Abstract available via the hyperlink above

Abstract: This study examined approaches to predict electricity consumption of a Heating, Ventilation and AirConditioning (HVAC) system in a multi-complex building using two neural network models: Back Propagation (BP) and Radial Basis Function (RBF) with input nodes, e.g., temperature, humidity ratio, and wind speed. Predicting HVAC energy consumption of buildings is a crucial part of energy management systems. We used two main neural network models, BP and RBF, to evaluate the prediction performance of electricity consumption of HVAC systems. The BP neural network method exhibited good performance, but it exhibited relatively large fluctuations and slow convergence in the training process. In contrast, RBF exhibited relatively fast learning and reduced computing costs. The HVAC energy consumption rate of working days was higher than that of non-working days. The results indicate that the prediction of HVAC energy consumption using neural networks can effectively control the relationship between the HVAC system and environment conditions.
Permalink: https://hdl.handle.net/11250/2839080

Abstract: The energy efficiency of new buildings in Norway has been steadily improved over the last decades, but with less heating, hydronic heating systems have adversely increased in price. Lessening electric power consumption in new buildings is an important part of the government’s plan to de-carbonize, in which hydronic heating is a suitable alternative for direct electric heating. In this regard, a developer claimed to have found a potential cost-efficient hydronic solution in terms of investment cost. This solution is based on two measures, using the Domestic Hot Water (DHW) circulation loop to cover both DHW demand as well as space heating demand in the building, and significantly reducing the number of heat emitters. In this work, we studied the possible benefits and the issues associated with this solution and performed an analysis based on the following accounts, i) the distribution system, ii) indoor climate, iii) energy demand/consumption, iv) hygienic security. A newly finished apartment complex located in central Oslo is chosen for this purpose. Two apartments and the central heating are examined by inspection, experimental measurements, and Computational Fluid Dynamics (CFD) simulations. The distribution system is examined to confirm the alleged cost efficiency with a simplified cost calculation based on the BIM-model and the documentation provided by the developers. We estimated an additional cost of 67 NOK per square meter in comparison to direct electrical heating. The end user could also financially benefit from using less expensive district heating. Using fan-coils as main heat emitter in each apartment was found to produce satisfactory indoor climate, however, in one apartment it was found that poor planning sabotaged its intended function which negatively affected indoor climate. Additionally, we found a lack of measures to protect the DHW from Legionella-growth, which is a violation of Norwegian building code TEK17.
Permalink: https://hdl.handle.net/11250/2839073

Abstract: The ventilation airflow rates in a demand-controlled ventilation strategy typically vary between a base (Vmin) and a maximum ventilation rate (Vmax). Classrooms have relatively short but intense hours of occupancy and a low Vmin can result in high energy savings. Our study aims to examine how different Vmin (1.1 versus 2.0 l/s per m²) affect subjective symptoms, perceived indoor environment quality (IEQ), and performance for young adults. Symptom intensity and perceived IEQ were recorded on a visual scale, and performance was examined by identifying three different letters in a nonsense text. Tests were done immediately after entering the classroom. We found no significant effects of increasing Vmin from 1.1 to 2.0 l/s per m² on learning performance, symptoms, or perceived IEQ.
Permalink: https://hdl.handle.net/11250/2839069

Abstract: This study aimed to assess whether building materials, furniture, and user equipment are sources of pollution that would influence the need for ventilation. Between 2017-2020, measurements were taken in four regular classrooms in a low emitting school and four modular classrooms in a prefabricated school. Weekly passive sampling of volatile organic compounds (VOCs) and aldehydes were carried out in the classrooms under the following four conditions: 1) emptied, 2) furnished, 3) with furniture and user equipment, and 4) during normal use. For the first three conditions, the classrooms were measured with either no ventilation or \”low\” airflow rates. Total VOC (TVOC) concentrations were up to ten times higher in the unventilated classroom at the prefabricated school compared to classrooms at the low emitting school (<450 µg/m3 for conditions 1-2). Our results show the importance of selecting low emitting building materials and proper ventilation.
Permalink: https://hdl.handle.net/11250/2839367

Abstract: Some take-home messages from Mahrdad Rabani’s PhD-thesis: • He describes a methodology (Graphical Scripting linking GenOpt & IDA-ICE) for nZEB deep-retrofit. • Optimal retrofit packages (LCC & comfort/daylight) including controls, were developed for case studies of typical office buildings from years 1987 & 2010, in cold climate*. • High-quality windows (approx 0.6-0.8 W/m²K*) and external walls (approx 0.10-0.12 W/m²K*) should always be part of the retrofit package. • Roof & ground floor retrofitting are costliest; use only when priority is energy, not investment. • Retrofit DCV all-air heating/cooling with 85% heat-recovery (rotor) replaces the need for distributed hydronic heating (existing radiators). • Optimum external shading (Bronze screen), combined with window airing, both controlled by external facade-mounted irradiance sensor (>70 W/m²*) & room temp. (>22°C*). • If there’s opportunity to adjust window/floor area-ratio, then approx 15-17%* is a multicriterion optimum (LCC & thermal/daylight/glare comfort). • Roof-mounted polycrystaline PV (45%* of floor area, 14% efficient, 35° tilt*) has lower LCA than monocrystaline (18% eff.). [We need more efficient mass-produced BIPV!]. • These retrofit installations reduce the GHG footprint of the 1987 office building (The increace in embodied GHG due to retrofit, is offset by a larger reduction in operational GHG emissions). • The above optima are on condition of keeping original electric boiler (EU28 mix). Retrofitting district heating (CHP plant) gives lowest GHG, or GSHP is 2nd best. Further study needed on this. * interdependent, and depends on climate (Oslo values shown here).
Permalink: https://hdl.handle.net/11250/2834040

Abstract: This proceedings contains all accepted full papers from the virtual Healthy Buildings Europe 2021 conference, sponsored by the International Society for Indoor Air Quality and Climate (ISIAQ) and organized By OsloMet University, SINTEF and Norwegian University of Science and Technology (NTNU).

Abstract: The current situation of Coronavirus Disease 2019 (COVID-19) prevention and control coupled with the need to work in high-temperature harsh environments makes it necessary to ensure the health and efficiency of medical staff. An experimental outdoor work tent was set up and university students were used to study the thermal comfort of personnel wearing protective clothing in hot and humid environments. The experiment was carried out simultaneously through subjective and objective field tests and physiological tests of personnel. The wet bulb globe temperature (WBGT) index was investigated to divide the outdoor thermal environment into four working conditions: 21–23 °C, 23–25 °C, 25–27 °C and 27–29 °C. Under the different thermal environment intensities, the variations of physiological parameters of test personnel were monitored. The results showed that when WBGT was increased to 27–29 °C, 100% of the participants expected the external temperature to become cooler and the humidity to decrease after one hour. When the temperature was close to 30 °C and the relative humidity was close to 60%, it was necessary to take cooling measures to reduce the thermal stress of the participants. Moreover, relationships between subjective feelings and physiological parameters of the nucleic acid sampling personnel were obtained. Results also found that the forehead, chest and back were the highest skin temperature parts, so it is most effective to give priority to improving the thermal comfort of these three locations. As an early attempt to conduct the real outdoor experimental study on the thermal comfort of COVID-19 nucleic acid sampling staff, this study provided a theoretical basis for follow-up research to develop cooling strategies for protective clothing in hot and humid outdoor environments.
Permalink: https://doi.org/10.3390/app112311492

Abstract: This study investigated the impact of outdoor air pollutants on indoor air quality in a high-rise building, considering factors related to the seasons and air infiltration. Further, the impact of atmospheric weather conditions on air infiltration has been analysed in a downtown area of Suzhou, China. The influence of the outdoor air pollution rate on indoor air quality in the office building was investigated based on onsite measurements and computer simulations. Results showed that the impact of outdoor air pollutants on indoor air quality was highest in winter, followed by spring, autumn and summer. Furthermore, multiple factors, which affect the indoor air quality in a high-rise building, have been further investigated in this study, including stack effect, wind effect, infiltration rate, outdoor air pollution rate, seasonal change and air filter efficiency. The significant influence of these factors on the indoor air quality level with floor height variations has been verified. Based on the analysis, a high-efficiency filter is recommended to maintain healthy indoor air quality. Meanwhile, a double-filter system is required if a building is exposed to heavily polluted outdoor air considering the most substantial impact of outdoor air pollutants on indoor air quality in winter. Moreover, a numerical model of steady-state indoor PM2.5 concentration was established to determine the suitable air filter efficiency and airtightness.
Permalink: https://doi.org/10.1177/1420326X211038279

Abstract: The precise measurement and positioning of the outline of high-altitude massive special-shaped structure has a guiding role in the installation of its external curtain wall and other ancillary facilities. Traditionally, total station measurement and other technical methods are mostly used, which have the disadvantages of large workload, long time-consuming and low accuracy. This paper takes the high-altitude corridor enclosure structure of Chongqing Raffles Square as the research object, combines the characteristics of Leica Nova MS60 high-precision three-dimensional laser scanning total station which can accurately locate and Faro x330 three-dimensional laser scanner which can scan quickly, and puts forward an excellent combination of two instruments. Based on the point scanning method and the mathematical optimization theory, a high-precision registration formula for point clouds with special-shaped structures is derived. On the premise of meeting the registration accuracy of point clouds, the rapid scanning and global positioning of a large number of special-shaped components are realized, and precise data are provided for the rapid extraction of contours. It has great application prospects and important applications in reverse modeling and deviation analysis.
Permalink: https://doi.org/10.1201/9781003191476-50

Abstract: This study explores investigation of applicability of impact factors to estimate solar irradiance by four machine learning algorithms using climatic elements as comparative analysis: linear regression, support vector machines (SVM), a multi-layer neural network (MLNN), and a long short-term memory (LSTM) neural network. The methods show how actual climate factors impact on solar irradiation, and the possibility of estimating one year local solar irradiance using machine learning methodologies with four different algorithms. This study conducted readily accessible local weather data including temperature, wind velocity and direction, air pressure, the amount of total cloud cover, the amount of middle and low-layer cloud cover, and humidity. The results show that the artificial neural network (ANN) models provided more close information on solar irradiance than the conventional techniques (linear regression and SVM). Between the two ANN models, the LSTM model achieved better performance, improving accuracy by 31.7% compared to the MLNN model. Impact factor analysis also revealed that temperature and the amount of total cloud cover are the dominant factors affecting solar irradiance, and the amount of middle and low-layer cloud cover is also an important factor. The results from this work demonstrate that ANN models, especially ones based on LSTM, can provide accurate information of local solar irradiance using weather data without installing and maintaining on-site solar irradiance sensors.
Permalink: https://doi.org/10.3390/app11188533

Abstract: The study investigates a hybrid radiant cooling system’s potential to achieve thermal comfort. The hybrid radiant cooling (HRC) system combines the best features of a typical all-air and conventional chilled radiant cooling system. An HRC system presents the advantages to (a) reduce vapour condensation and to (b) adjust the cooling output by using an Airbox convector. The three systems perceive thermal comfort in the predicted mean vote (PMV) between –0.5 and þ0.5 at 25 and 27C. In the room condition at 31C, the all-air system has a lower thermal comfort level because the elevated airspeed is less effective when the mean radiant temperature (MRT) is low. This study suggests a cooling strategy to maximize the thermal comfort level by effectively utilizing the HRC in extreme conditions without extra cooling sources. When the designed set point indoor temperature is 25C, the Airbox convector of the HRC fan can be off. However, if the indoor air temperature increases above 25C, an occupant can activate the Airbox convector; the actual thermal output of HRC is increased, and the elevated airspeed can reduce the predicted percentage dissatisfied (PPD) level. Even in an extreme indoor thermal condition at 31C, the HRC minimizes the PPD level.
Permalink: https://doi.org/10.1177/1420326X211040853

Abstract: This study explores the combination of photovoltaic (PV) panels with a reflector mounted on a building to improve electricity generation. Globally, PV panels have been widely used as a renewable energy technology. In order to obtain more solar irradiance and improve electricity output, this study presents an advanced strategy of a reflector combining PV panels mounted on a building in Calgary, Canada. Based on an experimental database of solar irradiances, the simulation presents an optimal shape designed and tilt angles of the reflector and consequently improves solar radiation gain and electricity outputs. Polished aluminum is selected as the reflector material, and the shape and angle are designed to minimize the interruption of direct solar radiation. The numerical approach demonstrates the improvement in performance using a PV panel tilted at 30◦ , 45◦ , 60◦ , and 75◦ and a reflector, tilted at 15.5◦ or allowed to be tilted flexibly. A reflector tilted at 15.5◦ can improve solar radiation gains, of the panel, by nearly 5.5–9.2% at lower tilt angles and 14.1–21.1% at higher tilt angles. Furthermore, the flexibly adjusted reflector can improve solar radiation gains on the PV panel, by nearly 12–15.6% at lower tilt angles and 20–26.5% at higher tilt angles. A reflector tilted at 15.5◦ improves the panel’s output electricity on average by 4–8% with the PV panel tilted at 30◦ and 45◦ respectively and 12–19% with the PV panel tilted at 60◦ and 75◦ , annually. Moreover, a reflector that can be flexibly tilted improves electricity output on average by 9–12% with the PV panel tilted at 30◦ and 45◦ and 17–23% with the PV panel tilted at 60◦ and 75◦ . Therefore, the utilization of a reflector improves the performance of the PV panel while incurring a relatively low cost.
Permalink: https://doi.org/10.3390/su13116115

Abstract: This study investigated the ventilation efficiency and energy performance of three ventilation strategies—an all-air system (AAS), a radiant panel system with a displacement ventilation system (DPS), and a radiant panel system with a decentralized ventilation system (DVS). The research analyzed the indoor air quality (IAQ) in a high-rise building based on the building’s height, the air handling unit (AHU) location, air infiltration rate, outdoor air pollution rate, seasonal change, and air filter efficiency. The results indicated that the AAS had the best performance in terms of IAQ in the high-rise building in winter; however, the AAS also had the highest annual energy demand. For the same conditions, the DVS consumed less energy but had the worst performance in maintaining a satisfactory IAQ. Considering energy consumption, it is worth developing the DVS further to improve ventilation performance. By applying a double-filter system on the lower floors in a high-rise building, the DVS’s ventilation performance was dramatically improved while at the same time consuming less energy than the original DPS and AAS. The application of DVS can also minimize the negative effect of the infiltration rate on indoor air quality (IAQ) in a building, which means that the DVS can better maintain IAQ within a healthy range for a more extended period. Moreover, it was found that the DVS still had a substantial potential for saving energy during the season when the outdoor air was relatively clean. Hence, it is highly recommended that the DVS is used in high-rise buildings.
Permalink: https://doi.org/10.3390/su13158453

Abstract: The aim of the Best Vent project was to find the optimal control strategy for demand-controlled ventilation (DCV) without compromising on indoor air quality. In this paper, we discuss control strategies that would ensure acceptable perceived air quality for unadapted users. This study is a part of a series of field studies where sensory panels of untrained persons visited classrooms at a school. The sensory panel visited classrooms occupied by different user groups, at different ventilation rates and temperatures, and in empty classrooms at different ventilation rates, and with different pollutant loads. This study aims to assess whether it would be reasonable to control the supply airflow rate towards a higher CO₂ setpoint at low air temperature, and still maintain the same perceived indoor air quality upon entry. The results indicate that the perception of indoor air quality does not deteriorate at higher CO₂ concentrations when the air temperature is kept at 21 °C as opposed to at 24 °C. Furthermore, an increase in air temperature yielded poorer perceived air quality scores at similar CO₂ concentrations in the classrooms. Our results indicate that a DCV-control strategy with a higher CO₂ setpoint in classrooms at low temperatures would not compromise perceived air quality. Further research would be needed to assess whether the same is true for indoor climate-related symptoms or performance.
Permalink: https://doi.org/10.1016/j.buildenv.2021.108180

Abstract: Through a systematic study, this paper conducted a life cycle assessment (LCA) consisting of evaluation of both embodied and operational emissions of different building retrofitting scenarios for a typical office building, located in Norway. LCA analysis was performed via the OneClick LCA tool. The emissions associated with the operational energy use were evaluated for both the reference and optimized building energy models developed in the IDA-ICE models from our previous studies. These models included two different HVAC systems: an all-air (AA) system equipped with a demand control ventilation (DCV) and a hydronic system with the radiator space heating (RSH) and a constant air volume (CAV) ventilation system. The findings showed that, through retrofitting measures, the net total emissions could be reduced up to 52%, from 1336–637 kg carbon dioxide equivalent (CO₂-eq)/m², which was achieved for the life cycle cost (LCC) optimal scenario equipped with the AA system. The share of operational energy use (B6) in the total CO₂-eq emissions was around 77% for the reference case, whereas it was around 43–46% for the retrofitting scenarios. The most embodied CO₂-eq emitted stages of the LCA through retrofitting concerned the product stage (19–23%), transport to construction site (24–31%), and the end-of-life service (around 25%). The findings confirmed that it was more environmentally friendly to further re-insulate the other parts of the building envelope instead of ground floor, as the latter retrofitting scenario was accompanied with a large increase of embodied emissions.
Permalink: https://doi.org/10.1016/j.buildenv.2021.108159

Abstract: This article presents an ongoing research project regarding blended education; Flexible Digital Class­room (FlexiDig), and a survey on full-time and part-time students’ experiences with blended education in a master’s degree programme in Art and Design Education. To optimise educational resources, the lectures for the full-time students were recorded, including the dialogue between the students and the lecturers, and made digitally available for all students. Generally, both the part- and full-time students participating in the questionnaire expressed their experience as “satisfactory” for the availability of the recorded lectures. Moreover, the capture of dialogues in the recording was found to be extremely useful for better understanding and learning, according to the students. This idea forms a basis to develop FlexiDig as simple as possible with a transfer value to other educational situations based on the approach of Student-Centered Learning and Teaching in Higher Education (SCLT).
Permalink: https://doi.org/10.7577/FORMAKADEMISK.4515

Abstract: Climate change is anticipated to affect the degradation of the building materials in cultural heritage sites and buildings. For the aim of taking the necessary preventive measures, studies need to be carried out with the utmost possible precision regarding the building materials of each monument and the microclimate to which they are exposed. Within the present study, a methodology to investigate the mold risk of timber buildings is presented and applied in two historic constructions. The two case studies are located in Vestfold, Norway. Proper material properties are selected for the building elements by leveraging material properties from existing databases, measurements, and simulations of the hygrothermal performance of selected building components. Data from the REMO2015 driven by the global model MPI-ESM-LR are used in order to account for past, present, and future climate conditions. In addition, climate data from ERA5 reanalysis are used in order to assess the accuracy the MPI-ES-LR_REMO2015 model results. Whole building hygrothermal simulations are employed to calculate the temperature and the relative humidity on the timber surfaces. The transient hygrothermal condition and certain characteristics of the timber surfaces are used as inputs in the updated VTT mold model in order to predict the mold risk of certain building elements. Results show a significant increase of the mold risk of the untreated timber surfaces due to climate change. The treated surfaces have no mold risk at all. It is also observed that the most significant increase of the mold risk occurs in the north-oriented and the horizontal surfaces. It is underlined that the mold risk of the timber elements is overestimated by the MPI-ES-LR_REMO2015 model compared to ERA5 reanalysis. The importance of considering the surface temperature and humidity, and not the atmospheric temperature and humidity as boundary conditions in the mold growth model is also investigated and highlighted.
Permalink: https://doi.org/10.3390/f12070819

Abstract: This paper presents a comprehensive approach to elucidate the mechanical and thermal aspects of coating layers integrated with organic-based PCMs. In that respect, three sets of cement mortars were studied experimentally to underline the significance of PCMs proportion. From a mechanical point of view, the strength of specimens cured at 20 °C resulted to be superior compared to 40 °C, with a more evident influence for cement mortars containing PCMs. Laboratory tests on specimens subjected to 50 wetting–drying cycles demonstrated an insignificant increase of the mass for coatings without PCMs and a slight increase for coatings containing PCMs. During this process, growth in strength for the base mix without PCMs and a loss in strength for mixtures with PCMs was exposed; an exponential decay relationship was noted between the compressive strength with the PCM proportion. Alongside this, a transient thermal analysis was carried out to assess the effect of PCMs on the dynamic thermal parameters of coating layers. A higher proportion of PCM ingredients leads to enhanced responsiveness since the heat wave penetrating the layer is smoothen and delayed. These issues can adequately address the defensive behaviour capacity of building components, without surpassing their carrying structural stability and mechanical properties.
Permalink: https://doi.org/10.1016/j.seta.2021.101349

Abstract: Straw bale is a low embodied energy and technically acceptable thermal insulation material. As per today, there is a lack of standardized technical data on utilizing straw bale in building construction, while the existing research studies rather focus on limited specific experimental or computational scenarios without summarizing in an organized way the behaviour of straw bale construction under different climate conditions and assembly configurations. This comparative study presents systematically the hygrothermal and energy performance of straw bale buildings with different exterior cladding and finishing mortar or sheathing board, exposed in various representative climates. The findings provide an insight into the optimal selection of materials and furthermore highlight the importance of climate adaptation of straw bale wall constructions. Overall, straw bale buildings show robust hygrothermal performance, when properly designed, and achieve very low energy use at a minimum of embodied emissions.
Permalink: https://doi.org/10.1016/j.enbuild.2021.111091

Abstract: The main objective of EE Settlement project is to provide a tool and guidelines for municipalities, regional and central authorities, as well as for professionals and other actors, for assessing the consequences and impacts of different housing development options, considering energy need, environmental impact, and costs over the lifecycle of buildings, infrastructure, and transport. This report aims to give an overview of the main research activities and deliverables generated by the project partners throughout the project duration of August 2017 – March 2021 to achieve the vision of the project.
Permalink: https://hdl.handle.net/11250/2780208

Abstract: Simultaneous satisfaction of both thermal and visual comfort in buildings may be a challenging task. Therefore, this paper suggests a comprehensive framework for the building energy optimization process integrating computational fluid dynamics (CFD) daylight simulations. A building energy simulation tool, IDA Indoor Climate and Energy (IDA-ICE), was coupled with three open-source tools including GenOpt, OpenFOAM, and Radiance. In the optimization phase, several design variables i.e., building envelope properties, fenestration parameters, and Heating, Ventilation and Air-Conditioning (HVAC) system set points, were selected to minimize the total building energy use and simultaneously improve thermal and visual comfort. Two different scenarios were investigated for retrofitting of a generic office building located in Oslo, Norway. In the first scenario a constant air volume (CAV) ventilation system with a local radiator in each zone was used, while an all-air system equipped with a demand control ventilation (DCV) was applied in the second scenario. Findings showed that, compared to the reference design, significant reduction of total building energy use, around 77% and 79% in the first and second scenarios, was achieved respectively, and thermal and visual comfort conditions were also improved considerably. However, the overall thermal and visual comfort satisfactions were higher when all-air system was applied.
Permalink: https://doi.org/10.3390/en14082180

Abstract: Decisions regarding urban density and form present an ongoing challenge to European municipalities. The project EE Settlement – Embodied Energy, Costs and Traffic in Different Settlement Patterns specifically addresses some of the currently overlooked or unquantified aspects of new development projects (or settlements) – the embodied and operational energy, greenhouse gas (GHG) emissions, & direct public costs attributable to buildings, infrastructure, facilities, services, & transport. One output of the EE Settlement project is a web-tool designed to allow users to quickly assess and compare metrics regarding the embodied and operational energy, GHG emissions, and costs related to new settlements. The objective of this report is to provide an overview of the theoretical background, methodology, reference models, data sources, and limitations for the Norwegian model. This report is intended as a supplement to both the web-tool and the series of reports published under EE Settlement.
Permalink: https://hdl.handle.net/11250/2755949

Abstract: This report is one of the main deliverables in the EE Settlement – Embodied Energy, Costs and Traffic in Different Settlement Patterns project. The objective of the report is to provide a guideline and recommendation that will enable authorities and professionals in the assessment of the expected impacts of new developments at the early-phase planning stage. The report provides basic background information about the potential and functionalities of the EE Settlement tool. The report also summarizes the lessons learnt from actual tool testing in case studies, discusses the limitations of the tool, and highlights suggestions for further work.
Permalink: https://hdl.handle.net/11250/2779872

Abstract: Phase change material (PCM) is an attractive solution for improvement of thermal performance in buildings, and have excited a vast amount of research in recent years. There are however practical challenges with ensuring adequate phase transitions of the PCM to exploit the passive heat storage benefits. Night ventilation (NV) with free cooling have surfaced as one of the most promising methods to properly utilize PCMs and maximize energy savings. This work deals with a novel spackling compound enhanced with microencapsulated PCM. The product is intended for use at inner walls and ceiling surfaces of buildings and is suited for new and retrofitting building applications. Ensuing former experimental studies, a validated simulation model is developed and used to study the PCM with natural and hybrid NV strategies in an office building during summer conditions in Oslo, Norway. Cooling load reduction and energy savings are analyzed with varying air flow rates of 0.5–5 air changes per hour (ACH) and 2–4 mm PCM layer thickness. It is shown how increasing air flow rates and PCM thickness greatly enhances energy performance, but at a diminishing rate. Although the NV alone can reduce the cooling load by 11.5% at 1 ACH, 40.2% at 3 ACH and 59.8% at 5 ACH, one can achieve further reduction up to 19.5%, 78.2% and 95.5% for the respective ACHs with 4 mm PCM. The natural NV provides more energy savings compared to the hybrid strategy. As energy requirement by fans increases with the increase of air flow rates in the hybrid strategy, the energy savings eventually start to reduce. The hybrid strategy can save 38% energy at most with 3 ACH, and the savings is increased to 50% with the inclusion of 4 mm PCM. On the other hand, the natural strategy saves 56% of energy at the same air flow rate, and 69% with 4 mm of PCM.
Permalink: https://doi.org/10.3390/app11041472

Abstract: Building retrofitting towards nearly zero energy building (nZEB) with comfortable visual and thermal conditions, requires a comprehensive parametric analysis of building retrofit measures. This paper presented an optimization method to automate the procedure of finding the best combination of measures minimizing the building energy use and achieving the nZEB target while enhancing both thermal and visual comfort conditions. The study was performed by coupling of an Indoor climate and energy simulation software (IDA-ICE) and a generic optimization tool (GenOpt) through a Graphical Script interface and the optimization was applied to a typical office building located in Norway. The adopted method allowed the concurrent optimization of building envelope, building energy supply, fenestration, and shading device material, and control methods. Two constraint functions including visual and thermal comfort criteria were considered. Afterwards, PV panels were integrated with the building site for on-site production of electricity towards ZEB level. Findings demonstrated that the inclusive optimization approach could significantly decrease the building energy use, up to 77%, and improve both the thermal and visual comfort simultaneously. Furthermore, the best performance for the optimal solution was achieved when the shading device and window opening control methods functioned with solar radiation and indoor air temperature setpoints.
Permalink: https://doi.org/10.1016/j.seta.2021.101020