Cost-optimal renovation of residential, educational and office buildings in Finnish climate toward nearly zero-energy buildings

Tuomo Niemelä

Research output: ThesisDoctoral ThesisCollection of Articles


Cost-effective renovation of existing buildings is a challenging and important task to significantly reduce the environmental impact of the built environment. Determining cost-effective renovation concepts for buildings inevitably leads to a multi-dimensional optimization problem because cost-effectiveness and energy efficiency are conflicting objectives with each other. The building owners are interested in solid renovation concepts that reduce the operating costs of the building but also deliver a reasonable return on investment and a reasonable payback period. The main objective of this thesis was to study and determine the cost-optimal renovation concepts for the common Finnish building types that also have a significant energy efficiency improvement and environmental impact reduction potential. The studied building types were typical brick apartment buildings, concrete large panel apartment buildings, educational buildings, and office buildings. The objective was to take all applicable energy efficiency improvement measures, including the modern heat pump and renewable energy production technologies, into account in the assessment of each building type. In addition to studying the economic viability of different renovation concepts, technical, functional, feasibility, and quality aspects, such as the indoor environment conditions and the productivity of occupants, were examined closely. A common solution of the cost-optimal renovation concepts of all the studied building types was that the investments should be focused on renewable energy production technologies and on technical systems of the buildings instead of investing in major renovations of the building envelopes. Especially the modern heat pump systems delivered significant improvements in both the energy performance of the buildings and in the cost-effectiveness of the deep renovation in all the studied building types. The studied heat pump systems delivered better cost-effectiveness than the district heating system in all the studied building types. According to the study, it is not cost-efficient or recommended to improve the energy efficiency of the building envelope beyond the current national building regulations regarding the energy performance of new buildings. According to the results, the minimum primary energy performance requirements of the current building regulations related to improving energy performance of buildings in deep renovations could be tightened by 10% for residential apartment buildings, 30% for educational buildings and 20% for office buildings, depending on the original condition of the building. The proposed national nearly zero-energy building requirements can be cost-effectively achieved in deep renovations. However, external financial support mechanisms and competitive financial solutions are essential factors and motivators to encourage the building owners to take the next step in deep renovations of buildings by lowering the economic risks related to the renovation.
Translated title of the contributionAsuin-, opetus- ja toimistorakennusten kustannusoptimaalinen peruskorjaaminen Suomen ilmastossa kohti lähes nollaenergiarakennuksia
Original languageEnglish
QualificationDoctor's degree
Awarding Institution
  • Aalto University
  • Kosonen, Risto, Supervising Professor
  • Kosonen, Risto, Thesis Advisor
  • Jokisalo, Juha, Thesis Advisor
Print ISBNs978-952-60-7813-7
Electronic ISBNs978-952-60-7814-4
Publication statusPublished - 2018
MoE publication typeG5 Doctoral dissertation (article)


  • cost-optimal renovation
  • cost-effectiveness
  • energy efficiency
  • renewable energy source
  • environmental performance
  • multi-objective optimization
  • thermal comfort


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