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Energy renovation of multi-family buildings in Sweden: An evaluation of life cycle costs, indoor environment and primary energy use, and a comparison with constructing a new building
Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, Faculty of Science & Engineering.ORCID iD: 0000-0001-7450-8489
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Residential buildings account for 27% of the final energy use in the European Union. In cold climates, space heating represents the largest proportion of the energy demand in residential buildings. By implementing energy efficiency measures (EEMs) in existing buildings, energy use can be significantly reduced. The Energy Performance of Buildings Directive states that renovations of buildings offer an opportunity to improve energy efficiency. Renovations that include measures implemented with the specific purpose of reducing energy use are referred to as energy renovations. In addition to improving energy efficiency, an energy renovation can also improve the indoor environment. Sweden, like many other European countries, faces the challenge of renovating an ageing building stock with poor energy performance. Improving energy efficiency and performing energy renovations in a cost-effective manner is central, and optimization approaches are often used to identify suitable EEMs and energy renovation approaches. New buildings usually feature better energy performance compared to older buildings, and one approach for reducing energy use in the building sector could be to demolish old buildings with poor thermal performance and build new buildings with better thermal performance.

The aim of this thesis is to evaluate energy renovations of multi-family buildings with regard to space heating demand, life cycle costs, indoor environment and primary energy use. The choice between energy renovation of a multi-family building and the demolition and construction of a new one is also investigated with regard to life cycle costs (LCCs). A Swedish multi-family building in which energy renovation has been carried out is used as a case study. The building was originally constructed in 1961 and has a lightweight concrete construction. The renovation included improving the thermal performance of the building envelope and replacing the exhaust air ventilation system with a mechanical supply and exhaust air ventilation system with heat recovery.

The methods used in the studies include dynamic whole building energy simulation, life cycle cost analysis and optimizations, and a questionnaire on indoor environment perception. Extensive field measurements have been performed in the building prior to and after renovation to provide input data and to validate numerical predictions. In addition to the studied building, the analysis of the choice between energy renovation and the demolition and construction of a new building includes three other building construction types, representing common Swedish building types from the 1940s, 1950s and 1970s.

The analysis shows that the energy renovation led to a 44% reduction in space heating demand and an improved indoor environment. The indoor temperature was higher after the renovation and the perception of the indoor temperature, air quality and noise in the building improved. The EEMs implemented as part of the energy renovation have a slightly higher LCC than the optimal combinations of EEMs identified in the LCC optimization. It is not cost-optimal to implement any EEMs in the building if the lowest possible LCC is the objective function. Attic insulation has a low cost of implementation but has limited potential in the studied building with its relatively good thermal properties. Insulation of the façade is an expensive measure, but has a great potential to reduce heat demand because of the large façade area. Façade insulation is thus required to achieve significant energy savings. Heat recovery in the ventilation system is cost-effective with an energy saving target above 40% in the studied building. The primary energy factors in the Swedish Building Code favor ground source heat pumps as a heat supply system in the studied building.

The LCC of renovation is lower compared to demolishing and constructing a new building. A large proportion of the LCC of demolition and new construction relates to the demolition of the existing building. In a building with a high internal volume to floor area ratio, it is not always possible to renovate to the same energy performance level as when constructing a new building. A more ambitious renovation approach is also needed compared to a building with a smaller volume to floor area ratio.

Abstract [sv]

Nära 27 % av den totala energianvändningen i den Europeiska Unionen sker i bostäder. I länder med kallt klimat används den största delen till uppvärmning. Genom att implementera energieffektiviseringsåtgärder i befintliga byggnaden kan energiprestandan signifikant förbättras. Europeiska Unionens direktiv om byggnaders energiprestanda framhåller att ett tillfälle att förbättra byggnaders energieffektivitet finns då byggnader ska renoveras. Byggnadsrenoveringar som innehåller åtgärder som implementeras med det primära syftet att minska energianvändningen kallas ofta energirenoveringar. Utöver energieffektivisering kan energirenoveringar ofta förbättra inomhusmiljön i byggnaden. Som många andra Europeiska länder står Sverige inför utmaningen att renovera ett åldrande byggnadsbestånd med låg energiprestanda. Kostnadseffektivitet är centralt vid energirenoveringar och energieffektivisering och optimeringsansatser är vanliga för att identifiera vilka energieffektiviseringsåtgärder som bör implementeras. Nya byggnader har som regel bättre energiprestanda jämfört med äldre byggnader, och en ansats till ett minska energianvändningen i byggnadssektorn överlag är således att riva äldre byggnader med låg energiprestanda och konstruera nya byggnader med bättre energiprestanda.

Syftet med denna avhandling är att utvärdera energirenoveringar av flerfamiljshus avseende effekterna på uppvärmningsbehov, livscykelkostnader, inomhusmiljö och primärenergianvändning. Valet mellan energirenovering kontra att riva och bygga en ny byggnad analyseras också utifrån ett livscykelkostnadsperspektiv. För att studera detta har en svensk flerfamiljsbyggnad som genomgått energirenovering studerats. Byggnaden konstruerades 1961 och har en lättbetongstomme. När byggnaden renoverades förbättrades prestandan hos byggnadens klimatskal och frånluftsventilationssystemet byttes ut mot ett balanserat mekanisk ventilationssystem med värmeåtervinning.

Metoderna som använts i studierna i denna avhandling är dynamisk byggandssimulering, beräkning och optimering av livscykelkostnader, samt en enkätstudie om hur de boende uppfattar sin inomhusmiljö. Omfattande mätningar har utförts i byggnaden och har använts som indata och för att validera resultaten. Utöver den studerade byggnaden har tre andra byggnadstyper inkluderats i analysen av valet mellan energirenovering och att riva och konstruera en ny byggnads. Dessa byggnadstyper representerar vanliga svenska byggnadstyper från 1940-, 1950- och 1970-talet.

Analyserna visar att den renovering som genomfördes i byggnaden ledde till en minskning av uppvärmningsbehovet med 44 % och en förbättring av inomhusmiljön. Inomhustemperaturen var högre efter renoveringen, och de boende uppfattade temperaturförhållanden, luftkvalitet och bullersituationen som bättre efter renoveringen. De energieffektiviserande åtgärder som implementerades vid renoveringen gav en något högre livscykelkostnad än de åtgärder som identifierades som optimala genom livscykelkostnadsoptimering. Det är inte kostnadseffektivt att implementera några energieffektiviseringsåtgärder som del av renoveringen om den lägsta livscykelkostnaden är målsättningen. Vindsisolering är en förhållandevis billigt åtgärd att genomföra, men har begränsad potential i den studerade byggnaden vars vind redan har relativt god termisk prestanda. Fasadisolering kräver en större investering, men har större potential att minska energianvändning på grund av den stora fasadytan. Detta innebär att det är nödvändigt att isolera fasaden för att uppnå hög energibesparing. Värmeåtervinning i ventilationssystemet är kostnadsoptimalt om ett energisbesparingsmål på mer än 40 % ställs på energirenoveringen. Primärenergifaktorerna i den svenska byggnadskoden gynnar bergvärmepump som energitillförselsystem i de studerade byggnaden.

Kostnaden för att energirenovera är lägre än att riva och bygga en ny byggnad. En stor andel av kostnaderna vid rivning och nybyggnation är kopplad till rivning och bortforsling av rivningsmassa. I byggnadstyper med stor inre volym i förhållande till uppvärmd golvyta är det inte alltid möjlig att energirenovera till en energiprestanda som är lika god som en ny byggnad. Det krävs också en mer ambitiös renovering för att uppnå samma energiprestanda som en byggnad med mindre inre volym i förhållande till uppvärmd golvyta.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2019. , p. 97
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 2008
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-160305ISBN: 9789176850077 (print)OAI: oai:DiVA.org:liu-160305DiVA, id: diva2:1352137
Public defence
2019-10-25, ACAS, A-huset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2019-09-18 Created: 2019-09-17 Last updated: 2019-10-15Bibliographically approved
List of papers
1. Energy Performance of a Renovated Multi-Family Building in Sweden
Open this publication in new window or tab >>Energy Performance of a Renovated Multi-Family Building in Sweden
2017 (English)In: Mediterranean Green Buildings & Renewable Energy / [ed] Sayigh, Ali, Springer International Publishing , 2017, p. 531-539Conference paper, Published paper (Refereed)
Abstract [en]

Increased attention is being directed towards reducing energy use in buildings, and implementing energy-saving measures when renovating buildings has become of central importance. The aim of this chapter is to study the effects on heat demand of a deep renovation of a Swedish post-war, multi-family building. The studied building was renovated in 2014, and the renovation measures included thermal improvement of the climate envelope and installation of a mechanical supply and exhaust air ventilation system with heat recovery. The effect on heat demand is studied through a whole-building energy simulation, using IDA Indoor Climate and Energy. The IDA model is empirically validated with regard to its ability to predict indoor temperature and energy use. The results indicate a technical potential for a 50.3 % reduction of heat demand from implemented renovation measures, but measured data indicate that actual energy use is around 15 % higher than the technical potential. The reasons for this gap could be overestimated heat recovery efficiency or airing.

Place, publisher, year, edition, pages
Springer International Publishing, 2017
National Category
Building Technologies Energy Systems
Identifiers
urn:nbn:se:liu:diva-160813 (URN)10.1007/978-3-319-30746-6_39 (DOI)9783319307459 (ISBN)9783319307466 (ISBN)
Conference
Springer Cham
Available from: 2019-10-09 Created: 2019-10-09 Last updated: 2019-10-09
2. Measured and predicted energy use and indoor climate before and after a major renovation of an apartment building in Sweden
Open this publication in new window or tab >>Measured and predicted energy use and indoor climate before and after a major renovation of an apartment building in Sweden
2017 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 146, p. 98-110Article in journal (Refereed) Published
Abstract [en]

This article presents a case study of a renovated Swedish apartment building with a common design built in 1961. The aim is to present numerical predictions, validation and evaluation of energy use and indoor climate for the building before and after renovation. Comprehensive field measurements were carried out before and after the renovation to be used as input data in the building energy simulation tool IDA ICE and for validation of model results. Indoor temperature is predicted with maximum standard deviation of 0.4 degrees C during winter. Annual heat demand is in good agreement with measurements. The building had an annual climate normalized district heat demand of 99.0 MWh before renovation and 55.4 MWh after, resulting in a 44% reduction. A slight under-prediction of the saving potential is noted, since the indoor air temperature has increased after the renovation. The results also show that assumptions of user behavior have significant impact on the energy-saving potential, and that choice of renovation measures, such as level of insulation, and efficiency of the ventilation heat recovery system need careful consideration. Choice of system boundaries also has a major effect on climate and resource impact from selected renovation measures. (C) 2017 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2017
Keywords
Renovation; Multi-family buildings; Building energy simulation; Field measurements; Validation; Energy use; CO2 emissions; Primary energy
National Category
Building Technologies
Identifiers
urn:nbn:se:liu:diva-138876 (URN)10.1016/j.enbuild.2017.04.042 (DOI)000403122200010 ()
Note

Funding Agencies|Swedish Research Council Formas

Available from: 2017-06-27 Created: 2017-06-27 Last updated: 2019-09-18
3. Energy Use and Perceived Indoor Environment in a Swedish Multifamily Building before and after Major Renovation
Open this publication in new window or tab >>Energy Use and Perceived Indoor Environment in a Swedish Multifamily Building before and after Major Renovation
2018 (English)In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 10, no 3, article id 766Article in journal (Refereed) Published
Abstract [en]

Improved energy efficiency in the building sector is a central goal in the European Union and renovation of buildings can significantly improve both energy efficiency and indoor environment. This paper studies the perception of indoor environment, modelled indoor climate and heat demand in a building before and after major renovation. The building was constructed in 1961 and renovated in 2014. Insulation of the facade and attic and new windows reduced average U-value from 0.54 to 0.29 W/m(2).K. A supply and exhaust ventilation system with heat recovery replaced the old exhaust ventilation. Heat demand was reduced by 44% and maximum supplied heating power was reduced by 38.5%. An on-site questionnaire indicates that perceived thermal comfort improved after the renovation, and the predicted percentage dissatisfied is reduced from 23% to 14% during the heating season. Overall experience with indoor environment is improved. A sensitivity analysis indicates that there is a compromise between thermal comfort and energy use in relation to window solar heat gain, internal heat generation and indoor temperature set point. Higher heat gains, although reducing energy use, can cause problems with high indoor temperatures, and higher indoor temperature might increase thermal comfort during heating season but significantly increases energy use.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
renovation; indoor environment; thermal comfort; building energy simulation; energy use; multifamily buildings
National Category
Building Technologies
Identifiers
urn:nbn:se:liu:diva-147818 (URN)10.3390/su10030766 (DOI)000428567100193 ()
Note

Funding Agencies|Swedish Research Council Formas

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2019-09-18
4. Energy Renovation versus Demolition and Construction of a New BuildingA Comparative Analysis of a Swedish Multi-Family Building
Open this publication in new window or tab >>Energy Renovation versus Demolition and Construction of a New BuildingA Comparative Analysis of a Swedish Multi-Family Building
2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 11, article id 2218Article in journal (Refereed) Published
Abstract [en]

This study addresses the life cycle costs (LCC) of energy renovation, and the demolition and construction of a new building. A comparison is made between LCC optimal energy renovations of four different building types with thermal performance, representing Swedish constructions from the 1940s, 1950s, 1960s, and 1970s, as well as the demolition of the building and construction of a new building that complies with the Swedish building code. A Swedish multi-family building from the 1960s is used as a reference building. LCC optimal energy renovations are identified with energy saving targets ranging between 10% and 70%, in addition to the lowest possible life cycle cost. The analyses show that an ambitious energy renovation is not cost-optimal in any of the studied buildings, if achieving the lowest LCC is the objective function. The cost of the demolition and construction of a new building is higher compared to energy renovation to the same energy performance. The higher rent in new buildings does not compensate for the higher cost of new construction. A more ambitious renovation is required in buildings that have a shape factor with a high internal volume to heated floor area ratio.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
renovation; energy renovation; demolition; new construction; energy use; energy performance; life cycle cost; optimization; OPERA-MILP; multi-family buildings
National Category
Building Technologies
Identifiers
urn:nbn:se:liu:diva-158988 (URN)10.3390/en12112218 (DOI)000472635900185 ()
Note

Funding Agencies|Swedish Research Council Formas

Available from: 2019-07-19 Created: 2019-07-19 Last updated: 2019-10-02

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