Cost-optimized energy-efficient building envelope measures for a multi-storey residential building in a cold climate

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Energy Procedia 158 Energy Procedia 00(2019) (2017)3760–3767 000–000 www.elsevier.com/locate/procedia

10th International Conference on Applied Energy (ICAE2018), 22-25 August 2018, Hong Kong, 10th International Conference on Applied Energy China(ICAE2018), 22-25 August 2018, Hong Kong, China

Cost-optimized energy-efficient building envelope measures for a Cost-optimized building envelope for a The 15thenergy-efficient International Symposium on District Heating andmeasures Cooling multi-storey residential building in a cold climate multi-storey residential building in a cold climate Assessing the feasibility of using the heat demand-outdoor Ambrose Dodoo11 *, Leif Gustavsson22, Uniben Y.A. Tettey22 Ambrose Dodoofor *, a Leif Gustavssondistrict , Uniben heat Y.A. Tettey temperature function long-term demand forecast Department of Building Technology, Linnaeus University, Växjö, sweden 1

1 Department of Buildingand Technology, Linnaeus University, Växjö, sweden Department of Built Environment Energy Technology, Linnaeus University, Växjö, sweden a a b c 2 a,b,c Department of Built Environment and Energy Technology, Linnaeus University, Växjö, sweden 2

I. Andrić a

*, A. Pina , P. Ferrão , J. Fournier ., B. Lacarrière , O. Le Correc

IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal

b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France Abstract In this study we analyse cost-optimal building envelope measures including insulation for attic roof, ground floor and exterior In this and study we analyse cost-optimal including insulation for attic roof, groundinfloor exterior walls, efficient windows and doorsbuilding for newenvelope buildings.measures The analysis is based on a multi-storey building southand of Sweden walls, efficient windows doors newWe buildings. The analysisenergy is based on a multi-storey south ofanalysis, Sweden with anand expected lifetime of atand least 100for years. integrate dynamic simulation, total and building marginal in economic Abstract with an expected lifetime of at least 100discount years. We integrate dynamic energy marginal analysis, and consider different scenarios of real rates and annual energy pricesimulation, increases. total Our and analysis showseconomic that cost-optimal and considerofdifferent scenarios real discount rateselements and annual price increases. Our analysis shows thicknesses insulations for theofbuilding envelope are energy significantly higher than those required to that meetcost-optimal the current District heating networksfor arethe commonly addressed in the literature as one ofhigher the most solutions for decreasing the thicknesses of insulations building envelope elements are significantly thaneffective those required meet current Swedish building code’s minimum energy requirements. For windows, the cost-optimal U-value is about the to same as the required to greenhouse gas emissions from theenergy building sector. These systems require high investments which are returned through the heat Swedish building code’s minimum requirements. For windows, the cost-optimal U-value is about the same as required to fulfil the minimum requirement of the Swedish building code. Overall, large energy and cost savings are achieved when the costsales.theDue to the requirement changed climate conditions and building renovation heatcost demand inare theachieved future could the decrease, fulfil minimum of theimplemented. Swedish building code. Overall, largepolicies, energy and savings costoptimal measures are cumulatively Compared to the reference, annual space heating reduction when of 28-43% is prolonging the investment return period. optimal measures are cumulatively implemented. Compared reference, annual of 28-43% is achieved for the building with the cost-optimal measures under to thethe analysed period of 50 space years. heating The costreduction savings varied between The mainforscope of this paper assess the feasibility usingthe theanalysed heat demand outdoor temperature for heatbetween demand achieved the building with is thetocost-optimal measuresofunder period– of 50 years. The cost function savings varied 21 and 188 k€. forecast. 21 and 188The k€. district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district Copyright © 2018 Elsevier Ltd. All rights reserved. ©renovation 2019 The Published by Elsevier Ltd. intermediate, deep). To estimate the error, scenarios wereLtd. developed (shallow, obtained heat demand values were Copyright ©Authors. 2018 Elsevier Allresponsibility rights reserved. Selection and peer-review under of the scientific committee of the 10th International Conference on Applied This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) th compared with results from a dynamic heat demand model, previously developed and validated by the authors. Conference on Applied Selection and peer-review under responsibility of the scientific committee of the 10 International Energy (ICAE2018). Peer-review under responsibility of the scientific committee of ICAE2018 – The of 10th International Conferencefor onsome Applied Energy. The results showed that when only weather change is considered, the margin error could be acceptable applications Energy (ICAE2018). (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation Keywords: Cost-optimal; energy efficeincy measures; real discount rate; annual energy price increase; building envelope; insulations; windows scenarios,Cost-optimal; the error value increased to 59.5% the weather andincrease; renovation scenarios combination Keywords: energy efficeincyup measures; real(depending discount rate;onannual energy price building envelope; insulations;considered). windows The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and 1.decrease Introduction renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the 1. Introduction coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and Energy with estimations. low-carbon energy supply are a key part of the strategy to reduce both primary improve theefficient accuracy buildings of heat demand

Energy efficient buildings with low-carbon energy supply are a key part of the strategy to reduce both primary

© 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. * Corresponding author. Tel.: +46470767812 * Corresponding Tel.: +46470767812 E-mail address:author. [email protected] Keywords: Heat demand; Forecast; Climate change E-mail address: [email protected]

1876-6102 Copyright © 2018 Elsevier Ltd. All rights reserved. 1876-6102 Copyright © 2018 Elsevier Ltd. All of rights reserved. committee of the 10th International Conference on Applied Energy (ICAE2018). Selection and peer-review under responsibility the scientific Selection and peer-review under responsibility of the scientific committee of the 10th International Conference on Applied Energy (ICAE2018). 1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling. 1876-6102 © 2019 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of ICAE2018 – The 10th International Conference on Applied Energy. 10.1016/j.egypro.2019.01.879

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energy use and greenhouse gases emissions in the European Union (EU) [1]. Space heating and hot water use account for 79% of total final energy use in EU households [2]. EU’s directives [1] call for member states to implement policies for improved energy efficiency in buildings. Sweden has set out a strategy to reduce specific energy use in buildings by 20% and 50% by 2020 and 2050, respectively, compared to 1995 levels [3]. Cost-effectiveness is a vital factor in implementation of building energy efficiency measures [4]. The EU’s energy performance of buildings directive indicates that member states should set minimum energy performance requirements for buildings and building elements considering cost-effective solutions which takes into account costoptimal balance between investment costs and saved energy costs [1]. Analyses for several EU member states show significant potential for cost-effective reduction of energy use compared to minimum energy requirements of building codes [5-8]. However, Ferrara et al. [9] found that the energy performance of the cost-optimal single-family house in France corresponds to the French RT2012 thermal regulation. In this study we investigate cost-optimal energy efficient building envelope measures for a recently built multifamily building in Sweden. The cost analysis is based on total and marginal optimisations considering incremental investment costs and NPV for the analysed measures under 50 years while the lifetime of the building is expected to be at least 100 years. 2. Methods As a starting point for this analysis, we model changes to the thermal envelope of a case-study multi-family building to reflect the minimum energy performance level of the current Swedish building code [11]. The newly modelled building is used as a reference to explore the cost-effectiveness of different energy efficiency measures and cost-optimal envelope design solutions for new construction in the Swedish context. The energy performance of the building with the package of cost-optimal envelope solutions is compared to the building version designed to the current Swedish building code. 2.1 Analysed building The building used for this analysis is a constructed six-storey multi-family house with 24 apartments and total heated floor area of 1686 m2, in the Swedish city of Växjö (latitude 56o 87′ 37′′ N; longitude 14o 48′ 33′′ E). Figure 1 shows photograph and typical floor plan of the building. The building has balanced ventilation system with heat recovery (VHR) and is heated with district heat supplied by Växjö Energy AB, a municipally owned energy company. To achieve reference building for the analysis, we adapted the constructed building to the minimum energy requirement of the current Swedish building code [11] by modelling changes to the insulation levels for the attic floor/roof, ground floor and exterior walls. Apart from these changes, the architectural and thermal characteristics of the reference building are identical to the constructed building. Table 1 summarizes the thermal envelope and construction characteristics of the reference building.

Figure 1. Photograph (left) and ground floor plan (right) of the constructed building in Växjö, southern Sweden.

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Table 1. Thermal envelope properties of elements in the adapted reference building, meeting the current Swedish building code. Building element Attic floor / roof Exterior walls Windows Doors at entrance & balconies Ground floor/ Foundation

Description (from outside to inside, where applicable) 250 mm prefab concrete + 350 mm loose fill mineral wool between roof trusses covered with plywood and asphalt-impregnated felt 100 mm prefab concrete + 100 mm styrofoam +230 mm prefab concrete Double glazed units with 12mm gap with argon infill and g-value of 0.62 Double glazed units with 12mm gap with argon infill and g-value of 0.62 200 mm crushed stone + 100 mm expanded polystyrene + 100 mm reinforced concrete slab + 20 mm wood flooring

U-value (W/m2K) 0.11

Area (m2) 287.5

0.32 1.20 1.20 0.30

1131.0 235.3 57.3 287.5

2.2 Modelling of cost-optimal measures We apply a two-step approach proposed by Dodoo et al. [10] to analyse cost-optimal energy-efficiency measures and their cost-effectiveness for the building. The approach integrates bottom-up economic calculations and hour-byhour energy balance simulation for analysis of cost-effectiveness and cost-optimal solutions, and considers different scenarios of real discount rate and annual energy price increase. Total and marginal investment costs of the measures and packages are compared against the NPV of resulting total and marginal energy cost savings over the lifetime of the measures. The NPV of saved energy must be higher than the investment cost for a measure or a package to be considered cost-effective. The analysis is limited to 50 years in this study. 2.2.1 Analysed energy efficiency measures We analyse energy efficiency measures related to the building envelope including a range of insulation thicknesses for attic roof, ground floor and exterior walls, and efficient windows including doors of different thermal transmittance (U-value). The explored insulation thickness ranges from 100 to 500 mm for both ground floor and exterior walls, and from 350 to 700 mm for attic roof. For windows and doors, configurations with U-values of between 1.2-0.7 W/m2 K are studied. Table 2 summarizes the range of insulation thicknesses or U-values analysed for the different building elements. Table 2. Analysed energy efficiency measures. Energy efficiency measure Ground floor/ foundation Exterior walls Windows & doors Attic roof

Description 100 to 500 mm expanded polystyrene insulation 100 to 500 mm mineral wool insulation 1.2 to 0.7 W/m2 K U-value 350 to 700 mm mineral wool insulation

2.2.2 Energy balance and savings calculations Analysis of the energy balance of the building is performed hour-by-hour using the VIP-Energy simulation program (v. 4.0.3)[12], which is validated by the IEA BESTEST, ASHRAE 140-2007 and CEN-15265. Hourly weather data for the city of Växjö for the year 2013 and key input parameter values for the Swedish context [13] are used for the calculations. The 2013 weather data, which reflects the Swedish normal climate, is obtained from the meteonorm database [14] and shows that average outdoor temperatures, solar radiation, wind speed and relative humidity for Växjö were 7 oC, 105 W/m2, 2 m/s and 81%, respectively. In the final energy calculations, space heating temperature set-point of 21oC is assumed for the building’s living area and 18oC for the common areas, based on Dodoo et al. [13]. 2.2.3 Economic calculations Three scenarios based on different real discount rates and real annual energy price increases are considered in the cost-effectiveness and cost-optimal analyses of the energy efficiency measures. The scenarios are summarized in Table 3 and include business-as-usual (BAU), intermediate and sustainability scenarios.

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Table 3. Scenarios analysed for real discount rate and annual energy price increase. Scenario Business-as-usual (BAU) Intermediate Sustainability

Real discount rate (%) 5 3 1

Real annual energy price increase (%) 1 2 3

Based on modelled final energy savings of the measures and the scenarios, NPV of total and marginal energy cost savings are calculated for the different measures (Table 2). The NPV of energy cost savings are calculated using the 2017 district heating tariff for Växjö [15]. The net energy savings of the measures and district heating prices (considering the real annual energy price increase) are multiplied to give the energy cost savings for the measures. The marginal saved energy for a measure is calculated as the difference in NPV of energy cost savings for the incremental measure with reference to the prior applied measure. The analysis is limited to 50 years and the measures are implemented when the building is being constructed. To calculate the investment costs for the measures, we use construction costs data for 2016/2017 from Sektionsfakta [16], a Swedish database for costs related to materials, on-site installations and man-hours for new building works in Sweden. The total investment costs consist of costs for materials and their on-site installations. The slab-on ground, roof overhangs and windows as well as door sills may need to be adjusted when the exterior walls insulation is increased and this is considered in the investment cost calculations. The calculated costs are expressed in euros, using the year 2017 average exchange rate of SEK 9.64/€. The marginal cost of investment for a measure is calculated as the change in investment cost relative to the preceding applied measure. 3. Results Table 4 shows the annual final operation energy use of the reference building with specific final energy demand of 80 kWh/m2 including space heating, tap water heating and electricity for ventilation fans and pump. Space heating accounts for 47% of the total energy use, dominating the operation final energy. Table 4. Annual final operation energy demand of the reference building. Description Reference building

Space heating 51.3

Tap water heating 24.9

Ventilation electricity 3.8

Household electricity 29.9

Total 109.9

Tables 5-7 show the thermal transmittances (U-value), total investment cost, marginal investment cost, space heating demand, final heat savings and hourly peak load for different insulation thicknesses when implemented for elements of the reference building including ground floor, attic floor/roof and exterior walls. Table 5. Thermal transmittances (U-value), total investment, marginal investment, space heating demand, final heat savings and hourly peak load for different ground floor insulation thicknesses. Styrofoam insulation to foundation / ground floor

U-value (W/m2K)

Total investment cost (k€)

Reference (100 mm) 150 mm 200 mm 250 mm 300 mm 350 mm 400 mm 450 mm 500 mm

0.30 0.21 0.17 0.13 0.11 0.10 0.09 0.08 0.07

2.5 3.9 5.3 7.9 9.3 10.6 13.2 14.6

Marginal investment cost (k€) 1.4 1.4 2.6 1.4 1.3 2.6 1.4

Space heating demand (MWh/year) 86.4 84.0 82.7 81.9 81.4 81.0 80.7 80.4 80.2

Final heat savings (MWh/year) 2.4 3.7 4.5 5.0 5.4 5.7 6.0 6.2

Hourly peak load (kW) 48.8 48.1 47.7 47.5 47.3 47.2 47.1 47.0 46.9

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Table 6. Thermal transmittances (U-value), total investment, marginal investment, space heating demand, final heat savings and hourly peak for different attic floor insulation thicknesses. Mineral wool insulation to attic floor

U-value (W/m2K)

Reference (350 mm) 400 mm 450 mm 500 mm 550 mm 600 mm 650 mm 700 mm

0.11 0.10 0.09 0.08 0.07 0.07 0.06 0.06

Total investment cost (k€) 0.6 1.1 1.7 2.8 3.6 4.3 5.3

Marginal investment cost (k€) 0.5 0.6 1.1 0.9 0.7 0.9

Space heating demand (MWh/year) 86.4 85.9 85.5 85.2 85.0 84.7 84.6 84.4

Final heat savings (MWh/year) 0.5 0.9 1.2 1.4 1.7 1.8 2.0

Hourly peak load (kW) 48.8 48.7 48.5 48.4 48.3 48.3 48.2 48.2

Table 7. Thermal transmittances (U-value), total investment, marginal investment, space heating demand, final heat savings and hourly peak for different exterior wall insulation thicknesses. Mineral wool insulation to exterior walls

U-value (W/m2K)

Reference (100 mm) 150 mm 200 mm 250 mm 300 mm 350 mm 400 mm 450 mm 500 mm

0.32 0.22 0.17 0.14 0.12 0.10 0.09 0.08 0.07

Total investment cost (k€) 10.6 14.6 19.3 29.5 34.6 39.9 50.8 56.5

Marginal investment cost (k€) 4.0 4.7 10.2 5.1 5.3 10.9 5.7

Space heating demand (MWh/year) 86.4 75.7 70.1 66.6 64.3 62.6 61.3 60.3 59.5

Final heat savings (MWh/year) 10.7 16.3 19.8 22.1 23.8 25.1 26.1 26.9

Hourly peak load (kW) 48.8 45.4 43.6 42.5 41.7 41.1 40.7 40.4 40.1

Table 8 shows thermal transmittances (U-value), solar transmittance, total investment cost, marginal investment cost, space heating demand, final heat savings and hourly peak load for different new windows options when applied for the reference building. Relative to the reference window U-value of 1.2 W/m2K, the windows of 1.1-0.7 W/m2K U-values give annual final energy savings of 2.2-13.1 MWh (2.5-15%). Table 8. Thermal transmittances (U-value), solar transmittance, total investment, marginal investment, space heating demand, final heat savings and hourly peak load for different efficient windows. Thermal transmittance of windows Ref. (1.2 W/m2 K) 1.1 W/m2 K 1.0 W/m2 K 0.9 W/m2 K 0.8 W/m2 K 0.7 W/m2 K

Solar transmittance (gvalue) 0.62 0.58 0.54 0.52 0.51 0.50

Total investment cost (k€) 13.4 49.2 74.5 105.8 147.6

Marginal investment cost (k€) 35.8 25.3 31.3 41.8

Space heating demand (MWh/year) 86.4 84.2 81.9 79.2 76.2 73.3

Final heat savings (MWh/year) 2.2 4.5 7.2 10.2 13.1

Hourly peak load (kW) 48.8 47.6 46.5 45.3 44.1 42.9

Figs. 2-4 show the NPV of total as well as marginal energy savings, and also total and marginal investment costs, for the studied thermal envelope insulation measures for the different scenarios. For a measure to be costeffective, NPV of total heat cost savings must at least exceed that for total investment costs, shown in the total techno-economic modelling. The optimal insulation thickness is determined in the marginal techno-economic modelling and occurs around where the curve for NPV of marginal heat cost savings intersects that for marginal investment costs. The marginal investment cost curves move up and down for every additional insulation thickness

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of 50 mm, due to practical means of applying the insulation. In some cases there is no difference in working time when increasing the insulation by 50 mm or 100 mm. For the ground floor (Fig. 2), the techno-economic modelling shows that all considered thicknesses of insulation are cost-effective under sustainability and intermediate scenario while insulation thicknesses up to 300 mm are cost-effective under BAU scenario. The marginal techno-economic modelling shows that optimal ground floor insulations are 200, 250 and 500 mm for BAU, intermediate and sustainability scenarios, respectively. Investment costs

NPV of cost savings- BAU NPV of cost savings- Sustainability 12

40

30

20

10

0

150

200

250 300 350 400 Insulation thickness (mm)

450

500

Investment cost or NPV of savings (k€)

Investment cost or NPV of savings (k€)

NPV of cost savings- Intermediate

(a) Total techno-economic modelling

8

4

0

150

200

250 300 350 400 Insulation thickness (mm)

450

500

(b) Marginal techno-economic modelling

2

12

Investment cost or NPV of savings

Investment cost or NPV of savings (k€)

Fig. 2. Total investment costs and total NPV of energy savings (left) and marginal investment costs and marginal NPV of energy savings (right) for various ground floor insulation thicknesses.

9

6

3

0

400

450

500 550 600 Insulation thickness (mm)

650

700

1

0

400

450

500

550

600

650

700

Insulation thickness (mm)

(a) Total techno-economic modelling

(b) Marginal techno-economic modelling

200

150

100

50

0

150

200

250 300 350 400 Insulation thickness (mm)

(a) Total techno-economic modelling

450

Investment cost or NPV of savings (k€)

Investment cost or NPV of savings (k€)

Fig. 3. Total investment costs and total NPV of energy savings (left) and marginal investment costs and marginal NPV of energy savings (right) for various attic floor insulation thicknesses.

500

40

30

20

10

0

150

200

250 300 350 400 Insulation thickness (mm)

450

500

(b) Marginal techno-economic modelling

Fig. 4. Total investment costs and total NPV of energy savings (left) and marginal investment costs and marginal NPV of energy savings (right)

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for various exterior wall insulation thicknesses.

Fig. 5 shows the total investment costs and NPV of total energy savings for the analysed window options under different scenarios. All the analysed windows are not cost-effective under BAU as well as intermediate scenarios, and only window with U-value of 1.1 W/m2K is cost-effective under sustainability scenario. Hence no marginal techno-economic modelling is conducted in this case. NPV of cost savings- BAU

NPV of cost savings- Intermediate

NPV of cost savings- Sustainability

Investment cost or NPV of savings (k€)

Investment costs 150

100

50

0

0.7

0.8 0.9 1.0 U-values of windows (W/m2K)

1.1

Total techno-economic modelling Fig. 5. Total investment costs and total NPV of energy savings for various thermal transmittances for efficient windows.

Table 9 presents a summary of the cost-optimal building envelope measures under the different scenarios. Compared to the reference building which fulfils the minimum energy requirement of the Swedish building code, space heating demand is reduced by 28%, 34% and 43% for the cost-optimised measures under BAU, intermediate and sustainability scenarios, respectively. The cost-optimised measures for the building also give significant economic benefits. Table 9. Cost-effective envelope measures for the building under the different scenarios and their energy and economic implications. BAU

Intermediate

Sustainability

Reference building (to Swedish building code level)

Foundation / ground floor insulation (mm)

200

250

500

100

Attic floor insulation (mm) Exterior wall insulation (mm) Efficient windows (W/m2K)

400 250 1.2

500 350 1.2

650 500 1.1

350 100 1.2

Final space heating demand from all measures (kWh/m2/year)

37.0

33.8

29.3

51.3

NPV of energy cost savings for 50 years (k€)

44.8

100.5

276.7

-

Total investment cost compared to reference (k€)

23.8

41.6

88.8

-

NPV energy cost savings – investment costs (k€)

21.0

58.9

187.9

-

Description

4. Discussion and conclusions In this study we have analysed cost-optimal energy efficient building envelope measures for a recently constructed Swedish multi-storey building. The analysed measures include insulation for attic roof, ground floor and exterior walls, and efficient windows including doors. Our analysis integrates dynamic energy simulation and total as well as marginal economic analysis and considers different scenarios of real discount rates and annual energy price increase. Our calculations show that cost-optimal thicknesses of insulations for attic roof, ground floor and exterior walls for the analysed building are significantly higher than those required to meet the current Swedish building code’s minimum energy requirement. For windows, the cost-optimal U-value is 1.2 W/m2K for BAU and

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intermediate scenarios, the same as required to fulfil the minimum requirement of the Swedish building code. For sustainability scenario, window with U-value of 1.1 W/m2K is cost-effective and hence cost-optimal solution for the analysed building. Overall, large energy savings are achieved when the cost-optimal measures are cumulatively implemented. Compared to the reference, annual space heating reduction of 24.1-37.0 MWh (28-43%) is achieved for the building with the cost-optimal measures under the different scenarios. Total investment cost is k€ 88.8 while NPV of cost savings is k€ 276.6 for the package of cost-optimal measures under sustainability scenario. For BAU scenario, total investment costs is k€ 23.8 while NPV of cost savings is k€ 44.8 for the package of cost-optimal measures. Thus, large economic benefit is achieved under sustainability scenario compared to the other scenarios. This study shows that the cost-optimal envelope measures are sensitive to factors as discount rate and development of energy price over time. In future studies the analysis will be extended so that the expected lifetime of the building of at least 100 years is considered. Acknowledgements We gratefully acknowledge financial support from the Swedish Energy Agency and Växjö Kommun. References 1. 2. 3.

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

Directive 2010/31/EU, Directive 2010/31/EU of the European Parliament and of the Council of 19 May2010 on the energy performance of buildings (Recast), Official Journal of the European Union. L 153, 18/06/2010. European Commission, An EU Strategy on Heating and Cooling, {SWD(2016) 24 final}. Brussel, 2016. Swedish Government Bill 2005/06:145, Swedish Government Bill 2005/06:145 National Programme for Energy Efficiency and Energy-smart Construction. Accessed at http://www.government.se/informationmaterial/2006/05/national-programme-for-energy-efficiency-and-energy-smart-construction/ on 12/04/2017. IPCC, Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. 2014. European Commission, Report from the Commission to the European Parliament and the Council. Progress by Member States in reaching cost-optimal levels of minimum energy performance requirements. 2016. Hasan, A., M. Vuolle, and K. Sirén, Minimisation of life cycle cost of a detached house using combined simulation and optimisation. Building and Environment, 2008. 43(12): p. 2022-2034. Congedo, P.M., et al., Cost-optimal design for nearly zero energy office buildings located in warm climates. Energy, 2015. 91(Supplement C): p. 967-982. Pikas, E., M. Thalfeldt, and J. Kurnitski, Cost optimal and nearly zero energy building solutions for office buildings. Energy and Buildings, 2014. 74(Supplement C): p. 30-42. Ferrara, M., et al., A simulation-based optimization method for cost-optimal analysis of nearly Zero Energy Buildings. Energy and Buildings, 2014. 84(Supplement C): p. 442-457. Dodoo, A., L. Gustavsson, and U.Y.A. Tettey, Final energy savings and cost-effectiveness of deep energy renovation of a multi-storey residential building in a cold climate. Energy Journal, 2017. 135: p. 563-576. Boverkets Byggregler, Boverkets Författningssamling, The national Board of Housing Building and planning, Karlskrona. Accessed at http://www.boverket.se on 10/04/2017, (In Swedish). 2015. StruSoft, VIP+ software, Sweden. 2010, Available from http://www.strusoft.com/products/vip-energy on 10/01/2017. Dodoo, A., U.Y.A. Tettey, and L. Gustavsson, On input parameters, methods and assumptions for energy balance and retrofit analyses for residential buildings. Energy and Buildings, 2017. 137: p. 76-89. Meteotest, METEONORM 7: Global meteorological database for engineers, planners and education,. 2015, Meteotest. VEAB, Fjärrvärme- priser, connection price (In english: District heating-prices). Accessed on http://www.veab.se/foretag/fjarrvarme/priser/ 19/04/2018. 2018. Wikells Byggberäkningar AB, Sektionsfakta-NYB 16/17. 2017, Växjö: Elanders.