Evaluation of alternatives for reducing thermal bridges in metal panel curtain wall systems

Building envelopes incorporate thermal bridges, through which heat is transferred in either two or three dimensions. These thermal bridges lead to undesirable heat transfer, thereby resulting in an overall reduction in the insulation performance. In this study, alternatives were proposed to reduce the linear and point thermal bridges found in steel truss metal panel curtain wall systems in which metal panels fabricated by covering six faces of insulation with metal are fixed to the truss. Three-dimensional heat transfer simulations and mock-up tests were conducted to evaluate the insulation performance of the alternatives. Also, life-cycle costs were analyzed to evaluate the economic feasibility of the selected alternative. The evaluation results showed that the alternative 2, in which the lengths of the aluminum molding at the sides of the metal panel were reduced and for which thermally broken brackets were used, was the most effective alternative. The mock-up test performed in winter showed that the alternative 2 largely reduced the heat loss through the thermal bridges and had better insulation performance. Assuming a lifetime of 40 years, the alternative 2 would reduce the life cycle costs by 10.9% relative to the existing case.