High-performance Building Envelope Research Articles

Solar neighborhoods: the impact of urban layout on a large-scale solar strategies application

The article addresses the challenges of evaluating energy performance in different neighborhood settings under various energy efficiency measures and proposes a methodology for selecting appropriate solar strategies on a neighborhood scale. The study selects five representative neighborhoods from various climatic zones with different building and street layouts. The proposed methodology involves a systematic three-step multi-domain workflow for implementing energy efficiency measures and solar strategies in the existing neighborhoods. The first step involves typical energy performance simulation, the second step involves energy simulation using high performance building envelope, and the third step involves the addition of solar strategies in combination with retrofitting materials to achieve net-zero status. The results of the study show that modifying the building envelope leads to a significant reduction in energy consumption, with up to 60% reduction observed. The study also finds that the optimal mix of solar strategies depends strongly on the type of neighborhood, its street layouts, and the type of buildings. The article highlights the importance of considering these factors when implementing solar strategies on a neighborhood scale to achieve energy efficiency and net-zero status. It provides urban planners with a systematic decision-making approach to evaluate and optimize neighborhoods to achieve net-zero energy status.

A French Residential Retrofit toward Achieving Net-Zero Energy Target in a Mediterranean Climate

Cities are paying more attention to building energy use and carbon footprint for attaining sustainability. Within this building sector, there is a growing attention toward development and adoption of energy efficient retrofit strategies. Plagued by the lack of efforts in achieving comprehensive energy efficient retrofit solution sets (passive, active, and renewable energy systems), the authors acknowledge the concept of NZEB toward achieving energy efficiency by 2050. Toward this end, a numerical energy simulation modeling is carried out to retrofit an existing French “Puccini house” using ‘passive, energy efficient building systems and renewable energy’ strategies toward an NZEB target in the Mediterranean climate of Nice. Using Design builder 7.0, the simulated baseline energy model (Case A) is retrofitted through variations in the proposed energy efficient retrofit measures using two case scenarios (Case B: passive retrofit; Case C: energy-efficient building) to achieve NZEB (Case D). Assessing the performance of energy efficient retrofits using % energy reduction, the implementation of a high-performance building envelope is achieved using a thermally insulated external wall (46.82%), upgraded airtightness (20.39%), thermally insulated pitched roof component (33.03%), and high-performance window type—a glazing system (3.35%) with maximized window-to-wall ratio (5.53%). The maximum energy-saving retrofit solutions provide an ambitious reduction in energy consumption by approximately 90% from the baseline. A deep retrofitting of the French house meets the NZEB targets, as it reduces the baseline energy consumption from 194.37 kWh/m2/year to 23.98 kWh/m2/year using both passive and active strategies. The remaining energy demand is met by the integration of on-site PV panels (EUI= −27.71 kWh/m2/year), which achieve an increase in energy production by 15.5%, while returning energy back to the grid (−3.73 kWh/m2/year). Findings of this study serve as a guideline for retrofitting traditional French single-family residences, while contributing toward the NZEB goal.

Post-consumer waste recycling for high performance building envelopes in cold climates: Assessing energy and environmental impacts

This paper examines selected post-consumer waste materials for use in the building envelope including end of life tires, polyethylene terephthalate (PET) bottles and paper/cardboard fibres. Three use types within the envelope are analysed according to uses in existing literature: thermal mass, insulation, and interior panelling. The materials are simulated in EnergyPlus, within a high performing residential base case located in Calgary, Alberta. The associated embodied energy and global warming potential of each material scenario are evaluated in OpenLCA.Most cases, excluding tire chip insulation, yield annual heating and cooling loads within a 10% margin of the base case, making them suitable for high performing buildings. Thermal mass components which prioritise reuse and undergo minimal processing such as whole earth-filled tires and whole PET bottles set in concrete blocks, are most effective at mitigating base case impacts. These cases result in a reduction of embodied energy and global warming potential by up to 70%, and lifetime energy by up to 40–50% when compared against an envelope using conventional construction materials.

Comprehensive Carbon Emission and Economic Analysis on Nearly Zero-Energy Buildings in Different Regions of China

Considering the comprehensive effect of building carbon emissions, cost savings is of great significance in nearly-zero-energy buildings (NZEBs). Previous research mostly focused on studying the impact of technical measures in pilot projects. The characteristics of different cities or climate zones have only been considered in a few studies, and the selection of cities is often limited. At times, only one city is considered in each climate zone. Therefore, this study selected 15 cities to better cover climate zone characteristics according to the variation in weather and solar radiation conditions. A pilot NZEB project was chosen as the research subject, in which the energy consumption was monitored and compared across different categories using simulated values by EnergyPlus software. Various NZEB technologies were considered, such as the high-performance building envelope, the fresh air heat recovery unit (FAHRU), demand-controlled ventilation (DCV), a high-efficiency HVAC and lighting system, daylighting, and photovoltaic (PV). The simulated carbon emission intensities in severe cold, cold, and hot summer and cold winter (HSCW) climate zones were 21.97 kgCO2/m2, 19.60 kgCO2/m2, and 15.40 kgCO2/m2, respectively. The combined use of various NZEB technologies resulted in incremental costs of 998.86 CNY/m2, 870.61 CNY/m2, and 656.58 CNY/m2. The results indicated that the HSCW region had the best carbon emission reduction potential and cost-effectiveness when adopting NZEB strategies. Although the incremental cost of passive strategies produced by the envelope system is higher than active strategies produced by the HVAC system and lighting system, the effect of reducing the building’s heating load is a primary and urgent concern. The findings may provide a reference for similar buildings in different climate zones worldwide.

Summer performance of a naturally ventilated double-skin facade with adjustable glazed louvers for building energy retrofitting

Facade energy retrofitting marks an important step toward a low-carbon building industry. As a high-performance building envelope, the double-skin facade is increasingly applied to existing buildings with proven effectiveness. To improve energy efficiency and solve the lingering overheating problems in summer, a new type of double-skin façade (DSF) integrated with adjustable glazed louvers is proposed. Experimental investigations were conducted in a Chinese city with a typical temperate continental climate, covering basic configurations, thermal optimizations, operation strategies, and energy performance. The study demonstrated that cavity ventilated and interior ventilated configurations perform best during daytime and nighttime, respectively. The open configuration of the external skin improved the daytime cavity ventilation by leveraging wind pressure instead of thermal buoyancy. It also allowed cavity height to be lowered, giving DSF the prospect of application to buildings with low floor-to-floor height. While tilted louvers reduced cavity ventilation, they avoided reflecting sunlight into the room and gaining heat. The tilt angle proposed is equal to the noon solar altitude angle in late summer. During the nighttime, the louver skin significantly improved indoor ventilation, but a reasonable way to open internal windows is also needed. Additionally, switching between different configurations based on the dynamic, localized temperature thresholds maximized climate responsiveness and indoor comfort while minimizing cooling loads. Compared with the conventional design, the optimized louver-type DSF delivered significant energy savings of 11.9% and 5% in summer, daytime and nighttime, respectively, successfully reducing the overheating risks.

Energy and environmental assessment of high-performance building envelope in cold climate

This research assesses the energy performance and environmental damages of a high thermal performance building envelope (HTPBE) designed for cold-climate regions compared to the conventional stud wall (baseline) using the life cycle assessment (LCA) method. Four types of wall assemblies with two different thermal resistance (R-values 17 and 50) are assessed and compared with the baseline with R-value 17. The declared unit of the LCA study is the envelope walls used in the conditioned area of a two-storey building in Calgary, Canada. HTPBE walls analyzed in this work include Double stud walls, Structural Insulated Panels (SIP), and Insulated Concrete Form (ICF). Results show that using R-50 HTPBE can decrease about 85 % of the HVAC energy consumption, which brings 80% natural gas saving compared to the baseline. The analysis also shows that CO2 emissions for Double-Stud Wall (DSW) range between 5438 and 10014 kg CO2 eq at the product stage. These values range 9492 and 47618 kg CO2 eq for Structural Insulated Panels (SIP) that may use different insulations (expanded polystyrene-EPS- and extruded polystyrene-XPS). Also, the CO2 emissions of ICF are between 9200 and 22600 kg CO2 eq at the product stage. Comparing the kg CO2 emissions of scenarios to their weights shows that ICF R-17 and R-50 have the lowest CO2 emissions compared with other R-17 and R-50 scenarios. Other environmental damages of the scenarios are also discussed in the research. The balance of CO2 emissions and the mitigated CO2 emissions caused by the saved energy in R-50 HTPBEs shows that they are reliable options to be implemented in cold climates.

LCA of Primary Embodied Energy and Carbon emissions of a Commercial High Performance Building Structure and Envelope

The Building’s material embodied energy plays major role in Carbon Emissions at its production stage. Assessment of Carbon emissions at initial stages for a high performance commercial building is overlooked and the building life cycle has not found an eminent place in the country mandatory norms. An early LCA can be instrumental in taking key decisions in design and material choice to lower building Carbon emissions. This paper aims at comprehensively evaluating and analyzing a fully glazed Certified high performance Office building in Gurgaon, Haryana. Process based Life Cycle Assessment of Building Envelope and Structure for Embodied energy and Carbon emissions is done by applying recently published Indian Database. The Building is modelled using Autodesk Revit Architecture for Bill of quantities extraction. Thereafter, LCA is done in tabular format as per Global standards for two cases, Base case with conventional material and As-built case with used material. Major reductions in emissions are due to Building Envelope material and not Structure. Concrete and Steel are major contributors. Fly Ash block and Gypsum plaster play major role in carbon emission reduction whereas double glazing, Aluminum and ACP contribute towards increasing emissions. Analysis done at early stages can be beneficial in exploring more design optimized techniques that are less Carbon intensive.

Experimental study and multi-objective optimisation of a novel integral thermoelectric wall

The development of a high-performance building envelope is critical to the improvement of building energy efficiency. As the building-integrated thermoelectric envelope (BITE) has a complex structure, development of a simple and practical thermoelectric wall is relevant. Therefore, this study proposes an integral thermoelectric wall (ITEW) with a simple structure that can easily be integrated into a building wall. The ITEW not only eliminates the heat losses or gains of the wall but also provides indoor cooling and heating capacity. A theoretical model of the ITEW was first established and verified using detailed experiments. To realise the highest performance of the ITEW, the optimal ranges of five key parameters—the direct current, number of PN couples, thermoelectric element leg length, thermoelectric element cross-sectional area, and heat dissipation condition—were determined. Thereafter, taking these value ranges as constraints, the Non-dominated Sorting Genetic Algorithm-II was used to perform a multi-objective optimisation in summer and winter conditions. The results show that the cooling and heating performances of the ITEW can be simultaneously improved. The cooling coefficient of performance ranged from 2 to 7, and the cooling capacity per unit area ranged from 2 to 70 W/m2. Meanwhile, the heating coefficient of performance ranged from 1 to 8 and reached values greater than 4 under conventional building heat load demand. The results of this study, therefore, establish a foundation for the development and application of the ITEW system.

Analysis of green building performance in cold coastal climates: An in-depth evaluation of green buildings in Dalian, China

This study described here evaluated certified green building projects in Dalian, a typical coastal city in a cold region of China, from 2008 to 2017. Of 16 surveyed cases in Dalian, 73% adopted a high-performance building envelope system. Energy-saving technologies were favored and demonstrated worthwhile economic benefits. In 80% of the cases high-performance green materials had been used. Resource-saving technologies also were widely adopted. In addition to analyzing all the data collected, the study under-took an in-depth analysis of one building. A representative three-star green public building in Dalian, China, was chosen as a case study for analyzing the energy consumption and operating performance. The study found that energy use intensity of the case-study building is 68.02 kW-hours per square meter per year(kWh/(m2・a)). It saves 44.14 kWh/m2・a compared with a conventional building in the same climate, thanks to its energy efficiency systems and integration of renewable energy. The water consumption of the building when operating was 0.41 cubic meter per square meter(m3/m2) per year, which is even lower than the design value. The case-study building also demonstrated good indoor environmental quality throughout different seasons. Finally, practical methods and suggestions were derived from evaluating and discussing effective technologies in the 16 buildings surveyed. The research led to recommendations for developing green buildings in cold and coastal climates. It also provides a substantial guidance for the energy-saving design of green buildings and the application of appropriate technologies in cold coastal cities.

Performance evaluation of a novel building envelope integrated with thermoelectric cooler and radiative sky cooler

Heat loss or heat gain through building envelopes accounts for a large part of heating or cooling loads. The development of high-performance building envelopes is the key towards building energy efficiency. In this study, a novel building envelope integrated with thermoelectric cooler and radiative sky cooler (TEC-RSC) was proposed, not only for the elimination of heat gain through itself but also for space cooling. Considering the mismatched heat flux generated by radiative sky cooler and that by thermoelectric cooler, the spacing of thermoelectric elements in TEC-RSC was redesigned. To evaluate the performance of TEC-RSC, a global sensitivity analysis was conducted based on the TEC-RSC model. Four key parameters including direct current, area enlargement coefficient, thermoelectric element height and cross-sectional area were identified and their combined effects on TEC-RSC were analyzed. Through optimization design, the TEC-RSC can provide a cooling capacity of 25.49 W/m2 with a COP of 2.00 under the condition of global solar radiation of 1000 W/m2, ambient temperature of 35 °C and outdoor relative humidity of 60%. Further study shows that it can provide a cooling capacity of 35.05 W/m2 with an averaged COP of 3.01 in typical hot climate regions.

Optimization of passive solar design and integration of building integrated photovoltaic/thermal (BIPV/T) system in northern housing

In the Canadian north, the cost of space heating is very high due to the harsh weather, its remoteness, lack of transportation, and dependency on the high cost of fossil fuel imported from the South. Since the North has an abundance of solar energy, significant energy savings with some added construction cost in houses could be achieved by applying high-performance building envelopes and solar design strategies. The objective of this paper is to investigate the potential of both passive and active solar design strategies in improving the energy efficiency of northern housing. Firstly, a reference house representing a typical single-family home in the North is modeled using EnergyPlus, and the key passive design parameters are optimized to minimize life-cycle cost. Then, the air-based building integrated photovoltaic/thermal (BIPV/T) system is applied to the optimized house and integrated with HVAC systems. It is found that optimal passive solar design can reduce the heating energy demand by 42% with an incremental cost of 8% for Yellowknife and by 27% without incurring an incremental cost for Kuujjuaq. Integrating BIPV/T with HVAC systems can reduce the defrost time of heat recovery ventilator (HRV), extend the working hours and improve the COP of air source heat pump (ASHP). The reduction in the total energy consumption is in the range of 1.4%–3.0% by integrating HRV and 0.3%–0.6% by integrating ASHP due to the mis-match of solar availability and heating energy demand. To maximize the utilization of solar energy available, the optimal use of thermal energy recovered from BIPV/T system in northern housing requires further investigation.

LCC-based framework for building envelope and structure co-design considering energy efficiency and natural hazard performance

This paper presents a life-cycle cost (LCC) informed co-design framework for building structures and envelope systems, holistically considering the influences of energy and natural hazard performance. The proposed method is consisted of a two-stage design and decision-making process, aiming to provide a quantitative guideline for building's structural and envelope co-design based on the its geographic locations. First, the building's structural configuration and envelope type are selected based on the life cycle cost. Then, the long-term cost effectiveness of various energy-saving building envelope options (e.g., high-performance glazing and insulation) is evaluated to refine the envelope design. The proposed co-design framework was demonstrated through the case study of a medium-size office building archetype in three locations with distinct climate conditions and seismic activities (i.e., Los Angeles, Memphis, and Boston). The results highlighted the interplay between building's structural (seismic) performance and the cost-effectiveness of energy-saving design options – e.g., for buildings located in high-seismic regions, seismic enhancing designs greatly reduce the paybak period of high performance building envelope by reducing the seismic loss; whereas for buildings located in regions with cold climate and low seismic risk such as Boston, spatial frame with high insulation building envelope shows the lowest LCC.

Assessing energy and emissions savings for space conditioning, materials and transportation for a high-density mixed-use building

This paper introduces a combined framework for the analysis of building-related and transport-related emissions, to allow the comparison of a new high-density mixed-use development concept with traditional urban development patterns. The framework accounts for the energy and emissions arising from the operation of the building, the materials needed to build it, and the transportation of the residents. This provides a novel means to compare the impact of urban form on both building-related and transport-related emissions simultaneously. The building analysis performs detailed building energy simulations and embodied energy calculations. The transportation analysis estimates emissions reductions from eliminating personal vehicle trips through the mixed-use nature of the building, provision of an electric vehicle car sharing fleet, and a public transit hub with a rapid transit line. The framework is used to assess the new concept, referred to as a ‘Mothership’, which provides a potential holistic solution to urban sprawl through high-density mixed-use development that meets the needs of 10,000 people. It includes a high-performance building envelope, advanced energy systems, a public transportation hub and electric car sharing fleet. The analysis compares this method of development to the ‘urban sprawl’ that has characterized new development in North America. The comparison is performed for two case studies in British Columbia, Canada. Results show that the Mothership could reduce operational and embodied emissions by 73% and transportation emissions by 58% compared to low-density suburban development. A key takeaway is that transportation and embodied emissions become much more significant as operational emissions are reduced through high performance building design and clean electricity.

Embodied and Operational Energy Analysis of Passive House–Inspired High-Performance Residential Building Envelopes

Abstract High-performance building envelopes are designed to achieve target reductions in operational energy (OE). However, these wall assemblies often require initial, upfront investments in mater...

Evaluation of the energy performance of a net zero energy building in a hot and humid climate

In the past 20 years, the U.S. Army has made significant progress in making their facilities more energy efficient. Currently, the Army is required by law to eliminate fossil fuel use in new and renovated facilities by 2030 and to reduce overall facility energy usage 30% by 2030. As part of this on-going energy efficiency effort, the U.S. Army has designed and constructed a Net Zero Energy Building (NZEB) at the Fort Hood army base in Texas, which is currently being tested as a prototype. In order to achieve net zero performance and reduce the energy demand, several low-energy building technologies were designed and built including high-efficiency heating, ventilation, and air conditioning (HVAC) system, a high-performance building envelope, energy efficient lighting and a solar PV system. This paper presents the results of an evaluation of the net zero energy performance of the office building at the Fort Hood army base using measured data. The analysis methods applied to the building include: an un-adjusted, measured energy use comparison of both portions of the building; a weather-normalized, change-point linear regression to estimate annual energy savings; and calibrated building energy simulations with thermostat schedules and occupancy conditions of both portions in the building. The results show savings of 37–50% for the renovated portion of the building (i.e., NZEB) compared to the un-renovated portion depending on the method of analysis.

Powerhouse Telemark: A plus energy building with a low exergy heating and cooling system

Powerhouse Telemark (PHT) is an eleven stories high office building in Telemark in Norway, built to plus energy standard. A plus energy building that is built according to the Powerhouse definition prior to 2019 must produce more renewable, locally produced energy during the lifetime of the building, and must produce enough renewable energy to cover the total embodied energy used for the production and transportation of the building materials used in the building. The local renewable energy production must also cover the yearly net energy needs for operations, renovations and demolition of the building. The local production of renewable energy on the building is not required to cover the energy needed for plug loads in the building.The building will have a unique diamond shape, and the roof of the building is oriented towards the south, and slopes at an angle of 24 degrees from the horizontal. The building will be a net supplier of electricity when seen over a whole year.In addition to other “normal” measures to achieve a plus energy building, like a high performance building envelope, and an extremely efficient ventilation system, energy efficient lighting and equipment and a solar PV system, a new low exergy heating and cooling system has been implemented in the building. This low exergy system (called Lowex) is based on low temperature heating and high temperature cooling, which together with an optimized energy well design will give extremely low demand for delivered energy (electricity). To design this Lowex system, a lot of different calculations and simulations had to be done, both with commercial software packages, but also with new develop dynamic simulation models. These design procedures and models are described in this paper. This paper also describes how these results will be used for the operation of the building.The building is currently under construction and will be commissioned in late 2019/early 2020. The main experience from the design phase and early construction phase is that the Lowex system sets strict demands on both façade design and the interior design. Transparent vs. opaque area ratios, solar shading and glazing solutions set boundaries for the architectural concept, and must be taken into account early in the design process. Flooring materials, ratio of landscape vs. office cells, and thermal zoning of the building affects the interior design. The acoustic concept and the carbon footprint of the building as well as the design of the supplementary HVAC-system are also important factors that need to be taken into account at an early stage in the design phase. To solve these interdisciplinary problems it requires a design team that can work together closely. The architect, and the engineer that is responsible for the energy performance of the building, have a central role to play at the very beginning of the design phase when the geometry and the general parameters of the building is still in flux.

Modelling of a net-zero energy condo in a cold climate using an interdisciplinary design framework

Developing buildings which generate the amount of energy that they use (energy net-zero) in cold climates has the potential to significantly reduce overall energy consumption and Greenhouse Gas (GHG) emissions in these locations. This study introduces a design methodology which first iteratively reduces building loads from a synthesis of architectural, engineering, and building science strategies to achieve a minimized annual energy consumption. Then this optimized load is generated via on-site systems, and finally the overall design is validated within the goals of sustainability and high performance (as compared to benchmark designs). This strategy was applied to a detailed design-based analysis of a mid-rise, net-zero energy residential condo in Toronto, Canada. The building was developed within this iterative and computational process that draws on literature from passive house design, R2000, and ASHRAE 90.1 standards - as well as existing efficient building designs across various climates. Modelling using the eQuest building energy simulation software, relevant weather data, and hourly use profiles yielded energy consumption data which informed design modifications. Loads were systematically reduced by optimizing across building orientation, building layout and footprint, building materials, and architectural modifications. Furthermore, the use of Heat Recovery Ventilation (HRV) and Variable Refrigerant Flow (VRF) HVAC systems reduced heating and cooling demand and emissions in this mid-rise multi-unit residential building (MURB). Energy demand was further reduced by designing a high-performance building envelope with an improved window-to-wall ratio, triple glazed windows, airtight building enclosure, and high R-value insulation. On-site energy generation via the rooftop and facade solar array allowed for net-zero operation. The proposed methodology yielded a building design with annual energy consumption and GHG emissions reduced by 54.3% and 95.3% respectively.

An innovative method for the design of high energy performance building envelopes

In this paper, an innovative method to minimise energy losses through building envelopes is presented, using the Proper Generalised Decomposition (PGD), written in terms of space x, time t, thermal diffusivity α and envelope thickness L. The physical phenomenon is solved at once, contrarily to classical numerical methods that cannot create a parameter dependent model. First, the PGD solution is validated with an analytical solution to prove its accuracy. Then a complex case study of a multi-layer wall submitted to transient boundary conditions is investigated. The parametric solution is computed as a function of the space and time coordinates, as well as the thermal insulation thickness and the load material thermal diffusivity. Physical behaviour and conduction loads are analysed for 76 values of thermal insulation thickness and 100 types of load material properties. Furthermore, the reduced computational cost of the PGD is highlighted. The method computes the solution 100 times faster than standard numerical approaches. In addition, the PGD solution has a low storage cost, providing interesting development of parametric solutions for real-time applications of energy management in buildings.

The homeostasis solution – Mechanical homeostasis in architecturally homeostatic buildings

We already know, for energy-saving potential, the necessary architectural features in well-designed buildings: high performance building envelope, sufficient interior thermal mass, and hydronic-network activated radiant surfaces for cooling and heating. Buildings with these features may be referred to as architecturally homeostatic buildings (AHBs); such a building-system is thermally semi-autonomous in the sense that its temperature variation stays within a certain range even without conditioning equipment, and, with conditioning equipment in operation, its thermal regulation is handled by its hydronic heat-distribution-network for controlling the temperature level of the building. At the present time conventional HVAC equipment is used for maintaining the heat-distribution-network: this arrangement, however, has resulted in great energy saving only for AHBs with accessible natural water bodies. In operation of general AHBs, a case is made here for a new kind of mechanical equipment having the attribute of mechanical homeostasis (MH). MH is a new energy transformation concept in a triadic framework. Superlative energy efficiency is predicted as a result of combined improvements in higher triadCOPs and lower total (inducted+removed) heat rates—evincing existence of synergy in architectural and mechanical homeostasis, which together will be referred to as the homeostasis solution.

Effects of Thermophysical Properties of Wall Materials on Energy Performance in an Active Building

Abstract A high-performance building envelope is the prerequisite and foundation to a zero energy building. For the non-transparent part of envelope, the thermal conductivity and volumetric heat capacity are two thermophysical properties which can strongly influence the energy performance of the envelope. Although a lot of case studies have been performed on these two properties, the results could not give a comprehensive picture of the roles of thermal conductivity and volumetric heat capacity on the energy performance in an active building. In this work, a traversal study on the energy performance of a standard room with all potential wall materials was provided. These materials were differentiated by distinct thermal conductivity and volumetric heat capacity. It was revealed that the external wall requires a material with a low thermal conductivity and a high volumetric heat capacity, and the internal wall needs a material with a high volumetric heat capacity. These requirements for wall materials are consistent under various climate conditions.