Any ideas for low humidity levels

I have a 2.5m x 2.5m x 2.0m grow tent,2x 600watt HPS,inlet fan bringing fresh air into the bottom of the tent and an extractor fan with rhino charcoal filter taking out into the chimney breast plus two desk fans circulating the air around the tent,my temperature is a constant 79-83 degrees fahrenheit.I'm growing 10 cheese plants and 10 blue cheese plants all from seed and am about five weeks into the grow from germination.The plants don't seem to be growing upward very quickly but seem to be bushing out instead,they're all around 8-9 inches in height,anyway back to the point.Everyone says you need to have 40 to 80 % humidity but can i get above 30%,it's even in the low 20's most of the time.I've tried putting cups of water everywhere,wet towels,spraying a fine mist around the whole tent(which works but an hour later its dowwn in the 20's again and today I spent £100 on two humidifiers which still don't raise it.Now obviously it's winter here in London and the air being sucked in is quite cold and dry but all the moisture gets sucked out by the extractor fan but if you turn both inlet and outlet fans down,the temp goes through the roof.I'm getting real disheartened cos I'm sure the plants growth is stunted.Does anybody know whether low humidity can harm the plants and has anybody got any ideas on how to overcome all of the obstacles i have and can suggest a way to get a constant humidity between 40 and 80%?

well the best way in your situation is to get a sealed grow room, but thats pretty expensive. You'll need to get an a/c unit and a co2 generator. Are you sure your hygrometer just isn't broken? are you taken the air directly from outside or bringing it from within the building you grow tents in. maybe your buildings HVAC System has a really good dehumidifier? I'm confused cuz on the weather channel it says the outside humidity is 70-90%.

take your hygrometer outside and see what the humidity is. It says its raining so humidity should be close to 100%. if your hygrometer is reading much lower than that than its just your hygrometer. If your hygrometer is reading correctly, then take your hygrometer inside the building, not grow tent, and see the humidity. if it really low, 20%, then you buildings ventilation system has some crazy dehumidifier. If this is the case try to take the air from the outside into your grow tent.

Where are you measuring the humidity?

You should be measuring it near to your plants.

The plants themselves can cope with RH that low I've grown in 19%RH until the plants themselves got bigger. As they get bigger they exude more moisture into the air creating more RH. so it won't last forever.

A bucket with an airstone and an oscillating fan blowing at the bucket should help more than the towels as the towels can dry out pretty quick.



J

Thanks guys for your advice.I am bringing the air straight in from outside the house(via the loft or attic as some people call it) straight into a sealed(as best it can)grow tent.I've got 2 Temp/humidity meters at plant level and both show 20% humidity cos i had one to start but bought another one thinking it was broken.Today i'll take both of the hygrometers into the garden and find out what the real humidity is.My inlet ducting comes in from the loft of the house which is basically very cold up there,maybe all the loft insulation is sucking out the humidity somehow.Anyway,the plants dont seem to mind too much,maybe i'll get a good level when they get bigger.I'm gonna swith 'em over to 12/12 in a couple of days time so hopefully that'll put some moisture back in the air.

hello guys , i also have humidity problems so i added a dimplex dehumidifier , it is working fine but for some reason the RH is only saying its 70 % without it it says its 76 rh is 6 rh a normal correct kinda drop or do u think my hygrometer ( Digital ) is giving me an incorrect reading ?? it stays roughley 70 RH when lights are on and off im trying alsorts of stuff , i currentley have a 2.4 x 1.2 x 2 secret jardin thermol tent i have 2 . 4 " inline fans (rvk) with carbon filters either end of tent and 2 x 600 w hps on 12/12 with a stand up oscilater and a 4 inch inline bringing in fresh cold air from outside , i have the probe hung at approx same height as plants in middle of tent , situiation is driving me a bit crackers lolany help is good help so what u think i should do ..... ? ?