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.     

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.     

Optimum insulation thickness of residential roof with respect to solar-air degree-hours in hot summer and cold winter zone of china

Thermal protection of building envelope is one of the most effective ways for building energy conservation. In this study, the determination of optimum insulation thickness for residential roof with different surface colors is studied based on life cycle cost analysis and solar-air degree-hours in four typical cities of hot summer and cold winter zone of China. Four insulation materials including expanded polystyrene, extruded polystyrene, foamed polyurethane and foamed polyvinyl chloride are analyzed. The solar-air degree-hours are calculated considering night time operation and 24-h operation of the cooling and heating equipments. Life cycle total costs (LCT), life cycle savings (LCS) and payback period resulting from the use of optimum insulation thickness are calculated. Depending on different cities, insulation materials and roof surface colors, optimum insulation thicknesses of a typical roof vary from 0.065 to 0.187 m and payback periods vary from 0.9 to 2.3 years for 24-h operation of cooling and heating equipments; optimum insulation thicknesses are between 0.051 and 0.149 m and the payback periods are between 1.1 and 2.8 years for night time operation. At last, the effects of present worth factor, thermal resistance and climate on the optimum thicknesses are studied which is very useful for practical use to estimate the optimum thickness of insulation material.     

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.     

夏热冬冷地区居住建筑节能窗传热系数和遮阳系数优化研究

居住建筑的围护结构中,门窗的保温隔热性能最差,是影响室内热环境质量和建筑节能的主要因素之一,提高其保温隔热性能可显著降低建筑能耗。本文以夏热冬冷地区典型城市南京为例．选择最具代表性的三类居住建筑为研究对象,通过DeST-h模拟软件,探讨不同居住建筑外窗的最佳传热系数和遮阳系数,旨在为建筑师和开发商在选用节能窗产品的过程中,提供较为切实可行、直观明了的参考依据。     

Key elements of and material performance targets for highly insulating window frames

The thermal performance of windows is important for energy efficient buildings. Windows typically account for about 30-50 percent of the transmission losses though the building envelope, even if their area fraction of the envelope is far less. The reason for this can be found by comparing the thermal transmittance (U-factor) of windows to the U-factor of their opaque counterparts (wall, roof and floor constructions). In well insulated buildings the U-factor of walls, roofs and floors can be between 0.1 and 0.2 W/(m² K). The best windows have U-factors of about 0.7-1.0. It is therefore obvious that the U-factor of windows needs to be reduced, even though looking at the whole energy balance for windows (i.e., solar gains minus transmission losses) makes the picture more complex.In high performance windows the frame design and material use are of utmost importance, as the frame performance is usually the limiting factor for reducing the total window U-factor further. This paper describes simulation studies analyzing the effects on frame and edge-of-glass U-factors of different surface emissivities as well as frame material and spacer conductivities. The goal of this work is to define material research targets for window frame components that will result in better frame thermal performance than is exhibited by the best products available on the market today.     

节能建筑外墙保温层厚度的经济性优化

节能建筑外端的保温层能起到减少建筑物外墙能耗损失的目的,但在实际建设中保温层的厚度小能无限制的增大,往往在建设方的一次性建设投资和用户对建筑外墙的保温性能的要求相联系。本文利用生命周期价值的方法,建立了外墙保温层厚度经济性优化数学模型,使外墙在保温层生命周期内所造成的能耗费用和保温层造价之和最低,并且对最佳保温层厚度几项影响因素进行分析。利用该数学模型,以长沙地区为例,计算了《湖南省居住建筑节能设计标准》中6种基层墙体的最佳保温层厚度。     

Performance assessment of low-energy buildings in central Argentina

This paper summarizes the results obtained from the energy and thermal performance assessment of residential and non-residential low-energy buildings that were designed to minimize fossil energy use. They are located in the province of La Pampa, central Argentina, in a temperate continental climate that shows extreme hot and cold records during the summer and winter seasons, respectively. The common applied technologies for saving energy were passive solar heating, natural ventilation for cooling and daylighting. The glazing area in the principal functional spaces facing to the North oscillates between 11 and 17% of the building useful areas. All the studied buildings are massive, with the exception of an auditorium that was designed with a lightweight insulated technology. The mean thermal transmittance of the envelope is 0.45 W/(m² K). Double glazing and hermetic carpentry were used to reduce thermal losses (U-value = 2.8 W/(m² K)). The volumetric heat loss coefficient (G-value) oscillates between 0.90 and 1.00 W/(m³ K). During the design and thermal simulation convective-radiative heat transfer coefficients were estimated through a dimensional equation (h = 5.7 + 3.8 ws, wind speed). On internal surfaces, convective-radiative heat transfer coefficients of 8 and 6 W/(m² °C) (for surfaces with and without solar gain, respectively) were applied. The monitoring process provided information on the energy and thermal behaviour under use and non-use conditions. The measured value of energy consumption was similar to the expected value that was used during the pre-design stage. Building technologies work well during the winter season, allowing 50–80% of energy savings. However, overheating is still an unresolved problem during the summer. Interviews with occupants revealed that they need both, information about functional details, and good-practice guidance to manage thermal issues of the building. In most cases, the annual consumption of energy was lower than those established by the Low Energy Housing German Standards and the Minirgie Switzerland Certificate. Despite their relative cost increase during the last years, the use of insulation technology and the application of passive solar devices involved an extra cost of only 3% in our works. Provided the expected depletion of natural gas production in the coming decade, the importance of applying energy-efficiency guidelines will increase very soon in Argentina in order to match the requirements of a new national energy matrix.     

Optimal location and thickness of insulation layers for minimizing building energy consumption

This work aims to optimize the position and thickness of insulation layers in building external wall for climates in the coastal Mediterranean zone and in the inland plateau of Lebanon. A space and an air-conditioning system performance models are developed to predict the space and system loads and associated thermal comfort of occupants. A genetic algorithm is used for the optimization of the life cycle cost of the insulation based on energy load while including the productivity loss associated with thermal discomfort during transient periods. For continuous operation of building HVAC system, adding insulation reduces life cycle cost by 20% over current thermal code requirements. During intermittent operation, locating the insulation at the inner side of the walls results in 15% reduction in energy load compared to locating it on the outer wall. The optimum thickness varied between 3 cm and 5 cm depending on wall orientation climate season.     

办公建筑外墙外保温系统绝热层经济厚度研究

以重庆地区某办公建筑为研究对象,采用能耗模拟软件eQuest,对采用不同绝热层(膨胀聚苯板)厚度(0～70 mm)外墙外保温系统的供暖、供冷能耗进行了模拟.通过节能效益及经济性综合分析,得到该办公建筑外墙外保温系统绝热层的经济厚度为30 mm.     

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.     

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.     

Determination of optimum thickness of double-glazed windows for the climatic regions of Turkey

In this study, the optimum air layer thickness of double-glazed windows is determined using the degree-days method. Calculations are obtained for ?skenderun, Kocaeli, Ankara and Ardahan which are in different climate zones of Turkey. Heating cost of the objective function is calculated for natural gas, coal, fuel-oil, electricity and LPG. The optimum air layer thickness is obtained for three different base temperatures which are 18, 20 and 22 °C. The results show that the optimum air layer thickness varies between about 12 and 15 mm depending on the climate zone, fuel type and base temperature. The effect of the fuel type and the base temperature on the optimum air layer thickness diminishes in cold zones. It is shown that with a well-optimized glazed window, up to 60% energy saving can be achieved.     

真空玻璃在节能住宅的应用前景

本文针对当前建筑能耗较大的现状,从门窗入手,对比分析真空玻璃与中空玻璃的性能,得出结论：真空玻璃结构简单、牢固,在隔音、隔热、环保等方面有明显优势,应用前景广阔。     

夏热冬冷地区住宅节能改造能耗模拟分析

清华大学开发的利用建筑能耗模拟分析软件DeST-h,以某住宅建筑为模型,对夏热冬冷地区三个典型城市的建筑能耗进行模拟分析。从外墙保温砂浆厚度和窗户类型两方面对住宅建筑进行节能改造,模拟分析其对住宅建筑全年能耗的影响情况,为夏热冬冷地区住宅建筑的节能改造提供一些参考。     

Experimental investigations of a decentralized system for heating and hot water generation in a residential building

Nowadays, modern heat supply technologies are preferred by the decentralized municipal sector because they considerably reduce heat transfer losses. One such solution is a heating system using residential thermal stations (RTS). The advantages of a heating system with RTS, as compared with hot water storage vessels, include stabilizing heat costs, saving energy and a decrease in heat transfer losses.This paper presents the results of an experiment investigating heat consumption in a residential building using RTS. The building, located in Lublin, Poland, was supplied by the local district heating network. The energy consumption was monitored from April 2007 to April 2009. The efficiency of this system was 71.4% during the period when heat was required (winter) and 61.5% during the summer; an annual average efficiency of 67.1%. The energy consumption of the space heating system varied from 0.03 to 0.53 GJ m⁻² of the flat's surface area, with the average value being 0.22 GJ m⁻². The influences of the location of the flat within the building and the surface area of the flat on the quantity of heat required for space heating were analysed. Specific attention was paid to the occurrence of local heat flows between flats.     

Exergetic life-cycle assessment (ELCA) for resource consumption evaluation in the built environment

Resource management becomes a key issue in the development of sustainable technology. This paper envisages a quantification of all energy and material needs for a family dwelling, both for the construction aspects (‘embodied energy and materials’) and usage aspects. To do so, an exergetic life-cycle assessment has been carried out that enables the quantification of all necessary natural energy and material resources simultaneously. The case study covered 65 optimized Belgian family dwelling types with low energy input (56 MJ/(m³ year)). The study shows that cumulative annual exergy demand is of the order of 65 GJ_exergy/year, with a limited dependency on the construction type: cavity wall, external insulation or wooden frame. For the cavity wall and external insulation building type, non-renewable inputs are dominant for the construction with 85–86% of the total exergy to be extracted out of the environment. For the wooden frame, non-renewable resource intake for construction remains 62%. Despite the low-energy building type, heating requirements during the use phase are dominant in the overall resource intake with a 60% of the total annual exergy consumption. In order to make family dwellings less fossil resource dependant, the study learns that particularly reduction of heating requirements should be envisaged.     

西北新农村居住建筑外墙经济保温层厚度分析

利用DeST-h软件对10组0~90 mm不同外墙保温层厚度的典型西北新农村建筑采暖能耗进行了模拟分析,并确定了最佳外墙经济保温层厚度。结果表明外墙保温可明显降低建筑采暖能耗,采暖节能率可达到26%,外墙保温层厚度的增加在降低建筑采暖能耗的同时增大了外墙保温投资费用,采用生命周期成本分析法确定西北新农村建筑采用挤塑保温板为保温材料时最佳外墙经济保温层厚度为55 mm。     

严寒地区建筑外墙外保温构造保温层经济厚度研究

外墙保温技术是提升严寒地区建筑热工性能的重要途径之一,可以显著降低建筑能耗,节约运行成本。虽然随着保温层厚度增加,节能率有所提高,但还要考虑到改造成本的问题,需要兼顾外墙改造的节能性和经济性,从而确定保温层的最佳厚度。文章以严寒地区（A区）城市伊春市某多层办公建筑为例,对3种不同材料的外墙外保温系统进行全年能耗分析,同时运用全寿命周期法确定不同保温系统的保温层经济厚度,为设计人员提供方法及数据参考。     

Experimental study on the performance of insulation materials in Mediterranean construction

It is well known that it is necessary to insulate the buildings to decrease the thermal demand and to decrease the use of heating and cooling. Due to the high cost of fossil fuels and to the necessity to reduce CO₂ emissions, and also due to the new building regulations more attention is paid to the insulation of buildings. Different insulation materials are available in the market. Usually, they are compared by their thermal conductivity and with theoretical calculations, but there are no experimental comparisons available, where the behavior of such insulation materials in a building is compared over time. This is why the authors started a comparison of three typical insulation materials, polyurethane, polystyrene, and mineral wool. For this purpose, four house-like cubicles were constructed (with a size of 2.4 m × 2.4 m × 2.4 m) and their thermal performance throughout the time was measured. The cubicles were built under a conventional Mediterranean construction system, differing only in the insulation material used. During 2008 and the first months of 2009 the performance of these cubicles was evaluated, and the results are presented in this paper.