Q about heat and humidity...

Most of my day is spent working in a warehouse environment. While we do not have air-conditioning, we do have fans. We have an on-going debate (as the temperature rises) about the benefits of leaving the dock bay doors open for fresh air. Some of us think the outside air has no affect on the humidity inside the building. Some think that the humidity increases indoors when outside air is pulled into the building. Can humidity actually be held at bay, or does it exist regardless of the doors being open?

I would guess that, humidity (relative humidity) being comprised of water vapor, if you leave the bay doors open, some of that moisture is going to seep into the warehouse, raising its RH.

But what of the moisture eminating from all the sweaty warehouse workers?

Enough bodies in an enclosed space will raise the relative humidity.

I would guess that it would depend upon the relative moisture between the inside of the warehouse and the outside, as to which way the moisture would go. Maybe some one versed in physics can hop in. But if I were that sweating inside a warehouse, I certainly would want the doors open.

If all you have is fans, then they’re not going to do anything to lower the humidity in a warehouse.

The water vapor concentrations in the outside air and the inside air will have already reached equilibrium before the fans were turned on, and the mixing of air with the door closed isn’t going to lower the humidity any. Where is the moisture going to go?

Let me put it another way: You’ve seen air conditioners drip on humid days, right? This is the moisture they’ve removed from the air. Do you ever see fans drip?

You’re probably better off opening a door or window on the shady side of the building, as close to floor level as possible. Then, either use a fan to pump in air from that location, or use a fan to exhaust air near the ceiling. Or both.

I think in the OP, it’s a given that the fans would be on. The question was, with the fans on but with no AC, would opening the doors decrease the humidity? The useless answer is “yes, if the humidity outside is lower than the humidity inside.”

So during the day, is the humidity indoors likely to be higher than humidity outside? I have no idea, but my WAG is that Biggirl is correct. I can think of no mechanism that decreases the indoor humidity, and there are many sources of additional humidity (human bodies).

*Originally posted by scr4 *

Isn’t that what the dehumidifier in my basement is for? It certainly collects moisture from the air, and forms water which needs to be emptied on a regular basis…

Um, yes. By “mechanism” I meant any natural effect that causes the indoor humidity to be lower than the outdoor humidity. You can artificially lower the humidity by using air conditioners, dehumidifiers, or even by opening the refrigereator door. Sorry for the confusion.