A wider deployment of nearly zero energy buildings (NZEBs) is expected to contribute to the transition to a decarbonized and energy-efficient building sector in Europe. This study proposed an integrated energy-economic analysis to exemplify the feasibility of NZEB renovation in temperate climate. A parametric analysis was performed to identify technical building system configurations that give minimum share of renewable energy systems contributing to NZEB level. Final energy savings, global costs and cost-effectiveness of renovating a building to NZEB level are analysed, considering active and passive energy efficiency measures (EEMs). The active EEMs included efficient water taps and heat recovery ventilation, and the passive EEMs encompassed insulations to roof, exterior walls and ground floor, and improvements of windows and doors. The building had initial final energy use of 133 kWh/m2 year for space heating, domestic hot water production (DHW) and facility electricity. The results show that NZEB level is achieved with active and passive EEMs, without renewable energy systems for scenarios with low discount rates and high future energy price escalations. The annual final energy use for space heating, DHW and facility electricity is reduced cost-effectively by 37-54%. Furthermore, increasing size of PV-system enhanced cost-effectiveness by lowering total global costs.

In line with the Swedish target of carbon neutrality by 2045, the municipality of Växjö in Kronoberg County has set its own target to be carbon neutral in 2030. Currently, the Municipality's partially decentralized energy system relies heavily on interconnected electricity supply from the national grid, and fuels imports from other parts of Sweden. Under this circumstance, several concerns arise, including: in which ways future demand changes induce supply changes, and whether a future carbon-neutral energy system will be less costly in a sustained-electricity supply condition. In this study, techno-economic evaluations are conducted for different carbon-neutral scenarios for Växjö’s future energy system in 2030 and 2050, using an hour-by-hour dynamic energy simulation tool of EnergyPLAN. Projections for the future energy demands for Växjö were developed and modeled, based on the development strategies and on the national sustainable future scenarios in Sweden. Results for the Växjö’s carbon-neutral scenarios showed that the current energy system is sufficient to satisfy future heat demand. However, fulfilling demands of electricity for all sectors and fuels for transport and industry is a challenge. In the short term and at increased energy demand and price, being carbon neutral is technically viable without major changes in energy supply technologies. However, in the long term, investment for intermittent renewable energy resources, together with carbon capture and storage is considered to be viable financially. Therefore, planning for a carbon-neutral Växjö based on local investments showed to be a feasible strategy.

A municipal housing company located in the south of Sweden has energy renovatedseveral buildings with a total of 380 apartments to meet today’s energy standards. Several energyefficient technologies and solutions were implemented and the energy consumption for thesebuildings were lowered by 50%. One of the buildings functions as a demonstration building forinnovative solutions such as low temperature district heating, waste water heat recovery, andsolar photovoltaic and thermal (PVT) panels. The solar PVT panels are cooled down with themain purpose to increase the electricity production. The cooling medium for these panels iscirculated through two bedrock boreholes to dissipate the collected heat. The heat from theboreholes is then used for an electric heat pump to produce heat to send to the local districtheating company. The electricity produced is primarily used in the building. The objective ofthis paper is to assess the electricity production from real-life outdoor Photovoltaic-thermal(PVT) plant. The plant was installed on the roof top of an energy renovated multi-familyapartment building located in the south of Sweden. The cooling of the panels were turned on andoff to assess if the electricity production would increase or not. The electricity production didnot increase when the cooling was applied. The temperature measuring equipment which wasinstalled at the wrong position and was supposed to measure the temperature at the back of thePVT is needed to compare the efficiency of the PVT plant and draw further conclusions.

Low-carbon buildings and construction products can play a key role in creating a low-carbon society. Cross-laminated timber (CLT) is proposed as a prime example of innovative building products, revolutionising the use of timber in multi-storey construction. Therefore, an understanding of the synergy between structural engineering design solutions and climate impact of CLT is essential. In this study, the carbon footprint of a CLT multi-storey building is analysed in a life cycle perspective and strategies to optimise this are explored through a synergy approach, which integrates knowledge from optimised CLT utilisation, connections in CLT assemblies, risk management in building service-life and life cycle analysis. The study is based on emerging results in a multi-disciplinary research project to improve the competitiveness of CLT-based building systems through optimised structural engineering design and reduced climate impact. The impacts associated with material production, construction, service-life and end-of-life stages are analysed using a process-based life cycle analysis approach. The consequences of CLT panels and connection configurations are explored in the production and construction stages, the implications of plausible replacement scenarios are analysed during the service-life stage, and in the end-of-life stage the impacts of connection configuration for post-use material recovery and carbon footprint are analysed. The analyses show that a reduction of up to 43% in the life cycle carbon footprint can be achieved when employing the synergy approach. This study demonstrates the significance of the synergy between structural engineering design solutions and carbon footprint in CLT buildings.

Ahead of heat exchanger network (HEN) design, setting an optimal pinch temperature difference for pinch analysis depends vitally on the capital cost target. Conventional methods based on the spaghetti (SPA) structure ignoring matching optimization might result in calculated cost targets of large deviations. This work evolved the SPA structure via four stages by shifting energy towards low-cost matching. The fourth structure evolved from the SPA structure (ESPA-IV structure) with the lowest-cost matching after loops elimination forms the base to establish the ESPA method. It is validated by numerical experiment and applied to a case reported in literature, meanwhile comparisons are always made to the SPA method. The numerical experiment proves that the ESPA method can obtain capital cost targets with higher accuracy than the SPA method. The target deviations (often within ±5%) given by the ESPA method are much lower than those (well above 10%) derived by the SPA method. In the case study, the given HEN is further optimized as hinted by ESPA method results. Of two target methods, the cost target indicated by ESPA method is closer to the optimum capital cost newly derived after optimization. The high accuracy of the ESPA method is further verified.

Forests can help mitigate climate change in different ways, such as by storing carbon in forest ecosystems, and by producing a renewable supply of material and energy products. We analyse the climate implications of different scenarios for forestry, bioenergy and wood construction. We consider three main forestry scenarios for Kronoberg County in Sweden, over a 201-year period. The Business-as-usual scenario mirrors today’s forestry while in the Production scenario the forest productivity is increased by 40% through more intensive forestry. In the Set-aside scenario 50% of forest land is set-aside for conservation. The Production scenario results in less net carbondioxide emissions and cumulative radiative forcing compared to the other scenarios, after an initial period of 30–35 years during which the Set-aside scenario has less emissions. In the end of the analysed period, the Production scenario yields strong emission reductions, about ten times greater than the initial reduction in the Set-aside scenario. Also, the Set-aside scenario has higher emissions than Business-as-usual after about 80 years. Increasing the harvest level of slash and stumps results in climate benefits, due to replacement of more fossil fuel. Greatest emission reduction is achieved when biomass replaces coal, and when modular timber buildings are used. In the long run, active forestry with high harvest and efficient utilisation of biomass for replacement of carbon-intensive non-wood products and fuels provides significant climate mitigation, in contrast to setting aside forest land to store more carbon in the forest and reduce the harvest of biomass.

A considerable share of the existing buildings in Europe has low energy performance and are expected to last at least for the next 50 years. The operation of these buildings causes high atmospheric greenhouse gases emissions, besides low thermal comfort for occupants. In Sweden, most of the existing buildings are residential, consisting of multi- and single-family houses. Large final energy savings can be achieved by integrating energy efficient measures (EEMs) to the thermal envelopes of these buildings. However, it is often a challenge to achieve a considerable energy savings and realize cost effectiveness simultaneously. This study investigates the effect of carbon taxes implementation on the cost effectiveness of EEMs applied to an existing multi-apartment building in southern Sweden. It explores the implications of different additional insulation thicknesses for exterior walls and roof, and high-performance windows and doors, for the final energy use and carbon dioxide (CO2) emissions of the building. The final energy savings of the EEMs are estimated through dynamic energy balance simulations and the CO2 emissions are calculated considering the full energy chains. The cost effectiveness of the EEMs are analyzed with and without carbon abatement costs considering the investment costs and associated net present value of costs savings of the EEMs. The results show that replacing the existing windows give the highest final energy savings, reducing the building’s space heating demand by 23 %. The cost optimal analysis without carbon abatement costs shows that all the analyzed thicknesses of roof insulation and high-performance windows are cost effective. Considering the carbon abatement costs altered the cost effectiveness of the EEMs, with exterior walls as well as ground floor insulations and door replacement becoming cost effective for certain thicknesses and U-values, respectively.

A large potential for energy savings can be found in building envelopes of the existing Swedish dwelling stock. This study analyzes the final energy savings and cost implications of energy efficiency measures for an existing multi-apartment building in Sweden. Energy efficiency improvements consisting of high-performance windows as well as doors, and additional insulation to attic floor and exterior walls were modelled to the building’s thermal envelope. Dynamic energy balance simulations were performed to determine the final energy savings of the improvements. The cost-effectiveness of the improvements were then analyzed considering the net present value of the energy cost savings and the investment costs of the improvement measures. The results showed that additional insulation to the attic floor is the only cost-effective measure for the building under the existing operating conditions. The other improvement measures give high final energy savings but are not cost effective due to their high investment costs.

Here we analyze the cost, primary energy and CO2 implications of supplying district heat, considering different supply and return temperatures, to a new residential area in Växjö, Sweden. We explore four land exploitation alternatives consisting different types of buildings with various heated floor areas as well as occupancy densities and two levels of building energy efficiency, based on the Swedish building code and passive house criteria. The analysis shows that energy performance of the buildings and land exploitation alternatives strongly influence the annual heat demand and its profile, which steers the design of the local heat distribution network. Additionally, supply and return temperatures of district heat somewhat influence the design of the network. The distribution heat losses could be reduced by 25% and 50% if district heating systems of 65/30 °C and 50/20 °C, respectively, are used instead of a conventional 80/40 °C system. However, for the same land exploitation alternative, the local distribution heat losses are about the same whether or not the buildings are designed to meet the Swedish building code or passive house criteria, since the same pipe distance is required and the variation of pipe diameters is small. A 50/20 °C system increases electricity use to boost hot water temperature to avoid the risk of legionella bacteria, and this influences quantity of district heat supply, primary energy use and costs. Therefore, a 65/30 °C system appears to be more primary energy and cost efficient than a 50/20 °C system. Increased insulation of district heating network reduces heat losses but this is not cost effective due to increased investment cost. The results are similar whether or not the analysis is based on current energy supply or future renewable based energy supply. This study increases understanding of strategies for planning and designing new urban residential areas and their energy supply systems to reduce primary energy use as well as monetary costs, and to minimize the climate impacts of the built environment.