建筑节能有关法规及热工计算方法探讨（下）

为了定量地说明体型系数、窗墙比、建筑朝向、窗户材质、外墙及屋顶的保温及遮阳等对于该模型综合指标的影响程度，我们做了大量的计算，并总结出如下规律。利用这些规律，对于类似的建筑，我们可以不通过计算就能基本定量地进行评估。     

建筑间遮挡对光伏发电系统输出功率影响的研究

城市建筑屋顶的光伏发电利用潜力与其遮挡条件密切相关。因此,仅根据太阳辐照度评估城市建筑屋顶光伏发电利用潜力,未考虑城市建筑之间的相互遮挡因素,会导致一些情景下的评估结果偏大。为了准确评估城市建筑屋顶光伏发电利用潜力,采用建筑相对朝向、容积面积比及建筑群垂直和水平分布这3个城市形态参数作为预测变量,采用3D建筑模型进行实验,模拟不同形态建筑遮挡,获得多组有效实验数据,对城市不同形态建筑间的遮挡系数进行了量化分析;借助数据统计分析软件SPSS对多组实验数据完成统计分析后,建立了建筑群预测遮挡统计模型,并以长沙市某小区为例对该统计模型的适用性进行了验证,预测了该小区不同情景下的建筑屋顶光伏发电利用潜力。结果显示：利用该统计模型可得到被遮挡建筑的阴影遮挡水平,从而能更好地利用建筑屋顶光伏发电。研究结果提供了一种量化城市屋顶光伏组件遮挡系数的方法,对实现光伏建筑一体化和可持续城市发展有推进作用,可在城市区域建筑规划阶段模拟和预测屋顶遮挡情况。     

建筑给排水PPR管道延迟冻结保温层计算模型

建立一种建筑给排水PPR管道延迟冻结保温层计算模型,提出PPR管道延迟冻结保温层厚度计算的方法,分析比较了该方法与《工业设备及管道绝热工程设计规范》、《设备及管道绝热设计导则》进行建筑给排水管道延迟冻结保温层厚度计算的结果,给出常用PPR管道延迟冻结保温层厚度的减少率与保温材料节省量为建筑给排水管道延迟冻结保温层厚度设计计算提供参考与借鉴。     

外墙保温技术对空调负荷的影响

采用建筑热环境模拟工具DeST对同一住宅建筑进行模拟计算,分析了不同气候地区外墙保温形式及保温层厚度对空调负荷的影响,并讨论了空调运行模式及自然通风模式的影响,可为不同气候地区的住宅建筑外墙隔热保温设计提供依据。     

建筑围护结构节能技术与发展趋势

建筑围护结构节能技术是建筑节能的重要方面.本文对建筑围护结构中外墙、门窗和屋顶三个方而节能技术进行了介绍,并展望了三个方面建筑节能技术的发展趋势.     

聚苯颗粒砂浆保温效果研究

墙体材料主体采用240 mm厚MU10混凝土多孔砖,保温层为25 mm聚苯颗粒保温砂浆。采用热流计法进行了建筑外墙保温性能检测,检测结果表明该种气候条件下25 mm聚苯颗粒保温砂浆无法满足节能标准要求。从采暖能耗、保温材料造价角度出发计算了该墙体的经济保温层厚度为79 mm。     

绝热反射膜在建筑保温上的应用

对房屋建筑,特别是对既有房屋建筑外墙和屋顶进行保温隔热的技术改造,是实现降低建筑能耗的重要措施.北京中建建筑科学技术研究院(以下简称中建院)于近几年研制、开发的绝热反射膜就是一种新的保温隔热技术.北京源深节能技术有限责任公司(以下简称"源深公司")与中建院一道,先后于2003年冬季和2004年冬季选择使用分户式蓄能电采暖的用户进行了试验.     

反照率影响建筑热环境的实验

针对城市建筑物外墙墙面反照率变化，建立两个建筑物理模型，在不同反照率墙面材料的条件下，对夏季建筑室内热环境进行了分析研究，验证了采用高反照率的墙面材料是一种有效的、主动的隔热节能方式；采用积分拟合方法对墙面材料的反照率进行了拟合，其结果为实际情况下城市建筑外墙墙面材料的选择及其隔热性能分析、反照率的计算及其对建筑热环境的影响评价提供了一条有效的途径。     

严寒地区建筑本体设计参数与采暖空调能耗的定量关系

将影响建筑能耗的设计参数分为体型设计参数和热工设计参数,体型设计参数的代表变量为平面尺寸、建筑高度、窗墙比和朝向,热工设计参数的代表变量为屋顶、外墙、外窗传热系数。通过建立寒冷地区办公建筑的建筑模型,对以上变量确定变化范围及步长,进行全工况的全年动态能耗模拟。通过单变量敏感性分析,得到以上变量对能耗的影响,并定量表述其与能耗的关系。     

北京市某高校建筑围护结构对能耗影响敏感性研究

以北京市某高校教学建筑为例，采用局部因素敏感性分析法，分析围护结构参数对建筑采暖能耗和制冷能耗的影响规律。结果显示：各围护结构参数对建筑采暖、制冷能耗影响程度的平均敏感度排序为外窗遮阳系数>外窗传热系数>外墙传热系数>屋顶传热系数。     

Life cycle energy analysis of a residential building with different envelopes and climates in Indian context

In this paper life cycle energy (LCE) demand of a residential building of usable floor area about 85.5 m² located at Hyderabad (Andhra Pradesh), India is evaluated under different envelopes and climates in Indian context. The house is studied with conventional (fired clay) and alternative wall materials (hollow concrete, soil cement, fly ash and aerated concrete) under varying thickness of wall, and insulation (expanded polystyrene) on wall and roof. The house is modelled for five different climatic zones of India, i.e. hot and dry, warm and humid, composite, cold and moderate. Study suggests that alternative wall materials alone (without insulation) reduce LCE demand of the building by 1.5-5%. Aerated concrete (AC), as wall material, has better energy performance over other materials. LCE savings are significant when insulation is added to external wall and roof. It varies from 10% to 30% depending on the climatic conditions. Maximum LCE savings with insulation are observed for warm and humid climate and least for moderate climate. For same thickness of insulation, LCE savings are much more with roof insulation than wall insulation. But wall insulation is found to be preferable to a thicker wall. It is also observed that there is a limit for thickness of insulation that can be applied on external walls and roof from life cycle point of view. This limit is found to be about 10 cm for composite, hot and dry, warm and humid, and cold climates and 5 cm for moderate climate.     

Effect of electricity tariff on the optimum insulation-thickness in building walls as determined by a dynamic heat-transfer model

Thermal insulation is one of the most effective energy-conservation measures in buildings. Despite the widespread use of insulation materials in recent years, little is known regarding their optimum thickness under dynamic thermal conditions. Insulated concrete blocks are among the units most commonly used in the construction of building walls in Saudi Arabia. Typically, the insulation layer thickness is fixed at a value in the range 2.5–7.5 cm, regardless of the climatic conditions, type and cost of insulation material, and other economic parameters. In the present study, a numerical model based on a finite-volume, time-dependent implicit procedure, which has been previously validated, is used to compute the yearly cooling and heating transmission loads under steady periodic conditions through a typical building wall, for different insulation thicknesses. The transmission loads, calculated by using the climatic conditions of Riyadh for a west-facing wall, are fed into an economic model in order to determine the optimum thickness of insulation (L_opt). The latter corresponds to the minimum total cost, which includes the cost of insulation material and its installation plus the present value of energy consumption cost over the lifetime of the building. The optimum insulation thickness depends on the electricity tariff as well as the cost of insulation material, lifetime of the building, inflation and discount rates, and coefficient of performance of the air-conditioning equipment. In the present study, the effect of electricity tariff on the computed optimum insulation thickness is investigated. Different average electricity tariffs are considered; namely, 0.05, 0.1, 0.2, 0.3 and 0.4 SR/kWh (designated as Cases 1–5, respectively; 1 US$ = 3.75 Saudi Riyals). Results using moulded polystyrene as an insulating material show that the values of L_opt are: 4.8, 7.2, 10.9, 13.7 and 16.0 cm for Cases 1–5. Under the conditions of optimal insulation thickness for each electricity tariff, Case 1 gives the lowest total cost of 17.4 SR/m², while Case 5 gives the highest total cost of 53.1 SR/m². Corresponding thermal performance characteristics in terms of yearly total and peak transmission loads, R-value, time lag and decrement factor are presented.     

Optimal roof structure with multilayer cooling function materials for building energy saving

Both cool roof and phase change thermal storage are promising technologies in decreasing building energy consumption. Combining these two technologies is likely to further enhance the thermal comfort of the building as well as reduce air condition loads. In this paper, the cooling performance and energy-saving effects of four types of roof (normal roof, phase change material [PCM] roof, cool roof, and cool PCM roof [cool roof coupled with PCM]) were investigated under a simulated sunlight. Experimental results indicate that compared with normal roof, the other three roofs are able to narrow the indoor temperature fluctuation and decrease the heat flow entering into the room. Among them, cool PCM roof gave the best energy-saving effect that can lower the indoor temperature and heat entering into rooms by 6.6°C and 52.9%, respectively. Besides, the PCM location, PCM thickness, and insulation thickness exerted great impacts on the cooling performance of the roof. Placing the PCM on the internal layer beneath the extruded polystyrene (XPS) insulation board can make the indoor temperature 1.2°C lower than that on the middle layer. Although thicker PCM panels or insulation boards can provide a better thermal insulation, 5 mm in PCM thickness and 20 mm in insulation thickness are enough to guarantee the indoor temperature of cool PCM roof system at a comfortable range (22°C-28°C) for a whole day. These findings will give guidance in designing buildings with a light and compact roof structure to decrease energy consumption and improve comfort level.     

Effect of wall orientation on the optimum insulation thickness by using a dynamic method

A comprehensive economic analysis has been performed to inter-relate the optimum thickness of insulation materials for various wall orientations. The yearly cooling and heating transmission loads of building walls were determined by use of implicit finite-difference method with regarding steady periodic conditions under the climatic conditions of Elaz??, Turkey. The economic model including the cost of insulation material and the present value of energy consumption cost over lifetime of 10 years of the building was used to find out the optimum insulation thickness, energy savings and payback periods for all wall orientations. Considered insulation materials in the analysis were extruded polystyrene and polyurethane. As a result, the optimum insulation thickness of extruded polystyrene was found to be 5.5 cm for south oriented wall and 6 cm for north, east and west oriented walls. Additionally, the lowest value of the optimum insulation thickness and energy savings were obtained for the south oriented wall while payback period was almost same for all orientations.     

BIPV: a real-time building performance study for a roof-integrated facility

Building integrated photovoltaic system (BIPV) is a photovoltaic (PV) integration that generates energy and serves as a building envelope. A building element (e.g. roof and wall) is based on its functional performance, which could include structure, durability, maintenance, weathering, thermal insulation, acoustics, and so on. The present paper discusses the suitability of PV as a building element in terms of thermal performance based on a case study of a 5.25?kW_p roof-integrated BIPV system in tropical regions. Performance of PV has been compared with conventional construction materials and various scenarios have been simulated to understand the impact on occupant comfort levels. In the current case study, PV as a roofing material has been shown to cause significant thermal discomfort to the occupants. The study has been based on real-time data monitoring supported by computer-based building simulation model.     

A study on optimum insulation thickness in walls and energy savings in Tunisian buildings based on analytical calculation of cooling and heating transmission loads

In Tunisian climate, both heating in winter and cooling in summer are required to reach comfort levels. Due to the significant increase in building energy consumption, insulation of external walls is recently applied with a thickness typically ranging between 4 cm and 5 cm regardless of structure and orientation of walls and of economic parameters. In the present study, optimum insulation thickness, energy saving and payback period are calculated for a typical wall structure based on both cooling and heating loads. Yearly transmission loads are rigorously estimated using an analytical method based on Complex Finite Fourier Transform (CFFT). Considering different wall orientations, the west and east facing walls are the least favourite in the cooling season, whereas the north-facing wall is the least favourite in the heating season. A life-cycle cost analysis over a building lifetime of 30 years shows that the south orientation is the most economical with an optimum insulation thickness of 10.1 cm, 71.33% of energy savings and a payback period of 3.29 years. It is noted that wall orientation has a small effect on optimum insulation thickness, but a more significant effect on energy savings which reach a maximum value of 23.78 TND/m² in the case of east facing wall. A sensitivity analysis shows that economic parameters, such as insulation cost, energy cost, inflation and discount rates and building lifetime, have a noticeable effect on optimum insulation and energy savings. Comparison of the present study with the degree-days model is also performed.     

Energy analysis of buildings employing thermal mass in Cyprus

In this paper the effects on the heating and cooling load resulting from the use of building thermal mass in Cyprus are presented. This is achieved by modelling and simulation with the TRNSYS program of a typical four-zone building with an insulated roof in which the south wall of one of the zones has been replaced by a thermal wall. Despite the fact that the diurnal temperature variations in Cyprus are ideal for the application of thermal mass, no such application is presently available. Therefore the main objective of this paper is to investigate the possible benefits resulting from such an application. The results of the simulation show that there is a reduction in the heating load requirement of the zone by about 47%, whereas at the same time a slight increase of the zone-cooling load is exhibited. Optimisations of the various construction parameters have also been carried out. The optimum overhang size is found to be equal to 1.2 m with minor variations in the range of 1 to 1.5 m. The effect of the air gap size between the glazing and the thermal wall is insignificant. The optimum value of wall thickness obtained is equal to 25 cm. The effect of roof insulation is investigated and it is found that insulation is a must for better comfort conditions. Also, the effect of applying ventilation whenever the ambient temperature is lower than the indoor temperature during summertime is investigated. A reduction of 7.5% is obtained when air at 3 air changes per hour is directed into the house. In conclusion it can be said that the thermal wall offers some advantages and should be used whenever buildings are erected with south-facing walls.     

Thermal performance of a non-air-conditioned building with PCCM thermal storage wall

This paper presents a time-dependent periodic heat transfer analysis of a non-air-conditioned building having a south-facing wall of phase-changing component material (PCCM). A rectangular room (6 × 5 × 4 m) based on the ground is considered. The effects of heat transfer through walls and roof, heat conduction to the basement ground and furnishings, heat gain through window and heat loss due to air ventilation have been incorporated in the periodic time-dependent heat transfer analysis. The time-dependent heat flux through the PCCM south-facing wall has been obtained by defining the effective thermal properties of the PCCM for a conduction process with no phase change. Numerical calculations are made for a typical mild winter day (7 March 1979) at New Delhi for heat flux entering through the wall and inside air temperature. Further, a PCCM wall of smaller thickness is more desirable, in comparison to an ordinary masonry concrete wall, for providing efficient thermal energy storage as well as excellent thermal comfort in buildings.     

Thermal network analysis of a conditioned building: The effect of location of insulation

Thermal network analysis has been applied to an air-conditioned enclosure to predict the daily variation of heat flux. The effect of putting the insulation on the concrete roof/wall has been analysed in detail. It is found that, when only the ceiling is insulated, the difference in concrete thickness, either on the top side or bottom side with a fixed thickness of insulation sandwiched in between, total concrete thickness remaining the same, does not affect the total heat flux appreciably. The contributions to the heat flux from the south and west walls are also found to be quite significant. The effect of putting the insulation on the south, as well as on the west, walls is also significant.     

Investigation on the thermal performance of different lightweight roofing structures and its effect on space cooling load

The lightweight aluminum standing seam roofing system (LASRS) has been widely used as a building element in the construction of either commercial or governmental buildings, and has been proven to be an economic roofing system. However, little research has been conducted into its thermal performance and the effect of the absorptivity (colour) of its external surface on space cooling load in the hot humid area. This paper aims to investigate the thermal performance of the LASRS. A dynamic model is introduced for analyzing the transient heat transfer through the roofs, which was solved by the control volume finite-difference method employing an explicit scheme and validated by measured data. The simulation results show that the heat flux through the roofing system with a polyurethane insulation layer is smaller than that through the lightweight roof with glasswool insulation R1. The space cooling load reduction ratio for light painted envelop could reach about 9.3% compared with black painted one. The cooling load reduction ratio ranges from 1.3% to 9.3% for the roof structure R1 with various surface colour. Therefore, the space cooling load for air conditioning of the building can be considerably reduced (up to 20%) by employing a lightweight roof using polyurethane insulation with white painted surface colour.