def mrt_delta_from_erf(erf, fract_efficiency=0.725, rad_trans_coeff=6.012):
    """Calculate the mean radiant temperature (MRT) delta as a result of an ERF.

    Args:
        erf: A number representing the effective radiant field (ERF) on the
            person in W/m2.
        fract_efficiency: A number representing the fraction of the body
            surface exposed to radiation from the environment. This is typically
            either 0.725 for a standing or supine person or 0.696 for a seated
            person. Default is 0.725 for a standing person.
        rad_trans_coeff: A number representing the radiant heat transfer coefficient
            in (W/m2-K).  Default is 6.012, which is almost always the case.
    """
    return erf / (fract_efficiency * rad_trans_coeff)
