Idk why they even use the room temps. Leaf surface temp and rh are the only things that matter for your true kPa’s.
Vpd is really underestimated. I mean iv seen 4 weeks of growth in 2 weeks with a vpd kPa level under 1.0. It’s quite incredible. You can experiment with heavier feedings without burn. Just make sure you keep that rh up. I run my kPa’s at around .7-.9 during veg. Around 70-80% humidity and an ambient air temp of 84-86F. But my Lst are around 76F.
Yes. Your ambient air temps will reflect lst. But most of us maintain a relatively simple environment. Other than I see people very afraid of high humidity levels. Leaving levels low. Around 55-65%. I flower at those levels. But all that stuff runs the same factory. Humidity will reflect ambient air temps. Vice verse and air temp and humidity reflect lst. And VISE VERSE. This why humidity will rise with bushy plants. More leave more stomatas. More transparency.
So I guess keep in mind that your leaf surface temps are the key part of the equation. Amazon has lasers temp guns for the low. And you’ll use it for everything lol