Two methods for U-value measurements
A new unique look at measuring suspended floor U-values
Heat-flow variability of suspended timber ground floors: Implications for in-situ heat-flux measuring:
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. 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 decision-making.
Researchers at the Sheffield School of Architecture, the University of Salford and UCL examined suspended timber ground floor heat-flow by undertaking and presenting high resolution in-situ heat-flux measurements at 15 point locations on the floor of the Energy House at the University of Salford.
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, high-resolution in-situ monitoring methodology used in this study for further research in this area.
The Arcada/University of Salford Project: Rapid U-value Measurement, results now available.
The problem of assessing the measured U-values of solid walls is a major issue for the UK, with over 7 million solid wall properties, representing a major energy efficiency issue. To help establish a lower cost and quicker approaches to establish the performance of solid walls the UK Government held a competition conducted by the UK’s Building Research Establishment (BRE) inviting companies and research organisation to submit innovative approaches to measuring U values. The completion was won by a joint submission from the Dr Richard Fitton from University of Salford (UK) and Mikael Paronen, Arcada (Finland), who developed original technology.
We could see the technology developed by Arcada had real potential and we developed the case for the completion with them by running tests in the Salford Energy House ; the results from this showed the system delivered U-values in line with expected values in just over an hour, when compared with a minimum of three days using current methodologies.
Supported by funding from the Department for Business, Energy and Industrial Strategy (formerly the DECC), the tool underwent a laboratory and field-based test programme focused on measurement accuracy and speed, ease of use and financial viability. The detailed testing undertaken by BRE indicated that the Rapid U-Value Sensor was robust and results were accurate, and more importantly, they indicated that the system was easy to use. This indicates a potential to take the measurement of in situ U-values from a costly and time consuming research method to something that may be available for practitioners as a form of in-line testing.
Richard Fitton, The University of Salford