Levels Of Thermal Insulation Research Articles

Households' response to changes in electricity pricing schemes: Bridging microeconomic and engineering principles

This paper presents a computational take on households' response to price changes. Many studies use assumptions (i.e., price elasticities) that were estimated using historical information; however, if a price change has not been experienced in the past, the response may not be statistically predicted. While other papers have explored price response behavior internally through microeconomic principles, many factors affect a household's electricity use, including the construction of the dwelling, outdoor air temperature, and efficiency of the air conditioner. We have superimposed a physical model, which determines hourly power loads, with a utility maximization component.The dwelling itself is calibrated to one in Saudi Arabia, but we test households that have various preferences in their utility function, levels of thermal insulation, and income. We further analyze a wide range of electricity pricing schemes; some are progressive tariffs, while one is defined hourly. The extent to which the prices are raised in the alternative schemes has never been experienced in Saudi Arabia. Our analysis shows that households with low electricity preferences exhibit a larger short-run response than would be derived from the aggregate price elasticities estimated statistically. Moreover, improved building insulation affects the household's decision-making process.

Hygrothermal assessment of internally insulated brick wall based on numerical simulation

Massive walls exposed to external climate are characterized by low levels of thermal insulation. Unfortunately in many cases, due to the historic character of the building, the only possible way to improve their thermal insulation is the use of internal insulation. However, such solutions are associated with the risk of frost damage, mould growth or interstitial condensation. Calculations regarding the occurrence of these risks require complex calculation methods. Therefore, in the present work, the evaluation of the hygrothermal behavior of the internally insulated solid brick wall was performed based on the numerical simulations using the program WUFI Pro. Various material solutions of internal insulations, based on both synthetic and natural materials, were compared. The focus was on a particularly sensitive interface between the insulation and the original wall

A model to compare convective and radiant heating systems for intermittent space heating

In this paper, a dynamic heat transfer model based on thermal-electrical analogy has been built to compare convective and radiative heating systems for intermittent heating. An experiment has been set up to validate the model we built. The RMS Error was within 0.5 °C, confirming the accuracy of the model. The validated model was then applied to compare four typical space heating systems, namely all-air, radiator, in-slab floor heating, and lightweight floor heating systems. The concept of “ineffective heat” has been proposed to explain why the intermittent heating could reduce heating load. Two ideal characters of heating systems have been identified for intermittent heating, i.e. high heating capacity and low thermal mass, both of which are crucial to shorten the preheat time and to reduce the ineffective heat. The results indicate that convective heating systems were more comfortable (more rapidly raise the indoor temperature) and more energy efficient (lower heating load) for intermittent operation than radiative heating systems. The performance gap between radiative and convective heating systems would be enlarged in colder conditions. Among the four heating systems, convective heating system was the most suitable one for intermittent heating, and floor heating was the most unsuitable one. Though belonging to radiative heating systems, the radiator performs differently from floor heating for its potential to enhance heating capacity and relatively low thermal mass. Additionally, outdoor climate and building thermal insulation level also affect the choice of the most suitable heating system and heating mode. The findings of this research might shed some light on the debate of the choice of space heating systems in areas with similar climate conditions with China’s Hot Summer Cold Winter region.

On the limits of the quasi-steady-state method to predict the energy performance of low-energy buildings

The recent European energy policies progressively introduced more restrictive energy performance requirements aimed at achieving the nearly zero-energy building target for all new buildings and major renovations. To check compliance with these requirements, the building energy performance can be evaluated through different calculation methods, as widely presented in literature. The present article is aimed at identifying in which boundary conditions (e. g. climate, use category, building size, thermal insulation level) a simplified steady-state calculation method can predict with sufficient accuracy the energy performance of low-energy buildings if compared with a dynamic simulation model. The analysis was performed on two building types, representative of the Italian residential typology, located in three different climatic zones and characterised by two insulation levels. The insulation levels fit the U-values of the notional reference building, established by the Italian legislation for checking compliance with energy performance requirements in two different steps; the first level is in force until 2020, while the second level is that of a reference nearly zero-energy building in force from 2021 onwards. The building energy performance, in terms of net energy needs for space heating and space cooling, was assessed by means of both the monthly calculation method of CEN standards and the detailed simulation model of EnergyPlus. Consistency options were applied to the models to guarantee that their outputs could be comparable. The quasi-steady-state method demonstrated to predict the cooling energy need quite well, but to lose in accuracy when the weight of the thermal transfer in the energy balance increases.

Optimization of the level of thermal insulation of enclosing structures of civil buildings

In the work, methods of an estimation of economic efficiency of additional heat insulation of building enclosing structures and definition of an optimum thermal resistance are considered, deficiencies of the given techniques are marked. A model is proposed for determining the optimal level of heat protection in the new economic conditions.

Practice of net Positive Energy House in the Suburb of Tokyo

To satisfy the energy saving standard will be mandatory for all architecture until 2020 in Japan. Furthermore, after the Tohoku earthquake in 2011, the positive energy house has been paid more attention to. ZEH, means “Zero Energy House”, is the significant key word for the Japanese. An advanced ZEH in the suburb of Tokyo was planned by authors. The novel point in the design process was the confirmation of the effects of passive and active system by simulation at many phases, even if the target was a small house. At first, we analyzed the local weather data recorded in Expanded AMeDAS Weather Data to decide the appropriate volume and position on the site. Secondly, we proposed the better level of thermal insulation than the level of the energy saving standard in Japan. The average U-value of the standard house in the located region was 0.87 W/m2·K, but the value of our planned house was 0.35 W/m2·K. Thirdly, we confirmed the effects of passive strategies and the high-efficiency equipment, such as the control of solar heat gain and daylight around the windows in all seasons, cross-ventilation, mechanical ventilation with heat exchanger and photovoltaic panel, judging the simulated results from EnergyPlus, Radiance, CFD and the program for calculating primary energy consumption of each usage in house made by the Japanese ministry. After the completion in February 2016, we have been measuring the power consumption of each circuit breakers, total gas and water consumption and indoor environment. The amount of real energy use and generation was shown to confirm the achievement of real ZEH or net positive energy house.

Multi-Objective Optimization of Building Energy Design to Reconcile Collective and Private Perspectives: CO2-eq vs. Discounted Payback Time

Building energy design is a multi-objective optimization problem where collective and private perspectives conflict each other. For instance, whereas the collectivity pursues the minimization of environmental impact, the private pursues the maximization of financial viability. Solving such trade-off design problems usually involves a big computational cost for exploring a huge solution domain including a large number of design options. To reduce that computational cost, a bi-objective simulation-based optimization algorithm, developed in a previous study, is applied in the present investigation. The algorithm is implemented for minimizing the CO2-eq emissions and the discounted payback time (DPB) of a single-family house in cold climate, where 13,456 design solutions including building envelope and heating system options are explored and compared to a predefined reference case. The whole building life is considered by assuming a calculation period of 30 years. The results show that the type of heating system significantly affects energy performance; notably, the ground source heat pump leads to the highest reduction in CO2-eq emissions, around 1300 kgCO2-eq/m2, with 17 year DPB; the oil fire boiler can provide the lowest DPB, equal to 8.5 years, with 850 kgCO2-eq/m2 reduction. In addition, it is shown that using too high levels of thermal insulation is not an effective solution as it causes unacceptable levels of summertime overheating. Finally a multi-objective decision making approach is proposed in order to enable the stakeholders to choice among the optimal solutions according to the weight given to each objective, and thus to each perspective.

Intelligent clothing: first and second generation clothing with adaptive thermal insulation properties

This paper deals with the idea that one of the inner thermal insulation layers of a garment may be replaced by expanding the air chambers in the form of an expanding thermal insert, which is inflated with air causing the chamber thickness and thermal insulation properties to change. The chambers are controllable so that the thermal insulation properties can be changed, and by connecting with an appropriate control, the architecture of an article of clothing can be designed such that it can independently monitor changes in its environment and change its thermal insulation properties in accordance with changes in its external and internal environment. In this way, it acquires the characteristics of intelligent clothing. The paper presents idea concepts, development, structural architecture and general characteristics of two generations of intelligent clothing with adaptive thermal insulation properties. The expanding thermal inserts are situated between the outer shell and the lining and are the key element of this type of new clothing. In the first generation of intelligent clothing the expanding inserts were designed in combination with three horizontal chambers that can be sealed in three horizontal layers, whereby it is possible to make six adaptable discontinuous levels of thermal insulation. In the second generation, ribbed expandable chambers were used. Their thickness is continuously changeable according to the pressure change in the chambers, whereby the value of thermal insulation of the chambers can be continuously adapted. The functioning of this clothing is based on the integration of sensors for internal and external temperature and air pressure in the chambers, on a microcontroller with regulation software and actuators to control the expanding insert. When wearing this kind of clothing, the microcontroller system monitors changes in ambient temperature and clothing microclimate depending on the wearer’s physical activity, compares them with the achieved thermal protection and makes autonomous decisions on the required increase or decrease in thermal protection. Since this clothing follows changes in its internal and external environment, estimates the real and necessary state, makes decisions and independently performs the adaptation of thermal insulation to a level that it ensures constant thermal comfort, it can be claimed that such a garment has the basic attributes of intelligent clothing. The paper describes the functioning of two types of thermal insulation chambers, the sensor system used, micropneumatic components, the microcomputer system, the flow chart of the algorithm of intelligent behavior, the complete built-in architecture of all technical subsystems, features of the first and second generation and the observed good and bad points of the conceptual approach to the development of intelligent clothing with adaptive thermal insulation properties.

Optimization of roof solar reflectance under different climate conditions, occupancy, building configuration and energy systems

Cool roofs have been widely proved to represent an effective strategy for building thermal-energy performance improvement during the cooling season. However, their effectiveness along the whole year can be affected by building features and other boundary conditions. The present work aims at assessing the energy performance of high solar reflectance roof solutions in different climate zones, when implemented in a variety of building typologies. Therefore, an optimization study was carried out to select the optimum roof solar reflectance able to minimize building annual HVAC energy consumption. In this work, Italian climate zones were considered as case study conditions. The analysis was performed through dynamic simulation of validated standard ASHRAE building reference models. Moreover, the role of (i) type of HVAC system operating, (ii) presence and intensity of internal gains, and (iii) roof thermal insulation level was evaluated on the resulting optimum roof reflectance capability. Results show that the optimum roof solar reflectance varies under different climate conditions, mainly depending on heating or cooling dominated conditions. However, all further analyzed boundary conditions, i.e. building typology, HVAC system, internal gains, and roof insulation level, affect building energy performance and, therefore, the optimum roof reflectance identification. In the hottest climate, the optimum roof solar reflectance resulted to be consistently equal to the maximum considered, i.e. 0.8, also with varying the other parameters. Moreover, the annual HVAC energy need is more sensitive to roof reflectance in the apartment building, showing 17% of energy savings with standard model characteristics. On the other hand, in heating dominated climates, the optimum roof solar reflectance is more variable, ranging over all the considered values, because it is affected by the additional boundary conditions. On the contrary, the variability of HVAC need due to roof solar reflectance variation is generally lower.

Comfort properties of 3D-knitted seamless female body armour vests

This paper reports the comfort properties of 3D-knitted seamless female body armour vests evaluated by using a thermal manikin. The vests were designed as a complete garment with eliminating the conventional cutting and sewing, to improve fit and comfort for female police officers. The vests were tested on thermal manikin dressed with vests only and manikin dressed with a police officer’s uniform including the vests. Both dry thermal insulation and evaporative resistance were evaluated for comfort properties. The results showed that five-layer assembly of fitted-vest provided an acceptable level of thermal insulation. However, the evaporative resistance of the loose-vest showed better results compared to the fitted-vest, which was proved by the lower surface temperature on the thermal imaging. This research established that the 3D-knitted seamless body armour vests can provide an effective solution for the body armour requirement for female officers. The results also suggested that increasing the number of layers will increase the weight and reduced level of comfort, however they were effective in providing the necessary protection from low-level stab threats, which was shown in the earlier publication.

Avaliação de dispositivos de proteção solar fixos e automatizados para edifício residencial

Os sistemas de proteção solar cumprem um importante papel no controle seletivo de radiação solar no ambiente interior, interferindo, portanto, no desempenho luminoso, térmico e energético das edificações. Este artigo tem como objetivo realizar um estudo comparativo do desempenho de sistemas de proteção solar (fixos e móveis mecanizados) de uma edificação com elevado nível de isolamento térmico utilizando para isso a ferramenta Energy Management System (EMS) do software Energy Plus. As estratégias metodológicas propostas envolvem a análise da configuração de oito diferentes sistemas de proteção solar para os fechamentos transparentes, modelagem dos brise-soleils fixos, implementação do EMS para brise-soleis mecanizados e por fim, análise dos resultados das simulações realizadas. Foram avaliados os percentuais de conforto térmico e de consumo de energia elétrica considerando as zonas bioclimáticas brasileiras 1 e 8. Dentre os casos testados, o modelo com a utilização de persianas externas automatizadas pelo sistema EMS nos fechamentos transparentes apresentou os maiores percentuais de conforto térmico e o menor consumo de energia elétrica nas duas zonas bioclimáticas brasileiras analisadas.

Effectiveness of passive measures against climate change: Case studies in Central Italy

This paper focuses on the effectiveness of passive adaptation measures against climate change, in the medium (2036–2065) and long term (2066–2095), for three case studies located in Florence (central Italy). In order to identify and highlight the passive measures which can provide comfort conditions with the lowest net heating and cooling energy demand, the input assumptions consider a constant thermal comfort level and don’t take into account either the effect of HVAC system’s performance and the degradation of the materials by ageing. The study results show that, in case of poorly insulated buildings, on the medium term, the reduction of energy needed for heating could be bigger than the increase for cooling, resulting in a total annual net energy need decrease, while in the long term the opposite happens. Conversely, considering a high level of thermal insulation, due to the large increase in cooling demand, the total annual energy need rises in both periods. Furthermore, attention should be paid to internal loads and solar gains that, due to the projected climate change, could become main contributors to the energy balance. In general, since the magnitude of energy need increase for cooling and decrease for heating is very significant on the long term, and varies in function of the type of building, the passive measure adopted and the level of thermal insulation, the research results lead to pay close attention to different types of energy refurbishment interventions, that should be selected in function of their effectiveness over time.

METHOD FOR DECREASE OF STANDARD HEAT LOSSES IN RESIDENTIAL BUILDINGS

A simplified method for calculation of standard coefficient for heat transfer in a residential building has been developed in the paper. Investigations have been carried out with the purpose to determine influence of building size, level of thermal insulation in external enclosures and share of heat regeneration in ventilation system on total heat losses. The paper considers buildings of a simple geometrical form (“matchbox”) with number of floors 1, 2, 4, 8, 16 and living area from 100 up to 25600 m 2 at the level of thermal resistance of walls 1; 3 and 5 m 2 ⋅°C/W and share of heat regeneration in ventilation air stream of 0; 0.5 and 0.66. The investigation results have shown that while increasing building size then there is a sudden transformation of dimensions and structure in external enclosures: share of overlapping area is reduced by 3-fold and share of wall area is increased by 2-fold. Surface area of building external envelope is reduced by 6-fold in comparison with its heated area. An average coefficient of building heat transfer assigned to heated area is decreased by 3-fold. It has been shown that the most efficient methods for further decrease of standard heat losses for residential buildings are the following: heat recovery in the ventilation system: it is deeper if heat protection rate is higher and climate of a building construction zone is colder; enlargement of building size through decrease of their number; limit-exceeding increase in heat protection of small apartment buildings and cottages; cubic form of 2–3-floor buildings for Far North.

MODELLING AND EXPERIMENT OF BUILDINGS THERMO-AERAULIC BEHAVIOR ACCORDING TO THE LEVEL-COMPACTNESS IN SAHARAN CLIMATE CONDITIONS

A large number of studies of building energy simulation neglect the humidity, or well represented, with a very simplified method. It is for this reason that we have developed a new approach to the description and modelling of multizone buildings in Saharan climate. The concept of the form factor and index compactness “quotient of external walls area and volume of the building” are two of the key elements for analyzing the building geometry. We can introduce it’s as validation tools in some cases. In this paper, governing equations of physical phenomena allow to build a model of the thermo-aeraulic behavior. The primary objective is the validation of numerical results able to determine the humidity and temperature in a multizone space. The calculated results were compared with firstly, experimental values, and secondly with simulated results using TRNSYS software. We check if the results change radically for an invariable compactness index. The comparison shows that the found results are to some extent satisfactory. For buildings of similar thermal properties, especially, the used construction materials, the thermal insulation and thermal inertia level, orientation, etc., the result proves that temperature and specific humidity varie slightly when the compactness index is constant.

Thermal Conductivity and Volumetric Specific Heat of Low-Density Wooden Mats

Abstract Using wooden waste as insulation material benefits society by using waste products, reducing building thermal load, and sequestering carbon dioxide. In this study on heat insulating materials, a novel low-density wooden mat was fabricated from wood shavings and kenaf fibers. This research addressed the influences of fabrication conditions on the thermal conductivity and volumetric specific heat of the materials used. The raw materials (wood shavings and kenaf fibers) were mixed with a binder component, and the mixture was thermoformed. The thermal conductivity and volumetric specific heat of the mats were measured, and the influence of mixing ratio, density, and heat flux was evaluated. The results demonstrated that thermal conductivity was largely affected by the mat density and mixing ratio but was largely unaffected by changes in the heat flux. The volumetric specific heat of the mats was largely unaffected by the raw material mixing ratio but was greatly affected by the mat density. The tendency of the thermal conductivity decrease was changed according to the combination ratio of the wood shavings and the kenaf. The wood shavings are flake shaped and curled, and the kenaf is fibrous. It was thought that the internal void was made smaller effectively by mixing two different shaped fibers and the thermal conductivity was minimized. As a result, the thermal performance of the subject mats, as compared with glass wool, exhibited a slightly lower thermal insulation level and higher heat capacity. The results are important in improving efficiency and the commercial design of insulation materials.

Thermal resistance of cut pile hand tufted carpet and its prediction

A mathematical model based on the principles of conductive heat transfer is presented to predict the thermal resistance of cut pile carpet. The cut pile carpet assembly is considered as a network of thermal resistances of the tuft yarns, trapped air, and the primary backing fabric. A straightforward calculation of the thermal resistance was not possible as the data for thermal conductivity of the tuft yarns along their axes was not known. Therefore, the calculation of thermal conductivity in the direction of the yarn axis was based on the construction of surface pile and on the measured thermal resistance of carpet for a set of samples. Theoretical thermal resistances of another set of cut pile carpets were calculated by applying the developed thermal model. The results show that the simple network model is robust and gives reasonable values by using the carpet construction parameters. The model can be used for engineering of cut pile carpets to provide a desired level of thermal insulation.

Parametric study of a cost-optimal, energy efficient office building in Serbia

Recent building regulations in Serbia prescribe the design of highly insulated, airtight buildings with low U-value glazing. Serbia has continental climate with hot summers, so that for office buildings, whose internal gains are higher from the presence of people, computer systems and lighting, this means that far more focus has to be put on cooling demands than on heating demands. This shift toward cooling is studied here through exhaustive simulation of combinations of selected passive solar design parameters for a model of an office building in Belgrade. Design parameters include glazing type, window-to-wall ratio of façades, presence of exterior shading and U-value of opaque envelope components. Optimal variants of the model have been determined with respect to construction cost and heating, cooling and lighting energy use. Results reveal that exterior shading, which has to sustain occasional strong winds in Belgrade, is too expensive to appear in cost-optimal solutions. Hot summers of Belgrade climate imply that cost-optimal solutions have close-to-minimal window-to-wall ratio at the southern façade and significantly larger window-to-wall ratio at the northern façade. Results further show that glazing in cost-optimal solutions has to have small U-value and medium solar heat gain coefficient, although specific choices of optimal glazing type, as well as thermal insulation level, depend on future electricity prices. The case study is repeated for climates of Frankfurt and Stockholm as well, which yield similar results with respect to glazing type and the absence of exterior shading, but with different patterns of window-to-wall ratios at the southern and northern façades.

Environmental impact trade-offs in building envelope retrofit strategies

Purpose The use of high levels of thermal insulation is a common practice towards reducing the energy consumption of the existing building stock; however, the embodied burdens associated with the additional insulation material are usually not taken into account and questions regarding the risks of over-specifying the insulation levels have been emerging, particularly for mild climate regions. This article addresses the issue presenting an integrated approach that combines life cycle assessment and thermal dynamic simulation to assess alternative retrofit strategies for the roof and exterior walls of two dwellings (from the beginning of the twentieth century), in the historic city center of Coimbra, Portugal. A comprehensive analysis of alternative insulation thicknesses (no insulation, 40, 80, and 120 mm of expanded polystyrene) was made to identify optimal thickness levels minimizing life cycle (LC) environmental impacts for a single-family house and an apartment.

The Building Fabric Thermal Performance of Passivhaus Dwellings—Does It Do What It Says on the Tin?

The Passivhaus (or Passive House) Standard is one of the world’s most widely known voluntary energy performance standards. For a dwelling to achieve the Standard and be granted Certification, the building fabric requires careful design and detailing, high levels of thermal insulation, building airtightness, close site supervision and careful workmanship. However, achieving Passivhaus Certification is not a guarantee that the thermal performance of the building fabric as designed will actually be achieved in situ. This paper presents the results obtained from measuring the in situ whole building heat loss coefficient (HLC) of a small number of Certified Passivhaus case study dwellings. They are located on different sites and constructed using different technologies in the UK. Despite the small and non-random nature of the dwelling sample, the results obtained from the in situ measurements revealed that the thermal performance of the building fabric, for all of the dwellings, performed very close to the design predictions. This suggests that in terms of the thermal performance of the building fabric, Passivhaus does exactly what it says on the tin.

Influence of External Surface Resistance and Thermal Insulation Level on Energy Need for Cooling

The value of the external surface resistance on the outside of the structure in the summer season affects the energy need for cooling buildings. The paper analyzes the convection and radiation in the external environment for the current climate conditions of Slovakia in terms of their impact on the value of the external surface resistance to heat transfer in the months when it is expected cooling of buildings. Analysis of the external surface resistance to heat transfer on the outside of the structure for the monthly method of calculating the energy need for heating and cooling.