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Buildings 2018, 8(3), 46; https://doi.org/10.3390/buildings8030046

Variations in the U-Value Measurement of a Whole Dwelling Using Infrared Thermography under Controlled Conditions

1
School of the Built Environment, University of Salford, Manchester M5 4WT, UK
2
School of Engineering, the University of Reunion Island, Sainte-Clotilde, 97715 Reunion Island, France
*
Author to whom correspondence should be addressed.
Received: 28 February 2018 / Revised: 14 March 2018 / Accepted: 16 March 2018 / Published: 19 March 2018
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Abstract

U-values of building elements are often determined using point measurements, where infrared imagery may be used to identify a suitable location for these measurements. Current methods identify that surface areas exhibiting a homogeneous temperature—away from regions of thermal bridging—can be used to obtain U-values. In doing so, however, the resulting U-value is assumed to represent that entire building element, contrary to the information given by the initial infrared inspection. This can be problematic when applying these measured U-values to models for predicting energy performance. Three techniques have been used to measure the U-values of external building elements of a full-scale replica of a pre-1920s U.K. home under controlled conditions: point measurements, using heat flux meters, and two variations of infrared thermography at high and low resolutions. U-values determined from each technique were used to calibrate a model of that building and predictions of the heat transfer coefficient, annual energy consumption, and fuel cost were made. Point measurements and low-resolution infrared thermography were found to represent a relatively small proportion of the overall U-value distribution. By propagating the variation of U-values found using high-resolution thermography, the predicted heat transfer coefficient (HTC) was found to vary between 183 W/K to 235 W/K (±12%). This also led to subsequent variations in the predictions for annual energy consumption for heating (between 4923 kWh and 5481 kWh, ±11%); and in the predicted cost of that energy consumption (between £227 and £281, ±24%). This variation is indicative of the sensitivity of energy simulations to sensor placement when carrying out point measurements for U-values. View Full-Text
Keywords: building fabric; dwellings; heat flux; heat loss; in situ performance; IR thermography; U-value building fabric; dwellings; heat flux; heat loss; in situ performance; IR thermography; U-value
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Marshall, A.; Francou, J.; Fitton, R.; Swan, W.; Owen, J.; Benjaber, M. Variations in the U-Value Measurement of a Whole Dwelling Using Infrared Thermography under Controlled Conditions. Buildings 2018, 8, 46.

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