Solid-wall<i>U</i>-values: heat flux measurements compared with standard assumptions

Li, Francis G.N.; Smith, Anne B.; Biddulph, P.; Hamilton, Ian; Lowe, Robert; Mavrogianni, Anna; Oikonomou, Eleni; Raslan, Rokia; Stamp, Samuel; Stone, Andrew; Summerfield, Alex; Veitch, David; Gori, Virginia; Oreszczyn, Tadj

doi:10.1080/09613218.2014.967977

Cited by 112 publications

(91 citation statements)

References 11 publications

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“…(13). The present paper confirms but also complements the research done by Li [40] demonstrating that the measurements of heat flux in inhabited estates are very difficult. Li is describing large sources of errors, such as: poor contact between the heat flux sensor and the wall, difficulties to identify measurement points beyond thermal interference, etc.…”

Section: Analysis Of Results and Discussionsupporting

confidence: 86%

Estimation of thermal transmittance based on temperature measurements with the application of perturbation numbers

et al. 2017

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Fast estimation of thermal transmittance based on temperature measurements is uncertain, and the obtained results can be burdened with a large error. Nevertheless, such attempts should be undertaken merely due to the fact that a precise measurement by means of heat flux measurements is not always possible in field conditions (resentment of the residents during the measurements carried out inside their living quarters), and the calculation methods do not allow for the nonlinearity of thermal insulation, heat bridges or other fragments of building envelope of diversified thermal conductivity. The present paper offers the estimation of thermal transmittance and internal surface resistance with the use of temperature measurements (in particular with the use of thermovision). The proposed method has been verified through tests carried out on a laboratory test stand built in the open space, subjected to the influence of real meteorological conditions. The present elaboration involves the estimation of thermal transmittance by means of temperature measurements. Basing on the mentioned estimation, the authors present correction coefficients which have impact on the estimation accuracy. Furthermore, in the final part of the paper, various types of disturbance were allowed for using perturbation numbers, and the introduced by the authors Bcredibility area of thermal transmittance estimation^was determined.

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Section: Analysis Of Results and Discussionsupporting

confidence: 86%

Estimation of thermal transmittance based on temperature measurements with the application of perturbation numbers

et al. 2017

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“…For example, in-situ measurement of U-values in solid walls were found to be lower than those predicted [37,39,40], which affects the predicted energy savings and payback. However, while insulation of suspended timber ground floors was a Green Deal approved intervention measure [41], the heat-flow through this element, both uninsulated and insulated, is not well characterised at present, hindering retrofitting decision-making.…”

Section: Introductionmentioning

confidence: 99%

Heat-flow variability of suspended timber ground floors: Implications for in-situ heat-flux measuring

Pelsmakers

Fitton

Biddulph

et al. 2017

Energy and Buildings

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Reducing space heating energy demand supports the UK's legislated carbon emission reduction targets and requires the effective characterisation of the UK's existing housing stock to facilitate retrofitting decisionmaking. Approximately 6.6 million UK dwellings pre-date 1919 and are predominantly of suspended timber ground floor construction, the thermal performance of which has not been extensively investigated. This paper examines suspended timber ground floor heat-flow by presenting high resolution in-situ heat-flux measurements undertaken in a case study house at 15 point locations on the floor. The results highlight significant variability in observed heat-flow: point U-values range from 0.56 ±0.05 to 1.18 ±0.11 Wm -2 K -1 .This highlights that observing only a few measurements is unlikely to be representative of the whole floor heat-flow and the extrapolation from such point values to whole floor U-value estimates could lead to its over-or under-estimation. Floor U-value models appear to underestimate the actual measured floor U-value in this case study. This paper highlights the care with which in-situ heat-flux measuring must be undertaken to enable comparison with models, literature and between studies and the findings support the unique, highresolution in-situ monitoring methodology used in this study for further research in this area.

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“…However, on almost every occasion in which thermal performance has been measured, the values obtained have shown both significant variation within samples and overall divergence from predictions. For example, in situ U-value measurements have reported measured values typically 20% higher than predicted in cavity walls [1], but often lower than predicted in traditional stone and brick constructions [2][3][4][5][6]. Just as importantly, these studies have often revealed a large range in measured performance.…”

Section: Introductionmentioning

confidence: 99%

Assessing the Relationship between Measurement Length and Accuracy within Steady State Co-Heating Tests

2017

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Evidence of a fabric performance gap has underlined the need for measurements of in situ building performance. Steady state co-heating tests have been used since the 1980s to measure whole building heat transfer coefficients, but are often cited as impractical due to their 2-4 week test duration and limited testing season. Despite this, the required conditions for testing and test duration have never been fully assessed. Analysis of field tests show that in 12 of 16 cases, a heat loss estimate to within 10% of the result achieved across a full test period can be achieved within just 72 h. These results are supported by simulated tests upon a wider range of dwellings and across wider environmental conditions. However, systematic errors may still exist, even in cases of convergence and cases with significant uncertainties may never converge. Simulated examples of traditional dwellings and those built in line with current building regulation limits may be tested for more than half the year. However, even when simulated with reduced uncertainties, dwellings with low heat loss and high solar gains, such Passivhaus dwellings and apartments, could be successfully tested for just 22% and 12% of a year respectively, demonstrating the limitations of the co-heating method in assessing such dwellings.

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Solid-wallU-values: heat flux measurements compared with standard assumptions

Cited by 112 publications

References 11 publications

Estimation of thermal transmittance based on temperature measurements with the application of perturbation numbers

Estimation of thermal transmittance based on temperature measurements with the application of perturbation numbers

Heat-flow variability of suspended timber ground floors: Implications for in-situ heat-flux measuring

Assessing the Relationship between Measurement Length and Accuracy within Steady State Co-Heating Tests

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