Abstract: A conventional radiant panel system offers advantages in terms of energy savings; however, compared with an all-air system, it has limitations such as moisture condensation risk, slow air movement, difficult space zoning, slow air pollutants removal from a highly polluted room, and time delay in start-up of the radiant panel system. This research performs an energy consumption analysis of a hybrid radiant cooling system for buildings in summer. The hybrid radiant cooling system combines a typical radiant panel with a decentralized air convector connected in series. The hybrid radiant panel system generates additional cooling output through its air convector, dehumidifies indoor air, increases indoor air movements, and reduces the time delay in start-up and a filter in the air convector removes air pollutants. This study exhibits the energy performance of the hybrid radiant cooling system compared with an all air system and a typical radiant panel system via numerical modeling using experimental data. This hybrid radiant panel system is effective for energy-saving, because it has a higher cooling impact ratio, and larger coefficient of performance of the chiller, and because the air movement increases the offset effect of the operation indoor temperature rise by an enhanced mixed convection effect. Thus it can reduce cooling energy consumption. The hybrid radiant cooling system can be used very effectively for saving energy in the summer season.
Permalink: https://doi.org/10.1016/j.buildenv.2018.04.006

Abstract: This study considered combinational control approaches for predicting electricity consumption in a building based on an optimized back-propagation (BP) neural network. Forecasting the electricity consumption of buildings is an important part of power management systems because it directly affects power dispatching and safe production. The BP neural network prediction method is used widely for this purpose because of its high plasticity and simple structure, but it has disadvantages such as slow convergence, fluctuations, and oscillation during training. We propose the use of the Levenberg–Marquardt back-propagation (LM-BP) neural network to enhance the accuracy of predictions by combining the gradient descent and Quasi-Newton method, thereby ensuring the fast convergence speed and maintaining better overall performance. Additionally, the network weights can be optimized by adaptive adjustment between the steepest gradient descent method and the Gauss–Newton method so the network can converge effectively. Hence, the accuracy and stability of the LM algorithm are improved, and a building electricity consumption prediction model can be established based on the improved BP neural network. Our results demonstrate that the forecasting model based on LM-BP neural network improves the accuracy and stability of predictions, and it is suitable for the short-term prediction of building electricity consumption.
Permalink: https://doi.org/10.1016/j.scs.2018.05.050

Abstract: The retrofitting of existing buildings offers significant opportunities to reduce global energy consumption and greenhouse gas emissions in the build environment. Therefore, it is considered as one of the main approaches to achieve sustainability in the built environment at a relatively low cost and high acceptance rates. Although there is a wide range of retrofitting technologies available, methods to identify the most cost-effective measures for each project remain a major technical challenge. Numerous projects have been developed worldwide to face this challenge with different approaches; however, many of the tools meet only local objectives, which is why they are unknown in the international arena, showing a limited knowledge transfer. This review organizes the results under three categories: renovation assessment, financial assessment and Transfer of knowledge. The tools focusing on promoting the renovation of buildings differ in the type of user to whom the tool targets for example, the owners need information and recommendations to renovate their own buildings. Where other tools focus on providing information to politicians and investors were the scale of information is greater, pointing out areas where an energy potential that can be improved through renewal or the use of renewable energy sources is highlighted. Finally, other tools to comply with policies that seek to register, evaluate and characterize the existing buildings. These tools commonly called certification tools, have different degrees of sophistication and approaches. This review, provides researchers, construction professionals, and politicians with a better understanding of the advances made to effectively design buildings retrofitting measures, promote energy conservation and the assessment of the building stock for the development of policies. The review shows that many tools have the potential of joining their capabilities, which can produce many opportunities for innovation in the retrofitting area.

Abstract: Energy Performance Building Directive (EPBD) ask the Member of States to develop a mandatory energy labelling scheme for new and existing buildings, which should include a label rating of the energy efficiency of the building and a list of recommended energy saving measures. The label will provide prospective buyers and tenants of a building with correct information about the energy performance of the building to compare with other options. However, some countries use only one or a limited number of weather zones. In a country like Norway, with significant variations in weather conditions between locations, this is likely to cause a deviation when comparing with the reality. This study aims to present the implication of using only one weather zone in Norway. The method used is based on the comparison of three types of weather files. The first one is used in the labelling system, which is a typical year, while the others are typical reference years from the local site from different providers. The results show significant differences in energy consumption, savings and labelling ratings when applying files with local weather data instead of the official weather data file used in Norway.
Permalink: https://doi.org/10.3384/ecp18153342

Abstract: Use of massive wood has increased during the last decade. The concept of massive wood, mainly as cross laminated timber elements (CLT), has become a popular building method for new constructions, both in public and private sector. Massive wood elements take advantage of wood as building material, also as an indoor climate buffer. Moholt 50|50 is a new student-housing project in Trondheim, Norway, which consists of five mass timber towers. Each of them with eight stories built in CLT on top of a concrete storey. Apart from the student homes, the buildings host facilities, such as activity center, kindergarten, commercial areas and a library, also built in CLT. This makes Moholt50|50 a significant wooden living lab in Trondheim. The building technique follows the development from the first Norwegian CLT stu-dent housing built in Ås in 2012, and reproduced later on in similar p atterns in other Norwegian cities, as Tromsø, Haugesund, Drammen, Fredrikstad, Halden, Hønefos s, Porsgrunn and Trondheim. Research on comfort and operation cost coupled to indoor surfaces are included in project Moholt 50|50. The towers are built according to Norwegian low energy stand-ards. All surfaces are treated with water solvent varnish, apart from two stories in one of the Moholt timber towers. Four stories are instrumented to document the difference in the behavior of untreated and treated wooden surfaces. Measurements show a different indoor climate of the stories with untreated surfaces. The measurements presented give preliminary results of a measurement period which, when finished, will include one year of inhabited studios from the date of moving in.
Permalink: https://doi.org/10.1007/978-3-030-00662-4_71

Abstract: This work conceives a numerical modeling approach for the practical application of phase change materials (PCM). Momentum, energy and mass conservation are implemented in a coupled manner including auxiliary algebraic equations for phase change functionality. Key element of the modeling approach is the introduction of a socalled mushy zone at the interface between solid and liquid where the thermophysical properties are smeared out over an user-defined range of melting temperature. A 2D square cavity test-case shows the influence of natural convection on the melting front propagation. For practical application the model has been adapted to an 1D case representing the wall-crosssection of a typical Norwegian wooden cabin. The model can quickly reveal energetic optimization potential as well as provide orientation among the vast selection of PCM for the target-oriented choice of a suitable material.

Abstract: The present study conceives a numerical model for phase change materials following the apparent heat capacity method where the phase change occurs within a chosen temperature interval. A multiphysical modeling approach to satisfy the coupled momentum, energy and continuity conservation equations whilst avoiding numerical singularities is applied. By means of a 2D test-case geometry with variable boundary heating the influence of natural convection within the melted liquid zone is visualized. Corresponding non-dimensional governing equations are analysed to quantify the dominant contributing terms. It turns out that for sufficiently small Grashof number, or consequently small Rayleigh numbers the influence of natural convection can be neglected, thus simplyfing the problem substantially. The modeling approach has been adapted to a 2D-axisymmetric geometry within the scope of experimental validation. The simulation results and experimental data show reasonably good agreement. The model is numerically stable and suitable to facilitate design of latent heat storage systems.
Permalink: https://doi.org/10.3384/ecp18153103

Abstract: This work presents a numerical analysis of a planar moving shock wave with Mach number Ms = 1:3, travelling through a square cavity geometry with rigid boundaries. A high-order artificial viscosity based Discontinuous Spectral Element Method (DSEM) is used for this purpose. The explicit numerical scheme utilizes entropy generation based transport coefficients to solve the conservative form of the viscous compressible fluid flow equations. Numerical prediction of the shock propagation and diffraction is found to be in excellent agreement with the experimental results of the literature. The stable numerical scheme resolves the detail of the complex flow dynamics for varying reference Reynolds number (Ref). The range of values of the artificial coefficients and the relative contribution of the components of the artificial energy dissipation rate are investigated and compared for different cases. Artificial energy dissipation is less for low Ref. The dilatational dissipation dominates over other components till the incident shock wave resides in the flow domain.
Permalink: https://doi.org/10.3384/ecp18153111

Abstract: We present numerical analysis of a cold storage room with a product load, a fan, and a sliding door by solving compressible form of the conservative 3D Navier-Stokes equation (without Boussinesq approximation) together with the energy and mass fraction equations. The commercial computer program StarCCM+ is used for this purpose. The sliding door is treated with an overset mesh on a suitable background mesh. A rigid body translation is applied by a field-function to model the opening and closing of the door. The preliminary study captures essential features of the effect of the energy transport and the cooling of the product load by the fan and the hot, moist air exchange through the doorway. The airflow behavior and heat/mass transfer mechanisms are studied and presented for several numerical experiments.
Permalink: https://doi.org/10.3384/ecp18153201

Abstract: Demand-Controlled Ventilation is emerging as a dominant ventilation strategy in non-residential buildings in Norway. The ventilation airflow rate is controlled between pre-set minimum (Vmin) and maximum (Vmax) values, based on the signal from room-sensors. The choice of Vmax is based on current knowledge about necessary airflow rate to reach an acceptable IAQ (indoor air quality) with maximum likely personal load and emission load from building materials. The choice of Vmin has an obvious impact on energy use, but there are few studies about its impact on IAQ. Vmin varies typically from 0.7 to above 2 (l/s)/m² in Norway. In several buildings, Vmin is set to the upper range of this interval due to technical limitations of the specific equipment used. We have performed blind cross over intervention-studies with an untrained test panel to evaluate PAQ (perceived air quality) when entering 20 PAQ-rooms. All the rooms have low-emitting building materials, but extra pollution sources were introduced in some of the rooms for this study. Supplementary, intervention studies were performed in a dedicated test room to assess the impact of airflow rate on PAQ, performance and well-being during the first 20 min of occupation. We found that increasing Vmin has a significant positive impact on PAQ in rooms with extra pollution sources. This effect was not consistently present in the low-emitting rooms. Airflow rates did not noticeably affect PAQ, performance and well-being during the first 20 min of occupation. This indicates that Vmin above 1 (l/s)/m² has limited benefit to IAQ in low emitting rooms.
Permalink: https://doi.org/10.1007/978-3-030-00662-4_29

Abstract: In the Nordic countries, as well as in much of the industrialized world, mechanical heat-recovery ventilation is a common way to ventilate schools and office buildings. Demand Controlled Ventilation (DCV) is emerging as the dominating ventilation strategy in Norway, as well as in the rest of the Nordic countries, motivated by national requirements to reduce greenhouse gas (GHG) emissions as well as profitability, enabled by recent technological developments. In our study, we investigate the best strategy for DCV in terms of low energy consumption in combination with optimum indoor air quality. The main objective is to define robust strategies for demand-controlled ventilation of schools and office buildings to maximize air quality in occupied spaces and minimize energy use for ventilating empty spaces. In order to assess the objective, several methodologies have been applied and evaluated. The aim of this study is a discussion on the representativeness of the currently used methods of assessing indoor air quality and their reproducibility.

Abstract: Use of Demand Controlled ventilation (DCV) can potentially save more than 50% of energy use for ventilation purposes compared to constant air volume (CAV) ventilation. Correct and updated calculation of preset minimum (Vmin) and maximum (Vmax) airflow rates are important to maximize energy saving and to ensure good indoor quality. Furthermore, earlier studies have shown that controlling units’ ability to actually handle V min is lacking and causes instability in the DCV systems. State of the art study of leading Norwegian consulting firms documented that use of advanced Spreadsheet-sheets is the common approach for calculation ventilation rates, where the main focus is on Vmax. This even if use of BIM (Building Information Modeling) is common in this kind of firms. Based on this knowledge, we have developed a BIM-integrated Design tool for calculation of ventilation rates. This tool defines a method for using specific data for each space within the model as basis for the calculations. By running different scripts, recommended ventilation rates are easily calculated. The tool can save hours of work and ensure correct values in line with changes done during the design phase. The tool has a built-in check of the VAV-dampers ability to control air flow rates from Vmix to Vmax. This will increase the focus on Vmin, and implemented recommendations are new research-based values. The tool also includes first recommendations on ventilation rates based on CO₂ calculations. These calculations will be further developed.

Abstract: This paper dealt with simulating a typical occupied office equipped with displacement ventilation using CFD method. The STAR-CCM+ commercial software was employed for performing the simulations in order to analyze the trend of the indoor air temperature profile in the office occupied space. Understanding this trend is a key parameter to ensure that the occupants are comfortable and thereby further conclusions on energy efficiency could be extracted. The simulations were carried out for incompressible, turbulent, and constant property air flow in the steady state condition. The results showed that increasing the number of occupants, while Archimedes number was constant, would increase the throw length of the incoming cold jet leading to an overall lower temperature profile for the case with five occupants.
Permalink: https://doi.org/10.3384/ecp1815317

Abstract: Dwellings built between 1945 and 1980 have the largest energy demand in the EU, which by 2009 represented 70% of the final energy use in buildings. A great portion of these dwellings have not been retrofitted and most of them were not built with any energy efficiency measures, since most of the energy regulations were implemented after the oil crisis in the 70s. To face this issue several actions were taken in the EU, among these, the implementation of Energy Performance Certification, which includes a Recommendation List of Measures (RLMs) to retrofit the property. The main objective of this study is to identify the weaknesses of the RLMs and to suggest changes to improve the quality and impact of this feature. The results indicate that to retrofit an existing building, the RLMs lack information for decision-making. The study suggests important barriers to overcome for achieving potential energy reductions in existing residential buildings, highlighting improvements to the recommendation content and its implementation.
Permalink: https://doi.org/10.3390/en11102516

Abstract: After the oil crisis in the 70s energy regulation codes were implemented, but a great portion of existing dwellings have not been retrofitted to current requirements. To face this issue several actions were taken in the European Union (EU), among these, the implementation of Energy Performance Certificates (EPC), which include a Recommendation List of Measures (RLMs) to retrofit buildings. Some concerns exist about the lack of confidence on these recommendations. The main objective of this study is to analyze the usefulness of the EPC, answering if it is possible to deliver a realistic financial assessment about renovation strategies using these tools. The study is based on three indicators: Consumption, energy saving variations and profitability. The study is based on a renovation project case study, where simulations and Life Cycle Cost Assessment (LCCA) were performed, in order to identify the different results that EPC’s and an energy efficiency assessment could lead to. The results show important differences in all the concepts evaluated
Permalink: https://doi.org/10.3390/su10093159

Abstract: Background In Norway, 91% of children aged 1–5 attend kindergarten where they are exposed to indoor microbiomes which can have relevance for development and health. In order to gain a better understanding of the composition of the indoor microbiome and how it is affected by occupancy over time, floor dust samples from a newly opened kindergarten were investigated. Samples were collected during an 11-month period. Samples were analyzed for bacterial composition using 16S rRNA gene sequencing. Samples were also screened for four clinically relevant antibiotic resistance genes. In addition, Petrifilm analyses were used to evaluate surface hygiene. Results Significant changes in the microbial community composition were observed over time (PERMANOVA, P < 0.05). Particularly, changes in the abundance and the proportions of human associated bacteria were found. A decrease in the prevalence of Propionibacterium from over 16% abundance to less than 1% and an increase in Streptococcus from 10 to 16% were the most significant findings. Four classes of clinically relevant antibiotic resistance genes were tested for; three were detected in the dust, indicating the presence of resistant bacteria and a potential for resistance spread. Petrifilm analysis showed that some surfaces in the kindergarten were of consistent poor hygienic quality, and new hygienic routines are required. Conclusions This study, which is the first of its kind performed at a newly opened kindergarten, reveals changes in the microbiome over time as well as the presence of antibiotic resistance genes and hygiene issues which are of relevance for occupant health.
Permalink: https://doi.org/10.1186/s40168-018-0553-x

Abstract: Demand-Controlled Ventilation (DCV) are often underperforming regarding energy saving potential and indoor climate. This is caused by reasons like design, components, specifications, handover documentation, or communication errors. We developed guidelines and commissioning procedure to improve the performance of DCV-systems in 2013. In this paper we present the first experiences from a cost and time-efficient spot checking procedure for functional control of DCV-systems. The purpose of the procedure is to reveal if the systems have any hidden shortcomings, errors or defects after the hand-over procedure is accomplished. The control procedure was taken into use summer 2016 and has so far been performed in 22 school buildings in Oslo. 11 schools passed the control. The main experience is that DCV-systems can roughly be divided into two groups, “well-functioning VAV” and “malfunctioning VAV”. Well-functioning VAV seems to be designed and assembled with a top-down awareness on competence and quality. They are close to faultless and well fitted for the operation phase. Malfunctioning VAV might have almost countless errors or defects, easy to reveal in a simplified control procedure. We also see that the newest schools have an overall better VAV-performance, indicating that the control procedure has increased the DCV quality.

Abstract: The ability of large-eddy simulations (LES) to resolve the most energetic coherent structures of a spatially-evolving supersonic turbulent boundary layer over a flat plate at M∞ = 2 and Re_θ ≈ 6000 is analyzed using three different local subgrid scale models. Additionally, an Implicit LES (ILES), which relies on the intrinsic numerical dissipation to act as a subgrid model, is investigated to assess the consistency and the accuracy of the method. Direct comparison with data from high resolution DNS calculations (Pirozzoli and Bernardini, 2011) provides validation of the different modeling approaches. Turbulent statistics up to the fourth-order are reported, which help emphasizing some salient features related to near-wall asymptotic behavior, mesh resolution and models prediction. Detailed analysis of the near-wall asymptotic behavior of all relevant quantities shows that the models are able to correctly reproduce the near-wall tendencies. The thermodynamic fluctuations, T_rms and ρ_rms, show a lack of independence from SGS modeling and grid refinement in contrast to the velocity fluctuations. The pressure fluctuations, which are associated with the acoustic mode, are not significantly affected by the modeling and the mesh resolution. Furthermore, the comparison of different contributions to the viscous dissipation reveals that the solenoidal dissipation plays the most dominant role regardless of the model. Finally, it is found that the ILES is more likely to produce consistent near-wall behavior even with a numerical scheme that has a small amount of numerical dissipation to emulate the effects of unresolved scales.
Permalink: https://doi.org/10.1016/j.euromechflu.2017.09.005

Abstract: The microbial content of dust collected from intake and exhaust air filters in six Norwegian nurseries was determined using 16S rRNA pyrosequencing and plate count analyses. The concentration of endotoxins was also estimated. About 96% of the sequences were classified as Actinobacteria, Proteobacteria, Firmicutes, Bacteroidetes and Cyanobacteria. At the genus level, about 30% of sequences from the exhaust filter were classified as bacteria of probable human origin, such as Streptococcus and Corynebacterium species. These were close to absent in intake dust samples (<1%). This suggests that occupancy shapes the indoor microbiota, creating an environment relatively rich in genera of potential health significance. There were significantly greater counts of culturable bacteria and fungi in exhaust samples, indicating that passage of air through the nursery causes deterioration in the general air quality. Although there was more endotoxin in exhaust dust, the endotoxin levels per colony forming unit were similar in both samples. This study explores, for the first time, the bacterial composition of ventilation filter dust in Norwegian nurseries, and is important as it reveals what types of microorganisms nursery users are exposed to. In addition to possible direct health issues, the nature of our early exposure to microbes may be significant in the development of immunological conditions.
Permalink: https://doi.org/10.1177/1420326X17713831