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Highlights • Definition of passive envelope indexes and caracterization of libraries in La Plata. • Environmental monitoring: achievement of preventive conservation indexes. • Correlation between passive envelope indexes and preventive conservation indexes. • Determination of the most influential passive envelope indexes for the achievement of preventive conservation indexes. Abstract The common approach for libraries to preserve their paper-based collections from irreversible deterioration is by controlling quantitative parameters, such as temperature and relative humidity. Variations of these parameters for preventive conservation can be expressed by the "performance index" (PI) and the "amplitude index" (AI). Building envelope is the first filter of the external climate, buffering the external weather fluctuations and maintaining the building's indoor climate stable. Its shape, window areas and envelope materials are the most influential parameters. As they capture the relationship of a few geometric and physical variables with the building's performance, the envelope characteristics can be expressed as certain passive envelope indexes. This paper studies the relationship of certain passive envelope indexes and the preventive conservation indexes for books for several libraries and archives located in La Plata, Argentina. The results show the impact of every passive envelope index upon the preventive conservation indexes. The compactness, heaviness, adjacency to spaces and adjacency to ground have a positive linear correlation meanwhile transparency and global transmittance are parameters with a negative correlation. In general, the most influential parameter is the relative area adjacent to other spaces, followed by global transmittance, transparency, heaviness, relative area adjacent to ground and compactness. [ABSTRACT FROM AUTHOR]

Paper-based materials, due to their availability, environmental benefits and high thermal properties, have already been implemented in several building envelope designs. However, most of them either did not optimise the use of the material or did not provide sufficient thermal insulation for use in permanent buildings. The presented research analyses six original paper-based building envelope core proposals, suitable for use in permanent buildings in temperate climate of Europe, in terms of thermal and environmental efficiency. Proposals include cores with embedded paper tubes structural elements, timber-cardboard studs and sandwich designs. The heat transfer coefficient of the envelopes was obtained for repeatable modules via 2D computer simulations (ThermCAD software), and the environmental impact was assessed for a representative square metre of the envelope via LCA analysis, based in ecoinvent 3.8 database. All analysed designs showed high thermal insulation properties and met the requirements for U max = 0.20 W/m2K, did not cause the risk of surface condensation, nor have excessive thermal bridges. The analysed building envelope designs based on embedded frame wall structure showed environmental superiority over conventional envelopes (timber frame and SIP panels). The research may serve as a proof of concept, for using paper-based building envelopes in sustainable architecture. [ABSTRACT FROM AUTHOR]

[Display omitted] • A numerical analysis of a lightweight concrete roof with PCMs was performed. • Different roof configurations with and without PCM were numerically analyzed. • OpenFoam was used to model each roof configuration and code verifications were accomplished. • All roofs with PCM showed lower inner surface temperatures regarding the base case. • A maximum reduction of 65.5% in energy was achieved by case D-PCM-SP25Eu. The use of phase change materials in building envelopes has attracted the attention of researchers to minimize cooling and heating loads and for thermal comfort regulation. A research gap was found regarding the numerical analysis of lightweight roofs with PCM considering conjugate heat transfer. Thus, this paper aims to evaluate the thermal performance of a lightweight hollow concrete roof with a phase change material (PCM) in a subhumid climate. Three roof configurations with two PCMs were numerically analyzed through computational fluid dynamics. Simulations were conducted using the open-source code OpenFoam and were verified and validated with good agreements proving the confidence of the proposed methodology for building envelope design purposes. The roof configurations with fully-filled PCM exhibited the best thermal behavior, reaching higher temperature reductions between 1.4 °C to 2.0 °C, respectively, and reductions of indoor peak heat flux by approximately 47 % compared with the reference case. The roof fully-filled with an inorganic PCM with a melting temperature of 25 °C was the most energy-efficient roof configuration because it achieved the highest energy savings of 65.5 %, lowest electricity costs of 0.85–4.33 USD m−2, and lowest CO 2 emissions of approximately 18.31 kgCO 2 e m−2. The results demonstrated that the utilization of PCM into lightweight concrete roofs in subhumid climates is very promising. [ABSTRACT FROM AUTHOR]

• The impact of insulation moisture ingress and thermal bypass are investigated. • 2D computational fluid dynamics is used to simulate thermal bypass in buildings. • Moisture ingress can increase thermal transmittance by a factor of ∼2.2. • Thermal bypass can increase thermal transmittance by a factor of ∼3.5. • Insulation detailing and installation can significantly impact heat loss in buildings. Improving the performance of buildings is a key part of the global effort to limit greenhouse gas emissions and reduce energy consumption. Reducing the designed thermal transmittance of building envelopes through the addition of insulation is one of the primary measures adopted in many nations aiming to address the building sector. In theory, these globally adopted measures to improve design should result in considerable energy savings. The reality however is different. And a mismatch between design and in-use performance has been widely cited. This performance gap is extensively attributed to changes in occupant behaviour – the rebound effect. Considerably less research has investigated technical performance gap rationale. This paper aims to address this literature gap by investigating two technical reasons why design and in-use performance might differ; namely: i) moisture presence in the building's insulation and ii) thermal bypass of the insulation system. The study uses a combination of thermal resistance analogies and computational fluid dynamics, to ascertain the extent to which compromised insulation would impact the performance of building envelopes. An increase in envelope heat loss results in an increase in a building's energy consumption, and hence its associated greenhouse gas emissions. The study concluded that, in extreme cases, the presence of moisture in the insulation layers can increase the thermal transmittance of highly insulated envelopes by a factor of 2.2, while closed- and open-loop thermal bypass can increase it by a factor of 3.5 and 3.7 respectively. Although these might be considered extreme cases, the results align with findings from several past studies that quantified the gap between in-situ and design thermal transmittance. The results suggest that, while ensuring building envelopes are designed with adequate levels of insulation is important, ensuring that the insulation is adequately installed is potentially of equal importance. [ABSTRACT FROM AUTHOR]

This paper deals with the minimization of a building's external wall thermal transmittance, with the aim of improving the energy efficiency of the building. The wall's thermal transmittance must abide by the current legislation, but also suit the limitations of other construction parameters, mainly budget and thickness, but also time limit, workforce, number and thickness of the layers and availability of materials depending on the approach. The optimization is achieved formulating an Integer Linear Programming (ILP) problem involving the parameters mentioned above. Therefore, any available ILP solver can be run to obtain the best combination of the different materials and thicknesses for the layers, in order to minimize the thermal transmittance. This paper presents a case study of a common but representative external wall consisting of 6 layers, with more than 670,000 possible combinations of materials and their thicknesses. The study concludes with a comparison of the lowest thermal transmittance obtained for a selection of budget and thickness combinations for the mentioned wall. [ABSTRACT FROM AUTHOR]

Energy efficiency retrofit of buildings represents a key effort in reducing EU energy demand by 20% by 2020. However, predictions tend to overestimate savings by large percentages. The shortfall in savings can be attributed to incorrect predictive techniques, comfort takeback along with other behavioural and workmanship variables. Common predictive techniques related to heat loss tend to be based on the U-value of the building envelope. This paper presents the design of a more straightforward and compact version of the traditional Hot-Box apparatus (measures U-value) which instead determines the thermal resistance of samples of building envelope. U-value includes the need to measure/predict the effective surface resistances. In situ surface resistances, which include radiation and convection, are difficult to predict and vary depending on climatic conditions, exposure levels, surface emissivities among many other influences. The design of the test facility eliminates the need to incorporate these surface behaviour variables. This paper details the replicable apparatus and test methodology. The results of testing a hollow block wall of typical construction using the rig is then presented. The determined R-value is found to be within 1% of calculated values and the thermal time constant also matches closely with the most accurate predictive estimates. [ABSTRACT FROM AUTHOR]

This paper presents validation of the neural network model for predicting airtightness of residential and non-residential units. Proposed model developed in previous research utilizes a neural network in prediction of airtightness and it is obtained based on in situ measurements at 58 units in Croatia. Model applicability earlier was tested by independent validation through 20 additional measurements in Croatia and on 5 measurements in Serbia. This paper presents validation of neural network model for predicting airtightness of residential and non-residential units on database formed beyond the regional area. Database used for model validation in this paper consists of 20 residential and non-residential units from Poland with building construction technology similar to Croatian ones. Comparison of the results obtained by measurements and prediction model indicates that the model gives consistent results on the validation data set with similar building construction technology and demonstrates that model is not locally conditioned. [ABSTRACT FROM AUTHOR]

In this paper, potential energy savings by implementing different energy saving methods to enhance the building envelope are presented and calculated through transient simulations using TRNSYS software. To do that, a reference building was selected. In order to develop an accurate model, a dwelling of that building was monitored during 3 months, and data obtained in that monitoring study was used to calibrate and adjust the simulation model. The monitoring study as well as the definition of the building model and the different assumed hypothesis are presented in this paper. Then, different energy saving measures (ESM) are defined for roof, façade and windows, and 64 combinations are simulated. Those results, which are evaluated under economic and energy criteria, are assessed using as reference thermal requirements fixed by Spanish regulation (both for new buildings and for building renovations). These results show how energy renovations in buildings involve important benefits not only under an energy or environmental approach, but also considering economic issues. Moreover, they evidence how the Spanish thermal regulation can be still toughened in order to meet European goals led to the mitigation of CO 2 emissions. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the use of an internationally recognized validation and diagnostics procedure to test the fidelity of a simplified calculation method. The case study is the simplified model for calculation of energy performance of building envelopes, introduced by the Brazilian regulation for energy efficiency in commercial buildings. The first step of the assessment consisted on evaluating the simplified model results using the BESTEST. This paper presents a straightforward approach to apply the BESTEST in other climates than the original one (Denver, USA). The second step of the assessment consisted on applying the simplified model to evaluate four building typologies, and compare the results with those obtained using a state of the art building energy simulation (BES) program. For some BESTEST cases, the simplified model presented results inside of a confidence interval calculated by the authors. However, the simplified model was found to yield significant difference in the four building typologies analysed. Moreover, in all four building typologies analysed, the simplified model led to a lower energy efficiency label when compared to the label obtained using BES. The paper concludes that the simplified model may require improvements to properly indicate the actual energy performance of commercial building envelopes. [Copyright &y& Elsevier]

Abstract: The paper suggests a multi-criteria approach for the energy refurbishment of historical buildings, proposing methodologies for the performance analysis, coupling several experimental and numerical studies. The target consisted in a rigorous evaluation procedure, in order to guarantee the necessary reliability of a numerical model of the system “building envelope/technical plants”, on which testing the technical and economical convenience of energy retrofit solutions. The paper collects the long work carried out by several Institutions during the last years, on Building “Palazzo dell’Aquila Bosco-Lucarelli”, a historical building located in Benevento (Southern Italy), currently analyzed in order to define the technical adoption of possible improving actions. The carried out studies, beyond the proposition of an operational methodology, are aimed to evidence a best-practice specified for the Italian territorial context, which has several historical buildings needing restoration. Carefully applied investigations, based on various methodologies and through several instrumentations, allowed the definition of a numerical model correspondent to the real building, defined also comparing the results with the historical requests of gas and electricity. Moreover, dynamic energy simulations tested the effectiveness, singularly and coupled, of several solutions for the building energy optimization. A significant potentiality of energy and economic optimization has been demonstrated. [Copyright &y& Elsevier]

Abstract: The shortcomings or limitations of the traditional approach to developing energy efficient buildings are that they can not determine: (1) the ideal thermophysical properties of building envelope material, where “ideal” means that such material can use ambient air temperature variation and/or solar radiation efficiently to keep the indoor air temperature in the thermal comfort range with no additional space heating or cooling; (2) the best natural ventilation strategy; (3) the minimal additional energy consumption for space heating in winter or air-conditioning in summer. To overcome these problems, some new concepts for developing energy efficient buildings are put forward in this paper. They are the ideal thermophysical properties of the building envelope material, the ideal natural ventilation rate, and a minimal additional space heating or cooling energy consumption. A new approach for determining these properties is also developed. In contrast to the traditional approach (the thermophysical properties of building envelope material are known and constant so that the relating equations describing the indoor air temperature tend to be linear differential equations), the new approach solves the inverse problem (thermophysical properties, etc. of a buildings are unknown), whose solution can be a function instead of a value. As a first step, the ideal specific heat of the building envelope material for internal thermal mass is analyzed for buildings located in various cities in different climatic regions of China, such as Beijing, Shanghai, Harbin, Urumchi, Lhasa, Kunming and Guangzhou. We found that the ideal specific heat is composed of a basic value and an excessive one which is of δ function for the cases studied. Some limitations that would need further study are introduced in the end of the paper. [Copyright &y& Elsevier]

Abstract In the construction sector, strong efforts are being made to reduce energy consumption in buildings, particularly regarding thermal insulation in northern countries. However, the objectives set for the thermal insulation performance of the building envelopes are rarely achieved in practice. For this reason, there is increasing interest in taking onsite measurements. This paper presents the new achievements obtained by the ISABELE (In Situ Assessment of the Building EnveLope pErformances) method for data treatment to evaluate the global transmission heat transfer coefficient of a building with a consolidated uncertainty and within a short unoccupied period. Most of the work relates to the quantification and propagation of systematic errors and to the adaptation of the thermal model used for the inverse method. Practical applications on a test cell and a demonstration on a low-energy house in real outdoor conditions are presented, as are comparisons with other measurement methods (coheating, Quick U-Value of Buildings (QUB)) and the resulting calculated parameters, which show coherent outcomes. The test cell results reveal that a stabilized, repeatable measure with an acceptable uncertainty range (± 10 % in average) can be obtained within 2 days. The house results are slightly less precise (± 15-20 %) but can be obtained just as quickly, assuming that both configurations are insulated from the inside. [ABSTRACT FROM AUTHOR]

Highlights • This study presents a detailed review on IRT for the investigation of building envelope defects. • The literature survey is conducted regarding existing IRT methodologies for building envelopes. • The previous studies with measurement methods, analysis schemes and analysis types are categorized in the literature matrix. • Recent advances and future trends on IRT methods are presented. Abstract Thermal radiation generated by limited resources is emitted from the surfaces and interpreted as temperature. On the other hand, the limited resources necessitate prevention of energy leakages causing noticeable temperature differences on surfaces. Providing sensitive information on temperature contrast, infrared thermography (IRT) is a prominent tool for detecting infrared energy on the surfaces of the objects. IRT is also very promising method for detecting thermal irregularities, air leakages and even moisture abnormalities on building envelopes. Since the concept of nearly zero energy buildings is to be the main target of energy policies in European Union published by European Commission, improving thermal performance of buildings becomes crucial in the last decade. Therefore, implementation of IRT for visualizing and analyzing concealed defects on building envelopes is very promising for improving the energy efficiency of buildings. Given recent regulations and benefits of emerging thermogram technologies mentioned above, a detailed review of the previous studies investigating the abnormalities of building envelopes by IRT is presented in this paper. Furthermore, the applications with measurement methods, analysis schemes and analysis types are classified to highlight the potential of IRT in inspection of building envelopes for providing energy efficient solutions. Finally, recent advances and practical future opportunities are presented for additional contribution of the IRT methods previously employed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A state-of-the art review and discussion is presented for the ADBEIPCM. • Experiment studies were needed to show the long-term performance of the ADBEIPCM. • Organic PCMs and the macro-encapsulated methods were most used. • Intelligent control methods determine the performances of the ADBEIPCM. • Outlooks and recommendations for ADBEIPCM can facilitate its further development. the research of PCMs in the field of building energy efficiency has developed rapidly over the past decade. The static PCM-built envelopes cannot flexibly adjust their heat storage and release according to the changes in weather conditions and occupants' demands, resulting in low heat storage and release efficiency. The application of the adaptive dynamic building envelope integrated with PCM (ADBEIPCM) addresses this problem. This paper systematically reviewed the ADBEIPCMs for the first time, including their system configuration, working principles, control strategies, and system performance. The research methods and the PCM properties were also well summarized. The results show that the ADBEIPCM can store solar energy and release heat in time to reduce building load and improve comfort mainly by rotating, moving, flipping, and controlling the state of vents. This review divided the ADBEIPCMs into two categories: opaque envelopes and transparent envelopes. The experiment studies and simulation studies accounted for 15.28% and 84.62% of the research on opaque envelopes, and each accounted for 50% of the research on transparent envelopes. But onsite monitoring studies on transparent envelopes only accounted for 25%. In the design of ADBEIPCM, the main encapsulation method of PCM was macro-encapsulation, and the type of PCM was mainly organic. This review analyzed the shortcomings of existing studies and gave recommendations for engineers, architects, and scholars. Future research should focus on the development of novel PCMs with high strength and stability, the development of artificial intelligence-based short-term control strategies, and the development of ADBEIPCM based on bionic technology and powered by renewable energies. [ABSTRACT FROM AUTHOR]

Built environments contribute significantly to mitigating climate change. However, existing buildings, which form most urban infrastructures, do not typically meet contemporary stringent energy efficiency standards. They are naturally continuously deteriorating, making them a continuous negative contributor to their surrounding environments, which keeps getting worse. Therefore, there is a need to develop performance diagnosis frameworks and approaches for accurate Building Energy Model (BEM) simulations to develop impactful retrofitting design solutions that could make existing buildings perform closer to current efficiency measures. This paper reports on research that focuses explicitly on calibrating envelopes of existing BEMs using drones equipped with thermography sensors. The study specifically focuses on the automation of on-the-fly envelope U-value estimations and verification of calibrated envelope BEMs. The paper examines a renovated campus building in Boston, MA., representing material degradation, thermal bridging, and insulation failures using thermal imaging. A BEM is then calibrated, and post-renovation metered and modeled wintertime heating energy are compared. Goodness of fit measures showcase BEM performance improvement from 21.8%to 0.9%, which demonstrates the utility of the proposed framework. Further research is recommended to expand the focus on anomalies in the envelope and increase the scope from the building scale to the neighborhood scale. [ABSTRACT FROM AUTHOR]

The paper contributes to the fulfilment of the environmental targets of the EU by introducing an innovative solution for envelopes of nearly zero-energy buildings (nZEB). It presents the development of an environmentally friendly alternative to aluminium curtain wall systems for new constructions or renovations. The research and development were from the early stages led by design strategies for low embodied energy and embodied carbon structures. The first technical concept was analysed using comparative life cycle assessment (LCA). Prototypes were tested to verify their technical performance (air- and water tightness, fire resistance, acoustic properties, short- and long-term hygrothermal monitoring). The final pre-production design was subjected to a detailed LCA, and various possibilities for its improvement were suggested and assessed. The early-stage LCA showed a high potential for reduction of the embodied environmental impact by utilization of natural materials. The results of the experimental testing proved that thus developed curtain wall system fulfilled the standard technical requirements. The detailed pre-production LCA study proved that the fabrication of one panel of the curtain wall system being developed causes significantly lower environmental impact compared with a panel of a common aluminium curtain wall system. [ABSTRACT FROM AUTHOR]

Building integrated Photovoltaics (BIPV) receives growing attentions from both architectural and energy saving perspectives. Large commercial building envelopes can be utilized due to their great potential of reducing building energy consumption and increasing PV integration impact, especially in climate zones with rich solar resources. Most current studies have been focused on predicting electricity generation of BIPV systems with existing envelope geometries, while few studies have discussed the generation of proper envelope shapes for PV integration due to the challenge of integrating architecture and engineering. This paper introduces a novel optimization method for BIPV shape development based on the shape grammar theory. The method reforms given building shapes/envelopes to produce a set of better BIPV shape alternatives, as well as determines the best placement and matching BIPV systems for the optimized envelopes. The main set of criteria considered during the generation and optimization process include PV power generation, PV economic impact and building energy consumption. Architectural preferences are included in generating preferred design alternatives, such as view consideration and shape direction. Commercial buildings in Egypt are used to demonstrate and validate the applications of the developed method and tool. The method and tool can help designers in achieving an optimal design of building envelope that is most suitable for maximizing PV integration. [ABSTRACT FROM AUTHOR]

As of 2007 more than half of the world’s population is living in urban areas (a figure expected to rise to 60% by 2030). Thus, the liveability of the high-density city is gradually becoming a central point of focus and concern. A successful skyscraper model of urban planning could provide the possibility to increase city-space vertically as opposed to the current continuous expansion outward, which has obvious environmental consequences. However, skyscraper development, as well as all other new construction and gradually the older building stock, has to comply with current strict regulations on building energy efficiency. Contemporary high-rise examples do not present a sustainable solution to an increasing population or as models of prosperity, as they are linked to high-energy demand, environmental and social imbalances. This paper looks at design strategies towards promoting skyscraper energy efficiency by considering a climatically responsive design, where orientation, the thermal properties of the building envelope and the effect of altitude, become the main design tools. Initial simulations were performed for a residential and an office reference structure 100 m high. Different scenarios were implemented for gradually upgrading the building envelope and studying its relationship with the changing microclimate with altitude (wind speed increase and dry bulb temperature drop) between ground and top level. The advanced envelope was then simulated to up to 400 m high (120 stories high), and heating and cooling loads were compared in relation to different building heights and uses. EnergyPlus is used as the main simulation tool as it accounts for wind speed increase and dry bulb temperature drop with height. The location chosen is Tel Aviv, Israel, a city already growing upwards and expected to have a significant increase in skyscraper construction in the coming years. The results of the simulations performed present the base upon which further design strategies can be implemented towards reducing the environmental impact of this challenging building type. [ABSTRACT FROM AUTHOR]

This paper investigates the influence of occupant lifestyle patterns on the energy performance of the residential buildings with various building envelopes in different climate zones. For this purpose, an existing multi-family apartment building in Iran was selected as the experimental residential building and the validity of energy simulation was examined based on the real data of the building energy consumption. The energy demand of the building before and after renovation was simulated via EnergyPlus for different climate zones. The sensitivity analyses confirmed that the occupants’ behavior has a significant impact on the building's thermal energy usage especially in hot climate areas and can change the heating and cooling loads up to about 90%. Using the validated model, a parametric study was performed to investigate the influences of the occupant's behavior on the efficiency of the building envelope including window and cladding materials in different climate zones. The results show that the interaction between the occupants’ behaviors and envelope materials is significant in that the occupant behaviors can change the strategy of choosing the envelop material types. Fluctuation of thermal energy consumption caused by changing of window types can rise to 20% for this case study. Also, it is shown that underestimating the level of occupancy loads can exaggerate the effects of the envelope on the thermal energy consumption rate. Overall, this study emphasizes the importance of applying near actual user behavior data on energy simulation analyses performed for the studies of building sustainability and lifecycle assessment. [ABSTRACT FROM AUTHOR]

The main objective of the paper is to assess the impact of different factors which include building and human comfort parameters on indoor temperature conditions and energy need for heating for complex system “heat source – human comfort – building envelope”. The proposed method of mean radiant temperature calculation for human comfort models, which takes into account incoming solar radiation, will increase the accuracy of calculations by 1.3% – 4.7%. Regression models for comfort room air temperature determination, developed on the basis of energy and exergy human comfort approaches, significantly simplify further calculations and can be incorporated in complex system. As comfort temperature, determined in accordance with exergy approach is lower than based on energy one, the exergy concept use for providing comfort conditions accounts for less energy need for heating. Modelling results of various factors impact on energy need for heating are obtained based on energy and exergy approach to human comfort. [ABSTRACT FROM AUTHOR]

• An optimization method for thermal properties of envelopes of BIHP is proposed. • Thermal design principle of envelopes of BIHP is obtained. • Optimal BIHP greatly improves indoor thermal discomfort by 36 %–100 %. • BIHP is recommended in areas with RRTD greater than 5 W/(m2·K). Building Integrated Heat Pipes (BIHP), specifically a novel passive solar house integrated with gravity heat pipes, realizes envelopes with variable thermal properties and makes effective and efficient use of solar energy to reach zero-carbon heating, and can greatly improve the indoor thermal environment in winter. In this paper, an efficient method based on particle swarm optimization for the optimization of thermal properties of the BIHP interior envelope is proposed. The key thermal properties of the heat pipe and the exterior and interior envelopes are optimized, and the solar application potential of improving indoor thermal discomfort by BIHP in five representative cities of northern China is obtained. The results show that the equivalent thermal conductivity of the heat pipe is suggested to be greater than 2 × 104 W/(m·K). The optimal BIHP should have exterior envelopes with high thermal resistance and interior envelopes with large thermal capacity. In the selected areas, the optimal BIHP improves indoor thermal discomfort by 36 %–100 % and increases the minimum indoor operative temperature by 5.1–10.5 °C compared to the reference building. BIHP is recommended in areas with the ratio of radiation to temperature difference greater than 5 W/(m2·K) and can reach zero-carbon heating in Lhasa and Yinchuan. This research provides a global matching and optimization method for the effective and efficient utilization of solar energy to reach zero-carbon heating and evaluates the application potential of BIHP. [ABSTRACT FROM AUTHOR]

The paper presents a study of the effect of geometric design of equatorial-facing, double skin façade on energy performance of multi-story office buildings. The investigated parameters relate to the outer skin surface geometry and to the associated air cavity depth between the two skins of this façade system. Two main geometrical designs are investigated. A simple folded plate geometry – saw-tooth that consists of a single fold, and a more complex folded-plate units based on pyramids. The results indicate that although deviation from the basic flat façade leads generally to an increase in heating load, this is counterbalanced by a reduction in cooling load, and a considerable increase in energy generation potential from façade integrated photovoltaic systems. The position of fold and the depth of the cavity have a significant effect on thermal load and energy generation potential. Under the studied climatic conditions (Calgary, Alberta, Canada – 52°N), The total annual electricity generation potential, by the multifold configurations can exceed that of the flat façade by up to 80%. The increase in total electricity generation potential of some designed configurations is accompanied by an increase in time spread of functional electricity over extended period of time. Multifold façade configurations that combine east and west orientations can provide a peak spread of some 4–5 hours. [ABSTRACT FROM AUTHOR]

• A model-based integrated envelope performance evaluation method is proposed. • Model with paralleled internal mass is recommended for Nearly Zero Energy Building. • The proposed model could keep robustness under of internal heat gain uncertainty. • The evaluation was demonstrated by a Nearly Zero Energy Building renovation case. The thermal transmittance plays a decisive role in building energy efficiency design, which determined by standard in-situ measurement are obviously not equivalent to the practical building load level. There is still a lack of post-evaluation method that can separately evaluate the energy saving effect provided by integrated building envelope, especially for the nearly-zero energy building (NZEB) whose thermal inertia cannot be neglected. This paper proposed a model-based integrated building envelope performance evaluation method, which contains a reverse parameters identification and a forward load calculation. The data-driven lumped-parameter model represented by resistance–capacitance network (RC-model) reflects the integrated envelope performance, and four different model structures were designed for different treatment of thermal mass were compared. The applicability of the selected 7R6C model in the simulation of NZEB is demonstrated by the accuracy verification, sensitivity analysis of initial values of temperature node and uncertainty assessment of internal heat gain. A renovation case achieved an annual heating demand assessment result of 14.0 kWh/(m2·a) under typical annual meteorological data, which is lower than the limit value of a NZEB in cold region of 15.0 kWh/(m2·a). The evaluation results show that the envelope renovation meets the requirements of energy efficiency design. On the way to low-carbon buildings, the corresponding post-evaluation method needs to be gradually improved. [ABSTRACT FROM AUTHOR]

Green building design is presently among the hottest research topics in the world. Maintaining a comfortable indoor environment with minimum energy consumption is a challenging task that attracts the attention of experts around the world. With the recent advances in building performance simulation tools, it is now possible to predict and assess building performance at the design stage. Simulation-based optimization of building design is a potential application that connects building performance simulation with optimization algorithms. In this paper, numerous studies on the optimization of building envelope design were assembled and reviewed. Popular optimization algorithms were compared and discussed. Targeted objectives were collected and summarized. Based on the statistical results, the limitations in this research area were identified, and some potential breakthroughs were suggested. [ABSTRACT FROM AUTHOR]

Typically the effect of thermal bridges on the energy performance of buildings is taken into account by implementing an average U-value in 1D whole building energy simulation program, which is referred to as the equivalent U-value method. This treatment accounts for the effect of thermal bridges on the overall thermal transmittance of envelope details, while their thermal inertia effect is ignored. In this paper, the dynamic effect of balcony slab as thermal bridges on the energy performance of a high-rise residential building is investigated by comparing the annual space conditioning loads obtained by the equivalent U-value method to that obtained from 3D dynamic modeling of the balcony junctions implemented in WUFI Plus program. The simulation results show that the equivalent U-value method underestimates the annual heating loads by 2.8–4.4% for the building as-designed. With the increase of balcony portion and better insulated walls, the difference in annual space heating loads modeled using these two methods is increased to 8.6–15.2%. With the implementation of balcony thermal break the annual heating loads are reduced by 8.8–25.7% and the difference between these two modeling methods is also reduced to 1.9–11.5% for the cases investigated. [ABSTRACT FROM AUTHOR]

Although numerous technologies – such as double skin façade (DSF), double glazing window (DGW), etc. – have been applied in the glass envelope, the heat transfer of the glass envelope is still considerable. Cooling pipes embedded in the venetian blinds of a double-skin envelope are presented in this study as a system for reducing the heat transfer of the glass envelope in summer. Solar radiation is taken away directly by pipes through which cooling water is circulated, and the water can be produced from natural cooling. CFD software is employed in this paper to simulate the conjugated heat transfer in the double-skin envelope and the numerical model has been validated. The effect of embedded pipes is numerically investigated based on DGW. Different DGW structure and glass assemblies are taken into consideration. The results show that the cooling pipes can significantly reduce the temperature of the venetian blinds and air cavity, which will in turn lower heat transfer and improve thermal comfort. With pipe embedded, cooling water averagely takes away about 60% of the solar radiation directly and the average solar energy transmittance is only 13%. In addition, cheap glass can be employed to the pipe-embedded DGW with only small negative influence. [ABSTRACT FROM AUTHOR]

Lightweight structures have suffered long from low thermal inertia making them more vulnerable to climatic conditions. The adoption of phase change material (PCM) can potentially reduce this climatic deficiency. In order to evaluate its thermal potential, computational modeling has shown to be promising design tools. In this paper, a new TRNSYS type is developed and validated for simulating PCM-enhanced walls. Using the validated module, it is found that the best PCM's configuration is when placed in direct contact with the indoor controlled environment. Additionally, a wide range of PCM's thermal properties were simulated under typical U.S. climates to evaluate the thermal performance and identify the optimal thermal properties. The results show that a maximum saving of 0.8–15.8% is achieved on annual cooling load depending on the climate. For heating dominated climates, the savings on annual heating load is insignificant being less than 4%. The saving in peak loads was found to show more potential than annual loads for some climates. The maximum savings in peak cooling load range from 6.8 to 13.3% while savings in peak heating load range from 7 to 10.5%. For maximum savings in zonal loads, the optimal thermal properties of PCM are found to hover around the operational thermostat setpoints. [ABSTRACT FROM AUTHOR]

Thermal energy storage (TES), together with control strategies, plays an increasingly important role in expanding the use of renewables and shifting peak energy demand in buildings. Different control strategies have been developed for the integration of TES into building-related systems, mainly including building envelopes, HVAC systems and hot water tanks (HTWs). A systematic survey of control strategies using TES in the building-related systems is still lacking. This paper presents a comprehensive review of these control strategies. It provides a summary of the applied strategies and makes recommendations for future studies. Considering that control techniques serve as a basis for the implementation of control strategies, typical control techniques utilized in the building systems, as well as their strengths and weaknesses associated with the application, are also introduced to help users gain a better understanding. [ABSTRACT FROM AUTHOR]

The existence of thermal bridges in building envelopes affects the energy performance of buildings, their durability and occupants’ thermal comfort. Typically the effect of thermal bridges on the energy performance is taken into account by implementing an equivalent U -value in 1D whole building energy simulation program. This treatment accounts for the effect of thermal bridges on the overall thermal transmittance, while their thermal inertia effect is ignored. The presence of thermal bridges not only reduces the overall thermal resistance but also changes the dynamic thermal characteristics of the envelope. This paper investigates the dynamic effect of thermal bridges on the energy performance of residential buildings through simulations. A two-story residential building is used as a case study. Three methods, namely equivalent U -value method, equivalent wall method, and direct 2D/3D modeling method, are implemented in WUFI Plus, a whole building Heat, Air and Moisture (HAM) modeling program. Simulations are carried out for two climates with different insulation levels. Simulation results show that for the cold climate the annual heating load of this building with the inclusion of thermal bridges modeled using 3D dynamic method is 8–13% higher than that modeled using the equivalent U -value method, and 4–9% higher than that modeled using the equivalent wall method. With the increase of the insulation level, the percentage effect of thermal bridges on the heating load increases, while the difference among the three methods decreases. For the hot climate, simulation results show that the presence of thermal bridges increases the annual cooling load by 20%. Compared to the 3D dynamic method, the annual cooling load is underestimated by 17% using the equivalent U -value method and by 14% using the equivalent wall method, respectively. [ABSTRACT FROM AUTHOR]

Grey box models are a solution for evaluating and quantifying the effect on building thermal performance of different energy saving measures. They are usually used to predict a building thermal performance, and applied to energy systems. This paper presents the application of a grey box model to evaluate the thermal performance of a reference social housing building, focusing on its potential to evaluate the thermal performance of building passive elements (building envelope). A methodology to be used by public administration (to evaluate the effectiveness of a given energy renovation work) is also proposed. Firstly, a monitoring carried out in an empty social housing dwelling during 3 months is presented. Afterwards, a grey box model development is carried out using obtained monitoring data. Model development as well as some general model results are presented and evaluated. Finally, a methodology proposal to be applied by public administration is presented. By monitoring and developing a grey box model of a social housing building, this research aims to explore the possibilities of grey box models as a tool to represent in an accurate way the thermal performance of a dwelling, focusing on evaluating building passive elements and their effects on building energy consumption. [ABSTRACT FROM AUTHOR]

Contemporary ceramic blocks with the cavities filled by thermal insulation materials appeared in some European countries as a reaction of the brick industry to the increasing requirements on the energy efficiency of buildings. Their dual load-bearing and thermal insulating function, together with the good building-physical qualities and technological advantages makes them competitive on the building materials market. The assessment of their thermal properties is, however, a demanding task which often involves using large-scale experimental facilities for considerable time periods. In this paper, an alternative to the commonly used methods for determination of thermal performance of ceramic blocks with complex internal geometry is presented. The proposed approach is based on the computational modeling of heat transfer in the block, using the thermal properties of involved materials measured in a laboratory experiment as input parameters. The calculated temperature fields and heat fluxes are used for the determination of the effective thermal conductivity, thermal resistance and thermal transmittance. A practical applicability of the method is demonstrated for three ceramic blocks with different thermal insulation materials in the cavities. An uncertainty analysis of the calculated thermal parameters is performed and the results are compared with the data obtained by two different experimental approaches. [ABSTRACT FROM AUTHOR]

Heating and cooling loads are the major reasons for energy use in buildings. Buildings are usually subject to schedules and set-points which are not optimized in response to the dynamic weather conditions, internal loads, and occupancy patterns. The thermal network model has been widely applied for real-time building load estimation, which is crucial for optimizing the operation of the HVAC system. However, there has been limited exploration of the capabilities of the thermal network model due to constraints imposed by the solution method adopted. In this paper, the exponential matrix method was adopted to simplify the state space equations and solve the thermal network model analytically. This enhances the applications of a simplified thermal network model for investigation of multiple scenarios of HVAC system operations and equipment sizing, and for more accurate estimation of heating and cooling loads. This study also proves that the analytical solution method is asymptotically stable regardless of time step. A typical office was used as a case study and the predicted building loads are compared with measured data and numerical results from EnergyPlus. For the case study, the model demonstrated better accuracy and is seen to be robust for thermal load estimation for cooling season. [ABSTRACT FROM AUTHOR]

In Italy, historic buildings constitute 20% of the built environment. Although historic buildings are usually excluded from the obligation of adopting specific energy standard, energy related aspects should be nevertheless faced and managed in order to exploit the building “usability” potential, to attain indoor environmental quality and energy efficiency conditions. The energy refurbishment of this kind of building is, however, a very complex matter that leads to a number of question concerning buildings conservation and valorisation aspects. A non-invasive technique, that is, the application of thermal plaster to the internal side of a building envelope, has been investigated in this paper. Thanks to its relatively easy installation and reversibility, thermal insulating plaster seems to represent a very interesting solution as it is able to offer a good compromise between energy and conservation aspects. The aim of this work is to present a thermal, vegetal based, insulating plaster, which has recently been developed within a research project, and to investigate its potential to reduce the heat flux exchanged through the vertical envelope of historic buildings, by means of measurements carried out in both the laboratory and in the field, for a real case application. [ABSTRACT FROM AUTHOR]

Taking the joint advantages of the thermal energy storage capacity of phase change materials (PCM) and the excellent thermal insulation performance of rigid polyurethane (PU) foams, much attention has been paid to an idea that incorporates PCM into PU foam to promote energy efficiency in buildings. In this paper, a comprehensive review of PU–PCM foams was conducted from the perspectives of synthesis methods, phase change characterization, mechanical strength, cell morphology, thermal performance et al. It is shown that thermal energy storage capacity in PU–PCM foam is enhanced significantly while mechanical strength is decreased with respect to pure PU foam. Thermal conductivity was only investigated by one group with a conclusion that it maintains nearly constant when having PCM content increased. The authors strongly suggest more research work on this topic. In order to modify this new thermal insulating material, some other future research opportunities, such as formulation recipe improvement, thermal insulation performance, thermal aging and general energy saving evaluations, are explored to improve this composite. A challenge is also raised related to the low active thermal capacity of the PCM with fixed phase change temperature within a temperature gradient in the PU layer with low thermal conductivity. [ABSTRACT FROM AUTHOR]

Approximately 30% of energy use in Canada is consumed in buildings, specifically space heating, which can be reduced by constructing thermally-resistant building envelopes. This study evaluates potential innovative energy-efficient wall systems for mid-rise (four to six storeys) wood-frame buildings in terms of thermal and structural performances. Regarding the thermal resistance performance, four wall systems are developed, installed in a full-scale test house, and examined, along with a baseline wall system, using the field data collected. The selection of the wall systems is based on current practice, structural analysis, pre-fabricability, and energy-efficiency. Several sensors are installed on each wall system to measure temperature, heat flow, and relative humidity. In addition, structural tests are conducted to determine the compressive loading capacity of the tested wall systems for both concentric and eccentric loads, where full-scale panels are constructed and tested in laboratory. As a general finding, all the tested wall systems achieved ASHRAE's minimum assembly R -value recommendation of RSI 3.45, where the I-joist wall system had the highest R -value, while the conventional wall system had the highest load-bearing capacity. This paper recommends I-Joist wall systems for their higher energy efficiency suggesting more future research on efficient end connections to achieve consistent structural performance. [ABSTRACT FROM AUTHOR]

An effective analytical method for analyzing the transient thermal performance of building envelopes is very important to optimize their thermal performance design. However, the influence of thermal mass and insulation material distribution cannot be analyzed well by using the current steady state thermal resistance (i.e. R value) and thermal inertia index (i.e. D value). Moreover, the substitution effect between the thermal resistance R and the thermal capacitance C has not been theoretically studied before. A novel analytical approach based upon thermal impedance of evaluating the transient thermal performance of building envelopes is developed in this paper. By using that, the optimal material distribution (corresponding to the minimal space heating or cooling load due to building envelope heat loss or gain) can be analytically determined. In addition, the substitution relationship between R and C can be theoretically derived. The results show that putting concrete material in the middle and evenly distributing the insulating materials on the inside and outside surface can maximize the module of thermal impedance for given conditions. The proposed approach provides an effective way to theoretically optimize the transient thermal performance of building external wall. [ABSTRACT FROM AUTHOR]

Research about building strategies for energy saving is taking a growing interest worldwide. New solutions for building envelopes require increasingly sophisticated investigation to analyze the thermal-energy in-field dynamic response of constructions. Moreover, in-lab experiments are difficultly able to represent real environment boundary conditions. In this paper, effect of dynamic properties of building opaque envelope is investigated in winter conditions through an extensive continuous monitoring campaign of a dedicated experimental field. The field consists of: two full-scale buildings, an outdoor weather station, and two indoor microclimate stations. The two buildings were designed with the same stationary envelope characteristics, but different envelope technologies, materials and, therefore, different dynamic properties. Nevertheless, following Italian regulations about building energy performance in winter, they should behave the same. With the purpose to verify this hypothesis, a continuous long-term comparative monitoring is developed. The results only partly confirm that simplified hypothesis. In fact, in winter, while the two buildings exhibit equivalent long-term energy behavior, a weak difference is registered in terms of air temperature in free-floating, transient, and operative HVAC systems’ regime. Additionally, non-negligible discrepancies are registered in terms of mean radiant temperature, indoor humidity and internal–external envelope surface temperature, given the different transpiration rate of the two envelope systems and different solar reflectance values of the roofs. [ABSTRACT FROM AUTHOR]

• Changes of building airtightness of 61 houses are evaluated on different time scales. • Airtightness of houses may deteriorate mainly during the first two years. • 2-Storey houses with wood frame roofs present a higher risk of airtightness deterioration. • The increase in the number of leakages is not correlated with changes in the airtightness. • The airtightness of the houses tested is not affected by seasonal variations. The main objectives of this paper are to quantify and qualify changes in building airtightness on different time scales, and to identify factors that may explain the variations observed. A special measurement protocol, based on ISO 9972 but with some additional requirements, was defined after a detailed literature review. For the mid-term campaign, 30 new detached houses were measured once per year over a 3-year period. It was observed that air permeability increases slightly during the first year (a mean increase of 18%), and then stabilizes during the second and third years. Five of them were measured twice per year but did not show any significant seasonal variation. For the long-term campaign, 31 detached houses built during the last 10 years were remeasured once. Air permeability shows a similar increase to that of the mid-term campaign after 3–10 years (a mean increase of 20%). The results show an overall increase in the number of leakages detected for all houses, but this increase is not always correlated with the change in air permeability. Results pointed to three factors that could explain the deterioration of airtightness: the number of levels, the type of roof and the type of building material and air-barrier. [ABSTRACT FROM AUTHOR]

Abstract: In Brazil, a low-latitude country characterized by its high availability and uniformity of solar radiation, the use of PV solar energy integrated in buildings is still incipient. However, at the moment there are several initiatives which give some hints that lead to think that there will be a change shortly. In countries where this technology is already a daily reality, such as Germany, Japan or Spain, the recommendations and basic criteria to avoid losses due to orientation and tilt are widespread. Extrapolating those measures used in high latitudes to all regions, without a previous deeper analysis, is standard practice. They do not always correspond to reality, what frequently leads to false assumptions and may become an obstacle in a country which is taking the first step in this area. In this paper, the solar potential yield for different surfaces in Brazilian cities (located at latitudes between 0° and 30°S) are analyzed with the aim of providing the necessary tools to evaluate the suitability of the buildings’ envelopes for photovoltaic use. [Copyright &y& Elsevier]

Abstract: The adoption of Phase Change Materials (PCMs) in building components is an up-to-date topic and a relevant number of research activities on this issue is currently on the way. A particular application of PCMs in the building envelope focuses on the integration of such a kind of material into transparent envelope components. A numerical model that describes the thermo-physical behaviour of a PCM layer in combination with other transparent materials (i.e. glass panes) is developed to perform numerical analyses on various PCM glazing systems configurations. The paper illustrates the structure of the model, the main equations implemented and the hypotheses adopted for the model development. The comparison between numerical simulations and experimental data of a simple PCM glazing configuration is also presented to show the potentials and the limitations of the numerical model. While a good agreement between simulations and experimental data can be shown for the surface temperature of the glazing, the comparison between simulated and measured transmitted irradiances and heat fluxes does not always reach the desired accuracy. However, the numerical tool seems to predict well the thermo-physical behaviour of the system and may therefore represent a good starting point for simulations on different configurations of PCM glazing systems. [Copyright &y& Elsevier]

Abstract: This paper examines the behaviour in energy consumption of buildings that have polygonal and prismatic envelopes and are located in Mediterranean climates. More specifically, it aims at studying the differences in energy consumption of these kinds of buildings compared to orthogonal building envelopes. For this purpose a contemporary building was chosen and modelled in two different versions, one being the original prismatic form and the other a model of the same building with right angles, however retaining all area and volume data of the original prismatic building. Calculations reveal that the prismatic formed building has lower solar gains compared to its orthogonal counterpart and consumes less energy in an annual cycle. The results show a mean annual energy consumption difference of 7.88% in favour of the prismatic building envelope. Also, depending on the orientation, the difference in annual energy needs has a range between 2.51% and 16.01%. [Copyright &y& Elsevier]

Abstract: This paper introduces a comparison of different measuring methods of buildings fabric thermal resistance, including the test wall measuring points arrangements and measurement results, conducted in a test chamber in Cagliari (Italy) in summer 2009. Two methods and their measurement uncertainties are presented and compared by the compatibility of measurement study. The non-destructive method involves the heat-flow rate measurement through the test wall and its surface temperatures. The reliability of this method depends on the temperatures difference between the two environments separated by the building envelope. Thus two measurement series with different temperatures were carried out on the test wall. The destructive method instead foresees the acquisition of a sample by the use of a hollow drill, the building envelope layers thickness measurement and the thermal properties assignment to each different material. The wall R-value is the sum of each layer thermal resistance. The comparison shows that the R-values measured by the non-destructive method with a temperature difference of 10°C and 7°C and the one calculated from the destructive method obey the compatibility of measurement principle. [Copyright &y& Elsevier]

Abstract: This paper addresses the application of Energy Efficiency Rating Technical Quality Regulations for Commercial, Service and Government Buildings – RTQ-C in order to ascertain whether the conventional construction system for buildings complies with these requirements. Additionally, it investigates the contribution of labeling to reducing electricity consumption by the building. To do so, the RTQ-C was applied to two buildings in order to calculate the efficiency levels of their envelopes and possible alterations are proposed for upgrading the envelope performance where pertinent. It is noted that conventional buildings adopting measures such as painting the walls and roof white, in addition to using smoked glass, are sufficient to bring the rating up to an A grade. As no specific concern was noted in the architectural designs for the buildings studied, making use of design strategies that minimize the use of electricity in these buildings, the findings of these case studies may well indicate that the RTQ-C has adopted technical requirements that are not particularly stringent. Consequently, it is believed that these requirements should be reviewed during a second stage, in order to make them more restrictive and attain further improvements in the constructed environment with better energy efficiency for buildings. [Copyright &y& Elsevier]

Abstract: Active transparent façades constitute a building envelope component that is becoming more and more common in high-rise office buildings. Many designers have opted for a ventilated façade, claiming that this technology is sustainable, reduces energy consumption and enhances indoor comfort conditions, but these claims have often proved to be wrong. From the thermofluid-dynamic analysis point of view, few design procedures or sufficiently detailed, reliable and easy to use simulation software are available for ventilated façades. A numerical model that has been developed to simulate the thermal behaviour of mechanically ventilated active transparent façades is presented in this paper. The model, developed in the Simulink/Matlab® environment, simulates the façade in both steady-state and transient conditions and provides the temperature of the different layers of the façade structure and the corresponding heat fluxes as output data. The model has been validated by comparing the simulation results with experimental data obtained in the laboratory. A test has also been performed on a real façade under actual operating conditions. The model performance has resulted to be quite promising. The accuracy of the prediction of the temperature is good, while the simulations of the heat fluxes are slightly less reliable for some operative conditions. [Copyright &y& Elsevier]

Abstract: While the EU Directive 2002/91/CE on the Energy Performance of Buildings (EPBD) clearly establishes regulations for the thermal insulation of buildings for saving energy in winter, the summer strategy is described by a little more than qualitative provisions. As a consequence, in the national requirements, the high insulation of the building envelope is considered as the principal strategy to control energy consumption even in summer, regardless of the different climates. This approach leads to a homologation of the building trade, and imposes construction technology and materials which do not adhere to the traditional way of making buildings, like in Southern Europe. Here, the “over insulation” of buildings runs the risk of reducing the effectiveness of traditional passive cooling strategies (thermal mass, air permeability of the roof covering, roof ventilation) and could have adverse effects on internal comfort. In this paper, we focus on the effects of over insulation on the thermal performance of roofs in summer, by analyzing experimental data from monitoring a full-scale mock-up in Italy. Results show how an increase in insulation thickness reduces the effectiveness of traditional passive cooling strategies, as an effect of the thermal decoupling between the interior and the upper layers of the roofs. [ABSTRACT FROM AUTHOR]

Abstract: The recent rise in the environmental and economic costs of energy demands a need to design and build more sustainable building systems. Curtain wall assemblies show great promise—the spandrel panels within them can be natural solar collectors. By using a solar dynamic buffer zone (SDBZ) in the spandrel cavity, solar energy can be efficiently gathered using the movement of air. There is a need for a numerical model capable of predicting performance of this system. This paper presents the quantification of a prototype SDBZ curtain wall system through experimental testing in a laboratory environment. Results from the experimental testing were used to validate a one-dimensional numerical model of the prototype. This research shows a SDBZ curtain wall system as an effective means of reducing building heating energy consumption. The numerical model showed good correlation with experimental results in the expected operating range of the system. Given the lack of published literature for similar systems, this research acts to validate a simple, innovative approach to collect solar energy that would otherwise be lost to the exterior using already existing components within a curtain wall. This research shows the SDBZ curtain wall has the potential to act as a significant solar collector. [Copyright &y& Elsevier]

Abstract: This paper presents a comprehensive study of the thermal performance of the diffusive building envelope. As the infiltration air moves through the building envelope, it exchanges heat with the solid matrix. The temperature profile in the building envelope deviates from that of pure conduction, because of the heat exchange between infiltrated air and solid matrix. Numerical study was carried out to determine the contribution of air infiltration to the heat gain/loss through the diffusive building envelope. The model validation process was carried out at two different levels: inter-model comparison; validation with experimental data. At the inter-model level, the infiltration heat exchange efficiency of a wall was compared with the infiltration heat exchange efficiency predicted by an existing model in the literature. The results show good agreement between two models. The second level of validation compares the model''s prediction with the existing experimental data. The results confirm that there are excellent agreement between prediction made by the numerical model and the experimental data. Furthermore, a simplified analytical model was developed to the prediction of the thermal performance of the diffusive building envelope. In the model, the whole wall was divided into ventilated and non-ventilated areas, and the ventilated area was modeled by adopting a uniform velocity distribution. By comparing the results obtained by the validated numerical model and the analytical model, it was shown that the analytical model can accurately predict the performance of a diffusive building envelope. [Copyright &y& Elsevier]

Abstract: Free-cooling is understood as a means to store outdoors coolness during the night, to supply indoors cooling during the day in summer, while free-heating is understood as a means to store the solar radiation during daytime, to supply indoors heating during the night in winter. In principle, free-cooling or free-heating can make the indoor air temperature in the comfortable region all the year if the thermophysical properties of building envelope material are in the desired range (defined as ideal thermophysical properties in this paper). Those properties are obviously related to the outdoor climate condition, internal heat source intensity, building configuration, ventilation mode etc. For a given region and a given building, the critical values of those ideal thermal physical properties can be determined through modeling and simulation. Two parameters, I win and I sum, are defined to describe the overcool degree in winter and the overheat degree in summer, respectively. To illustrate, the critical values of thermophysical properties of building envelope of a building located in Beijing are obtained through modeling and simulation. The simulated results are validated with experiments. The model, the methodology and the results are helpful for selection of suitable building envelope materials and for design of energy efficient buildings. [Copyright &y& Elsevier]

This paper draws the attention to the importance of a correct modelling of the inlet temperature of naturally and mechanically ventilated multiple-skin facades. Measurements demonstrate that the assumption of an inlet temperature equal to the interior or exterior air temperature is usually not valid. A sensitivity study illustrates the significance of the inlet temperature as a boundary condition for numerical multiple-skin facade models. Finally, the inlet temperature model and multiple-skin facade model are used in a whole building energy simulation to indicate the importance of a correct inlet temperature on the energy performance. [Copyright &y& Elsevier]

One of the most important functions of a building by human beings is to provide thermally comfortable spaces for the users. Therefore, a great deal of artificial energy is consumed for heating to satisfy thermal requirements in cold zones. In order to satisfy thermal comfort and reduce heating energy consumption at the same time, building parameters affecting indoor climate should be determined properly during the design stage. Building form and building envelope are the most important parameters affecting indoor climate. Building form is an important determinant of total heat loss through the whole building envelope in cold climates. Therefore in this paper, a methodology to determine building form which provides minimum heat loss through the whole building envelope is introduced with its application for Erzurum region that representative city of Turkey for cold climatic zones. [Copyright &y& Elsevier]