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Improving the performance of building envelope is essential to energy conservation and emission reduction. Adaptive building envelope (ABE) has the potential to effectively reduce ...building energy consumption at a lower cost. Movable window insulation is an instantiation of the ABE with great application potential in buildings, but it has not been systematically studied. Trying to fill this gap, this paper proposes an automatic control system and a manual control rule for movable window insulation. The energy consumption of double-glazed windows, triple-glazed windows, movable insulation with automatic/manual control, and electrochromic windows is compared in different scenarios using building energy simulation (BES). In some scenarios, the optimal solar heat gain coefficient (SHGC) for windows with movable insulation is higher than that required by the building code. Triple-glazed windows are only effective in reducing the heating energy, while electrochromic windows are only effective in reducing the cooling energy. Infiltration has a great impact on the performance of movable insulation. The net preset value (NPV) analysis shows that movable insulation has a great application potential in Minneapolis, Atlanta, and Phoenix, while triple-glazed windows are only viable in some cases in Minneapolis. Electrochromic windows are not a profitable investment at their current prices.
When multiple thermal retrofits are to be installed in a building envelope for improving its energy performance, several questions arise such as “what should be the thickness of retrofits and where ...they should be placed within the wall/roof”, “which retrofit should be installed towards the exterior and which one should be installed towards the interior of the envelope”. Such judgements are made in contemporary studies by comparing limited predefined configurations where either the thickness or the location of retrofit assumes only a few discrete values within the envelope. The novel approach proposed in this study utilizes spatial discretization of structural layers in a composite envelope for two fold benefit. A new version of Genetic Algorithm (GA) is developed for this purpose by modifying its key operational stages. The GA is implemented in a practical scenario to optimally configure a multi-retrofit envelope (carrying phase change material and thermal insulator) of a common residential building in hot climate of India. Analysis of a single housing unit demonstrates that up to 33.5% of heat gain reduction and 9.2 kWh/day of electricity saving are achievable with improved envelope design.
•Comprehensive guideline for designing multi-retrofit building envelope is presented.•All possible sizes and locations of thermal retrofits can be checked simultaneously.•Thermal performance assessment of multiple combinations of PCMs and insulators.•A multifaceted Genetic Algorithm is modelled to drive the optimization.•Optimized envelope resists up to 33.5% of diurnal heat gain in hot Indian climate.
According to the U. S. Department of Energy (DOE), infiltration accounts for 6% of the energy use and $11 billion in energy cost for U. S. commercial buildings. One strategy to reduce infiltration in ...commercial buildings is to provide more supply airflow than return and exhaust in order to “pressurize the building”. DOE has developed EnergyPlus models of several prototype buildings which assume that pressurization results in system-on infiltration rates that are 75% less than the system-off rates. However, airflow simulations of these buildings using the CONTAM multizone airflow software showed that pressurization reduced infiltration by an average of 44% only. To improve the infiltration rates calculated by the EnergyPlus models of prototype buildings, CONTAM infiltration rates were used to develop coefficients that can be input into EnergyPlus. CONTAM captures the effects of wind, temperature difference, and system operation on infiltration rates. Coefficients were developed for 11 prototype buildings, eight cities, and two levels of building envelope airtightness. Comparisons of the predicted infiltration rates were made between using the DOE prototype model inputs and the NIST infiltration correlations. Using the NIST correlations resulted in an average HVAC-EUI (HVAC-related energy use intensity) savings of 6% or 1.4 kBtu/ft2 due to airtightening. These results indicate that the effects of infiltration on HVAC energy use are important and that infiltration can and should be better accounted for in whole-building energy modeling.
•CONTAM simulations showed infiltration was reduced only 44% when HVAC system was on.•NIST infiltration correlations captured effects of wind, temperature & HVAC operation.•Study predicted annual HVAC energy savings of 6% with airtightening.•Study predicted 1.4 kBtu/ft2 more HVAC savings from airtightening than DOE models.•More accurate infiltration modeling results in greater savings from airtightening.
AbstractThe adoption of performance-based wind engineering (PBWE) is rapidly becoming recognized as a fundamental step to reducing the huge economic losses caused by severe windstorms. This has led ...to the recent introduction of a number of PBWE frameworks for the assessment of engineered building systems such as high-rise structures. Although these frameworks have resulted in significant progress toward the efficient and effective estimation of performance within a PBWE setting, there is still a significant lack of frameworks that can holistically model the performance of the envelope system of engineered buildings. Recognizing how accurate prediction of losses occurring during severe windstorms, such as hurricanes, cannot be made without detailed modeling of the losses caused by damage to the envelope system, this paper introduces a new PBWE framework that is focused on the performance assessment of the envelope system. The proposed framework is based on integrating a recently proposed building envelope damage model into a conditional stochastic simulation framework in which the directional wind and concurrent rain hazard is explicitly modeled together with the stochastic nature of the local wind pressure. By incorporating loss models, performance estimates are provided in terms of annual exceedance rates of system-level metrics such as repair costs. A full-scale building example is presented to illustrate the practicality of the proposed PBWE framework.
The building envelope is of great significance for building thermal comfort, and photovoltaic heat (PV/T) can be effectively utilized through phase change heat storage technology to reduce heating ...energy consumption. In this paper, a phase change heat storage structure with subzone rotation is proposed for the building envelope. A numerical model of a triplex-tube LHTES unit is established by using the enthalpy-porosity method and verified by experimental data. The study employs the Taguchi method to select rotation speed in different regions and fin/tube wall material as variables. The effects of different variables on heat release rate and solidification time are investigated, and the interaction of each parameter on solidification performance is analyzed through signal-to-noise ratio. The findings indicate that when the inner and outer tube speeds are 0.3 rpm and 0.5 rpm, respectively, compared to the initial model where both inner and outer tube speeds are 0.1 rpm, the average temperature response rate and the average heat release rate are increased by 51.47% and 61.04%, respectively. Meanwhile, the solidification time is shortened by 40.49%. However, the release of the total heat is reduced by 0.66%. The study concludes that increasing rotation speed or solidification consistency of PCM in different areas is of great value in enhancing overall solidification performance. Finally, the specific effect of increasing regional rotation speed on the solidification process is studied through temperature/flow rate monitoring in the unit.
Mosque building is characterized by its unique spatial requirements and intermittent occupancy pattern. In order to create a suitable ambiance for prayers, maintaining optimum thermal comfort of the ...interior is a must. As mosques are skin-load dominated buildings, the climatic conditions play a defining role in the thermal comfort of the users as well as the energy efficiency of the building. Therefore, appropriate building envelope designing that ensures optimal thermal performance is required to protect the interior from the external harsh climate and to ensure better thermal comfort for the users. Additionally, improving the overall thermal performance of the building allows reduced energy consumption and ensures improved energy efficiency. However, research in this niche is an emerging field and much work needs to be done to establish design standards. This review paper conducts a comprehensive literature review with the aim of identifying important aspects of mosque thermal performance. With this intent, the paper classifies findings from literature according to building design elements as well as different components of the mosque envelope such as walls, roofs and windows. Thereafter, it discusses the impact of the corresponding characteristics and parameters on the overall thermal performance of mosque buildings. As a result of this review, various research gaps and potential research prospects have been identified in different aspects of mosque designing. The paper concludes with suggesting prospective research scopes that may serve as a foundation for future research endeavors.
•Unique spatial and functional characteristics of mosque affect thermal performance.•Research on thermal performance and envelope design of mosques are reviewed.•Impact of design elements on the thermal performance of mosques is presented.•Important design parameters of mosque envelope thermal design are identified.•Various research gaps and scopes have been identified for further research.
•An environmental chamber is used to conduct full scale PCM wall experiments.•Validation study considered 1 microencapsulated PCM and 2 macroencapsulated PCMs.•Test done using 1-D wall panels with ...PCMS.•Experimental data are used to compare 5 heat transfer models for microencapsulated PCMs.•Model with highest accuracy is a full parallel path method of heat transfer.
Thermal Energy Storage (TES) has the potential to shift peak electricity demand. Passive TES is usually implemented in building envelope as micro and macro encapsulated phase change materials (PCM) to shift electric energy demand and therefore requires careful heat transfer analysis. Whole building energy modelling with simplified heat transfer analysis has become extremely important for designers, architects, engineers, and researchers to predict energy performance of buildings. It is important to validate PCM modelling algorithms used in building energy programs to quantify their error and prove their capacity to model different PCM encapsulation types. This study uses data from a microencapsulated PCM and two macroencapsulated PCMs (Bio based PCM and hydrate salts) tested in full-scale using the Advanced Multiscale Building Energy Research (AMBER) Lab located at the Colorado School of Mines and is used to validate a numerical algorithm written in MATLAB language. To approximate the heat transfer through a wall assembly with macroencapsulated PCM pouches, several modelling techniques that can reduce 3D heat transfer characteristics to 1D are explored in this research. A parallel path heat transfer modelling approach is found to give the closest agreement with the experimental data for the pouched PCMs in building envelope applications.
In current complex building designs, sustainability assessments are often performed after project completion, with limited impact on building performance which results in missed goals in terms of ...quality, cost, and time. We address this problem by proposing a hierarchical reference-based know-why model to answer the research question “what is a suitable decision support model to successfully integrate the sustainability requirements in the early design phase of buildings?”. The model presents a process that incorporates a life-cycle perspective and calculates design alternatives based on a defined reference and the DGNB building certification system. The results show that criteria synergies and trade-offs can be identified, leading to improved design by engineers and better building performance. Our findings pave the way for full integration of the model into building information modeling, combined with artificial intelligence. This can help manage the complexity of the sustainable design process on the path to carbon-neutral buildings.
•the hierarchical reference-based know-why model provides design support for the selection of sustainable building envelopes•the hierarchical reference-based know-why model identifies effects of building envelopes on building certification criteria.•applying the hierarchical reference-based know-why model allows individual stakeholder preferences to be taken into account.•applying the hierarchical reference-based know-why model supports transparent stakeholder communication in the design stage.
Excessive moisture inside building envelopes makes them vulnerable to moisture damages such as mould, algae growth, rot, corrosion, weathering, fading, etc. One of the main moisture sources for ...building envelopes is wind-driven rain (WDR). This paper characterizes the WDR for twenty-two locations in South Korea based on hourly measured weather data for 20 years and an artificial typical year from Meteonorm®. This study determines a wind-driven rain reference year using a semi-empirical method, taking into account the frequency of occurrence of the WDR and the correlation between the different wall orientations. The annual amount of the WDR shows a significant range from 125.4 kg/(m2∙a) to 904.4 kg/(m2∙a) with the individual prevailing orientations by location in South Korea. The deviations of the WDRs determined by the wind-driven rain reference year and the annual mean wind-driven rain can be characterized in two groups in terms of the amount and the distribution of the WDR. The first group has a characteristic that only the amount is changed while keeping the distribution across the wall orientations. The second group shows that the amount and the distribution are changing together. The wind-driven reference year can characterize the WDR by selecting and combining the most representative periods from the long-term measurements. By contrast, the artificial typical years from Meteonorm® hardly show any similar characteristics of the WDR determined with the long-term measured weather data.
•A semi-empirical method was applied to determine WDR exposures on 16 façade orientations.•The annual amount of the WDR by location in South Korea has a significant range with individual prevailing orientations.•A wind-driven reference year method can characterize WDR by combining the most representative seasons from long-term data.•Typical years from Meteonorm® hardly show any similar characteristics of the WDR determined by the long-term measured data.
•The study clarifies the impacts of various transparent envelope thermal parameters on glazing surface temperature.•It provides optimum condition design guidelines for EAW in hot climates by ...investigating the thermal performance of DGEW and TGEW with different parameters.•The study examined EAW’s thermal performance with varying air gaps, air velocity, return air temperature, and pressure values.•The outcomes add another level of validation to the experimental model by using the same CFD simulation to validate the experimental and mathematical models.
Window systems, particularly in hot climates, are the source of considerable heat transfer that affects the buildings’ indoor environment and energy consumption. Proper design and optimization of its thermal performance significantly contribute to the overall envelope energy performance. Using a multi-layer glazing system, Energy Active Window (EAW) adapts window insulation technology to reuse low-grade air from the HVAC system, keeping the temperature at the internal surface of the window close to the indoor air temperature, minimizing heat exchange between indoor and outdoor. This study aims to reduce energy consumption by optimizing EAW to increase its thermal resistance by channeling the return air (RA) from the HVAC system into the curtain frame, thereby lowering the temperature of the air gap and air film layer. The study examined the window system’s exhaust/return air behavior using the Computational Fluid Dynamics (CFD) tool (Fluent) to simulate the heat exchange between outdoor and indoor building environments. The CFD simulation was validated using experimental measurements. Results show a surface temperature decrease of 4 to 7 °C based on the inner and outer pane airflow conditions when the outdoor temperature is 45 °C with an 8 % margin of error. Various EAW components were tested, including air velocity, air–gap width, volume, and outdoor temperatures, examining both triple and double-glazing layers.
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