Objective: This study examines the extent that temperatures in English living rooms correspond to standard assumptions made in established UK building stock models. Methods: Spot temperature measurements taken every 45 min over 92 winter days in 248 homes in England were analyzed and compared to the assumed thermostat setting of 21 degrees C inside and outside the assumed heating periods. Results: Homes on average displayed lower internal temperatures during assumed heating periods and significantly shorter durations of heating to 21 degrees C than common models assume, with about 20% of homes never reaching the assumed demand temperature of 21 degrees C. Data showed a difference of only about 45 min in the duration of temperatures at or above the demand temperature for weekdays and weekends, contrary to the assumed difference of 7 h. Variability between homes was large. Conclusion: These findings suggest that currently used standard assumptions of heating demand and heating duration do not accurately reflect the living room temperatures of dwellings in England. Practice implications: Standard assumptions might have to be revised, in particular regarding the weekday-weekend differentiation. The prediction of internal temperature for a given home contains potential large error when using standard assumptions. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.