Vent question solar kiln

[Turkeyeyes]

I am drying 500bf  4/4 red oak, I air dried it to 21%, now I have it in my kiln and was wondering how much I should open the upper and lower vents, or not open at all. What do you think?

[GeneWengert-WoodDoc]

Open very slightly as we are really looking for heat.  Of course, the RH must be under 50% RH when the fans are running.  As the lumber gets drier and drier, the vents are closed  more and more, as heat becomes more critical.

For the record, vents open too much will stop the drying at about 11% MC and slow drying quite a bit before then.  Also, running the fans 24 hours a day will also do the same.  One or both of these reasons is why some folks report that drying of AD lumber sees to stop in the kiln.