Insulation can be used over the foundation of ground structures to protect them against cyclical freezing and thawing damage. However, if the structure is composed of metal, heat transfer through the structure can have significant thermal effects on the foundation (i.e., causing ground temperature changes). This paper presents analytical and experimental studies on thermal effects of a metal tower in a power transmission line foundation, particularly when the foundation is protected with ground surface insulations. The results indicate that the metal tower has seasonally variable effects on temperature variations in the tower foundation. Although ground surface insulation can reduce the temperature variations in the foundation, it cannot prevent adverse thermal effects of the metal tower. In this paper, other protective techniques are proposed to develop more effective thermal protection for tower foundations. (C) 2010 Elsevier Ltd. All rights reserved.