An infrared thermography passive approach to assess the effect of leakage points in buildings

• Published in: Energy and buildings 2017-04, Vol.140, p.224-235
• Main Authors: Barreira, Eva, Almeida, Ricardo M.S.F., Moreira, Mariana
• Format: Article
• Language: English
• Subjects: Aerial thermography; Air flow; Air leakage; Air temperature; Airtightness; Building envelopes; Buildings; Energy consumption; Energy efficiency; Energy management; Flow rates; Flow velocity; Greenhouse effect; Greenhouse gases; Infrared imaging; Infrared thermography; Leakage; Leakage points; Power efficiency; Pressure; Pressurization; Qualitative analysis; Quantitative analysis; Temperature effects; Temperature gradients; Test procedures; Thermography
• ISSN: 0378-7788; 1872-6178
• DOI: 10.1016/j.enbuild.2017.02.009

•IRT was successfully applied to assess air leakages.•A colder area near the leakage points can be detected by IRT.•Surface temperature tends to stabilize close to the outdoor temperature.•The first pressure step has major impact in the superficial temperature differences. Energy consumption is one of the major concerns of European citizens and governments. In the EU, buildings use 40% of total energy consumption and generate 36% of greenhouse gases. Therefore, buildings energy efficiency must be optimized, which requires, among others, minimizing infiltrations through the envelope. The measurement of the air leakages through a building envelope is usually carried out by means of the fan pressurization method (Blower Door Test). Although useful for assessing the airtightness of buildings no information is obtained regarding the air leakage pathways. For that, other techniques such as infrared thermography (IRT) can be used. This work presents the results of an experimental campaign that aimed to assess the applicability of IRT to detected air leakage through the roller shutter handle and the window frame of a room. A quantitative approach for results analysis was implemented and the contribution for airtightness of both roller shutter handle and window frame was also evaluated using the Blower Door Test. It was possible to conclude that the window frame had a larger contribution to the air flow rate than the roller shutter handle (109.4m3/h and 21.7m3/h, at a pressure difference of 50Pa). Qualitative analysis of the thermal images indicated that a colder area near the leakage point can be detected and that it grows with the increase of the pressure difference. The quantitative approach showed that a stabilization of the surface temperature close to the value of the outdoor temperature occurred and the relative differences are around 15% both for the window frame and the roller shutter handle. It also showed that, in most cases, the first pressure step (ΔP=25Pa) is responsible for about 60% of the differences in the superficial temperature. A good correlation was found between the proposed Pressurization Thermal Index and the temperature gradient between the exterior air temperature and the initial superficial temperature (ranging from 0.74 to 0.82).