An active pipe-embedded building envelope for utilizing low-grade energy sources

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.

Development of experimental study on coupled heat and moisture transfer in porous building envelope

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.

Simulation of the Hygrothermal Behavior of a Building Envelope Based on Phase Change Materials and a Bio-Based Concrete

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.

Building Envelope Rehabilitation Costs： Determination and Variability

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.

Performance Assessment of the Overall Building Envelope Thermal Performance-Building Envelope Performance(BEP)Metric

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.

Preliminary Study to Show the Effect of Building Envelope Materials on Thermal Comfort of Buildings Located in Hot Humid Climate

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.

Analysis of Thermal Behavior of Materials in the Building Envelope Using Building Information Modeling (BIM)—A Case Study Approach

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.

Investigation the Correlation between Thermal Bridging and Geometries in Concrete Buildings

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. .

A Theory on Increasing the Heat Transfer Performance of Building Wall

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.

Impact of light-weight external thermal insulation materials on building surrounding thermal environment in summer

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.

Assessment of green roof performance for sustainable buildings under winter weather conditions

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.

Building dynamic thermal simulation of low-order multi-dimensional heat transfer

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.

Future of Architecture: Buildings as Power Plants

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.

TOWARDS AN ACTIVE, RESPONSIVE, AND SOLAR BUILDING ENVELOPE

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).

INNOVATIVE FAÇADES Lightweight and Thin Systems with High Inertia for the Thermal Comfort Application in Office Buildings in Southern Europe

ABSTRACT This research demonstrates that lightweight,thin façade systems with innovative materials can combine a higher thermal inertia with a lower energy demand for heating and cooling as compared to massive façades.It is therefore very possible to use innovative light materials(originally developed in and for Central Europe)also in Southern Europe,where the main problem is the energy demand for cooling in summer(in contrast to the energy demand for heating in northern latitudes).Three of those systems were selected and investigated for three different climatic conditions in middle latitudes with respect not only to static energy performance parameters imposed by the Italian legislation(thermal transmittance U and superficial mass M_(S)),but also checking two dynamic energy performance parameters defined particularly for non massive structures(phase delay f_(a) and decrement factorφ).Additionally a recently introduced by European standard UNI-EN-ISO-13786 parameter(periodic thermal transmittance Y_(ia))was considered.Verification of the energy performance of the façade systems was performed using thermodynamic simulations.The results are:•Development and application of an experimental/simulation procedure for the evaluation of the thermal performance of façade systems in use(annual energy demand:[kWh],costs[€]and.CO_(2) produced[kg]).•Demonstration that energy performance of new lightweight systems is better than the one of a traditional Italian reference façade system with high MS.•Proposal of possibilities for improving the analyzed façade systems with respect to their application in middle latitudes.•Development of design criteria for the application of the analyzed façades in three climatic zones in Italy.

Dynamic thermal performance and energy-saving potential analysis of a modular pipe-embedded building envelope integrated with thermal diffusive materials

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.

Comparative Experimental Study on Heat Transfer Characteristics of Building Exterior Surface at High and Low Altitudes

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.

Comprehensive energy, economic, environmental assessment of a building integrated photovoltaic-thermoelectric system with battery storage for net zero energy building

To realize the goal of net zero energy building(NZEB),the integration of renewable energy and novel design of buildings is needed.The paths of energy demand reduction and additional energy supply with renewables are separated.In this study,those two are merged into one integration.The concept is based on the combination of photovoltaic,thermoelectric modules,energy storage and control algorithms.Five types of building envelope systems,namely PV+TE(S1),Grid+TE(S2),PV+Grid+TE(S3),PV+Battery+TE(S4)and PV+Grid+Battery+TE(S5)are studied,from aspects of energy,economic and environmental(E3)performance.The new envelope systems can achieve thermal load reduction while providing additional cooling/heating supply,which can promote advance of NZEBs.It is found that there is a typical optimum setting of thermal energy load for each one of them with minimum annual power consumption.Except for the S1 system,the rest can realize negative accumulated power consumption in a year-round operation,which means the thermal load of building envelope could be zero.The uniform annual cost for S1 to S5 under interest rate of 0.04 are 19.78,14.77,23.83,60.53,64.94$/m2,respectively.The S5 system has the highest environmental effect with 3.04 t/m2 reduction of CO_(2) over 30 years of operation.

nfluence of envelope insulation materials on building energy consumption

In this paper, the influence of different external wall insulation materials on the energy consumption of a newly built apartment in Germany is investigated. Three types of insulation materials commonly used in Germany including mineral fiber, polyurethane, and vacuum insula- tion panel are chosen for the case studies. An energy analysis model is established to clarify the primary energy use for production of the insulation materials and for building space heating. The calculation results show that the energy consumption for insulation material production increases with the insulation thickness, whereas the energy use for space heating decreases with the insulation thickness. Thus, there exists an optimum thickness to get the lowest total energy consumption for each kind of insulation material. The ascending order of the total energy consumption of the three materials is mineral fiber, polyurethane, and vacuum insulation panel. However, the optimum insulation thicknesses for the three insulation materials show a verse order at a certain heat transfer coefficient of the base envelope. The energy payback time （EPT） is proposed to calculate the payback time of the primary energy use for insulation material production. Mineral fiber has the shortest time, followed by poly- urethane and vacuum insulation panel. The EPTS is 10, 19 and 21 years, respectively when the heat transfer coefficient of the base envelope is 0.2 W/（m2.K）. In addition, the simulated results show that the theoretical value and the simulated value are basically identical.

Microstructure and Characterization of Capric-stearic Acid/Modified Expanded Vermiculite Thermal Storage Composites

In order to improve the thermal storage capacity of expanded vermiculite（EV） based formstable composite PCM（FS-PCM） via organic modification of EV, first, EV was modified with a sodium stearate（Na St） as surface modifier, and organic EV（OEV） with hydrophobicity and higher adsorption capacity for fatty acid was obtained. A novel capric-stearic acid eutectic（CA-SA）/OEV FS-PCM with high thermal storage capacity was then developed. OEV and CA-SA/OEV were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FTIR）, differential scanning calorimetry（DSC）, thermal gravimetry（TG）, and thermal cycling test. Results showed that OEV has obvious hydrophobicity and a higher adsorption capacity for fatty acid. Its adsorption ratio has increased by 48.71% compared with that of EV. CA-SA/OEV possesses high thermal storage density（112.52 J/g）, suitable melting temperature（20.49 ℃）, good chemical compatibility, excellent thermal stability and reliability, indicating great application potential for building energy efficiency. Moreover, organic modification of inorganic matrix may offer novel options for improving its adsorption capacity for organic PCMs and increasing heat storage capacity of corresponding FS-PCMs.