The overall energy consumption in a building could be minimized by controlling the heat gain or loss through its building components like walls, floors, roofs, window glazing etc. and for doing this, the thermal performance of the building materials should be evaluated. The U-value is one of the key measures of evaluating the thermal performance of any building material. The lesser the U-value, the less energy is required to maintain comfortable conditions inside the building. The U-value is measured using the Guarded Hot Box Test Facility. In the present work, two control strategies, one with a simple on-off and another with a Proportional-Integral-Derivative (PID) logic driven Pulse Width Modulation (PWM) technique, have been implemented, once with AC circulating fans and again with DC circulating fans inside the Guard box. Performance evaluation and comparison of them has been made in terms of three error indices viz, per unit time of Integral of Square Error (ISE); Integral of Absolute Error (IAE) and Integral of Time weighted Absolute Error (ITAE). From the experimental data obtained, it is found that the PID logic driven pulse width modulation technique with DC circulating fans installed inside the guard box shows the best temperature control profile. (C) 2015 Elsevier B.V. All rights reserved.