When heating mode reaches the set temperature, the HP09 continues to draw air through at a low rate, presumably to monitor air quality. This air gets blown out the front of the fan, which feels draughty, and seems counterproductive to using the fan as a heater. Given that it has the ability to blow air out of the back in diffuse mode, is it in any way possible to get this to happen when heating mode goes to idle?
It does this automatically when the air quality worsens, the fan will speed up and the air will be directed out the back to avoid a cooling effect on people in the room. Surely it would make sense for it to do the same when idling.