Advice sought on a ventilation / humidity issue

Hi all, I'm growing in a 1mx1mx2m (3.2ftx3.2ftx6.5ft) tent and the tent is in a storage room under the house which is 3mx2.5m within the basement.

I am running 400w HPS with a cool hood with a fan blowing air from the storage room through the side of the tent, into coolhood and out the other side of the tent and then out of the room in to the basement.

My temps are running fine and I have no issues with that, but my humidity.......

I am running a 4inch fan/filter and with an older dehumidifier within the tent, I can only get humidity down to 65%. (im flowering at the moment) I just ran a test and the humidity within the storage area where the tent is in, is sitting at 75%. True outdoor humidity is around 70%.

When the light goes on over night the humidity drops down to 50%, so that's fine.

If I increase the exhaust fan to say a 6inch or even an 8inch, would that reduce my humidity further? does adding more air flow have a big impact?

having a small clip on fan you circulating air will help with humidity a little but it seems strange that the humidity falls lower at night because usually when temperature drops humidity rises. a good way to keep it down is using a fan heater if you are able to raise the temp a bit, a fan heater will dry the air out as well. failing that buy a newer dehumidifier hope it helps mate
peace.

Put a good dehumidifier in the outer room, not the tent, near the intake.

You REALLY need a good dehumidifier if your in flowering. Humidity is one of the main factors effecting potency and trichome production. That's why I always get my humidity down to around 10-15% during flowering.