The present invention provides a thermal insulation panel (10) having two outer concaved layers (14, 16) and an inner tension (24) member formed by two substantially parallel panels (26,28). The peripheries of the layers and panels are secured to a thermal barrier (22) extending around the periphery of the panel (10) and a vacuum seal (25) seals the edge. In operation, a partial vacuum is created within the panel which causes concaved layers (14, 16) to flatten and tension panels (26, 28) to be placed under tension. This tensional loading creates a strong and rigid structure without the need for internal supports which can create thermal inefficiency.