New research finds potential for greater retrofit energy savings in homes

New research in paper titled 'Suspended Timber Ground Floors: Measured Heat Losses Compared with Models' reveals the actual heat loss from suspended timber ground floors might be nearly twice that of previous estimates. The potential for thermally upgrading such floors is much greater than formerly expected. 

The UK is committed to a target of 80% emissions reduction by 2050, which includes improved energy efficiency in buildings. The benefits of upgrading timber ground floors had been underestimated in models used for regulatory compliance which means the potential to reduce heating energy and related carbon emissions is not realised.  As a result, the estimations for building regulations and other public policies for thermally upgrading homes will need to be revised.

Approximately 6.6 million dwellings were built in the UK before 1919 and predominantly constructed with suspended timber ground floors. Until now, their thermal performance has not been extensively investigated.

A new study, led by Dr Sofie Pelsmakers, a graduate from the EPSRC Centre for Doctoral Training in Energy Demand (LoLo), measured the actual heat flow in a suspended timber ground floor. Dr Pelsmakers, now a lecturer at the University of Sheffield’s School of Architecture, conducted this study during her PhD, working with Dr Cliff Elwell and Dr Ben Croxford of University College London. The research compared the estimated whole floor thermal value (U-value) with detailed measurements of the floor's thermal performance. The study "Suspended Timber Ground Floors: Measured Heat Losses Compared with Models” by S. Pelsmakers, B. Croxford and C.A. Elwell is published in Building Research & Information. The full article will be live and free to read from 27 June 2017 here: https://doi.org/10.1080/09613218.2017.1331315

The analysis found a significant variability in heat-flow, with increased heat loss near the external perimeter. In-situ measured point U-values ranged between 0.54 ±0.09 W/m2K, away from the external wall perimeter, to values nearly four times as high (2.04 ±0.21 W/m2K) along the perimeter.

These findings suggest that the use of only a few measurements – which is how most in-situ monitoring campaigns are conducted – is likely to bias any attempts to calculate a whole floor U-value, which was estimated to be 1.04 ±0.12 W/m2K.

Dr Pelsmakers said: “The findings raise questions about the validity of using existing assumptions in housing stock models to inform retrofit decision-making and space heating reduction interventions. If this disparity between these models and measurements exists in the wider stock, then a wider reappraisal of the performance of suspended timber ground floors will be required to support the UK’s carbon emission reduction targets. If the existing assumptions in public policy and building regulations are incorrect, then the benefits of insulating the ground floor might be underestimated.”

Dr Cliff Elwell, deputy Director for the EPSRC Centre for Doctoral Training in Energy Demand (LoLo) commented: “This work is a great example of the high quality research that our students and graduates deliver. It highlights a potentially significant disparity between the expected and observed performance of houses of this type. The good news is that this suggests that there is untapped potential to reduce heat loss and carbon emissions.”

Notes to editors

The paper “Suspended Timber Ground Floors: Measured Heat Losses Compared with Models” by S. Pelsmakers, B. Croxford and C.A. Elwell is published in Building Research and Information. The article can be freely downloaded from: https://doi.org/10.1080/09613218.2017.1331315

Building Research & Information is an international peer-reviewed journal in its 45th year, published by Routledge / Taylor & Francis. www.rbri.co.uk

U-values are used to measure how effective elements of a buildings fabric are as insulators. It is a measurement of how effective a wall, floor or roof is at preventing heat from transmitting between the inside and the outside of a building. The lower the U-value of an element of a building's fabric, the more slowly heat is able to transmit through it, and so the better it performs as an insulator.  The lower numerical value of a building's U-value, the less energy is required to maintain comfortable conditions inside the building.

Thermal transmittance is the rate of transfer of heat (in Watts) through one square meter of a structure, divided by the difference in temperature across the structure. It is expressed in Watts per square meter kelvin, or W/m²K.

Interviews with Dr Pelsmakers can be arranged. Please contact Hannah Postles, Media Relations Officer, on 0114 222 1046, 07557 815009 or email h.postles@sheffield.ac.uk

About the UCL Energy Institute 

https://www.ucl.ac.uk/bartlett/energy/

The UCL Energy Institute delivers world-leading teaching, research and policy support in the fields of buildings, energy systems, people and energy, policy and law, smart energy and transport. These research themes are not mutually exclusive, and many researchers work across two or more themes, ensuring a truly interdisciplinary approach to energy research. Our approach blends expertise from across UCL, to make a truly interdisciplinary contribution to the development of a globally sustainable energy system.

About LoLo EPSRC Centre for Doctoral Training in Energy Demand

The EPSRC Centre for Doctoral Training in Energy Demand (LoLo CDT) is the premier centre for energy demand research in the built environment in the UK, bringing together two leading energy research universities, UCL and Loughborough University. LoLo focusses on lowering energy demand from our built stock, currently responsible for over 40% of UK emissions, and to addressing fuel affordability. We aim to undertake world class research addressing timely challenges and produce a new generation of multi-disciplinary thinkers and innovators capable of engineering a smart, low-energy future.

www.lolo.ac.uk

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