Better Fresh Air Venting Plan

[craigwmiller]

Originally Posted by e46er

Why do you not want it to run if the humidity outside is higher than inside?

If the humidity is higher outside, venting air from inside to out will draw more-humid air from the outside back in -- just making things worse

[e46er]

Originally Posted by craigwmiller

If the humidity is higher outside, venting air from inside to out will draw more-humid air from the outside back in -- just making things worse

If this is for a fish room which I assume you only need a small fan pushing 80 cfm to run a few minutes every couple hours I'd guess meaning it will take along time to get a negitive pressure in your house that will draw in the more humid air.

No different than turning on a bathroom fan when you shower every morning

[mark]

Originally Posted by craigwmiller

If the humidity is higher outside, venting air from inside to out will draw more-humid air from the outside back in -- just making things worse

putting my met training to use, you need to take in account a RH of 40% @ 20° is a different amount of water vapour than a RH of 40% @ 15° (@ 15° for a equal amount of water compared to 40%/20° your RH is up around 70%)

[neoh]

I had a problem with really high humidity in my sump area, as it's completely enclosed, and of course high humidity in the room - I wanted better CO2/O2 exchange through it due to pH fluctuation, so I added these fans to both sides:

http://www.jlaquatics.com/phpstore/s...t_ID=cv-sfan04

The humidity on the inside and outside thing is a little tough, and probably non-existent because it's not one of those problems a majority of people have.

They do come with a heat sensor, and the fan spins faster or slower depending on the amount of heat either inside, or outside the sump area. I have one on all the time with the fan drawing air into the sump depending on the temperature inside, and I have another that draws air out depending on the temperature outside the sump.

Not sure if that helps!

[craigwmiller]

Yeah, not many likely have the 'issue' that I do. I have 49.5 square feet of surface area, yes, feet... I am working to cover some of them with some form of acrylic to limit the evaporation somewhat.

But, say if it's raining outside, I don't want to be drawing in more humid air