An apparatus and method for reducing dosage time in ultraviolet germicidal irradiation systems. UV-C reflective adhesive film may be configured as sheets, or in a roll that may be cut to a desired size or shape. A user may apply UV-C reflective adhesive film to a desired surface of an interior room by exposing an adhesive surface to the desired interior surface. A reflective layer of the UV-C reflective adhesive film is configured to improve the reflectance percentage or reflectance pattern of a desired interior surface with respect to incident UV-C or near UV-C light. The improved reflectance properties of the desired surface functions to reflect a greater amount of light back to one or more closed-loop sensors in operation with a UV-C or near UV-C germicidal irradiation system. The improved reflectance thereby reduces the amount of time required for one or more closed-loop sensors in operation with a UV-C or near UV-C germicidal irradiation system to measure an effective kill-dose for surface disinfection.