Operation Primary Energy Research Articles

Life cycle assessment of energy efficient buildings

Life Cycle Analysis applications in the construction sector are growing due to the increased importance of embodied components in low energy buildings. In this study, standard building reference scenarios were compared with highly efficient building typologies, classified as low-energy or nearly Zero Energy Buildings. Energy consumptions were simulated starting from validated models while uniform assumptions, such as materials to be included, stages to be considered and coefficients of impact to be applied, were made for the LCA. The results show how the enhanced energy efficiency in the examined buildings and the reduction of their operational non-renewable primary energy requirement correspondingly causes a decrease of their life cycle non-renewable energy requirement, Cumulative Energy Demand and Global Warming Potential. A high potential in the reduction of non-renewable operational primary energy and GWP was found (until a maximum of 89% for the energy and 88% for the emissions). However, due to the shifting of impacts to the embodied components, the achievable life cycle reduction of non-renewable primary energy and emissions is lower (respectively 60% and 63% for the best performing retrofit). The benefit on life cycle CED is even lower due to the energy transition to renewables.

Retrofitting with different building materials: Life-cycle primary energy implications

The energy retrofitting of existing buildings reduces the energy use in the operation phase but the use of additional materials influence the energy use in other life cycle phases of retrofitted buildings. In this study, we analyse the life cycle primary energy implications of different material alternatives when retrofitting an existing building to meet high energy performance levels. We design retrofitting options assuming the highest and lowest value of final energy use, respectively, for passive house standards applicable in Sweden. The retrofitting options include the thermal improvement of the building envelope. We calculate the primary energy use in the operation phase (operation primary energy), as well as in production, maintenance and end-of-life phases (non-operation primary energy). Our results show that the non-operation primary energy use can vary significantly depending on the choice of materials for thermal insulation, cladding systems and windows. Although the operation energy use decreases by 63–78%, we find that the non-operation energy for building retrofitting accounts for up to 21% of the operation energy saving, depending on the passive house performance level and the material alternative. A careful selection of building materials can reduce the non-operation primary energy by up to 40%, especially when using wood-based materials.

Environmental and economic implications of energy efficiency in new residential buildings: A multi-criteria selection approach

The choice of the most appropriate technologies in buildings is often a challenge at the design stage, especially when many different criteria are taken into account. Consequently, the decision process relies often on one criterion only, such as costs or energy savings. We propose a multi-criteria approach based on multi-attribute utility theory to assess alternative energy efficiency measures, explicitly considering both environmental and economic criteria. We apply it to the design of a new residential building in Milan (Italy), with the aim to maximize CO2 emission savings related to electricity and gas consumption, and to minimize embodied energy and investment costs. After modelling the building prototype, alternative energy efficiency measures are assessed and ranked according to the selected criteria.The building optimized through the implementation of the best performing measures showed an overall 90% reduction in operational primary energy compared to the baseline building. The inclusion of the embodied energy altered the energy performance calculations resulting in 55–67% reduction in total energy over a 10-year period, and 77–82% over a 30-year period. Results point to the importance of a comprehensive implementation of measures, such as thermal improvements, high efficiency equipment, appliances, and renewable energy generation. The paper demonstrates the feasibility of this framework to support the decision process from a multi-criteria perspective, proposing a flexible method that can be adapted to other building types, environmental conditions, materials and technologies. It also highlights the importance of considering both environmental and economic criteria when designing a new building. It stresses how the embodied energy should be a criterion for technology selection, as current strategies to reduce operational energy often increase the amount of energy embodied into buildings with environmental consequences.

Lifecycle Impacts of Structural Frame Materials for Multi-storey Building Systems

In this study the lifecycle primary energy and greenhouse gas (GHG) implications of multi-storeybuilding versions with different structural frame materials as well as construction systems are analysedconsidering flows from the production, operation and end-of-life phases and the full natural resourceschains. The analysed building versions include conventional and modern construction systems withlight-frame timber, reinforced concrete-frame, massive timber frame, beam-and-column timber frameor modular timber frame structural systems and are designed to the energy efficiency level of thepassive house criteria. The results show that the lifecycle primary energy use and GHG emissions forthe reinforced concrete building system are higher than those for the timber-based building systems,due primarily to the lower production primary energy use and GHG emissions as well as greater amountof biomass residues when using wood-based materials. The operation primary energy use and GHGemission for the buildings are lower when heated with cogenerated district heating compared to whenheated with electric-based heat pump, showing the significance of heat supply choice. The findingsemphasize the importance of structural frame material choice and system-wide lifecycle perspective inreducing primary energy use and GHG emissions in the built environment.

Energy use implications of different design strategies for multi-storey residential buildings under future climates

The effects of climate change on the final and primary energy use of versions of a multi-storey residential building have been analysed. The building versions are designed to the Swedish building code (BBR 2015) and passive house criteria (Passive 2012) with different design and overheating control strategies under different climate scenarios. Future climate datasets are based on Representative Concentration Pathway scenarios for 2050–2059 and 2090–2099. The analysis showed that strategies giving the lowest space heating and cooling demands for the Passive 2012 building version remained the same under all climate scenarios. In contrast, strategies giving the lowest space heating and cooling demands for the BBR 2015 version varied, as cooling demand became more significant under future climate scenarios. Cooling demand was more dominant than heating for the Passive 2012 building version under future climate scenarios. Household equipment and technical installations based on best available technology gave the biggest reduction in total primary energy use among considered strategies. Overall, annual total operation primary energy decreased by 37–54% for the building versions when all strategies are implemented under the considered climate scenarios. This study shows that appropriate design strategies could result in significant primary energy savings for low-energy buildings under changing climates.

Life cycle assessment of buildings and city quarters comparing demolition and reconstruction with refurbishment

In the building sector, the energy and the greenhouse gases embodied in the building materials are becoming increasingly important. Combined with the operational primary energy demand and the end-of-life, the whole life cycle of buildings can be assessed.In this paper, a comprehensive method for calculating the life cycle of individual buildings is presented. First, their material composition has been determined and generic values for the embodied energy, embodied greenhouse gases, energy needed and greenhouse gases emitted during disposal of the different building materials have been calculated. Subsequently these values have been integrated into an urban energy simulation software to simulate energy and emission values for buildings.A given building geometry with four different building standards was considered. The results can help to decide between building refurbishment or demolition and new construction. For example it could be shown that the share of the life cycle stage production compared to the total value rises with a better building insulation standard, as the share of the use stage decreases. The highest building refurbishment standard resulted in the best life cycle performance when compared with less ambitious refurbishment or construction of a new building of today’s standards.

Primary energy implications of different design strategies for an apartment building

In this study, we explored the effects of different design strategies on final and primary energy use for production and operation of a newly constructed apartment building. We analysed alternatives of the building “As built” as well as to energy efficiency levels of the Swedish building code and passive house criteria. Our approach is based on achieving improved versions of the building alternatives from combination of design strategies giving the lowest space heating and cooling demand and primary energy use, respectively. We found that the combination of design strategies resulting in the improved building alternatives varies depending on the approach. The improved building alternatives gave up to 19–34% reduction in operation primary energy use compared to the initial alternatives. The share of production primary energy use of the improved building alternatives was 39–54% of the total primary energy use for production, space heating, space cooling and ventilation over 50-year lifespan, compared to 31–42% for the initial alternatives. This study emphasises the importance of incorporating appropriate design strategies to reduce primary energy use for building operation and suggests that combining such strategies with careful choice of building frame materials could result in significant primary energy savings in the built environment.

Primary energy implications of ventilation heat recovery in residential buildings

In this study, we analyze the impact of ventilation heat recovery (VHR) on the operation primary energy use in residential buildings. We calculate the operation primary energy use of a case-study apartment building built to conventional and passive house standard, both with and without VHR, and using different end-use heating systems including electric resistance heating, bedrock heat pump and district heating based on combined heat and power (CHP) production. VHR increases the electrical energy used for ventilation and reduces the heat energy used for space heating. Significantly greater primary energy savings is achieved when VHR is used in resistance heated buildings than in district heated buildings. For district heated buildings the primary energy savings are small. VHR systems can give substantial final energy reduction, but the primary energy benefit depends strongly on the type of heat supply system, and also on the amount of electricity used for VHR and the airtightness of buildings. This study shows the importance of considering the interactions between heat supply systems and VHR systems to reduce primary energy use in buildings.

Life cycle primary energy analysis of residential buildings

The space heating demand of residential buildings can be decreased by improved insulation, reduced air leakage and by heat recovery from ventilation air. However, these measures result in an increased use of materials. As the energy for building operation decreases, the relative importance of the energy used in the production phase increases and influences optimization aimed at minimizing the life cycle energy use. The life cycle primary energy use of buildings also depends on the energy supply systems. In this work we analyse primary energy use and CO 2 emission for the production and operation of conventional and low-energy residential buildings. Different types of energy supply systems are included in the analysis. We show that for a conventional and a low-energy building the primary energy use for production can be up to 45% and 60%, respectively, of the total, depending on the energy supply system, and with larger variations for conventional buildings. The primary energy used and the CO 2 emission resulting from production are lower for wood-framed constructions than for concrete-framed constructions. The primary energy use and the CO 2 emission depend strongly on the energy supply, for both conventional and low-energy buildings. For example, a single-family house from the 1970s heated with biomass-based district heating with cogeneration has 70% lower operational primary energy use than if heated with fuel-based electricity. The specific primary energy use with district heating was 40% lower than that of an electrically heated passive row house.

Technologies Turn the Balance - On Energies-of-Change

Energy for human needs is energy services, and energy services is two things: primary energy raw materials and conversion technologies for energy and matter. For solar energies operational primary energy raw materials are entirely lacking. What counts is only technologies for the linkwise exergetically efficient and environmentally responsible energy conv'9rsion along the energy conversion chain in its full length: 'Technologies compete, not fuels!" This is the prevalent criterion in the Second Solar Civilization. These reflections look for energy technologies-at-change typical for that civilization and dissimilarto those known and in operation in the fossil energyera. To give an indication, for the direct photo voltaic conversion of sOl'ar light into electricity the invention of the semiconductor was preconditionaJ. Or, for pollution-free total energy conversion the fuel cell is imperative. Are there comparable potential breakthroughs in the pipeline in other areas such as solar chemistry, non-Carnotian electrochemical conversion, or exergy optimization of energy conversion in general? Examples will be given. Favoring or hindering conditions for the development will be described, and lead-times will be outlined.