A quantitative methodology to evaluate thermal bridges in buildings

Asdrubali, Francesco; Baldinelli, Giorgio; Bianchi, Francesco

doi:10.1016/j.apenergy.2011.12.054

Cited by 182 publications

(121 citation statements)

References 17 publications

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“…Asdrubali et al [5] proposed a quick and approximate methodology to perform quantitative analysis of thermal bridges, through thermographic surveys of the wall surface followed by analytical processing. From the simple measurement of the air temperature and the analysis of the thermograph, the thermal bridge effect can be estimated as a percentage increase over the same wall, but with homogenous transmittance.…”

Section: Research Backgroundmentioning

confidence: 99%

Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

et al. 2016

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Thermal bridges in building walls are usually caused by mortar joints between insulated building blocks and by the presence of concrete columns and beams within the building envelope. These bridges create an easy path for heat transmission and therefore increase air-conditioning loads. In this study, the effects of mortar joints only on cooling and heating loads in a typical two-story villa in Riyadh are investigated using whole building energy analysis. All loads found in the villa, which broadly include ventilation, transmission, solar and internal loads, are considered with schedules based on local lifestyles. The thermal bridging effect of mortar joints is simulated by reducing wall thermal resistance by a percentage that depends on the bridges to wall area ratio (TB area ratio or A mj /A tot ) and the nominal thermal insulation thickness (L ins ). These percentage reductions are obtained from a correlation developed by using a rigorous 2D dynamic model of heat transmission through walls with mortar joints. The reduction in thermal resistance is achieved through minor reductions in insulation thickness, thereby keeping the thermal mass of the wall essentially unchanged. Results indicate that yearly and monthly cooling loads increase almost linearly with the thermal bridge to wall area ratio. The increase in the villa's yearly loads varies from about 3% for A mj /A tot = 0.02 to about 11% for A mj /A tot = 0.08. The monthly increase is not uniform over the year and reaches a maximum in August, where it ranges from 5% for A mj /A tot = 0.02 to 15% for A mj /A tot = 0.08. In winter, results show that yearly heating loads are generally very small compared to cooling loads and that heating is only needed in December, January and February, starting from late night to late morning. Monthly heating loads increase with the thermal bridge area ratio; however, the variation is not as linear as observed in cooling loads. The present results highlight the importance of reducing or eliminating thermal bridging effects resulting from mortar joints in walls by maintaining the continuity of the insulation layer in order to reduce energy consumption in air-conditioned buildings.

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Section: Research Backgroundmentioning

confidence: 99%

Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

et al. 2016

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“…As a consequence, the perfect times are either at midday, when outdoor temperature reaches its maximum and indoor temperature is usually colder allowing the detection of incoming heat, or at the beginning of the day in winter, with the heaters turned on, allowing the detection of incoming cold air. From a metric point of view, thermographies must be acquired from a position forming an approximate angle of 25º with the normal of the inspected wall in order to avoid angle effects and to minimize reflections due to radiation of nearby objects (Asdrubali et al, 2012). The metric survey is performed with a laser scanner, from which the 3D representation of the scene, rather than images, is obtained.…”

Section: Thermographic and Geometric Data Acquisitionmentioning

confidence: 99%

Automatic Procedure for the Registration of Thermographic Images With Point Clouds

Lagüela

Armesto

Arias

et al. 2012

Int. Arch. Photogramm. Remote Sens. Spatial Inf. Sci.

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ABSTRACT:This paper presents a procedure for the automatic registration of thermographies with laser scanning point clouds. Given the heterogeneous nature of the two modalities, we propose a feature-based approach, satisfying the requisite that extracted features have to be invariant not only to rotation, translation and scale but also to changes in illumination and dimensionality. As speed and minimum operator interaction are prerequisites for the viability of the process in the building industry, our automatic registration procedure includes automatic feature extraction with no human intervention. With this aim, a line segment detector is used to extract 2D lines from thermographies, and 3D lines are extracted through segmentation of the point cloud. Feature-matching and the relative pose between thermographies and point cloud are obtained from an iterative procedure applied to detect and reject outliers; this includes rotation matrix and translation vector calculation and the application of the RANSAC algorithm to find a consistent set of matches. An automatically textured thermographic 3D model is the expected result of these procedures once the point cloud is filtered and triangulated. * Corresponding author. susiminas@uvigo.es

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“…Insulation defects Air leakage spots ∆Ti-e >10°C during 4h prior to IR [20] ∆Ti-e >1,7°C during 4h prior to IR [20] ∆Ti-e > 10°C [10] ∆Ti-e > 3°C [10] ∆Ti-e > 10°C [21] ∆Ti-e > 5°C [21] ∆Ti-e > 10°C [11] ∆Ti-e > 3/U (min 5°C) during 24h prior to IR [8,16] ∆Ti-e > 15°C during 24h prior to IR [15,22] ∆Ti-e > 10 -15°C [13,23] ∆Ti-e > 5°C during 24h prior to IR [6,7,12] ∆Ti-e > 10°C during 4h prior to IR [2,24] ∆Ti-e > 10°C (>20°C if possible for U-value determination) [19] Wind velocity (m/s)…”

Section: Sky Radiationmentioning

confidence: 99%

Influence of environmental parameters on the thermographic analysis of the building envelope

Vijver¹,

Steeman²,

Bossche³

et al. 2014

Proceedings of the 2014 International Conference on Quantitative InfraRed Thermography

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Typically, thermographic measurements are used to analyze the building envelope in a qualitative way (e.g. detection of thermal bridges, missing insulation, etc.). Besides, thermography can also be used to obtain surface temperatures, which can give an indication of the thermal performance of the building envelope. In this paper the influence of the most important environmental parameters on the thermographic analysis of different wall types is examined using a multivariable parameter study. This results in guidelines that are in good accordance with the existing guidelines. Furthermore some remarks were made concerning the ambiguities in the existing guidelines. INTRODUCTIONEurope has high ambitions concerning energy efficiency and the reduction of greenhouse gas emissions. By 2050, one of the goals is to reduce the CO2-emissions by more than 80 %, which is impossible with the current policy. In order to reach this goal, the percentage of renovated buildings has to increase from 1% to around 2,5% per year by 2020 [1]. For new buildings, one of the key factors to satisfy the need for energy efficiency is a high performing building envelope, which can be achieved by a high insulation level and an excellent airtightness. In this context, infrared thermography (IR) is a valuable non-destructive tool which can be used both for evaluating the execution quality of the building envelope or for determining where renovation of the building envelope is necessary. For a proper assessment of the wall surface temperature the building envelope has to be as close as possible to steady-state conditions. Therefore an adequate knowledge of the influence of environmental parameters (solar irradiation, wind velocity, sky radiation, etc.) and building parameters (thermal mass of the structure) on the dynamic behavior of the building envelope is needed. Due to the large number of parameters that influence this dynamic behavior together with the limitations of the existing thermographic cameras, additional research is necessary to make quantitative surveys more reliable. In what follows an overview of the currently existing guidelines is given. Starting from the existing guidelines, simulations were conducted to investigate the dynamic behaviour of the wall surface temperature for different combinations of environmental parameters. Finally, feedback on the currently existing standards is given taking into account the results obtained by the simulations.

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A quantitative methodology to evaluate thermal bridges in buildings

Cited by 182 publications

References 17 publications

Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

Effect of Thermal Bridges in Insulated Walls on Air-Conditioning Loads Using Whole Building Energy Analysis

Automatic Procedure for the Registration of Thermographic Images With Point Clouds

Influence of environmental parameters on the thermographic analysis of the building envelope

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