduce costs through a reduction in the design or construction time. These include large-sized building blocks or pre-fabrication and project management solutions like Building Information Modelling (BIM), a digital tool for central integrated design, asset planning and cooperation throughout a building’s life cycle.”

Individualised solutions with some common ground

CoNZEBs developed at least four technical solution sets for each country that lowered the investment costs associated with NZEBs. Although they are country-dependent, some similarities were found. Insulation material with lower thermal conductivity enables thinner walls and more rentable – and profitable – living areas. Heating and domestic hot water systems with higher efficiencies requiring less insulation in the building envelope are other important areas enabling cost reduction. Erhorn-Kluttig continues: “Our goal was to find solution sets that reduce the investment cost gap between conventional buildings and NZEBs by about 60 %. In some countries, we closed the gap completely and even identified NZEB solution sets that have lower investment costs than conventional buildings.” The life cycle assessment showed that some solutions also result in lower global warming potential including the embodied energy.

Looking to the future

Extrapolating to 2030 revealed that some countries had not yet studied the future of impact factors such as primary energy factors, energy tariffs and technology costs. Thanks to its close relationship with policymakers through its national advisory groups, CoNZEBs initiated discussions and first studies in these countries. Final analyses showed that electrical-driven NZEB concepts and beyond-NZEB concepts will become more attractive in the future. In conclusion, Erhorn-Kluttig states: “CoNZEBs has demonstrated that NZEBs can be built with only slightly higher investment costs than conventional buildings. Further, there are interesting technology solution sets available that are more environmentally friendly and lead to even lower costs than conventional buildings.” CoNZEBs outcomes should support more widespread uptake of new NZEBs, contributing to EU goals for energy-efficient buildings.


CoNZEBs, NZEB, buildings, energy, investment cost, construction, insulation, technical solution, heating, nearly zero-energy building, thermal conductivity, domestic hot water, building envelope, life cycle assessment

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