A method of constructing a building including erecting a plurality of truss elements to form a framework including one or more walls, a roof structure and a floor structure. Each truss element includes at least two joists and a plurality of braces that maintain the joists in a parallel arrangement, the truss elements being arranged in the framework to provide an inner joist and an outer joist. An inner covering layer and an outer covering layer are attached to the framework, thereby forming an enclosed void between the inner and outer covering layers that extends substantially continuously around the framework. An insulating material is injected into the void to form a substantially continuous insulating layer between the inner and outer layers.