1.1 本规程涵盖了如何获取和使用建筑围护结构上温度和热通量的现场测量数据来计算热阻。热阻在术语中定义 C168 仅在稳态条件下。本规程提供了在测量温度和热流时遇到的温度范围的估计值。 1.2 本实践介绍了两种特定技术，求和技术和最小二乘法，并允许使用已正确验证的其他技术。 本规程提供了一种估算建筑构件平均温度的方法，用于估算测量温度的相关性 R -求和技术的温度值。最小二乘和技术可以计算热阻，热阻是平均温度的函数。 1.3 每个热阻计算适用于安装了仪表的建筑围护结构组件的一个子部分。每个计算都适用于与测量类似的温度条件。 根据现场数据计算的热阻代表了使用条件。然而，温度和热流的现场测量可能无法达到实验室设备中可获得的精度。 1.4 这种做法允许计算已正确安装温度和热流传感仪器的建筑围护结构部分的热阻。传感器的尺寸和建筑构件的结构决定了应使用多少传感器以及应放置在哪里。 由于可能的构造类型多种多样，传感器放置和随后的数据分析需要证明用户的良好判断。 1.5 每个计算仅适用于建筑围护结构的一个定义小节。结合不同小节的结果来表征整体热阻超出了本实践的范围。 1.6 本规程为计算热特性所需的数据收集技术设定了标准（见 注1 ). 任何有效的技术都可以为本规程提供数据，但本规程的结果不应被视为来自ASTM标准，除非仪器技术本身是ASTM标准。 注1: 目前仅限实践 C1046 可以为此实践提供数据。它还提供了如何以一种不仅仅代表建筑构件的仪表部分的方式放置传感器的指导。 1.7 这种做法与光有关- 通过中示例定义的中等重量结构 5.8 . 计算适用于观察到的室内和室外温度范围。 1.8 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.9 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.10 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 热阻测量的重要性- 了解新建筑的热阻对于确定施工质量是否满足设计师、业主或监管机构设定的标准很重要。 材料或工艺的质量差异可能导致建筑构件达不到设计性能。 5.1.1 对于现有建筑物- 对于旧建筑物的业主来说，了解热阻对于确定建筑物是否应进行隔热或其他节能改进非常重要。对材料的热特性或材料内部的热流路径的了解不足或材料的降解可能会导致使用已发布数据的计算中的假设不准确。 5.2 现场数据的优势- 本规程提供了基于测量数据的热性能信息。这可能决定新建筑的质量，以供业主或居住者验收，也可能为无法根据已发布的设计数据进行计算的节能投资提供理由。 5.3 热流路径- 本规程假设净热流垂直于给定分区内建筑围护结构构件的表面。 适当放置传感器需要了解测量区域的表面温度。通常使用适当的红外热成像来获取此类信息。热成像显示了由结构构件、对流、漏气和绝缘层中的水分引起的不均匀表面温度。实践 C1060 和 C1153 详细说明红外热成像的适当使用。请注意，作为将测量现场获得的结果外推到同一建筑物其他类似部分的基础的热成像超出了本规程的范围。 5.4 需要用户知识- 该实践要求用户了解所使用的数据代表足够的位置样本，以描述结构的热性能。这些知识的来源包括实践中的参考文献 C1046 以及 附录X2 . 计算的准确性在很大程度上取决于整个包络组件的温差历史。应正确使用传感和数据采集装置。 对流和水分迁移等因素影响现场数据的解释。 5.5 室内外温差- 本实践中描述的求和技术的收敛速度随着整个建筑围护结构的平均室内外温差的大小而提高。最小二乘和技术对室内外温差、小温差和漂移温差以及小累积热通量不敏感。 5.6 时变热条件- 现场数据表示不同的热条件。因此，获得时间序列数据的频率至少是最频繁的周期性热输入（如熔炉循环）的五倍。获取足够长时间的数据，以使两组数据在用户选择的时间段结束时不会导致热阻计算相差超过10 %, 如中所述 6.4 . 5.6.1 在适当的热条件范围内收集数据，以表示待表征条件下的热阻。 注2: 一些建筑构件的构造包括热性能取决于热流方向的材料，例如，在水平空气空间中对流和稳定分层之间的切换模式。 5.7 横向热流- 避免有明显横向热流的区域。报告每个温度源和热流数据的位置。确定可能的横向热流源，包括高导电表面、表面下的热桥、对流单元等。 ，这可能违反热流垂直于建筑围护结构构件的假设。 注3: 在建筑构件中存在横向热流的情况下，适当选择热流传感器和放置这些传感器有时可以提供有意义的结果。由于侧向热流，金属表面和某些混凝土或砌体构件可能会给测量带来严重困难。 5.8 轻型至中型结构- 这种做法仅限于光照- 室内温度变化小于3K的中等重量结构。本规程适用的最重结构重量为440 kg/m 2. 假设建筑结构中的大型构件的比热约为0.9 kJ/kg K。最重结构的示例包括:( 1. )a 390千克/米 2. 带有砖饰面、隔热层和内层混凝土砌块的墙或( 2. )76 mm混凝土板，带隔热层- 240 kg/m的上屋面 2. . 知识和经验不足，无法将实践扩展到重型施工。 5.9 热流模式- 热流模式是决定 R -包含空气空间的建筑中的价值。在水平结构中，空气分层或对流，这取决于热流是向下还是向上。在垂直结构中，例如带有空腔的墙壁，对流单元会影响 R -价值显著。 在这些配置中 R -该值是平均温度、温差和对流池高度沿线位置的函数。性能随条件变化的结构的测量超出了本规程的范围。

1.1 This practice covers how to obtain and use data from in-situ measurement of temperatures and heat fluxes on building envelopes to compute thermal resistance. Thermal resistance is defined in Terminology C168 in terms of steady-state conditions only. This practice provides an estimate of that value for the range of temperatures encountered during the measurement of temperatures and heat flux. 1.2 This practice presents two specific techniques, the summation technique and the sum of least squares technique, and permits the use of other techniques that have been properly validated. This practice provides a means for estimating the mean temperature of the building component for estimating the dependence of measured R -value on temperature for the summation technique. The sum of least squares technique produces a calculation of thermal resistance which is a function of mean temperature. 1.3 Each thermal resistance calculation applies to a subsection of the building envelope component that was instrumented. Each calculation applies to temperature conditions similar to those of the measurement. The calculation of thermal resistance from in-situ data represents in-service conditions. However, field measurements of temperature and heat flux may not achieve the accuracy obtainable in laboratory apparatuses. 1.4 This practice permits calculation of thermal resistance on portions of a building envelope that have been properly instrumented with temperature and heat flux sensing instruments. The size of sensors and construction of the building component determine how many sensors shall be used and where they should be placed. Because of the variety of possible construction types, sensor placement and subsequent data analysis require the demonstrated good judgement of the user. 1.5 Each calculation pertains only to a defined subsection of the building envelope. Combining results from different subsections to characterize overall thermal resistance is beyond the scope of this practice. 1.6 This practice sets criteria for the data-collection techniques necessary for the calculation of thermal properties (see Note 1 ). Any valid technique may provide the data for this practice, but the results of this practice shall not be considered to be from an ASTM standard, unless the instrumentation technique itself is an ASTM standard. Note 1: Currently only Practice C1046 can provide the data for this practice. It also offers guidance on how to place sensors in a manner representative of more than just the instrumented portions of the building components. 1.7 This practice pertains to light-through medium-weight construction as defined by example in 5.8 . The calculations apply to the range of indoor and outdoor temperatures observed. 1.8 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Significance of Thermal Resistance Measurements— Knowledge of the thermal resistance of new buildings is important to determine whether the quality of construction satisfies criteria set by the designer, by the owner, or by a regulatory agency. Differences in quality of materials or workmanship may cause building components not to achieve design performance. 5.1.1 For Existing Buildings— Knowledge of thermal resistance is important to the owners of older buildings to determine whether the buildings should receive insulation or other energy-conserving improvements. Inadequate knowledge of the thermal properties of materials or heat flow paths within the construction or degradation of materials may cause inaccurate assumptions in calculations that use published data. 5.2 Advantage of In-Situ Data— This practice provides information about thermal performance that is based on measured data. This may determine the quality of new construction for acceptance by the owner or occupant or it may provide justification for an energy conservation investment that could not be made based on calculations using published design data. 5.3 Heat Flow Paths— This practice assumes that net heat flow is perpendicular to the surface of the building envelope component within a given subsection. Knowledge of surface temperature in the area subject to measurement is required for placing sensors appropriately. Appropriate use of infrared thermography is often used to obtain such information. Thermography reveals nonuniform surface temperatures caused by structural members, convection currents, air leakage, and moisture in insulation. Practices C1060 and C1153 detail the appropriate use of infrared thermography. Note that thermography as a basis for extrapolating the results obtained at a measurement site to other similar parts of the same building is beyond the scope of this practice. 5.4 User Knowledge Required— This practice requires that the user have knowledge that the data employed represent an adequate sample of locations to describe the thermal performance of the construction. Sources for this knowledge include the referenced literature in Practice C1046 and related works listed in Appendix X2 . The accuracy of the calculation is strongly dependent on the history of the temperature differences across the envelope component. The sensing and data collection apparatuses shall have been used properly. Factors such as convection and moisture migration affect interpretation of the field data. 5.5 Indoor-Outdoor Temperature Difference— The speed of convergence of the summation technique described in this practice improves with the size of the average indoor-outdoor temperature difference across the building envelope. The sum of least squares technique is insensitive to indoor-outdoor temperature difference, to small and drifting temperature differences, and to small accumulated heat fluxes. 5.6 Time-Varying Thermal Conditions— The field data represent varying thermal conditions. Therefore, obtain time-series data at least five times more frequently than the most frequent cyclical heat input, such as a furnace cycle. Obtain the data for a long enough period such that two sets of data that end a user-chosen time period apart do not cause the calculation of thermal resistance to be different by more than 10 %, as discussed in 6.4 . 5.6.1 Gather the data over an adequate range of thermal conditions to represent the thermal resistance under the conditions to be characterized. Note 2: The construction of some building components includes materials whose thermal performance is dependent on the direction of heat flow, for example, switching modes between convection and stable stratification in horizontal air spaces. 5.7 Lateral Heat Flow— Avoid areas with significant lateral heat flow. Report the location of each source of temperature and heat flux data. Identify possible sources of lateral heat flow, including a highly conductive surface, thermal bridges beneath the surface, convection cells, etc., that may violate the assumption of heat flow perpendicular to the building envelope component. Note 3: Appropriate choice of heat flow sensors and placement of those sensors can sometimes provide meaningful results in the presence of lateral heat flow in building components. Metal surfaces and certain concrete or masonry components may create severe difficulties for measurement due to lateral heat flow. 5.8 Light- to Medium-Weight Construction— This practice is limited to light- to medium-weight construction that has an indoor temperature that varies by less than 3 K. The heaviest construction to which this practice applies would weigh 440 kg/m 2 , assuming that the massive elements in building construction all have a specific heat of about 0.9 kJ/kg K. Examples of the heaviest construction include: ( 1 ) a 390-kg/m 2 wall with a brick veneer, a layer of insulation, and concrete blocks on the inside layer or ( 2 ) a 76-mm concrete slab with insulated built-up roofing of 240 kg/m 2 . Insufficient knowledge and experience exists to extend the practice to heavier construction. 5.9 Heat Flow Modes— The mode of heat flow is a significant factor determining R -value in construction that contains air spaces. In horizontal construction, air stratifies or convects, depending on whether heat flow is downwards or upwards. In vertical construction, such as walls with cavities, convection cells affect determination of R -value significantly. In these configurations, apparent R -value is a function of mean temperature, temperature difference, and location along the height of the convection cell. Measurements on a construction whose performance is changing with conditions is beyond the scope of this practice.