HUMIDITY AT NIGHT? TO PREVENT MOLD

Cinco said:

There are a lot of mold resistant strains. You can look them up. Many commercially developed and viable strains are mold and PM resistant. Resistant being the key, nothing is mold proof.

I have done runs at peak flower VPD at 80% RH and not had any rot issues. Plants love it. But I use multiple fans blowing under and through the canopy. Not just a gentle breeze, on max blowing air through the canopy. What most people would call too much airflow, probably. Never an issue on my end.

Where people have issues, in my pure opinion anyway, is with big swings as @Renfro said. 30c and 80% RH runs great if you maintain it... the plants grow like you would expect they would in a lush tropical equatorial rain forest.

However, like running anything at its max, there is less margin for error — when the temp swings down at lights out, you hit the dew point very quickly. At those room specs (30c, 80% RH)the dew point is only 26.2c. Only 3.8 degrees margin, or 12.6% temperature delta — , and below that, and all that moisture starts crashing out of the air and accumulating on the surfaces of everything. PM and mold love it.

So maintaining roughly the same vPD at a lower temp provides better buffer. At 20c and 60% RH, for example, the dew point is at 12c. 8c difference, and a much bigger margin at 40% delta needed to hit the dew point.

Just my thoughts from years of growing things, most of it not weed.

Click to expand...

Cinco said:

There are a lot of mold resistant strains. You can look them up. Many commercially developed and viable strains are mold and PM resistant. Resistant being the key, nothing is mold proof.

I have done runs at peak flower VPD at 80% RH and not had any rot issues. Plants love it. But I use multiple fans blowing under and through the canopy. Not just a gentle breeze, on max blowing air through the canopy. What most people would call too much airflow, probably. Never an issue on my end.

Where people have issues, in my pure opinion anyway, is with big swings as @Renfro said. 30c and 80% RH runs great if you maintain it... the plants grow like you would expect they would in a lush tropical equatorial rain forest.

However, like running anything at its max, there is less margin for error — when the temp swings down at lights out, you hit the dew point very quickly. At those room specs (30c, 80% RH)the dew point is only 26.2c. Only 3.8 degrees margin, or 12.6% temperature delta — below that, and all that moisture starts crashing out of the air and accumulating on the surfaces of everything. PM and mold love it.

So maintaining roughly the same vPD at a lower temp provides better buffer. At 20c and 60% RH, for example, the dew point is at 12c. 8c difference, and a much bigger margin at 40% delta needed to hit the dew point.

Just my thoughts from years of growing things, most of it not weed.

Click to expand...