Solid-wall U-values: heat flux measurements compared with standard assumptions

The assumed U-values of solid walls represent a significant source of uncertainty when estimating the energy performance of dwellings. The typical U-value for UK solid walls used for stock-level energy demand estimates and energy certification is 2.1 Wm −2  K −1 . A re-analysis (based on 40 brick so...

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Bibliographic Details
Published in:Building research and information : the international journal of research, development and demonstration development and demonstration, 2015-03, Vol.43 (2), p.238-252
Main Authors: Li, Francis G. N., Smith, A.Z.P., Biddulph, Phillip, Hamilton, Ian G., Lowe, Robert, Mavrogianni, Anna, Oikonomou, Eleni, Raslan, Rokia, Stamp, Samuel, Stone, Andrew, Summerfield, A.J., Veitch, David, Gori, Virginia, Oreszczyn, Tadj
Format: Article
Language:English
Subjects:
buildings
Certification
Construction
Construction materials
Economics
energy demand
Energy efficiency
Energy use
epidemiology
Estimating techniques
heat flux measurements
Heat transfer
Heating
Heterogeneity
Homesteading
Parameter estimation
solid walls
thermal conductivity
U-value
Walls
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Summary:The assumed U-values of solid walls represent a significant source of uncertainty when estimating the energy performance of dwellings. The typical U-value for UK solid walls used for stock-level energy demand estimates and energy certification is 2.1 Wm −2  K −1 . A re-analysis (based on 40 brick solid walls and 18 stone walls) using a lumped thermal mass and inverse parameter estimation technique gives a mean value of 1.3 ± 0.4 Wm −2  K −1 for both solid wall types. Among the many implications for policy, this suggests that standard UK solid-wall U-values may be inappropriate for energy certification or for evaluating the investment economics of solid-wall insulation. For stock-level energy modelling, changing the assumed U-value for solid walls reduces the estimated mean annual space heating demand by 16%, and causes a proportion of the stock to change Energy Performance Certification (EPC) band. The analysis shows that the diversity of energy use in domestic buildings may be as much influenced by heterogeneity in the physical characteristics of individual building components as it is by variation in occupant behaviour. Policy assessment and guidance material needs to acknowledge and account for this variation in physical building characteristics through regular grounding in empirical field data.
ISSN:0961-3218
1466-4321
DOI:10.1080/09613218.2014.967977