Complexity in Designing Energy Efficient Buildings: Towards Understanding Decision Networks in Design

Most important decisions for designing energy efficient buildings are made in the early stages of design. Designing is a complex interdisciplinary task, and energy efficiency requirements are pushing boundaries even further. This study analyzes the level of complexity for energy efficient building design and possible remedies for managing or reducing the complexity. Methodologically, we used the design structure matrix for mapping the current design tasks and hierarchical decomposition of lifecycle analysis for visualizing the interdependency of the design tasks and design disciplines and how changes propagate throughout the system, tasks and disciplines. We have visualized the interdependency of design tasks and design disciplines and how changes propagate throughout the system. Current design of energy efficiency building is a linear and one-shot approach without iterations planned into the process. Broken management techniques do not help to reduce the complexit

Comparison of Simplified and Detailed Window Models in Energy Simulations

The purpose of this study is to quantify the gap between the calculated energy need of a building model with simplified and detailed windows and suggest a method for reducing the gap. We composed a model of a detached house in the cold climate of Estonia and studied its energy needs with triple and quadruple windows. Standard window models resulted in heating need lower by up to 7% and cooling need higher by up to 23%. In case of triple windows multiplying the U-value of standard window models by 1.15 minimized the mismatch in the calculated energy needs with different window models

Solar radiation-based method for early design stages to balance daylight and thermal comfort in office buildings

There is a lack of facade design methods for early design stages to balance thermal comfort and daylight provision that consider the obstruction angle as an independent variable without using modeling and simulations. This paper aims to develop easy-to use solar radiation-based prediction method for the design of office building facades (i.e., design parameters: room size, window-to-floor ratio, and glazing thermal/optical properties) located in urban canyons to balance daylight provision according to the European standard EN 17037:2018 and thermal comfort through specific cooling capacity. We used a simulation-based methodology that includes correlation analyses between building performance metrics and design parameters, the development of design workflows, accuracy analysis, and validation through the application of the workflows to a new development office building facades located in Tallinn, Estonia. The validation showed that the mean percentage of right/conservative predictions of thermal comfort classes is 98.8% whereas for daylight provision, it is higher than 75.6%. The use of the proposed prediction method can help designers to work more efficiently during early design stages and to obtain optimal performative solutions in much shorter time: window sizing in 73,152 room combinations in 80 s

Parametric Energy Simulations of a Nordic Detached House Heated by a Wood Stove

Wood stoves are widely used in Nordic countries. They offer a good opportunity to use biomass for space-heating and to reduce the peak power of all-electric buildings. However, wood stoves are highly concentrated heat sources with limited control compared to other typical heat emission systems, which makes the assessment of their impact challenging. This study introduces a simulation-based parametric study of a detached house equipped with a wood stove located in Oslo, Norway. The respective impact of different building parameters and stove nominal powers on the building performance is illustrated. The analysis shows that the annual total space-heating needs (i.e. the sum of the base load, modelled as ideal heaters representing the electrical radiators, the stove and the heating of the ventilation supply air) increased significantly due to the higher average indoor temperature. The resulting heat emission efficiency of the stove ranged between 66% and 90%. However, the stoves covered between 28% and 62% of the total space-heating needs. When using the stove, the maximum hourly-averaged power for the electrical radiators decreased between 5 W/m2 and 31 W/m2 during the peak hours of the electricity grid. The building thermal mass, insulation level, as well as the combination of internal door position with the bedroom temperature setpoint, had a significant impact on the calculated values. Finally, the study revealed that the occupant behaviour modelling should be improved to better capture the wood stove impact on the energy performance using building simulations. © The Authors, published by EDP Sciences, 2020.publishedVersio

Benchmarking the measured energy use of Nordic residential buildings and their Zero Energy-readiness

| openaire: EC/H2020/856602/EU//FINEST TWINSIt is well known that buildings are responsible for a nearly 40% share of the total energy consumption; in order to reduce it by improving the energy efficiency of the building stock, it is necessary to first evaluate their performance. Building energy benchmarking provides information to stakeholders and motivates energy retrofits, by evaluating and comparing a building to similar units and/or to a reference building in terms of energy consumption with the minimum amount of data possible. Towards this end, in this paper we analysed nearly 19000 Estonian Energy Performance Certificates (EPCs) of detached houses. By means of a systematic statistical investigation, we determined the time evolution of EPC labels and evaluated the impact of incentives pre/post renovations, drawing a comprehensive and updated picture of the Estonian detached houses. This allowed evaluating their readiness based on recent trends: unfortunately, new or renovated dwellings are not estimated to achieve the zero-energy status by 2050. Although marginally due also to the use of homeworking during the COVID-19 pandemic, we show that this is mostly determined by changes in the regulations. A benchmarking ranking for each construction type was also created by calculating rating tables based on a 0-100 coefficients scale; this allows comparing with the existing stock any building with known EPC, for energy Audit and other investigations aiming at energy efficiency

Thermal comfort and draught assessment in a modern open office building in Tallinn

Modern office building users have high expectations about the working environment and thermal comfort, which requires the installation of complex technical systems such as combined cooling and ventilation. Room conditioning units of these systems must ensure temperature and ventilation control in a way that air velocity is low and the air temperature in acceptable range. Achieving air distribution avoiding draught is one of the key elements of a thermal comfort in modern office landscape. Higher air velocity in occupied zone is easily perceived as draught, which causes occupant dissatisfaction and complaints, as well as decrease in the productivity or effective floor space area. To reduce complaints, room air temperature setpoints or ventilation airflow rates are often modified, which may result in higher heating energy demand. In addition, excessive heating setpoint rise will not only consume more energy, but may cause health problems. Compared to cellular offices it is more difficult to ensure thermal comfort conditions in open office spaces where there are no walls for air flows. In addition, due to the higher number of employees it is more difficult to meet satisfactory conditions for everyone. The aim of this study was to evaluate thermal comfort parameters such as room air temperature, air speed and supply air temperature and how the users sense it in a modern office building in Tallinn, Estonia. Design room air temperature setpoints and air exchange rate were evaluated on open office spaces. Measured data with web-based indoor climate questionnaire was analysed. Results show which design and measured parameters make it possible to match the user comfort at all times.Peer reviewe

Comparison of simplified and detailed window models in office building energy simulations

The aim of this study is to quantify the gap between the simulated energy need of an office building with simplified and detailed glazing models. We studied triple, quadruple and quintuple windows and concluded that differences in energy need of similar cases with different glazing models reached 1.9 and 6.4 kWh/m2 in space heating and cooling needs respectively. Significant relative differences in heating and cooling were up to 14% and 40% respectively. Largest differences appeared with triple glazing and smallest with quadruple glazing. Compared to detailed window models standard triple and quadruple glazing models resulted in lower heating and higher cooling needs, whereas in case of quintuple windows the results were the opposite.Peer reviewe

Validation of a Zonal Model to Capture the Detailed Indoor Thermal Environment of a Room Heated by a Stove

Using wood stoves is a common space-heating strategy in the Nordic countries. Currently, the lowest available nominal power of wood stoves is significantly oversized compared to the design space-heating load of highly-insulated houses. This oversizing might deteriorate the indoor thermal environment by causing overheating and a large vertical temperature stratification. Modelling the indoor thermal environment of rooms heated with a wood stove with acceptable computational time and accuracy, however, is a complex task. The purpose of this study is to analyze the accuracy of a new IDA-ICE zonal model currently under development and to calibrate it against measurements. For this, several experiments were conducted in a test cell, which was heated by an electric stove mimicking a wood stove with a nominal power of 4 kW. Room air temperatures in various positions were measured, while the stove that was placed in the middle of the room was run in cycles with different durations and surface temperature profiles, leading to a thermal stratification of 0.5–2.2 K/m. The zonal model could reproduce the temperatures at the bottom and top layers of the room with good accuracy. However, the model still needs further development and validation to reach good agreement with measurements in the middle layers of the zone. Nevertheless, already at this stage, the model could be used to roughly assess thermal stratification in rooms heated by wood stoves