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Cost-optimality approach for prioritisation of buildings envelope energy renovation: A techno-economic perspective
Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology.
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The existing residential buildings in the European countries are rather old and often fail to meet the current energy performance criteria. In Sweden, about 45% of the existing residential buildings have been constructed before 1960. Considering the significant contribution of existing buildings to Greenhouse Gas emissions, improving buildings energy performance could considerably help to achieve the national targets. Sweden’s fourth national action plan calls for 45% reduction in final energy use for heating of buildings by 2050, compared to 1995. Deep energy renovation of buildings envelope would significantly contribute to heat demand reduction. However, it is often subject to complex challenges from economic perspectives.

In this thesis, the cost-effectiveness and cost-optimality of building energy renovation have been studied in order to provide knowledge on where to start building renovation, in which order and to what extent. It aims at suggesting cost-effective approaches for prioritising the implementation of energy renovation measures in residential buildings, considering different techno- economic scenarios. An extensive building energy simulation work and analytical analysis were performed on a multi-family building and single- family houses.

The findings suggest how to prioritise the energy renovation of different envelope components in buildings located in different outdoor climates from energy saving and cost-effective perspectives. The findings indicate that the energy renovation of older buildings in northern climate zones are more cost- effective, compared to less old buildings in southern zones, when renovated to a cost-optimal level. The older buildings offer more energy saving when renovated to a cost-optimal level, compared to less old buildings or those in southern zones. The contribution of climate zones to the cost-effectiveness of energy renovation varies significantly in different components, depending on their level of exposure to outdoor climate.

An optimisation exercise was done in order to maximise energy saving by renovation of building envelope components under budget constraint condition. The enumerative algorithm of Brute-force was employed for this optimisation problem. The results suggest optimum renovation packages which could offer as much energy saving as a limited budget allows. It helps to develop a forward-thinking perspective that would guide individuals and financial institutions in their investment plans and incentives allocation policy.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2018. , p. 90
Series
Linnaeus University Dissertations ; 311
Keywords [en]
Building renovation, Energy efficiency, Cost-optimality, costeffectiveness, Building envelope, Residential buildings, Building energy simulation, Brute-force algorithm
National Category
Civil Engineering Building Technologies Environmental Engineering
Research subject
Technology (byts ev till Engineering), Sustainable Built Environment
Identifiers
URN: urn:nbn:se:lnu:diva-78059Libris ID: 22523422ISBN: 978-91-88761-33-0 (print)ISBN: 978-91-88761-34-7 (electronic)OAI: oai:DiVA.org:lnu-78059DiVA, id: diva2:1251658
Public defence
2018-03-08, Södrasalen, Hus M, Växjö, 12:00
Opponent
Supervisors
Available from: 2018-09-28 Created: 2018-09-27 Last updated: 2018-09-28Bibliographically approved
List of papers
1. Implications of energy efficiency renovation measures for a Swedish residential building on cost, primary energy use and carbon dioxide emission
Open this publication in new window or tab >>Implications of energy efficiency renovation measures for a Swedish residential building on cost, primary energy use and carbon dioxide emission
2013 (English)In: ECEEE Summer Study proceedings: rethink, renew, restart, European Council for an Energy Efficient Economy (ECEEE), 2013, p. 1287-1296Conference paper, Published paper (Refereed)
Abstract [en]

Building sector accounts for 40% of total primary energy use in the EU. Measures to improve energy efficiency in existing buildings may reduce primary energy use and carbon dioxide (CO2) emission. In this study, we analysed the potential final energy savings for space heating and cost-effectiveness of different energy efficiency measures for a Swedish multi-story residential building from building owner perspective. The implications of the measures on primary energy use and CO2 emission were also explored. Building envelope elements were considered as energy efficiency measures. Required investment for energy efficiency measures per saved energy price was used as indication for the cost-effectiveness of energy renovation. We analysed three scenarios of energy renovation where the building is in its initial state, once with and then without renovation need for repair and maintenance purpose and the scenario for the current state of building. The current state of the building has some modification compared to the initial state. We performed sensitivity analysis to study the influence of economic parameters on the cost-effectiveness of energy efficiency measures. The results showed that the energy savings and cost-effectiveness of the measures depend on building characteristics, energy efficiency measures and the assumed economic parameters. Modelling of final energy use, before and after energy renovation, and its cost analysis showed that the considered energy efficiency measures were not economically profitable with the initial economic assumption (6% discount rate and 1.9% annual energy price increase during 50-year lifespan). For the renovation package of all energy efficiency measures, energy renovation appeared to be profitable when discount rate and annual energy price increase were 3% and 2.5% (or larger), respectively. Primary energy use and CO2 emission were reduced by 45 to 50% for the same package for the building with cogeneration-based district heating.

Place, publisher, year, edition, pages
European Council for an Energy Efficient Economy (ECEEE), 2013
Series
eceee Summer Study, ISSN 1653-7025
Keywords
building envelope, energy efficiency measures, cost effectiveness, building retrofitting, CO2 emissions, primary energy
National Category
Civil Engineering
Identifiers
urn:nbn:se:lnu:diva-24877 (URN)978-91-980482-2-3 (ISBN)
Conference
ECEEE 2013, Belambra Les Criques, France, June 3-8, 2013
Available from: 2013-03-22 Created: 2013-03-22 Last updated: 2018-09-28Bibliographically approved
2. Cost-optimum analysis of building fabric renovation in a Swedish multi-story residential building
Open this publication in new window or tab >>Cost-optimum analysis of building fabric renovation in a Swedish multi-story residential building
2014 (English)In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 84, p. 662-673Article in journal (Refereed) Published
Abstract [en]

In this study, we analysed the cost-optimum level of building fabric elements renovation in a multi-story residential building. We calculated final energy use for space heating of the building considering a wide range of energy efficiency measures, for exterior walls, basement walls, attic floor and windows. Different extra insulation thicknesses for considered opaque elements and different U-values for new windows were used as energy efficiency measures. We calculated difference between the marginal saving of energy cost for space heating and the investment cost of implemented energy efficiency measures, in order to find the cost-optimum measure for each element. The implications of building lifespans, annual energy price increase and discount rate on the optimum measure were also analysed. The results of the analysis indicate that the contribution of energy efficiency measures to the final energy use reduces, significantly, by increasing the thickness of extra insulation and by reducing the U-value of new windows. We considered three scenarios of business as usual (BAU), intermediate and sustainability, considering different discount rates and energy price increase. The results of this analysis suggest that the sustainability scenario may offer, approximately, 100% increase in the optimum thickness of extra insulation compare to BAU scenario. However, the implication of different lifespans of 40, 50 or 60 years, on the optimum measure appears to be either negligible or very small, depending on the chosen scenario. We also calculated the corresponding U-value of the optimum measures in order to compare them with the current Swedish building code requirements and passive house criteria. The results indicate that all optimum measures meet the Swedish building code. None of the optimum measures, however, meet the passive house criteria in BAU scenario. This study suggests that the employed method of building renovation cost-optimum analyses can be also applied on new building construction to find the cost-optimum design from energy conservation point of view.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Energy renovation, Building refurbishment, cost-optimisation
National Category
Civil Engineering Building Technologies Energy Systems
Research subject
Environmental Science, Environmental technology; Technology (byts ev till Engineering), Civil engineering
Identifiers
urn:nbn:se:lnu:diva-37137 (URN)10.1016/j.enbuild.2014.09.003 (DOI)000345182000066 ()2-s2.0-84907485527 (Scopus ID)
Available from: 2014-09-19 Created: 2014-09-19 Last updated: 2018-09-28Bibliographically approved
3. The Implications of Climate Zones on the Cost-Optimal Level and Cost-Effectiveness of Building Envelope Energy Renovation and Space Heat Demand Reduction
Open this publication in new window or tab >>The Implications of Climate Zones on the Cost-Optimal Level and Cost-Effectiveness of Building Envelope Energy Renovation and Space Heat Demand Reduction
2017 (English)In: Buildings, ISSN 2075-5309, E-ISSN 2075-5309, Vol. 7, no 2, article id 39Article in journal (Refereed) Published
Abstract [en]

The cost-optimal level of energy performance for buildings shall be identified according to the European directive of 2010. The Swedish building stock needs comprehensive knowledge and an overall strategy for the cost-optimal level of renovation. This paper studies the contribution of Swedish climate zones to the cost-optimal level of renovation on a multi-story residential building in Sweden from the building owner perspective. The building space heat demand is simulated for four Swedish climate zones. The net present profit (NPP) method is defined and used in this study in order to analyze the cost-optimal level and the cost-effective renovation of building envelope components (e.g., attic floor, basement walls, exterior walls and windows). The implication of different discount rates is studied, as well. The results show that the optimum renovation of the building envelope offers 51% more energy savings for space heating when the building is in a northern climate zone compared to a southern zone. The study suggests that different renovation strategies for the building stock renovation need to be identified, separately, for each climate zone. The NPP analysis identifies the minimum required investment and maximum achievable energy savings that are needed to have a cost-effective renovation. The broad range of studied climate zones provides the opportunity to apply the obtained results to other climate zones by either interpolation or extrapolation of NPPs for the buildings with similar characteristics.

National Category
Building Technologies
Research subject
Technology (byts ev till Engineering), Sustainable Built Environment
Identifiers
urn:nbn:se:lnu:diva-65751 (URN)10.3390/buildings7020039 (DOI)000404438700013 ()
Available from: 2017-06-22 Created: 2017-06-22 Last updated: 2018-09-28Bibliographically approved

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Doctoral Thesis (Comprehensive Summary)(8219 kB)42 downloads
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Bonakdar, Farshid

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