An active pipe-embedded building envelope, which is an external wall or roof with pipes embedded inside, was presented. This structure may utilize the circulating water in the pipe to transfer heat or coolth inside di...An active pipe-embedded building envelope, which is an external wall or roof with pipes embedded inside, was presented. This structure may utilize the circulating water in the pipe to transfer heat or coolth inside directly. This kind of structure is named ＂active pipe-embedded building envelope＂ due to dealing with the thermal energy actively inside the structure mass by circulating water. This structure not only deals with thermal energy before the external disturbance becomes cooling/heating load by using the circulating water, but also may use low-grade energy sources such as evaporative cooling, solar energy, and geothermal energy. In the meantime, this structure can also improve the indoor thermal comfort by tempering the internal wall surface temperature variation due to the thermal removal in the mass. This work further presents the thermal performance of this structure under a typical hot summer weather condition by comparing it with that of the conventional external wall/roof with numerical simulation. The results show that this pipe-embedded structure may reduce the external heat transfer significantly and reduce the internal wall surface temperature for improving thermal comfort. This work also presents the effects of the water temperature and the pipe spacing on the heat transfer of this structure. The internal surface heat transfer may reduce by about 2.6 W/mE when the water temperature reduces by 1℃ as far as a brick wall with pipes embedded inside is concerned. When the pipe spacing reduces by 50 mm, the internal wall surface heat flux can also reduce by about 2.3 W/m2.展开更多
A new facility was presented which can expediently and cheaply measure the transient moisture content profile in multi-layer porous building envelope.Then,a common multi-layer porous building envelope was provided,whi...A new facility was presented which can expediently and cheaply measure the transient moisture content profile in multi-layer porous building envelope.Then,a common multi-layer porous building envelope was provided,which was constructed by cement mortar-red brick-cement plaster.With this kind of building envelope installed in the south wall,a well-controlled air-conditioning room was set up in Changsha,which is one of typical zones of hot and humid climate in China.And experiments were carried out to investigate the temperature and moisture distribution in multi-layer building envelope in summer,both in sunny day and rainy day.The results show that,the temperature and humidity at the interface between the brick and cement mortar are seriously affected by the changes of outdoor temperature and humidity,and the relative humidity at this interface keeps more than 80% for a long-term,which can easily trigger the growth of mould.The temperature and humidity at the interface between the brick and cement plaster change a little,and they are affected by the changes of indoor temperature and humidity.The temperature and humidity at the interface of the wall whose interior surface is affixed with a foam plastic wallpaper are generally higher than those of the wall without wallpaper.The heat transfer and moisture transfer in the envelope are coupled strongly.展开更多
Phase Change Materials(PCMs)have high thermal inertia,and hemp concrete(HC),a bio-based concrete,has strong hygroscopic behavior.In previous studies,PCM has been extensively combined with many materials,however,most o...Phase Change Materials(PCMs)have high thermal inertia,and hemp concrete(HC),a bio-based concrete,has strong hygroscopic behavior.In previous studies,PCM has been extensively combined with many materials,however,most of these studies focused on thermal properties while neglecting hygroscopic aspects.In this study,the two materials have been combined into a building envelope and the related hygrothermal properties have been studied.In particular,numerical studies have been performed to investigate the temperature and relative humidity behavior inside the HC,and the effect of adding PCM on the hygrothermal behavior of the HC.The results show that there is a high coupling between temperature and relative humidity inside the HC,since the relative humidity changes on the second and third days are different,with values of 8%and 4%,respectively.Also,the variation of relative humidity with temperature indicates the dominant influence of temperature on relative humidity variation.With the presence of PCM,the temperature variation inside the HC is damped due to the high thermal inertia of the PCM,which also leads to suppression of moisture evaporation and thus damping of relative humidity variation.On the second and third days,the temperature changes at the central position are reduced by 4.6%and 5.1%,compared to the quarter position.For the relative humidity change,the reductions are 5.3%and 5.4%on the second and third days,respectively.Therefore,PCM,with high thermal inertia,acts as a temperature damper and has the potential to increase the moisture buffering capacity inside the HC.This makes it possible for such a combined envelope to have both thermal and hygric inertia.展开更多
In recent decades, there has been a great deal of investment in Portugal in the construction of new buildings to the detriment of the rehabilitation of existing ones. As a result, the historic centres of towns and cit...In recent decades, there has been a great deal of investment in Portugal in the construction of new buildings to the detriment of the rehabilitation of existing ones. As a result, the historic centres of towns and cities are deteriorating, while their suburbs are spreading. One of the main problems affecting the rehabilitation of residential buildings is that it is extremely difficult to accurately estimate the costs involved. Although there are established methods （and technical documents available） to aid the costing of new buildings, there is a lack of official information about the costs of rehabilitation work, particularly as regards the external envelope of buildings. This article demonstrates how to determine rehabilitation costs （with particular emphasis on the envelope of residential buildings） by gathering information from specialized companies, assessing price variability and consulting databases of rehabilitation costs from other countries. It also presents some examples of costing for particular rehabilitation jobs.展开更多
Today,to describe the thermal performance of the building envelope and its components we use a variation of metrics;such as,R-value,ACH(air exchange rate per hour),SHGC(solar heat gain coefficient)of windows,U-factor ...Today,to describe the thermal performance of the building envelope and its components we use a variation of metrics;such as,R-value,ACH(air exchange rate per hour),SHGC(solar heat gain coefficient)of windows,U-factor etc.None of these performance indicators is meant to represent the overall thermal performance.In this paper,such a metric is introduced,the BEP(building envelope performance)value.Unlike the thermal resistance,typically expressed as an R-value,the BEP-value considers additional elements of heat transfer that affect the energy demand of the building because of exterior and interior(solar)thermal loads:conductive and radiant heat transfer,and air infiltration.To demonstrate BEP’s utility,validation studies were carried out by comparing the BEP-value to theoretical results using whole building energy simulation tools such as EnergyPlus and WUFI Plus.Results show that BEP calculations are comparable to calculations made using these simulation tools and that unlike other similar metrics,the BEP-value accounts for all heat transfer mechanisms that are relevant for the overall energy performance of the building envelope.The BEP-value thus allows comparing envelopes of buildings with different use types in a fair and realistic manner.展开更多
The main aim of this paper is to study the effect of building envelope constructed with different materials on thermal comfort of buildings located in Jeddah, Saudi Arabia. Four different buildings constructed with br...The main aim of this paper is to study the effect of building envelope constructed with different materials on thermal comfort of buildings located in Jeddah, Saudi Arabia. Four different buildings constructed with brick, glass, stone, and gypsum are taken into account to study the difference in temperature of the indoor and outdoor environments. Also, this paper explores the heat conducted by walls of different materials with different thicknesses. In addition, survey is conducted among the residents of Jeddah to know their perspective about thermal comfort of buildings. From the study, it is found that building envelope constructed with glass is more effective compared to envelope constructed with other materials of with least thickness of wall. Also, it is found that the envelope constructed with brick is more effective in absorbing the heat provided the thickness of the walls remains the same.展开更多
Building envelope is a fence that controls heat exchange between interior and exterior and plays an essential role in providing thermal comfort conditions of residents. In recent years, due to the necessity of conserv...Building envelope is a fence that controls heat exchange between interior and exterior and plays an essential role in providing thermal comfort conditions of residents. In recent years, due to the necessity of conserving energy and also preventing increased environmental pollution, the importance of sustainable construction has been doubled. Checking the problems of thermal behavior of the building envelope materials, and what influences in the heating and cooling loads exerted and energy consumption of buildings, are the questions that this research seeks to answer. In this regard, building information modelling analysis (BIM) has worthy contribution in the completion process of sustainable design;thus using software Design Builder, it is paid attention to simulation of the thermal behavior of two types of defined materials for the building envelope that was designed as a Research Institute of Renewable Energy of Yazd University. For Type 1 materials, two layers of brick have been selected, and for Type 2 a thermal insulation layer also added it. Results of the analysis showed that the use of materials Type 2 in the cooling load %4.8 and in the thermal load %62.5 reduction can be achieved which means reducing the load on active system and thus reducing the initial cost of building. Also reduction in annual energy consumption by almost %2.4 for cooling and %62.9 for heating buildings have been achieved, which makes saving non-renewable energy consumption, and consequently reducing environmental pollution as well as reducing current costs will be established.展开更多
Thermally activated building envelopes(TABEs)are multifunctional component that combines structural and energy properties.Based on re-examining the heat charging processes,an arc-shaped metal-fin-enhanced TABE(Arc-fin...Thermally activated building envelopes(TABEs)are multifunctional component that combines structural and energy properties.Based on re-examining the heat charging processes,an arc-shaped metal-fin-enhanced TABE(Arc-finTABE)with directional heat charging features is proposed to optimize the thermal barrier formation process.A comprehensive parameterized analysis is conducted based on a validated mathematical model to explore the influence of 5 fin-structure design parameters and the static insulation thickness.Results verified that the directional charging strengthening fins can improve transient thermal performances of Arc-finATBE and enlarge horizontal and vertical sizes of the thermal energy accumulation area surrounding the pipeline,while the maximum growth in extra heat loss is less than 3.17%.From the perspective of promoting heat injection into expected areas,the straight main fin configurations with the angle of main fins of 30°,shank length ratio of 0.4 and no leftward mounted fins are preferred in load-reduction mode,while the angle of main fins of 150°,shank length ratio of 0.8 and multiple fin designs,especially with one of the main fins horizontally toward the indoor side,are more favorable in auxiliary-heating mode.Besides,it is recommended to add one arc-shaped branch fin to each main fin to achieve a balance between performance improvement and material usage.Moreover,branch fins with larger arc angles are preferred in auxiliary-heating mode,while smaller arc angles are conducive to injecting heat into the wall along main fins in load-reduction mode and preventing the heat near the inner surface from being extracted.Under the direct influence of the strengthened invisible thermal barrier,Arc-finTABEs can reduce the amount of static insulation layer by 20%–80%while achieving equivalent thermal performances as conventional high-performance walls.展开更多
We have spent the last 40-50 years working for energy efficiency in our buildings, and we have done so by increasing the performance of the heating, cooling, lighting, and ventilation systems we use. Only recent...We have spent the last 40-50 years working for energy efficiency in our buildings, and we have done so by increasing the performance of the heating, cooling, lighting, and ventilation systems we use. Only recently have we realized the importance of the building envelope in this endeavor. The spaces within a building are created to support the purpose and programs of that building, and it is the envelope made up of the walls, windows, doors, roof, skylights, and floor that protect and shelter those programs and purpose. In this article we will explore various components of the building envelope and discuss ways to achieve optimal energy use.展开更多
Research has shown the environmental benefits of green envelopes,as well as performance in terms of energy efficiency.To date,there is no analysis of the economic sustainability of these systems,which has allowed the ...Research has shown the environmental benefits of green envelopes,as well as performance in terms of energy efficiency.To date,there is no analysis of the economic sustainability of these systems,which has allowed the realization of a few,albeit very well known,examples.The research has identified a green modular system integrated into the building envelope,designed to facilitate installation and maintenance,with competitive performance compared to other existing solutions;a system that wants to improve performance and flexibility of vertical applications,experimented on buildings,on the market,and able to adapt,above all,to the needs of the building process.It is important to distinguish architectural aesthetic requirements from those of the building process;the former aim to have an authentic vertical garden,with different kinds of plants where nature dictates the rules,the latter aims to achieve the economic sustainability of vertical greenery systems.This paper provides an analysis of a technique based on the installation of plant bearing modular panels with turf on substructures also provided with a micro-irrigation system,which allows the construction of a modular coating,characterized by reduced thickness,that can also be integrated with other materials;installation is quick and simple,since the panel comes perfectly planted on site.In addition to that it allows,from a botanical point of view,resorting to types of grass selected with a view to climate,exposure,environmental adaptability,color and shape.A comparative analysis of this green façade is also presented compared to other existing case studies,from a constructive and managerial point of view,highlighting both its economic and architectural advantages.展开更多
The key role of the building envelope in achieving building energy efficiency and indoor comfort for the user has been long established.The most promising-and innovative-strategy for the building envelope of the futur...The key role of the building envelope in achieving building energy efficiency and indoor comfort for the user has been long established.The most promising-and innovative-strategy for the building envelope of the future is based on a dynamic,active and integrated solution,that is able to optimize the thermal performance,integrate the active elements and systems,and exploit energy from renewable sources.This paper illustrates the most relevant results of a decade-long research activity carried out on active and integrated building envelopes at the Politecnico di Torino,in which numerical analyses and experimental campaigns,involving test cells and field monitoring,have been performed.The overall performances of different façade modules and the thermo-physical behaviour of various components,under different operating strategies,are presented and discussed.The analysis provides information on the contribution of each subsystem,e.g.glazing,sun-shading devices,natural and mechanical ventilation,...to the achieved energy efficiency and the overall performances of different typologies of Double-Skin Façades(DSFs)and Advanced Integrated Façades(AIFs).展开更多
This research is mainly focused on the experimental measurement of R-value by several different models.Building energy consumption accounts for about 40%of the total energy use in the U.S,and therefore accurate energy...This research is mainly focused on the experimental measurement of R-value by several different models.Building energy consumption accounts for about 40%of the total energy use in the U.S,and therefore accurate energy simulation is desired.The R-value is one of the key parameters that can influence the energy simulation results and therefore is of great importance.The Average Model has long been the most widely accepted method to measure the thermal properties of building components.However,its steady-state assumption and dependence on temperature difference limit its use especially for in-situ measurement.In this study,several dynamic models,including the Pentaur Model and R-C Network Models,are studied with test data obtained from a series of hot box tests performed in the Building Enclosure Testing Laboratory.The results show that the 3R2C model has the best performance and a desirable stability of accuracy with respect to different levels of temperature difference,and therefore is recommended for practical measurement.The results also indicate that unlike the Average Model,the accuracy of dynamic models does not necessarily depend on the level of temperature difference.展开更多
In the context of racing to carbon neutrality,the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element,which also provides an opportunity for thermal insulation s...In the context of racing to carbon neutrality,the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element,which also provides an opportunity for thermal insulation solutions to transform from high to zero-carbon attributes.Based on the re-examination of the heat transfer process of conventional pipe-embedded radiant(CPR)walls,the modular pipe-embedded radiant(MPR)wall integrated with thermal diffusive materials is proposed to enhance the heat transfer capacity of CPR walls in the direction parallel to the wall surface,thereby forming a more stable and continuous invisible thermal barrier layer inside the opaque envelopes.A comprehensive thermal and energy-saving analysis study regarding the influence mechanism of several key factors of MPR walls,e.g.,the inclination angle of the filler cavity(θ-value),geometry size of the filler cavity(a:b-value)and thermal conductivity of the filler(λf-value),is conducted based on a validated numerical model.Results show that the dynamic thermal behaviors of MPR walls can be significantly improved due to that the radial thermal resistance in the filler cavity of MPR walls can be reduced by 50%,while the maximum extra exterior surface heat loss caused by the optimization measures is only 2.1%.Besides,a better technical effect can be achieved by setting the major axis of the filler cavity towards the room side,where the interior surface heat load/total injected heat first decreases/increases and then increases/decreases with the increase of theθ-value.In particular,the MPR wall withθL=60°can obtain the best performance when other conditions remain the same.Moreover,the performance indicators of MPR walls can be further improved with the increase of the cavity size(a:b-value),while showing a trend of rapid improvement in theλf-value range of 2–5λC and slow improvement increase in theλf-value range of 5–12λC.In addition,the improvement effect brought by optimizing theθ-value is more obvious as the a:b-value orλf-value increases.展开更多
This article focuses on the investigation of the correlation between thermal bridging and various geometric configurations. The article employs QuickField software for conducting three-dimensional steady-state heat tr...This article focuses on the investigation of the correlation between thermal bridging and various geometric configurations. The article employs QuickField software for conducting three-dimensional steady-state heat transfer simulations to investigate the thermal behaviors of diverse geometric shapes. Significantly, this study involves the simulation of four distinct geometries including concrete circular, square, rectangular, and triangular column through an insulated concrete layer while all geometries maintain the consistent surface areas. The simulations yield findings indicating that circular thermal bridging has the best thermal performance, while rectangular thermal bridging displays comparatively the lowest thermal efficiency. Furthermore, the results indicate that alterations in the perimeter of thermal bridge interfaces, while maintaining a constant area, exert a more pronounced influence on the thermal performance of the geometries compared to proportional changes in area while preserving the perimeter. The study’s findings aid building designers and architects in creating more energy-efficient structural and architectural elements by incorporating thermally efficient geometries and forms. .展开更多
The target of traditional thermal conductivity of wall research is the spatial distribution form.In these studies,the change of thermal conductivity with temperature is neglected.Meanwhile,case studies are always used...The target of traditional thermal conductivity of wall research is the spatial distribution form.In these studies,the change of thermal conductivity with temperature is neglected.Meanwhile,case studies are always used.This method needs large computation and it is hard to obtain the optimal result.In order to overcome the problems,a new approach has been put forward in this paper.Different from the traditional approach,the new approach solves an inverse problem under the concept of passive ideal energy-saving buildings to obtain the optimal distribution of heat ability with temperature on an external wall.The result for a typical summer day shows the heat ability distribution of a wall in summer is a staircase.It is similar to the heat pipe.It is also found that the optimal heat transfer property of the external wall is closer to the heat pipe when its heat capacity per square meter(ρc_(p)L)is of extreme value.This study can provide guidance to researchers in building materials.展开更多
The method for calculating wall surface heat storage coefficient was introduced,and the coefficients of several common walls with light-weight external thermal insulation materials and the traditional solid clay brick...The method for calculating wall surface heat storage coefficient was introduced,and the coefficients of several common walls with light-weight external thermal insulation materials and the traditional solid clay brick wall were calculated.In order to study the impact of light-weight external thermal insulation materials,a contrasting experiment was carried out between an external insulated room and an uninsulated room in August,2010,in Chongqing,China.The result shows that outside surface heat storage coefficient of the insulated wall is much less than that of the traditional wall.However,during sunny time,the surface temperature of external walls of the insulated room is obviously higher than that of the uninsulated room.In different orientations,due to different amounts of solar radiation and being irradiated in different time,the contrasting temperature difference(CTD) appears different regularity.In a word,using light-weight external thermal insulation materials has a negative impact on building surrounding thermal environment and people's health.Finally,some suggestions on how to eliminate the impact,such as improving the surface condition of the building envelop,and plating vertical greening,are put forward.展开更多
A green roof is a specialized roof system that supports vegetation growth on rooftops.This technology is rapidly gaining popularity as a sustainable design option for buildings.In order to contribute to an understandi...A green roof is a specialized roof system that supports vegetation growth on rooftops.This technology is rapidly gaining popularity as a sustainable design option for buildings.In order to contribute to an understanding of green roof in regions with cold winters and snow,an on-site experimental investigation was present with a focus on the assessment of green roof performance during the winter.This field experiment took place on a six small buildings during the winter of 2010-2011.The work monitored three buildings with green roofs,two buildings with reference roofs and one building with a bare soil coverage for the roof.These six buildings were identically constructed and instrumented with sensor networks to provide heat flux data through the roofs.The 15 min averaged data were statistically analyzed for a week under the two separate periods,first without a snow cover and second with a snow cover.The results show that the roof type is a significant factor in affecting the thermal performance of these buildings.Most importantly,green roofs reduce heat flow through the roof and thus reduce the heating energy demand during the winter.However,the energy savings for buildings with the green roofs are reduced under snow conditions because the snow diminishes thermal resistance of the roof and increases the heat transfer process through the roofs.展开更多
Multi-dimensional heat transfers modeling is crucial for building simulations of insulated buildings,which are widely used and have multi-dimensional heat transfers characteristics.For this work,state-model-reduction ...Multi-dimensional heat transfers modeling is crucial for building simulations of insulated buildings,which are widely used and have multi-dimensional heat transfers characteristics.For this work,state-model-reduction techniques were used to develop a reduced low-order model of multi-dimensional heat transfers.With hot box experiment of hollow block wall,heat flow relative errors between experiment and low-order model predication were less than 8% and the largest errors were less than 3%.Also,frequency responses of five typical walls,each with different thermal masses or insulation modes,the low-order model and the complete model showed that the low-order model results agree very well in the lower excitation frequency band with deviations appearing only at high frequency.Furthermore,low-order model was used on intersection thermal bridge of a floor slab and exterior wall.Results show that errors between the two models are very small.This low-order model could be coupled with most existing simulation software for different thermal mass envelope analyses to make up for differences between the multi-dimensional and one-dimensional models,simultaneously simplifying simulation calculations.展开更多
After the energy crisis in 1970s,buildings began to be used as a platform for the elements which produce energy from renewable energies to return them into energy producing power plants.This is a safe,clean and econom...After the energy crisis in 1970s,buildings began to be used as a platform for the elements which produce energy from renewable energies to return them into energy producing power plants.This is a safe,clean and economic way to produce energy since the energy is produced where it is needed and they use renewable energy resources.So,it promises hope for the future energy production.Therefore,the aim of this study is to examine buildings which produce electricity by using renewable energy resources and to show that this is one of the safest,cleanest and most economic ways to be used to produce energy in the future.This is done by describing power plants and how buildings are used as power producing stations by the use of renewable energy resources or other energy producing materials,then by examining case studies which are constructed and already being used,case studies which are just a design that have not yet been constructed,and by making projections to the future energy producing techniques that are just a proposal in 2021.In the conclusion,buildings are proposed as the future power plants,either here on earth or on another planet like Mars.展开更多
The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the auth...The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively.The results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude area.The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained.Under the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low altitude.It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition.It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.展开更多
基金Project(51178201) supported by the National Natural Science Foundation of China Project(2011CDB292) supported by the Natural Science Foundation of Hubei Province,China
文摘An active pipe-embedded building envelope, which is an external wall or roof with pipes embedded inside, was presented. This structure may utilize the circulating water in the pipe to transfer heat or coolth inside directly. This kind of structure is named ＂active pipe-embedded building envelope＂ due to dealing with the thermal energy actively inside the structure mass by circulating water. This structure not only deals with thermal energy before the external disturbance becomes cooling/heating load by using the circulating water, but also may use low-grade energy sources such as evaporative cooling, solar energy, and geothermal energy. In the meantime, this structure can also improve the indoor thermal comfort by tempering the internal wall surface temperature variation due to the thermal removal in the mass. This work further presents the thermal performance of this structure under a typical hot summer weather condition by comparing it with that of the conventional external wall/roof with numerical simulation. The results show that this pipe-embedded structure may reduce the external heat transfer significantly and reduce the internal wall surface temperature for improving thermal comfort. This work also presents the effects of the water temperature and the pipe spacing on the heat transfer of this structure. The internal surface heat transfer may reduce by about 2.6 W/mE when the water temperature reduces by 1℃ as far as a brick wall with pipes embedded inside is concerned. When the pipe spacing reduces by 50 mm, the internal wall surface heat flux can also reduce by about 2.3 W/m2.
基金Project(51078127) supported by the National Natural Science Foundation of China
文摘A new facility was presented which can expediently and cheaply measure the transient moisture content profile in multi-layer porous building envelope.Then,a common multi-layer porous building envelope was provided,which was constructed by cement mortar-red brick-cement plaster.With this kind of building envelope installed in the south wall,a well-controlled air-conditioning room was set up in Changsha,which is one of typical zones of hot and humid climate in China.And experiments were carried out to investigate the temperature and moisture distribution in multi-layer building envelope in summer,both in sunny day and rainy day.The results show that,the temperature and humidity at the interface between the brick and cement mortar are seriously affected by the changes of outdoor temperature and humidity,and the relative humidity at this interface keeps more than 80% for a long-term,which can easily trigger the growth of mould.The temperature and humidity at the interface between the brick and cement plaster change a little,and they are affected by the changes of indoor temperature and humidity.The temperature and humidity at the interface of the wall whose interior surface is affixed with a foam plastic wallpaper are generally higher than those of the wall without wallpaper.The heat transfer and moisture transfer in the envelope are coupled strongly.
基金We thank to the China Scholarship Council(CSC)for its financial support to the first author,No.201808120084.
文摘Phase Change Materials(PCMs)have high thermal inertia,and hemp concrete(HC),a bio-based concrete,has strong hygroscopic behavior.In previous studies,PCM has been extensively combined with many materials,however,most of these studies focused on thermal properties while neglecting hygroscopic aspects.In this study,the two materials have been combined into a building envelope and the related hygrothermal properties have been studied.In particular,numerical studies have been performed to investigate the temperature and relative humidity behavior inside the HC,and the effect of adding PCM on the hygrothermal behavior of the HC.The results show that there is a high coupling between temperature and relative humidity inside the HC,since the relative humidity changes on the second and third days are different,with values of 8%and 4%,respectively.Also,the variation of relative humidity with temperature indicates the dominant influence of temperature on relative humidity variation.With the presence of PCM,the temperature variation inside the HC is damped due to the high thermal inertia of the PCM,which also leads to suppression of moisture evaporation and thus damping of relative humidity variation.On the second and third days,the temperature changes at the central position are reduced by 4.6%and 5.1%,compared to the quarter position.For the relative humidity change,the reductions are 5.3%and 5.4%on the second and third days,respectively.Therefore,PCM,with high thermal inertia,acts as a temperature damper and has the potential to increase the moisture buffering capacity inside the HC.This makes it possible for such a combined envelope to have both thermal and hygric inertia.
文摘In recent decades, there has been a great deal of investment in Portugal in the construction of new buildings to the detriment of the rehabilitation of existing ones. As a result, the historic centres of towns and cities are deteriorating, while their suburbs are spreading. One of the main problems affecting the rehabilitation of residential buildings is that it is extremely difficult to accurately estimate the costs involved. Although there are established methods （and technical documents available） to aid the costing of new buildings, there is a lack of official information about the costs of rehabilitation work, particularly as regards the external envelope of buildings. This article demonstrates how to determine rehabilitation costs （with particular emphasis on the envelope of residential buildings） by gathering information from specialized companies, assessing price variability and consulting databases of rehabilitation costs from other countries. It also presents some examples of costing for particular rehabilitation jobs.
基金This manuscript has been authored by UT-Battelle LLC under contract DE-AC05-00OR22725 with the US DOE(Department of Energy).
文摘Today,to describe the thermal performance of the building envelope and its components we use a variation of metrics;such as,R-value,ACH(air exchange rate per hour),SHGC(solar heat gain coefficient)of windows,U-factor etc.None of these performance indicators is meant to represent the overall thermal performance.In this paper,such a metric is introduced,the BEP(building envelope performance)value.Unlike the thermal resistance,typically expressed as an R-value,the BEP-value considers additional elements of heat transfer that affect the energy demand of the building because of exterior and interior(solar)thermal loads:conductive and radiant heat transfer,and air infiltration.To demonstrate BEP’s utility,validation studies were carried out by comparing the BEP-value to theoretical results using whole building energy simulation tools such as EnergyPlus and WUFI Plus.Results show that BEP calculations are comparable to calculations made using these simulation tools and that unlike other similar metrics,the BEP-value accounts for all heat transfer mechanisms that are relevant for the overall energy performance of the building envelope.The BEP-value thus allows comparing envelopes of buildings with different use types in a fair and realistic manner.
文摘The main aim of this paper is to study the effect of building envelope constructed with different materials on thermal comfort of buildings located in Jeddah, Saudi Arabia. Four different buildings constructed with brick, glass, stone, and gypsum are taken into account to study the difference in temperature of the indoor and outdoor environments. Also, this paper explores the heat conducted by walls of different materials with different thicknesses. In addition, survey is conducted among the residents of Jeddah to know their perspective about thermal comfort of buildings. From the study, it is found that building envelope constructed with glass is more effective compared to envelope constructed with other materials of with least thickness of wall. Also, it is found that the envelope constructed with brick is more effective in absorbing the heat provided the thickness of the walls remains the same.
文摘Building envelope is a fence that controls heat exchange between interior and exterior and plays an essential role in providing thermal comfort conditions of residents. In recent years, due to the necessity of conserving energy and also preventing increased environmental pollution, the importance of sustainable construction has been doubled. Checking the problems of thermal behavior of the building envelope materials, and what influences in the heating and cooling loads exerted and energy consumption of buildings, are the questions that this research seeks to answer. In this regard, building information modelling analysis (BIM) has worthy contribution in the completion process of sustainable design;thus using software Design Builder, it is paid attention to simulation of the thermal behavior of two types of defined materials for the building envelope that was designed as a Research Institute of Renewable Energy of Yazd University. For Type 1 materials, two layers of brick have been selected, and for Type 2 a thermal insulation layer also added it. Results of the analysis showed that the use of materials Type 2 in the cooling load %4.8 and in the thermal load %62.5 reduction can be achieved which means reducing the load on active system and thus reducing the initial cost of building. Also reduction in annual energy consumption by almost %2.4 for cooling and %62.9 for heating buildings have been achieved, which makes saving non-renewable energy consumption, and consequently reducing environmental pollution as well as reducing current costs will be established.
基金co-sponsored by the National Natural Science Foundation of China(No.52208103)Fundamental Research Funds for the Central Universities(No.JZ2024HGTB0229)+2 种基金Opening Fund of Anhui Province Key Laboratory of Intelligent Building&Building Energy Saving(No.IBES2024KF05,IBES2024ZR03)Anhui Province University Outstanding Scientific Research and Innovation Team(No.2022AH010021)Scientific Research and Cultivation Project of Anhui Jianzhu University(No.2021XMK04).
文摘Thermally activated building envelopes(TABEs)are multifunctional component that combines structural and energy properties.Based on re-examining the heat charging processes,an arc-shaped metal-fin-enhanced TABE(Arc-finTABE)with directional heat charging features is proposed to optimize the thermal barrier formation process.A comprehensive parameterized analysis is conducted based on a validated mathematical model to explore the influence of 5 fin-structure design parameters and the static insulation thickness.Results verified that the directional charging strengthening fins can improve transient thermal performances of Arc-finATBE and enlarge horizontal and vertical sizes of the thermal energy accumulation area surrounding the pipeline,while the maximum growth in extra heat loss is less than 3.17%.From the perspective of promoting heat injection into expected areas,the straight main fin configurations with the angle of main fins of 30°,shank length ratio of 0.4 and no leftward mounted fins are preferred in load-reduction mode,while the angle of main fins of 150°,shank length ratio of 0.8 and multiple fin designs,especially with one of the main fins horizontally toward the indoor side,are more favorable in auxiliary-heating mode.Besides,it is recommended to add one arc-shaped branch fin to each main fin to achieve a balance between performance improvement and material usage.Moreover,branch fins with larger arc angles are preferred in auxiliary-heating mode,while smaller arc angles are conducive to injecting heat into the wall along main fins in load-reduction mode and preventing the heat near the inner surface from being extracted.Under the direct influence of the strengthened invisible thermal barrier,Arc-finTABEs can reduce the amount of static insulation layer by 20%–80%while achieving equivalent thermal performances as conventional high-performance walls.
文摘We have spent the last 40-50 years working for energy efficiency in our buildings, and we have done so by increasing the performance of the heating, cooling, lighting, and ventilation systems we use. Only recently have we realized the importance of the building envelope in this endeavor. The spaces within a building are created to support the purpose and programs of that building, and it is the envelope made up of the walls, windows, doors, roof, skylights, and floor that protect and shelter those programs and purpose. In this article we will explore various components of the building envelope and discuss ways to achieve optimal energy use.
文摘Research has shown the environmental benefits of green envelopes,as well as performance in terms of energy efficiency.To date,there is no analysis of the economic sustainability of these systems,which has allowed the realization of a few,albeit very well known,examples.The research has identified a green modular system integrated into the building envelope,designed to facilitate installation and maintenance,with competitive performance compared to other existing solutions;a system that wants to improve performance and flexibility of vertical applications,experimented on buildings,on the market,and able to adapt,above all,to the needs of the building process.It is important to distinguish architectural aesthetic requirements from those of the building process;the former aim to have an authentic vertical garden,with different kinds of plants where nature dictates the rules,the latter aims to achieve the economic sustainability of vertical greenery systems.This paper provides an analysis of a technique based on the installation of plant bearing modular panels with turf on substructures also provided with a micro-irrigation system,which allows the construction of a modular coating,characterized by reduced thickness,that can also be integrated with other materials;installation is quick and simple,since the panel comes perfectly planted on site.In addition to that it allows,from a botanical point of view,resorting to types of grass selected with a view to climate,exposure,environmental adaptability,color and shape.A comparative analysis of this green façade is also presented compared to other existing case studies,from a constructive and managerial point of view,highlighting both its economic and architectural advantages.
文摘The key role of the building envelope in achieving building energy efficiency and indoor comfort for the user has been long established.The most promising-and innovative-strategy for the building envelope of the future is based on a dynamic,active and integrated solution,that is able to optimize the thermal performance,integrate the active elements and systems,and exploit energy from renewable sources.This paper illustrates the most relevant results of a decade-long research activity carried out on active and integrated building envelopes at the Politecnico di Torino,in which numerical analyses and experimental campaigns,involving test cells and field monitoring,have been performed.The overall performances of different façade modules and the thermo-physical behaviour of various components,under different operating strategies,are presented and discussed.The analysis provides information on the contribution of each subsystem,e.g.glazing,sun-shading devices,natural and mechanical ventilation,...to the achieved energy efficiency and the overall performances of different typologies of Double-Skin Façades(DSFs)and Advanced Integrated Façades(AIFs).
基金supported by the Pennsylvania Housing Research Center(PHRC).
文摘This research is mainly focused on the experimental measurement of R-value by several different models.Building energy consumption accounts for about 40%of the total energy use in the U.S,and therefore accurate energy simulation is desired.The R-value is one of the key parameters that can influence the energy simulation results and therefore is of great importance.The Average Model has long been the most widely accepted method to measure the thermal properties of building components.However,its steady-state assumption and dependence on temperature difference limit its use especially for in-situ measurement.In this study,several dynamic models,including the Pentaur Model and R-C Network Models,are studied with test data obtained from a series of hot box tests performed in the Building Enclosure Testing Laboratory.The results show that the 3R2C model has the best performance and a desirable stability of accuracy with respect to different levels of temperature difference,and therefore is recommended for practical measurement.The results also indicate that unlike the Average Model,the accuracy of dynamic models does not necessarily depend on the level of temperature difference.
基金the National Natural Science Foundation of China(No.52208103)the Youth Fund of Anhui Natural Science Foundation(No.2208085QE163 and No.2108085QE241)+2 种基金the Anhui Province University Outstanding Scientific Research and Innovation Team(No.2022AH010021)the Opening Fund of State Key Laboratory of Green Building in Western China(No.LSKF202303)the Housing and Urban-Rural Construction Science and Technology Program of Anhui Province(No.2022-YF062).
文摘In the context of racing to carbon neutrality,the pipe-embedded building system makes the opaque envelopes gradually regarded as the multi-functional element,which also provides an opportunity for thermal insulation solutions to transform from high to zero-carbon attributes.Based on the re-examination of the heat transfer process of conventional pipe-embedded radiant(CPR)walls,the modular pipe-embedded radiant(MPR)wall integrated with thermal diffusive materials is proposed to enhance the heat transfer capacity of CPR walls in the direction parallel to the wall surface,thereby forming a more stable and continuous invisible thermal barrier layer inside the opaque envelopes.A comprehensive thermal and energy-saving analysis study regarding the influence mechanism of several key factors of MPR walls,e.g.,the inclination angle of the filler cavity(θ-value),geometry size of the filler cavity(a:b-value)and thermal conductivity of the filler(λf-value),is conducted based on a validated numerical model.Results show that the dynamic thermal behaviors of MPR walls can be significantly improved due to that the radial thermal resistance in the filler cavity of MPR walls can be reduced by 50%,while the maximum extra exterior surface heat loss caused by the optimization measures is only 2.1%.Besides,a better technical effect can be achieved by setting the major axis of the filler cavity towards the room side,where the interior surface heat load/total injected heat first decreases/increases and then increases/decreases with the increase of theθ-value.In particular,the MPR wall withθL=60°can obtain the best performance when other conditions remain the same.Moreover,the performance indicators of MPR walls can be further improved with the increase of the cavity size(a:b-value),while showing a trend of rapid improvement in theλf-value range of 2–5λC and slow improvement increase in theλf-value range of 5–12λC.In addition,the improvement effect brought by optimizing theθ-value is more obvious as the a:b-value orλf-value increases.
文摘This article focuses on the investigation of the correlation between thermal bridging and various geometric configurations. The article employs QuickField software for conducting three-dimensional steady-state heat transfer simulations to investigate the thermal behaviors of diverse geometric shapes. Significantly, this study involves the simulation of four distinct geometries including concrete circular, square, rectangular, and triangular column through an insulated concrete layer while all geometries maintain the consistent surface areas. The simulations yield findings indicating that circular thermal bridging has the best thermal performance, while rectangular thermal bridging displays comparatively the lowest thermal efficiency. Furthermore, the results indicate that alterations in the perimeter of thermal bridge interfaces, while maintaining a constant area, exert a more pronounced influence on the thermal performance of the geometries compared to proportional changes in area while preserving the perimeter. The study’s findings aid building designers and architects in creating more energy-efficient structural and architectural elements by incorporating thermally efficient geometries and forms. .
文摘The target of traditional thermal conductivity of wall research is the spatial distribution form.In these studies,the change of thermal conductivity with temperature is neglected.Meanwhile,case studies are always used.This method needs large computation and it is hard to obtain the optimal result.In order to overcome the problems,a new approach has been put forward in this paper.Different from the traditional approach,the new approach solves an inverse problem under the concept of passive ideal energy-saving buildings to obtain the optimal distribution of heat ability with temperature on an external wall.The result for a typical summer day shows the heat ability distribution of a wall in summer is a staircase.It is similar to the heat pipe.It is also found that the optimal heat transfer property of the external wall is closer to the heat pipe when its heat capacity per square meter(ρc_(p)L)is of extreme value.This study can provide guidance to researchers in building materials.
基金Project(2011BAJ03B13) supported by the National Key Technologies R&D Program of China
文摘The method for calculating wall surface heat storage coefficient was introduced,and the coefficients of several common walls with light-weight external thermal insulation materials and the traditional solid clay brick wall were calculated.In order to study the impact of light-weight external thermal insulation materials,a contrasting experiment was carried out between an external insulated room and an uninsulated room in August,2010,in Chongqing,China.The result shows that outside surface heat storage coefficient of the insulated wall is much less than that of the traditional wall.However,during sunny time,the surface temperature of external walls of the insulated room is obviously higher than that of the uninsulated room.In different orientations,due to different amounts of solar radiation and being irradiated in different time,the contrasting temperature difference(CTD) appears different regularity.In a word,using light-weight external thermal insulation materials has a negative impact on building surrounding thermal environment and people's health.Finally,some suggestions on how to eliminate the impact,such as improving the surface condition of the building envelop,and plating vertical greening,are put forward.
基金Project(CMMI-0900486) supported by the National Science Foundation (NSF) in the Division of Civil, Mechanical, and Manufacturing Innovation, USA
文摘A green roof is a specialized roof system that supports vegetation growth on rooftops.This technology is rapidly gaining popularity as a sustainable design option for buildings.In order to contribute to an understanding of green roof in regions with cold winters and snow,an on-site experimental investigation was present with a focus on the assessment of green roof performance during the winter.This field experiment took place on a six small buildings during the winter of 2010-2011.The work monitored three buildings with green roofs,two buildings with reference roofs and one building with a bare soil coverage for the roof.These six buildings were identically constructed and instrumented with sensor networks to provide heat flux data through the roofs.The 15 min averaged data were statistically analyzed for a week under the two separate periods,first without a snow cover and second with a snow cover.The results show that the roof type is a significant factor in affecting the thermal performance of these buildings.Most importantly,green roofs reduce heat flow through the roof and thus reduce the heating energy demand during the winter.However,the energy savings for buildings with the green roofs are reduced under snow conditions because the snow diminishes thermal resistance of the roof and increases the heat transfer process through the roofs.
基金Project(51178023)supported by the National Natural Science Foundation of China
文摘Multi-dimensional heat transfers modeling is crucial for building simulations of insulated buildings,which are widely used and have multi-dimensional heat transfers characteristics.For this work,state-model-reduction techniques were used to develop a reduced low-order model of multi-dimensional heat transfers.With hot box experiment of hollow block wall,heat flow relative errors between experiment and low-order model predication were less than 8% and the largest errors were less than 3%.Also,frequency responses of five typical walls,each with different thermal masses or insulation modes,the low-order model and the complete model showed that the low-order model results agree very well in the lower excitation frequency band with deviations appearing only at high frequency.Furthermore,low-order model was used on intersection thermal bridge of a floor slab and exterior wall.Results show that errors between the two models are very small.This low-order model could be coupled with most existing simulation software for different thermal mass envelope analyses to make up for differences between the multi-dimensional and one-dimensional models,simultaneously simplifying simulation calculations.
文摘After the energy crisis in 1970s,buildings began to be used as a platform for the elements which produce energy from renewable energies to return them into energy producing power plants.This is a safe,clean and economic way to produce energy since the energy is produced where it is needed and they use renewable energy resources.So,it promises hope for the future energy production.Therefore,the aim of this study is to examine buildings which produce electricity by using renewable energy resources and to show that this is one of the safest,cleanest and most economic ways to be used to produce energy in the future.This is done by describing power plants and how buildings are used as power producing stations by the use of renewable energy resources or other energy producing materials,then by examining case studies which are constructed and already being used,case studies which are just a design that have not yet been constructed,and by making projections to the future energy producing techniques that are just a proposal in 2021.In the conclusion,buildings are proposed as the future power plants,either here on earth or on another planet like Mars.
基金supported by the National Natural Science Foundation of China(52078314)。
文摘The external surface heat transfer coefficient of building envelope is one of the important parameters necessary for building energy saving design,but the basic data in high-altitude area are scarce.Therefore,the authors propose a modified measurement method based on the heat balance of a model building,and use the same model building to measure its external surface heat transfer coefficient under outdoor conditions in Chengdu city,China at an altitude of 520 m and Daocheng city at an altitude of 3750 m respectively.The results show that the total heat transfer coefficient(h_(t))of building surface in high-altitude area is reduced by 34.48%.The influence of outdoor wind speed on the convective heat transfer coefficient(h_(c))in high-altitude area is not as significant as that in low-altitude area.The fitting relation between convection heat transfer coefficient and outdoor wind speed is also obtained.Under the same heating power,the average temperature rise of indoor and outdoor air at highaltitude is 41.9%higher than that at low altitude,and the average temperature rise of inner wall is 25.8%higher than that at low altitude.It shows that high-altitude area can create a more comfortable indoor thermal environment than low-altitude area under the same energy consumption condition.It is not appropriate to use the heat transfer characteristics of the exterior surface of buildings in low-altitude area for building energy saving design and related heating equipment selection and system terminal matching design in high-altitude area.
