One of the most common methods used in passive heating is the utilization of a massive wall for heat storage. Many factors affect the performance of the wall, such as the thickness and the media used for heat storage. A numerical study has been conducted on a zone heated by a thermal storage wall. Three different storage materials are examined, namely concrete, the hydrated salt CaCl2 center dot 6H(2)O and paraffin wax (N-eicosane). A numerical model is presented in this paper which judges the suitability of these materials as thermal storage mediums under the actual weather conditions of Iraq. For that purpose, the room temperature fluctuation in the zone is evaluated for each material using different thickness for each wall. The study concluded that an 8-cm-thick storage wall made from the hydrated salt is capable of maintaining the comfort temperature in the zone with the least room temperature fluctuation. (C) 2008 Elsevier B.V. All rights reserved.