Performance enhancing underlayment, underlayment assembly, and method

A method for on-site fabrication of a wall construction component/underlayment assembly, comprising:

• providing a first wall construction board;
• the first construction board having a length, a width, and a thickness;
• the first construction board having first and second major surfaces that are each defined by the length and the width of the first construction board;
• providing a second wall construction board;
• the second construction board having a length, a width, and a thickness;
• the second construction board having first and second major surfaces that are each defined by the length and the width of the second construction board;
• providing a plurality of underlayment strips comprising a nonwoven fiber mat and a phase change material that provides latent storage of thermal energy, wherein during use the phase change material undergoes a solid to liquid phase change between about 15° C. and about 27° C.;
• positioning the first major surface of the first construction board adjacent an interior side of structural support members of a wall;
• positioning the underlayment strips adjacent the second major surface of the first construction board on the interior side of the structural support members such that adjacent underlayment strips contact each another and securing the underlayment strips to the second major surface of the first construction board to form an underlayment layer;
• positioning the first major surface of the second construction board adjacent the underlayment strips on the interior side of the structural support members so that the underlayment layer is sandwiched between the first and second construction boards on the first side of the structural support members;
• and
• securing the second construction board to the first construction board and the underlayment strips via an adhesive or a plurality of mechanical fasteners with the underlayment layer sandwiched between the second and first construction boards to form an interior wall assembly;
• wherein after the second construction board is secured to the first construction board, the first construction board, the underlayment layer, and the second construction board are permanently affixed to each other, and the phase change material undergoes a solid to liquid phase change.