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Featured Application: The proposed method can be applied to a specific building renovation project for evaluating and selecting energy efficiency and renewable energy production measures, with the aim of reaching the NZEB standard. Reaching environmental targets set by the European Union (EU) requires a constant renovation of the existing building stock to nearly Zero Energy Buildings (NZEB) in a cost-optimal manner. Studies show that the renovation rate of the existing building stock is more than two times less than what is necessary to reach the targets. Furthermore, the majority of performed renovations across the EU reach just a small amount of energy savings, whereas NZEB renovations are rarely achieved. This paper proposes a methodology for the evaluation of renovation measures, aiming to provide decision support related to the selection of what to renovate and to what extent. The proposed method is rooted in the well-established cost-optimal methodology, yet it suggests a pre-step to package evaluation. This is done by means of a simplified cost-effective parameter (CEP), linking cost, lifetime, and energy savings. The methodology is demonstrated using a case study building in Denmark. The results show that the CEP provides good grounds for the compilation of single actions to packages. Further developments could focus on the sensitivity of the model inputs and integration of additional evaluation parameters to cost, such as environmental, architectural, comfort, risk, etc. [ABSTRACT FROM AUTHOR]

The "Comfort Houses" project is one of the most ambitious building projects for passive, single-family houses ever undertaken in Denmark. Thus far, different consortiums have designed and built 10 houses. Besides fulfilling the German passive-house standard, the goal of the project was to build the houses within Danish traditions of architecture and construction. The objective of the research presented in this paper is to compare the different design processes behind the making of passive houses in a Danish context. We evaluated the processes with regard to the integrated and traditional design processes. Data analysis showed that the majority of the consortiums worked in an integrated manner, though there was room for improvement. Additionally, the paper discusses the challenges of implementing the integrated design process in practice and suggests ways of overcoming some of the barriers. In doing so, we also provide suggestions for future work with low-energy houses. [ABSTRACT FROM AUTHOR]

Abstract: The concept of a Net Zero Energy Building (Net ZEB) encompasses two options of supplying renewable energy, which can offset energy use of a building, in particular on-site or off-site renewable energy supply. Currently, the on-site options are much more popular than the off-site; however, taking into consideration the limited area of roof and/or façade, primarily in the dense city areas, the Danish weather conditions, the growing interest and number of wind turbine co-ops, the off-site renewable energy supply options could become a meaningful solution for reaching ‘zero’ energy goal in the Danish context. Therefore, this paper deploys the life cycle cost analysis and takes the private economy perspective to investigate the life cycle cost of different renewable energy supply options, and to identify the cost-optimal combination between energy efficiency and renewable energy generation. The analysis includes five technologies, i.e., two on-site options: (1) photovoltaic, (2) micro combined heat and power, and three off-site options: (1) off-site windmill, (2) share of a windmill farm and (3) purchase of green energy from the 100% renewable utility grid. The results indicate that in case of the on-site renewable supply options, the energy efficiency should be the first priority in order to design a cost-optimal Net ZEB. However, the results are opposite for the off-site renewable supply options, and thus it is more cost-effective to invest in renewable energy technologies than in energy efficiency. [Copyright &y& Elsevier]

Currently, the built environment accounts for about 40% of the total energy consumed in the European Union and this level is continuing to increase. This high level of energy consumption is partially a result of attempts to create an optimum indoor environment for the occupants of buildings. New buildings and renovation projects on existing buildings need to improve their energy performance while maintaining a good and healthy indoor environment. One way of saving energy is to build passive houses. This paper presents the results of a case study of some of the first certified passive houses in Denmark, called Comfort Houses. The indoor environment is evaluated using both quantitative measurements of these houses and qualitative interviews with the occupants about their experiences of the indoor environment. The combination of these two sets of knowledge leads to a more complete and holistic picture of the indoor environment. It is shown that attention needs to be paid to the objectives in the design process, the documentation of the designs and on the occupant’s lifestyle and behaviour. Finally, it is important to educate the occupants on how to live in an appropriate manner to achieve a comfortable indoor environment. [ABSTRACT FROM AUTHOR]

Abstract: It is well recognized that in the long run, the implementation of energy efficiency measures is a more cost-optimal solution in contrast to taking no action. However, the Net ZEB concept raises a new issue: how far should we go with energy efficiency measures and when should we start to apply renewable energy technologies? This analysis adopts the LCC methodology and uses a multi-family Net ZEB to find the answer to this question. Moreover, it looks at the issue from the building owner’s perspective, hence it should be seen as a private economy analysis. The study includes three levels of energy demand and three alternatives of energy supply systems: (1) photovoltaic installation with photovoltaic/solar thermal collectors and an ambient air/solar source heat pump; (2) photovoltaic installation with a ground-source heat pump; (3) photovoltaic installation with district heating grid. The results indicate that in order to build a cost-effective Net ZEB, the energy use should be reduced to a minimum leaving just a small amount of left energy use to be covered by renewable energy generation. Moreover, from the user perspective in the Danish context, the district heating grid is a more expensive source of heat than a heat pump for the Net ZEB. [Copyright &y& Elsevier]

Abstract: Building performance can be expressed by different indicators such as primary energy use, environmental load and/or the indoor environmental quality and a building performance simulation can provide the decision maker with a quantitative measure of the extent to which an integrated design solution satisfies the design objectives and criteria. In the design of sustainable buildings, it is beneficial to identify the most important design parameters in order to more efficiently develop alternative design solutions or reach optimized design solutions. Sensitivity analyses make it possible to identify the most important parameters in relation to building performance and to focus design and optimization of sustainable buildings on these fewer, but most important parameters. The sensitivity analyses will typically be performed at a reasonably early stage of the building design process, where it is still possible to influence the most important design parameters. A methodology of sensitivity analysis is presented and an application example is given for design of an office building in Denmark. [Copyright &y& Elsevier]

This paper presents both experimental and numerical studies of PCM storage integrated with an HVAC system. The experiments focus on PCM storage in 3 different sizes, and study the temperature change in the PCM storage during the charge and discharge period, the impact of the PCM quantity on the charge and discharge rates of the PCM storage and the impact of the discharge air temperature and airflow rate on the discharge rate. The main conclusions are that the temperature effectiveness of the PCM storage depends more on the PCM quantity than the discharge inlet air temperature and airflow rate. The air path in the PCM storage should not be too long to achieve the longer PCM activation in time. The storage with 36 pieces of PCM plates and latent storage capacity of 5.23 MJ can be charged/discharged fast, with high and stable outlet air temperature (above 28 °C for 3 h), especially during the discharge period. The most promising configuration of the experimental study was chosen for a numerical study the energy flexibility of the HVAC system without PCM and with PCM. A model of the PCM storage integrated with an HVAC system is built with EnergyPlus and validated by experimental data. The study concluded that the HVAC heating setpoint control based on the electricity price without PCM storage has limited cost-saving potential due to the high electricity transmission and tax cost. The PCM storage integrated with an HVAC system can reduce the energy cost by 7 % while obtaining a similar indoor thermal comfort level compared to the HVAC heating setpoint control without PCM storage. The payback time of HVAC with PCM is seven years compared to HVAC system without PCM. The cost reduction of energy flexibility of the system is relatively limited because the electricity transmission cost and electricity tax account for 80% of the total electricity cost in Denmark. [ABSTRACT FROM AUTHOR]

Applying phase change material (PCM) for latent heat storage in sustainable building systems has gained increasing attention. However, the nonlinear thermal properties of the material and the hysteresis between the two-phase change processes make the modelling of PCM challenging. Moreover, the influences of the PCM phase transition and hysteresis on the building thermal and energy performance have not been fully understood. This paper reviews the most commonly used modelling methods for PCM from the literature and discusses their advantages and disadvantages. A case study is carried out to examine the accuracy of those models in building simulation tools, including four methods to model the melting and freezing process of a PCM heat exchanger. These results are compared to experimental data of the heat transfer process in a PCM heat exchanger. That showed that the four modelling methods are all accurate for representing the thermal behavior of the PCM heat exchanger. The model with the DSC Cp method with hysteresis performs the best at predicting the heat transfer process in PCM in this case. The impacts of PCM phase change temperature and hysteresis on the building energy-saving potential and thermal comfort are analyzed in another case study, based on one modelling method from the first case study. The building in question is a three-room apartment with PCM-enhanced ventilated windows in Denmark. The study showed that the PCM hysteresis has a larger influence on the building energy consumption than the phase change temperature for both summer night cooling applications and for winter energy storage. However, it does not have a strong impact on the yearly total energy usage. For both summer and winter transition seasons, the PCM hysteresis has a larger influence on the predicted percentage of dissatisfied (PPD) than the phase change temperature, but not a strong impact on the transition season average PPD. It is therefore advised to choose the PCM hysteresis according to whether it is for a summer night cooling or a winter solar energy storage application, as this has a significant impact on the system's overall efficiency. [ABSTRACT FROM AUTHOR]

Renovation of existing buildings is an indispensable part of achieving European efficiency and environmental targets. This paper applies different assessment methodologies to find optimal renovation, given different evaluation criteria. The performed literature study identifies the cost-optimal methodology employing Life Cycle Cost (LCC) calculation as one of the most common assessment methods. This paper proposes a new renovation assessment method targeted to the early design phases of specific building projects. The method has a simple structure, and can be used as a roadmap of necessary activities for obtaining solid building knowledge and required energy and cost calculations. The methodology is based on linking economic and energy efficiency parameters into defined cost-effective value, calculated for all investigated renovation actions. The cost-effectiveness value is used for ranking and selecting the most appropriate single renovation actions to form renovation packages, which can be further examined in detail (for example, with LCC). To demonstrate the method, evaluate the strengths, and identify the weaknesses, it is applied to case study buildings in Denmark and Switzerland. The results show that, in the initial stage, the proposed cost-effectiveness representation can be used successfully to compare and evaluate different envelope elements and systems. Cost-effectiveness also provides rational results on a package level. Further work is still required in the area of evaluation of energy supply and renewable energy production systems. [ABSTRACT FROM AUTHOR]

The research aims to develop control strategies for intelligent glazed façades and investigate the influence of different control strategies on energy and comfort performance in office buildings. The intelligent glazed façade is capable of controlling the thermal, solar and mass transmittance by controlling shutters, blinds and openings. The façade and building services are designed and controlled holistically to optimize the indoor comfort (thermal, visual comfort and indoor air quality) and minimize the energy demand by heating, cooling, lighting and ventilation. The study is conducted numerically utilising a simplified hourly calculation method developed to calculate yearly energy and comfort performance of an office room equipped with an intelligent façade. The simplified method is verified by the Danish dynamic building simulation tool BSim and experimental test in a full scale test facility at Aalborg University (Cube). Results show that the annual primary energy demand of an office building with intelligent glazed façade can be reduced by approx. 60% compared with the same building with a static façade. Utilising the properties of an intelligent glazed façade, buildings can more easily comply with the future Danish Building Class 2020 as stipulated in the Danish Building Regulation 2010, BR10. The comfort performance of the building can also be improved using an intelligent glazed façade. [ABSTRACT FROM AUTHOR]