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Reflectivity is 1 minus the absorptivity. By Kirchoff's law, absorptivity is equal to emissivity. Point your IR thermometer into a clear night sky, and you will measure a very low temperature. Place aluminum foil on the ground and measure the temperature (and keep your head out of the way), and you will get a similarly low temperature. Hold the aluminum foil above your head and take the temperature of the foil, and you will measure the temperature of the ground. For low-emissivity surfaces, adjusting the emissivity does not compensate for the blending of emitted and reflected radiation. For such surfaces, there is no easy way to measure the temperature of the surface from the radiation coming off the surface.