In this study, the effectiveness of a retrofitted natural ventilation system in a low energy building was evaluated, both subjectively and objectively, in response to an overheating scenario during shoulder seasons. Four ventilation configurations were evaluated including one control (no ventilation) configuration. Standardised questionnaires were used to evaluate the levels of subjective comfort based on ASHRAE guidelines and ISO 10551. Both subjective and objective evaluations were compared with three thermal comfort standards. Objectively, the strength of relationships between both individual parameters and indices were investigated and the errors between the actual and predicted mean thermal sensation was reported. The results indicated that the use of smaller openings provided a better mean thermal sensation than the use of a larger opening in response to an overheating scenario. Smaller louvre openings were found to achieve a sufficient level of subjective comfort in 30 min given a daily mean external temperature of 12 degrees C. This study found that standards varied in accuracy with ASHRAE 55 performing the best in predicting three out of four of the configurations accurately. The most accurate thermal comfort model was seen to be the effective temperature model with a mean absolute percentage error of 82%. (C) 2016 Elsevier B.V. All rights reserved.