def hourly_horizontal_infrared(self):
        """A data collection containing hourly horizontal infrared intensity in W/m2.
        """
        sky_cover = self._sky_condition.hourly_sky_cover
        db_temp = self._dry_bulb_condition.hourly_values
        dp_temp = self._humidity_condition.hourly_dew_point_values(
            self._dry_bulb_condition)

        horiz_ir = []
        for i in xrange(len(sky_cover)):
            horiz_ir.append(
                calc_horizontal_infrared(sky_cover[i], db_temp[i], dp_temp[i]))

        return self._get_daily_data_collections(
            energyflux.HorizontalInfraredRadiationIntensity(), 'W/m2', horiz_ir)
A data collection containing hourly horizontal infrared intensity in W/m2.