Gas-filled panels for building applications: A state-of-the-art review

With their thermal conductivity down to 10 mW/m K, gas-filled panels (GFPs) are regarded as possible high performance thermal insulating solutions for building applications. However, thermal conductivities of respectively 46 and 40 mW/m K have so far been achieved for prototype air-filled and argon-filled panels, values slightly higher than currently traditional building insulation materials. Compared to other high performance thermal insulation materials and solutions, e.g. vacuum insulation panels (VIPs), the future of GFPs may therefore be questioned. Nevertheless, the application of a low-conductive gas and reflective barriers may have a potential in the development of new high performance thermal insulation materials. Within this work, a state-of-the-art review is given on the knowledge of GFPs for building applications today.     

Aerogel insulation for building applications: A state-of-the-art review

Aerogels are regarded as one of the most promising high performance thermal insulation materials for building applications today. With a thermal conductivity down to 13 mW/(m K) for commercial products they show remarkable characteristics compared to traditional thermal insulation materials. Also the possibility of high transmittances in the solar spectrum is of high interest for the construction sector. With the proper knowledge they give both the architect and engineer the opportunity of re-inventing architectural solutions. Within this work, a review is given on the knowledge of aerogel insulation in general and for building applications in particular.     

Optimization of cooling load for a lecture theatre in a composite climate in India

A lecture theatre with dimension 16 m × 8.4 m × 3.6 m located at Roorkee (28.58°N, 77.20°E) in the northern region of India, is selected to calculate the monthly and annual cooling load (kWh) and cooling capacity of air conditioning system by a computer simulation. The paper also presents the results of a study investigating the effect of different glazing systems on windows and the reduction in building cooling load. DesignBuilder software has been used for the computer simulation for calculating the cooling load. The paper aims to investigate the reduction in thermal gains and cooling load requirements by varying the U-values of different glazing types, insulating the ceiling, providing cool roofs, interior and exterior insulation on walls, and replacing the conventional fluorescent tube lamp (FTL) by energy efficient compact fluorescent lamp (CFL). Installation of false ceiling, wall insulation, different glazing types and lighting systems are cost effective with normalized annual saving ranging from 17% to 19.8% from this retrofitting project. Furthermore, the study also highlights the potential of reducing the emission of CO₂ and equivalent carbon credit. Retrofitting techniques strongly influence the level of energy saving, although the payback period is generally quite long of order 8 years.     

An evaluation of the embedment of a Radio Frequency Integrated Circuit with a temperature detector in building envelopes for energy conservation

Concrete is the primary material for building envelopes in some parts of the world, and its ability to store heat as well as its dynamic temperature changes will not only affect the deterioration rate of the exterior wall but will also greatly influence the energy efficiency of interior air conditioning. There are many methods for measuring the inner temperature of concrete, but they often have limitations, such as indirect estimation, cable installation requirements, high cost, or heterogeneity of the sample structure. In order to measure the internal temperature of concrete, this study integrated a Radio Frequency Integrated Circuit (RFIC) with a temperature sensor chip and embedded the device in concrete structures. A Smart Temperature Information Material (STIM) was thus developed. This device overcomes the aforementioned constraints, allows direct measurement and wireless transmission, and is able to constantly monitor temperature changes from a distance. The experiment embedded STIM into 5 concrete specimens that simulated rooftop insulation (50 cm × 50 cm × 15 cm) to measure the thermal performance of each insulation material, and the effect of weather conditions and the heat release/absorption rates on the thermal performance. The results of the study can be used as a reference for selecting materials for building design or maintenance and analysis of the energy efficiency of building envelopes.     

Experimental study of using PCM in brick constructive solutions for passive cooling

This work presents the results of an experimental set-up to test phase change materials with two typical construction materials (conventional and alveolar brick) for Mediterranean construction in real conditions. Several cubicles were constructed and their thermal performance throughout the time was measured. For each construction material, macroencapsulated PCM is added in one cubicle (RT-27 and SP-25 A8). The cubicles have a domestic heat pump as a cooling system and the energy consumption is registered to determine the energy savings achieved. The free-floating experiments show that the PCM can reduce the peak temperatures up to 1 °C and smooth out the daily fluctuations. Moreover, in summer 2008 the electrical energy consumption was reduced in the PCM cubicles about 15%. These energy savings resulted in a reduction of the CO₂ emissions about 1-1.5 kg/year/m².     

Correlation between thermal conductivity and the thickness of selected insulation materials for building wall

Correlation between thermal conductivity and the thickness of selected insulation materials for building wall has been analyzed. The study has found that a relationship between the thermal conductivity (k) and optimum thickness (x_opt) of insulation material is non-linear which obeys a polynomial function of x_opt = a + bk + ck², where a = 0.0818, b = −2.973, and c = 64.6. This relationship will be very useful for practical use to estimate the optimum thickness of insulation material in reducing the rate of heat flow through building wall by knowing its thermal conductivity only.     

Vacuum insulation panels for building applications: A review and beyond

Vacuum insulation panels (VIPs) are regarded as one of the most promising high performance thermal insulation solutions on the market today. Thermal performances three to six times better than still-air are achieved by applying a vacuum to an encapsulated micro-porous material, resulting in a great potential for combining the reduction of energy consumption in buildings with slim constructions. However, thermal bridging due to the panel envelope and degradation of thermal performance through time occurs with current technology. Furthermore, VIPs cannot be cut on site and the panels are fragile towards damaging. These effects have to be taken into account for building applications as they may diminish the overall usability and thermal performance.This paper is as far as the authors know the first comprehensive review on VIPs. Properties, requirements and possibilities of foil encapsulated VIPs for building applications are studied based on available literature, emphasizing thermal bridging and degradation through time. An extension is made towards gas-filled panels and aerogels, showing that other high performance thermal insulation solutions do exist. Combining the technology of these solutions and others may lead to a new leap forward. Feasible paths beyond VIPs are investigated and possibilities such as vacuum insulation materials (VIMs) and nano insulation materials (NIMs) are proposed.     

Use of microencapsulated PCM in concrete walls for energy savings

This paper studies a new innovative concrete with phase change materials (PCM) on thermal aspects. The final objective is to develop a product which would achieve important energy savings in buildings. The work here presented is the construction and experimental installation of two real size concrete cubicles to study the effect of the inclusion of a PCM with a melting point of 26 °C. The cubicles were constructed in the locality of Puigverd of Lleida (Spain). The results of this study show the energy storage in the walls by encapsulating PCMs and the comparison with conventional concrete without PCMs leading to an improved thermal inertia as well as lower inner temperatures.     

Optimum insulation thicknesses for building walls with respect to cooling and heating degree-hours in the warmest zone of Turkey

Thermal insulation is one of the most effective energy conservation measures for cooling and heating in buildings. Therefore, determining and selecting the optimum thickness of insulation is the main subject of many engineering investigations. In this study, the determination of optimum insulation thickness on external walls of buildings is comparatively analyzed based on annual heating and cooling loads. The transmission loads, calculated by using measured long-term meteorological data for selected cities, are fed into an economic model (P₁−P₂ method) in order to determine the optimum insulation thickness. The degree-hours method that is the simplest and most intuitive way of estimating the annual energy consumption of a building is used in this study. The results show that the use of insulation in building walls with respect to cooling degree-hours is more significant for energy savings compared to heating degree-hours in Turkey's warmest zone. The optimum insulation thickness varies between 3.2 and 3.8 cm; the energy savings varies between 8.47 and 12.19 $/m²; and the payback period varies between 3.39 and 3.81 years depending on the cooling degree-hours. On the other hand, for heating load, insulation thickness varies between 1.6 and 2.7 cm, energy savings varies between 2.2 and 6.6 $/m², and payback periods vary between 4.15 and 5.47 years.     

Experimental and numerical investigation of a hollow brick filled with perlite insulation

The present study is focused on the investigation of the effective thermal properties of a modern vertically perforated masonry unit filled with perlite insulation. Based on measurements and numerical calculations, the thermal performance of the new hollow brick was determined. The authors suggest to use the following parameters for this building material: equivalent heat capacity equal to 855.1 J/kg K, equivalent heat conductivity equal to 0.09 W/mK and equivalent density equal to 653.15 kg/m³. The dependence of the equivalent thermal resistance of the whole wall made of this brick and mortar, is shown for different mortar joint thicknesses. All results, presented in this paper, can be used in energy balance calculations for buildings made of masonry unit.     

Renovation of existing office buildings in regard to energy economy: An example from Ankara,Turkey

Unit energy consumption of existing buildings in Turkey is excessive. While average energy consumption of residential buildings in Europe is 100 kWh/m² per year, it is about 200 kWh/m² per year in Turkey. The principle reason for this, is that there was not any regulation on thermal insulation issues until recent years. However, the fiscal value of total energy consumption in residential buildings is about $2.5 billion. Recent research has shown that 40% of this energy consumption could be saved, provided that using energy efficiently. Furthermore, every reduction in energy-usage has a significant influence on environmental protection and CO₂ emissions. This study has focused on energy efficiency in a building of public sector that had been inaugurated in 1988 in Ankara. During the pre-investigative step, it has been determined that 47% of total energy consumption of the building could be saved.     

Laboratory evaluation of the effectiveness of nanostructured and conventional particles in clearing smoke in enclosed spaces

The potential of nanostructured and conventional particulate materials in clearing smoke in enclosed spaces was evaluated. Aggregates of metal oxide nanostructured particles or conventional particles were sprayed into an enclosed experimental chamber (2.4 m×2.4 m×3.6 m) filled with glycol smoke. The times required for the light transmission in the room to reach 10% and 20% served as a measure of the effectiveness of the material in clearing smoke. The effects of material type and deployment pressure were considered. Results indicate the potential of some particles in increasing the rate of smoke dissipation and improving the visibility in the smoke-filled chamber.     

Indonesian residential high rise buildings: A life cycle energy assessment

This study evaluates the effect of building envelopes on the life cycle energy consumption of high rise residential buildings in Jakarta, Indonesia. For high rise residential buildings, the enclosures contribute 10-50% of the total building cost, 14-17% of the total material mass and 20-30% of the total heat gain. The direct as well as indirect influence of the envelope materials plays an important role in the life cycle energy consumption of buildings. The initial embodied energy of typical double wall and single wall envelopes for high residential buildings is 79.5 GJ and 76.3 GJ, respectively. Over an assumed life span of 40 years, double walls have better energy performance than single walls, 283 GJ versus 480 GJ, respectively. Material selection, which depends not only on embodied energy but also thermal properties, should, therefore, play a crucial role during the design of buildings.     

无机保温砂浆在太阳能建筑示范项目中的应用研究

本文以甘肃省建材科研设计院新型建筑材料中试基地既有建筑节能改造工程为例,通过对改造前后建筑物保温性能的测试,并结合建筑围护结构热工计算与测试数据进行分析研究,结果表明,用无机阻燃保温砂浆节能改造后建筑物节能效果显著。     

Impact of grey energy on optimal wall insulation thickness

For decades efforts have been made to reduce the greenhouse gases emissions of buildings by reducing their energy demand with governmental regulations in Europe, pushing towards very low thermal transmittances (U-values) with ever thicker insulation layers for new buildings. However, there is no linear relationship between the insulation thickness and the heat losses. Therefore, above a certain thickness the consumption of buildings does not decrease significantly. Hereafter a life cycle analysis, including emissions before the building becomes operational is applied to evaluate the impact of the increasing thickness of components on the overall emissions. Publicly available product data sheets are used to compare four insulation materials under three scenarios. These analyses yield interesting results showing that energy-intensive insulation materials lead to a negative impact in the overall energy balance after a certain thickness. Even though there is not always a pronounced optimum insulation thickness, it is logical that further reductions in U-value for new buildings should hence be carefully evaluated. The results show that the optimal thickness is around 20 cm for most materials, while the important major savings come from the first 10 cm.     

Facade design optimization for naturally ventilated residential buildings in Singapore

Parametric studies of facade designs for naturally ventilated residential buildings in Singapore were carried out to optimize facade designs for better indoor thermal comfort and energy saving. Two criteria regarding indoor thermal comfort for naturally ventilated residential buildings are used in this study. To avoid the perception of thermal asymmetry, temperature difference between mean radiant temperature and indoor ambient air temperature should be less than 2 °C [F.A. Chrenko, Heated ceilings and comfort. J. Inst. Heat. Ventilating Eng. 20 (1953) 375–396; F.A. Chrenko, Heated ceilings and comfort. J. Inst. Heat. Ventilating Eng. 21 (1953) 145–154]. Thermal comfort regression model for naturally ventilated residential buildings in Singapore was used to evaluate various facade designs either. Facade design parameters: U-values, orientations, WWR (window to wall ratio) and shading device lengths are considered in the investigation. The building simulation results for a typical residential building in Singapore indicated that the U-value of facade materials for north and south orientations should be less than 2.5 W/m² K and the U-value of facade materials for north and south orientations should be less than 2 W/m² K. From the coupled simulation results, it was found that the optimum window to wall ratio is equal to 0.24. Optimum facade designs and thermal comfort indexes are summarized for naturally ventilated residential buildings in Singapore.     

玻化微珠在仿古建筑外墙外保温中的应用

随着国家对建筑外墙保温的要求愈趋严格,建筑节能材料的发展十分迅速。因节能材料具有节省能源、降低热量消耗的作用,在实际工程项目中的应用十分广泛。仿古建筑不仅要满足中国传统的平面组合方式及立面造型,同时,还必须符合现代建筑设计相关规范。为仿古建筑选择合适的保温材料一直是人们关注的热点。通过对仿古建筑外墙外保温材料选择的相关分析,及各种保温材料的性能对比,得出玻化微珠保温砂浆是目前较适合仿古建筑的保温材料。     

Study on the influence of albedo on building heat environment in a year-round

The research of energy saving is one of the highlights of buildings environment. According to the albedo change of the wall-facing materials of urban buildings, two building models were constructed, of which the internal and external microclimate parameters were measured under certain meteorological conditions in different seasons. The experimental results show that the decrease of indoor air temperature was up to 4.67 °C with the average diurnal temperature decrease up to 3.53 °C in summer, and the increase was up to 2.81 °C in winter when the albedo changed from 0.21 to 0.86. Moreover, Laplace integral transform method was used to analyze building energy saving. The results indicate that the wall-facing materials with high albedo have the function of heat-protection and heat-insulation and could reduce 150.3 W per day of the buildings’ cooling load in summer and 69.5 W per day of heating load in winter. The research results confirm that employing high albedo coatings on the building exterior wall is an active and effective approach to improve the urban buildings’ micro-heat environment.     

Performance characteristics and practical applications of common building thermal insulation materials

Buildings are large consumers of energy in all countries. In regions with harsh climatic conditions, a substantial share of energy goes to heat and cool buildings. This heating and air-conditioning load can be reduced through many means; notable among them is the proper design and selection of building envelope and its components.The proper use of thermal insulation in buildings does not only contribute in reducing the required air-conditioning system size but also in reducing the annual energy cost. Additionally, it helps in extending the periods of thermal comfort without reliance on mechanical air-conditioning especially during inter-seasons periods. The magnitude of energy savings as a result of using thermal insulation vary according to the building type, the climatic conditions at which the building is located as well as the type of the insulating material used. The question now in the minds of many building owners is no longer should insulation be used but rather which type, how, and how much.The objective of this paper is to present an overview of the basic principles of thermal insulation and to survey the most commonly used building insulation materials, their performance characteristics and proper applications.