def ep_style_string(self):
        """Serialize object to an EnerygPlus SizingPeriod:DesignDay.

        Returns:
            ep_string: A full string representing a SizingPeriod:DesignDay.
        """
        # Put together the values in the order that they exist in the ddy file
        ep_vals = [self.name,
                   self.sky_condition.month,
                   self.sky_condition.day_of_month,
                   self.day_type,
                   self.dry_bulb_condition.dry_bulb_max,
                   self.dry_bulb_condition.dry_bulb_range,
                   self.dry_bulb_condition.modifier_type,
                   self.dry_bulb_condition.modifier_schedule,
                   self.humidity_condition.hum_type, '',
                   self.humidity_condition.schedule, '', '',
                   self.humidity_condition.wet_bulb_range,
                   self.humidity_condition.barometric_pressure,
                   self.wind_condition.wind_speed,
                   self.wind_condition.wind_direction,
                   self.wind_condition.rain,
                   self.wind_condition.snow_on_ground,
                   self.sky_condition.daylight_savings_indicator,
                   self.sky_condition.solar_model,
                   self.sky_condition.beam_shced,
                   self.sky_condition.diff_sched, '', '', '']

        # assign humidity values based on the type of criteria
        if self.humidity_condition.hum_type == 'Wetbulb' or \
                self.humidity_condition.hum_type == 'Dewpoint':
                    ep_vals[9] = self.humidity_condition.hum_value
        elif self.humidity_condition.hum_type == 'HumidityRatio':
            ep_vals[11] = self.humidity_condition.hum_value
        elif self.humidity_condition.hum_type == 'Enthalpy':
            ep_vals[12] = self.humidity_condition.hum_value

        # assign sky condition values based on the solar model
        if self.sky_condition.solar_model == 'ASHRAEClearSky':
            ep_vals[25] = self.sky_condition.clearness
        if self.sky_condition.solar_model == 'ASHRAETau':
            ep_vals[23] = self.sky_condition.tau_b
            ep_vals[24] = self.sky_condition._tau_d
            ep_vals.pop()

        # put everything together into one string
        comented_str = ['  {},{}{}\n'.format(
            str(val), ' ' * (60 - len(str(val))), self.comments[i])
                        for i, val in enumerate(ep_vals)]
        comented_str[-1] = comented_str[-1].replace(',', ';')
        comented_str.insert(0, 'SizingPeriod:DesignDay,\n')
        comented_str.append('\n')

        return ''.join(comented_str)
Serialize object to an EnerygPlus SizingPeriod:DesignDay.

        Returns:
            ep_string: A full string representing a SizingPeriod:DesignDay.