Abstract In many countries, the theoretical heating demand within the official energy performance assessment of houses is evaluated using simplified, single-zone quasi-steady state models, based on ISO 13790 and considering one standard, average user profile. Unpredictable variations in user behavior are acknowledged as a major cause of varying prediction errors. However, even considering a single, standard user profile, not heating the bedrooms and switching off the heating at night, requires the use of additional correction formulas, as such behavior appears contradictory to the single zone and quasi-steady state assumptions of the simplified models. This paper compares theoretical heating demands and indoor temperatures using the spatial reduction and intermittency correction formulas from the German (DIN 18599) and Dutch (NEN 7120) standards with results from the simplified, Flemish approach. Results from a multi-zone quasi-steady state model and measured values are added to the comparison. An old neighborhood of uninsulated houses is used as a case-study and renovation scenarios are considered. Results show that, between the German and Dutch approaches, the different predictions are mainly caused by the different standard user profile considered, much more than by the different formulas. Considering the real heating profiles is found to be indispensable, though not sufficient for accurate predictions. The multi-zone approach is proven to be of great value for supporting the selection of specific renovation measures.