Hygrothermische Wirkungen von Raum‐ und Außenoberflächen

The hygrothermal effect of inside and outside building envelope surfaces. In the past the protection of building constructions under outdoor and indoor climate conditions was one of the most important subjects building physics. Nowadays the energy balance and the hygrothermal performance of building envelopes are current topics. This paper deals with the coupled heat and moisture transfer on the internal and external envelope surfaces. By means of numerical simulation and laboratory investigation the influence of the internal surface of exterior walls on the indoor air humidity is demonstrated. The influence of evaporation cooling on the energy transfer in winter time and during the warm season requires investigations on dewing and driving. It depends on the hygroscopic parameters of the outside wall coating. The effect of infrared reflecting coating is determined. It is shown in which way heat sources integrated in exterior walls could be a possibility to avoid microbiological growth on building envelopes.     

Development of HAM tool for building envelope analysis

Moisture-related building envelope failures have resulted in costly rehabilitation in various regions of North America. To advance building envelope design towards an engineering approach and reduce the occurrence of future failures, an advanced numerical tool was developed, in conjunction with an extensive full-scale experiment, to investigate hygrothermal performance of various wood-frame wall assemblies. Major features of the tool are multi-dimensional and transient coupling of heat and moisture transport; natural air convection integrated in hygrothermal simulation through Darcy–Boussinesq approximation; heat transfer by conduction and convection of sensible and latent heat; moisture transport by vapor diffusion, capillary suction and convection; material database of common building materials in North America; experimental settings or weather data as boundary conditions; and moisture added in the building envelope to simulate the wetting process. The numerical tool achieves good compliances to the benchmarking cases of the HAMSTAD project, and its predictions have shown good agreement with data from the full-scale wall experiment. The numerical tool employs the commercial finite-element software to solve the governing equations. This approach provides building science researchers the flexibility to modify, maintain and share their modeling work efficiently.     

Experimental data set for validation of heat,air and moisture transport models of building envelopes

This paper reports experimental studies on heat, air and moisture (HAM) transfer through a full scale light weight building envelope wall under real atmospheric boundary conditions. The main objective of the article is to generate informative data so that it can be used for numerical validation of HAM models. The considered wall is a multilayered structure built up from outside to inside of external board, vented cavity, fibreboard sheathing, mineral wool between wooden studs and interior finishing. The global wall has a surface area of (1.80 × 2.68) m²; and is subdivided into three vertical parts. The parts differ from each other by the applied interior finishing. Between the different layers of each part and on the surfaces of the wall humidity, temperature and heat flux sensors are placed in a 3D matrix. At the outer surface of the wall, the applied sheathing is a bituminous wood board. In the board nine removable specimens are included. By regularly weighing the fibreboard samples, their moisture content could be quantified. Using data collected over a total time span of about two years, insight about the hygrothermal behaviour of the different envelope parts is obtained and at the same time a well-documented data set is generated that can be used for hygrothermal envelope model validation purposes.     

Sonnenschutz: Eine generelle Bewertungsmethode – auch für zwischenliegende Systeme – und zwei neue Behänge

Sun control: General evaluation method (also suitable for integrated systems) and two new blind types. A general method for realistic performance evaluation of solar control properties of facades with sun‐shading or other solar control systems has been developed. It is particularly designed to be used for venetian blinds. It can be used ‘stand‐alone’ or within building simulation programs. The new method has proven to be of great practical value to planning teams of huge office buildings in Germany, Austria and Switzerland. The method is presented in detail in [4]. It can be used either ‘stand‐alone’ (without building simulation) for comparisons of different facade variants or within building simulation programs. In this publication the extension of the methodology for the case of facades with solar control systems between the panes of an insulating glazing unit (IGU) is presented. Some parts of the proposed methodology could be used in standards (e.g. EN 13363) or to improve the accuracy of building simulation programs which are currently on the market. Practical experience with the new methodology led to insights which are the basis for the design of two new products. These new products are compared with state of the art products in [5] on the basis of the new methodology. We are currently linking the new method with the building simulation program ESP‐r in a project which is funded by the Veluxstiftung.     

光热建筑一体化Trombe墙体系统传热性能

为了改善建筑围护结构的保温隔热性能和利用太阳能,提出了一种光热建筑一体化Trombe墙体系统,建立了实验墙体和模拟计算模型,并对墙体系统的热传递性能进行了实验测试和模拟分析。研究结果表明:实验工况下集热板、主墙层外侧和内侧最高温度测量值分别为91.3、57.9、23.4℃,模拟值为88.4、58.3、17.2℃,墙体系统在冬季具有较好的保温性能;太阳辐射作用下,墙体系统的各材料层均产生竖向温度差,实验工况下竖向温度差为集热板17.9℃、主墙层外侧31.7℃、主墙层内侧2.2℃,模拟值为集热板17.2℃、主墙层外侧21.9℃、主墙层内侧1.2℃;墙体系统各材料表面的竖向温度差随太阳辐射照度增加而增大,随空气夹层厚度增大而减小。     

新建节能建筑墙体材料层及排布对干燥过程的影响

建筑围护结构内的热湿耦合传递是一个非常复杂的过程,其研究是降低建筑能耗、评估和预防湿害、提高室内热舒适性、室内卫生及优化围护结构性能的基础。新建节能建筑墙体具有初始含湿量大的特点,若墙体湿积累过大,则容易出现墙体表面剥蚀、渗漏、发霉甚至结构出现损坏的现象。墙体干燥时,传热传质过程同时发生且相互耦合。目前相关热物性仿真软件、理论研究和设计规范主要建立在热传递的基础上,忽略了湿传递的影响,对新建建筑墙体干燥不适用。WUFI~? Pro热湿仿真软件充分考虑了材料本身含湿量、风驱雨、太阳辐射、长波辐射、毛细传输和夏季结露等典型气候的影响,实现了对自然气候条件下建筑构件非稳态热湿性能的真实计算。节能墙体多在外墙添加内外保温层来增加围护结构的传热热阻,且在保温层内外两侧分别添加隔汽层和空气层的措施来防止保温层受潮,最终提高围护结构的保温性能。为墙体美观,多在围护结构的内外两侧分别黏贴墙纸和釉面砖。采用WUFI~? Pro对北京地区2种典型的建筑墙体进行热湿耦合传递模拟,分析新建建筑墙体在不同保温层材料和位置时的干燥过程,以及保温层两侧的隔汽层和空气层、墙体两侧的墙纸和釉面砖对墙体干燥过程的影响。模拟用室外条件为北京典型气象年小时室外气象参数,室内条件设定室内冬季供暖温度T_1=20℃,夏季室内温度设计值T_2=25℃,全年平均相对湿度为50%。模拟外围护结构属于西向,墙体温湿度初始条件为:相对湿度为100%,温度为15℃。模拟结果表明:内保温层的设置非常不利于围护结构的干燥,容易在内保温层和砌块之形成湿积累,降低围护结构的耐久性;EPS、PU和XPS都能降低围护结构含湿量,但EPS更有利于墙体干燥;隔汽层和空气层的添加可一定程度上阻止保温层受潮,避免造成湿积累,进而提高围护结构的保温性能;釉面砖和墙纸的黏贴将严重延缓围护结构的干燥过程,降低围护结构的保温性能,缩减建筑构件的使用寿命。     

Impact of combined moisture buffering capacity of a hemp concrete building envelope and interior objects on the hygrothermal performance in a room

In this article, a hygrothermal building model, taking into account the building envelope, indoor heat and moisture sources, indoor environment and moisture buffering capacity of interior objects, is presented and validated with the test cases found in the literature. The model is used to study the impact of hemp concrete and the moisture buffer capacity of the interior elements on the prediction of the hygrothermal comfort in the building. The numerical results show that the use of hemp concrete in buildings can ensure good hygrothermal comfort. Besides, taking into account the effect of moisture buffering of indoor objects increases the building performance. Our results also suggest that neglecting moisture transfer through the envelope increases significantly the predicted percentage of dissatisfied indices and reduces the acceptability of indoor air quality during the occupied period. This study also confirmed that the combined relative humidity-sensitive ventilation system and moisture buffering capacity of building envelope and of interior objects is a very efficient way to reduce the heating energy consumption.     

Hygrothermische Beanspruchung und Lebensdauer von Wärmedämm‐Verbundsystemen

Hygrothermal loads and service life of external wall insulation systems. Service life and aging behaviour of external wall systems depend on their hygrothermal loads. Apart from the fluctuating climatic conditions temperature, solar radiation and humidity there are often additional exterior or interior sources of moisture, e.g. driving rain, construction moisture or surface condensation acting on facades. External wall insulation systems (ETICS = E xternal T hermal I nsulation C omposite S ystems) are especially affected due to their low mass. However, the long‐term observation by repeated inspections of the same objects over a period of 30 years proves that ETICS show not more damage than traditional facades. Apart from minor esthetical problems due to soiling or microbial growth their long‐term behaviour is very encouraging. Maintained at normal intervals ETICS are as durable as traditionally rendered masonry walls.     

Bauen im Bestand – Lösungen für Dach und Fassade in Stahlleichtbauweise

Building redevelopment – Solutions for roof and façade using lightweight steel construction . The research project ”Building redevelopment – Solutions for roof and façade using lightweight steel construction“ investigates possibilities to improve energetically existing roof and façade systems in lightweight steel and massive construction by using lightweight steel systems. As refurbishment systems steel sandwich panels as well as modular lightweight steel constructions, consisting for example of steel supporting profiles, thermal insulation and steel sheet profiles, will be applied. Besides hygrothermal‐building‐physical studies also static‐mechanical reviews for the energetically optimized building systems will be conducted. The present paper shows selected results that have been developed within the project. On the one hand, the energetic quality of existing façades in lightweight steel construction is shown, and savings potentials due to heat transmission, which are opened up by the renovation of these façades, are clarified. On the other hand, some of the resulting building‐structural questions with regard to load‐bearing behaviour and loadings are discussed.     

A nodal thermal model for photovoltaic systems: Impact on building temperature fields and elements of validation for tropical and humid climatic conditions

This article deals with both an experimental study and a numerical model of the thermal behaviour of a building whose roof is equipped with photovoltaic panels (PV panels). The aim of this study is to show the impact of the PV panels in terms of level of insulation or solar protection for the building. Contrary to existing models, the one presented here will allow us to determine both the temperature field of the building and the electric production of the PV array. Moreover, an experimental study has been conducted in La Reunion Island, where the climate is tropical and humid, with a strong solar radiation. In such conditions, it is important to minimise the thermal load through the roof of the building. The thermal model is integrated in a building simulation code and is able to predict the thermal impact of PV panels installed on buildings in several configurations and also their production of electricity. Basically, the PV panel is considered as a complex wall within which coupled heat transfer occurs. Conduction, convection and radiation heat transfer equations are solved simultaneously to simulate the global thermal behaviour of the building envelope including the PV panels; this is an approach we call ‘integrated modelling’ of PV panels. The experimental study is used to give elements of validation for the numerical model and a sensitivity analysis has been run to put in evidence the governing parameters. It has been shown that the radiative properties of the PV panel have a great impact on the temperature field of the tested building and the determination of these parameters has to be taken with care.     

Experimental and numerical analysis of heat transfer and airflow on an interactive building facade

The envelope of a building is mainly responsible for its energy demand. Different kinds of double skin facades (DSFs) are nowadays used as a building envelope to reduce the energy demand and improve aesthetical view of buildings. Although DSF are already extensively used, their thermal performance is not well understood. This study presents a decoupling method capable to evaluate thermal performances and analyze fluid phenomena in a DSF. The solar radiation effects were evaluated with an analytical model and computational fluid dynamics (CFD) simulations were used to evaluate complex flow and thermal effect on a commercial DSF. With the decoupling approach to account for the effects of solar radiation and flow, the numerical results obtained by the CFD approach agree well with the experimental data collected on a full scale test room with a ventilated DSF. The method can be used to establish a database to develop a tool for DSF design.     

建筑方案设计中的太阳辐射模拟研究

合理利用太阳能资源是实现建筑节能的重要技术措施。为更合理的利用太阳能,运用Ecotect软件精确地对太阳辐射定量分析,建立太阳能辐射分析模型,对住宅建筑的设计方案进行模拟研究。根据建筑的功能特点以及周边区域的自然环境,建立分析模型,为建筑进一步深化设计以及施工提供可靠依据。以武汉蔡甸区一栋低层钢结构住宅为例,通过建筑场地太阳辐射、遮阳构件、光伏系统以及蓄热墙体的模拟分析,对建筑设计方案进行优化,并分析评价方案优化后的建筑采光及节能效果,为工程师在设计建造过程中提供科学指南。     

Einfluss der vom menschlichen Körper absorbierten Solarstrahlung für das Wärmeempfinden in Gebäuden

Influence of solar radiation absorbed by the human body on the thermal sensation of building occupants. One of the key aspects of sustainable building is the well‐being of occupants, which is greatly influenced by indoor climate conditions. Thermal comfort is a vital ingredient of satisfaction with people's surroundings. It is to be expected that solar radiation will have a favourable influence on indoor social areas particularly in the winter months when radiation is predominantly diffuse. In contrast, direct exposure to sunshine in summer or on very sunny days in winter can quickly make people feel uncomfortable near windows and this must be counteracted by appropriate measures to protect them from the sun. The significance of solar radiation for the thermal sensation is illustrated on the basis of a further development of Fanger's approach by means of simulations. The main results are summarised in this article.     

不同气候区建筑获得太阳辐射的动态分布特征

提高太阳能资源在建筑中的利用水平是减缓建筑对传统能源依赖程度的重要途径,也是推广可再生能源建筑应用的基本举措。基于全国五类气候分区代表性城市全年典型气象数据,结合计算模型研究分析了建筑屋面、东面、南面、西面、北面获得太阳辐射量的动态分布特征,确定了建筑各个方位利用太阳能资源的潜力。研究结果表明除了传统地发挥屋面利用太阳能的方法外,建筑立面接收太阳能辐射的能力也能达到良好的效果,即建筑立面利用太阳能具有较好的应用价值。     

夏热冬冷地区外墙遮阳对建筑热环境与空调能耗的影响

介绍了夏热冬冷地区外墙遮阳在建筑中的实际应用,并从墙体受太阳辐射热影响的机理,阐述了外墙遮阳对室内热环境与建筑空调能耗的影响。以南京地区一栋典型居住建筑为例,使用清华大学开发的建筑能耗模拟软件DeST—h,模拟并分析了对于两种不同构造的外墙,分别通过采取外遮阳措施,减小外表面太阳辐射吸收系数对夏季室内热环境和空调能耗的影响程度,并用实验方法对模拟结果进行了辅证。     

干热干冷地区围护结构热工设计对内表面温度及室内热舒适的影响

为了分析干热干冷地区围护结构热工性能对室内热环境的影响,采用物理环境实测结合动态模拟方法对比分析了2组墙体的保温、蓄热性能对内表面温度的影响,并结合太阳辐射季节变化探究了太阳辐射吸收比对室内热舒适的影响.研究表明:实测结果与模拟结果吻合较好,对于干热干冷地区,提高围护结构蓄热性能能够降低夏季内表面温度,对冬季内表面温度...     

太阳能富集地区住宅建筑非平衡保温研究——拉萨市供暖期太阳辐射分析与室内热环境测试

在有供暖需求的太阳能资源富集地区,由于太阳辐射强烈,住宅建筑各个朝向外墙,尤其是南北向的外墙所接收的太阳辐射量差异很大,为了更有效地利用太阳能并降低保温成本,这种差异应表现在建筑围护结构保温性能的设计中.本文通过对拉萨市标准年气象数据库的分析得到了其住宅建筑各朝向外墙供暖季内获得的太阳辐射量.与内地城市相比,拉萨市太阳能资源丰富且朝向差异很大,非平衡保温具有一定的实际意义.另外,冬季现场测试表明无供暖建筑的南北朝向房间热环境有所不同,南向房间测试周期内基本处于人体舒适范围内,而北向房间始终偏冷,远离人体热舒适区域,有供暖需求.     

Entwicklung und Validierung einer hygrothermischen Raumklima‐Simulationssoftware WUFI®‐Plus

Development and validation of the hygrothermal indoor climate simulation software WUFI®‐Plus. Well‐balanced conditions of thermal, moisture and air quality are very important in buildings because an imbalance of these factors could have significant influences on the construction and the inhabitants. The focus of this paper is the influence of different materials on the fluctuation of relative humidity specifically humidity peaks. In lieu of complicated and expensive laboratory testing several different software tools have been developed to estimate the indoor environmental conditions of buildings. The Fraunhofer‐Institute for Building Physics (IBP) developed a hygrothermal simulation tool. With this software the temperature and moisture conditions of the walls, ceiling and floor constructions, of the indoor air and the energy consumption for the building can be calculated. In the context of the IEA‐Annex 41 project “Moist‐Eng“ a common exercise has been carried out for the validation of such software tools. For the common exercise at the free field investigation area in Holzkirchen (Germany) two identical rooms were used to measure the moisture buffering capacity of several interior finish systems. To address the questions of buffering capacity the IBP developed a hygrothermal simulation tool, WUFI®‐Plus [1]. Using the measurement data from the common exercise calculations were carried out with several software tools for the validation of it. In this paper the results of the laboratory tests and simulation results are described.     

Development and validation of a new TRNSYS type for the simulation of external building walls containing PCM

In building construction, the use of phase change materials (PCMs) allows the storage/release of energy from the solar radiation and/or internal loads. The application of such materials for lightweight construction (e.g., a wood house) makes it possible to improve thermal comfort and reduce energy consumption. However, in order to assess and optimize phase change materials included in building wall, numerical simulation is mandatory. For that purpose, a new TRNSYS Type, named Type 260, is developed to model the thermal behavior of an external wall with PCM. This model is presented in this paper and validated using experimental data from the literature.