In Situ Evaluation of the U-Value of a Window Using the Infrared Method

Abstract

The amount of heat lost through the envelope of a building is one of the most important variables that affects the energy performance evaluation of a house. In addition, it is especially important to estimate and accurately diagnose the amount of heat produced by windows. In Korea, windows’ U-values reflect a building’s initial design values and thermal characteristics that determine the thermal performance of an existing building, and is a factor that can overestimate the energy performance of a building. Therefore, there is a need for a field measurement method that can accurately measure the total U-value of windows in an existing house. This study provides a method of quantitatively measuring the total U-value of windows using the infrared (IR) method in ISO 9869-2. As a result of measuring the U-value using the infrared (IR) method, the Korean Standard (KS F 2278) for window performance test result values and the root mean square error (cvRMSE) for the U-value measurements using the IR method showed a high accuracy of about 3.29%. In addition, we confirmed that the IR method is an effective (cvRMSE about 7% improvement) method that can measure the comparison result faster than the heat flow meter (HFM) method, which is a conventional thermal performance measurement method.

Heat and power plant chimneys thermal inspection with an infrared camera

“…Not only walls but also the windows may generate significant amount of heat loss. The results of thermographic analysis proved the accuracy of about 3.3% in case of U-value including glass and frame in situ for windows [20].…”

Degradation of Insulating Glass Units: Thermal Performance, Measurements and Energy Impacts

“…Park et al used ISO 9869-2 as a basis for determining the accuracy of infrared for measuring window U-factor [36]. In this paper, the authors measured U-factor of a window sample using the KSF 2278 performance evaluation standard, the heat flow method, and the IR method.…”

Review of the Experimental Methods for Evaluation of Windows’ Thermal Transmittance: From Standardized Tests to New Possibilities

“…Yüksel [34] considered the HFM method and saw the HFM apparatus as an accurate, fast, and easy-to-use method with a measurement uncertainty of between 3% (at room temperature) and 10% for insulations, plastics, and glasses. When the actual U-value of an existing glazing system in a real situation (or even in a laboratory) is going to be determined, portable heat flux sensors associated with thermocouples could be used for in situ measurements instead of an HFM apparatus [11].…”

“…Therefore, the need to improve the thermal performance of building envelopes seems undeniable. To improve the building envelope energy performance, we have to know which parts of the envelope show weaker thermal performance [10,11]. Windows are one of those envelope elements that have received special attention.…”