im looking at getting a mister/fogger thingy,but only if they are worth it?
it will be going in a 120cm x 120cm x 200cm grow tent
what do ya think to them? waste or worth it
ta!
DTBM

Hello Dan, Im bumping cos Ive asked myself the same thing mate

2 n half years on I'm bumping again. My humidity is less than 20%, I have 600m3 outtake and 480m3 intake. Would a mist maker help and if so how many membranes should I go for?

What other budget options are there for raising humidity? The bucket of water and wet towels hasn't helped at all so far.

Thanks

TTF

Get yourself a humidifier from Argos or someone like that, only about £15, well worth every penny. As the bottom of your profile says... if your going to do something..........................

Where are you extracting to and where is fresh air coming from?

Eri
I'm extracting through the chimney via a Rhino carbon filter and my intake is from outside.

DrGT
I don't mind shelling out £50 or a bit more if I know it is going to do what I need. What I don't want to do though is buy something that is going to be overpowered by the air exchange or big drain on electricity.

I use a honeywell ultrasonic humidifier that's was£45.I use in early veg and raises the humidity nicely but have too balance it at times as my air intake and extraction is quite strong.

mini fogger


try one of these bro £14 from maplin there the dogs bollacks mucka

Do you live in this country??

I don't understand how your humidity could be below 20% with that set up dude!

Take a reading from outside, then take a reading from your intake, then take a reading from your point of extraction and report back!

Yeah, In sunny Yorkshire!! when I've got home today the max humidity has been to 43% during lights off but I did get are lass to spray them with HALO (Harpein Protein) so that will have had some effect. Lights came on at 4:00pm and humidity is now 30% at 7:00pm. I'll see how things go tomorrow.

Cheers for that leepy - I've ordered one from ebay to have a play with

By the way Eri the time is now 9:00pm and the humidity is back down to 20%. My fans are on 24 hours.

I have a sock to stop anything getting in the air intake. I might try putting another screwed up wet cock in there see if that helps put a bit of moisture in the air but I'm not holding my breath.

What's your RH outside, at the point of intake, and at the point of extraction?

20% is fooking arid man! 25% is the average RH of the Sahara Desert, to give you some perspective here

I would strongly suggest your airflow is the problem.


, I think you meant screwed up wet sock mate, but I wouldn't suggest either tbh

It will just encourage mould, it's not a good idea.

Why have you put a sock over your intake? Do you think that might be reducing the airflow? Is it an active or passive intake?

humidity is low in my area at the mo (or it was yesterday, pissing with rain today) 28-34% lights on (at night) outside it's only 50% ish.

humidity at this time of year when it's not rainging will always be low in grow rooms if taking air from outside, as the outside air is so cold it can't hold much moisture, we then heat it up to the right temperature and the relative humidity plummets.


if you've got the room, get a swamp/evaporative cooler, there may be mini swamp coolers available?

Whats all this "wet cock" talk about?

why would low airflow create low humidity? low airflow INCREASES humidity as the plants transpire (assuming temps remain at the desired level), but lowering airflow to increase humidity causes temps to go above the desired level which in turn brings RH down anyway (Edit to add, if you're using a heater to bring temps up during lights on, you could actually lower your fan speed to help raise humidity a bit, as it just means your heaters wont be on so much to keep temps constant, if your fans have to be on full whack or are already lowered to a level that copes with your lights and keeps temps up, then this is obviously not an option). if temps are good, more airflow isn't going to help with humidity, as humidity is directly linked to the starting humidity against the number of degrees you heat it by... more airflow means drop in temperature, meaning it has to be raised again, decreasing humidity cancelling out any effect = pointless

It seems to me that if you increase the amount of fresh air coming in, you are likely to increase your RH. Where that air is coming from and how it's heated, sure, will affect how much humidity is lost.

I increased my extraction and used the old fan as an intake, and my humidity immediately rose by an average of 10% all day long.

I'm not trying to heat outside air though... when I used to have to heat it, I used oil radiators though and never had any problems with humidity.

20% seems incredibly low. Maybe the sensor is broken, or there is a fan heater being employed somewhere?

well i'm sorry but that's wrong. humidity is simply the volume of water held in the air RH is the volume of moisture held in the air in relationship to the total that the air at that temperature can hold. cold air can't hold as much water as hot air. so air that is 50% RH outside, but only 10'c will be 50% rh inside at 10'c............. but when you heat it to 26-27'c the RH will drop. this is fact, it will plummet in fact. the rule of thumb is that for every 10'c increase, RH drops by half!! so 20% is VERY easily done if you're bringing in fresh air in a cold climate! and all that increasing airflow will do is increase your heating bill as you'll still have to bring the temperature up massively, as excessively low temps are gonna do more damage than low humidity. if you increased your airflow, but didnt ring temps back up to their previous level, then this would increase RH but then you've just sacrificed your temps. dropping temperature will increase RH.

someone mentioned 20% being the same as that of the sahara desert? well actually it's the same as many parts of canada too, incredibly dry air over there. and i know, cos i lived there for nearly a decade. so it's irrellevant. a low humidity doesn't necessarily mean arid desert conditions. the sahara desert is also close to 50'c in the day!!so bit of a moo point, weed does love reasonably high humidity, like most plants, but 20% humidity shouldnt cause any stress if kept well water with good air circulation

it makes no difference HOW you heat the air either. fan heaters creating 'dry air' is a myth, rh is a direct relation between moisture content and temperature (although the air coming directly from the outlet will be very low humidity, because the temperature will be much higher than that of the room overall, so you wouldn't want one blowing directly at your plants same as you wsouldn't want your oil rad very close to your plants, the air directly surrounding the rad will be just as low as the fan heater)

.....

On a serious note I'm with Scrag the problem is likely to be the intaking of cool, damp air and heating it up to growroom temps causing the RH to plummet. I'm expecting around the 20% to 30% mark come mid winter.

As an example if you have a sealed room at 20oc with a RH of 50% and increase the temp to 25oC, RH will drop to maybe 35%. There is still the same absolute amount of water in the air, but warmer air ccould hold more water so the RH drops.

Maybe altering the intake arrangements to intake from indoors for the winter is an option?

Thanks for all the replies.

First of all just to clear up my earlier typo it was definitely a wet sock I used and not a wet cock!! I nearly spat my drink all over my laptop when I just read that!!

It did raise the humidity to 30% during the night (lights on is during the night) but I'm not sure for how long. the reason I have a sock over my intake anyway is to act as a filter to stop creepy crawlies and general dust etc getting in. I did use a ladies stocking originally but when I threw out out I couldn't be bothered walking to the shop so sacrificed an ld Christmas sock. Works a treat. You'd be surprised how much crap comes through and gets stuck in it!!

Taking the air from an internal source is not really an option for me so I'm stuck with trying to raise the humidity whilst bringing my air from inside.

I did order one of those ultrasonic misters / foggers but only one with a single membrane from ebay last night so I'll see how that goes. If that doesn't seem to do the trick then I'll try one of the evaporative coolers - thanks for the tip Scraggler. Do they have to cool though? I'm quite happy with my temps now!!

i have a mini humidifier bought from argos for about 25 quid

its great does what it says on the tin just a pain filling it up and adjusting the setting but it does solve or has solved my humidity problem.

btw i only have a humidity problem because i extract and take air from the same room (with window open as much as pos) there is no other option for me

Hi Scoob,

What wattage if the humidifier and what size fans are you using for intake and extraction?

Cheers, TTF

I didn't know the dry air from certain heaters thing was a myth, that's interesting.

I see what you're saying, but my RH went up when I improved my intake and extraction. I guess that's because I'm not taking air directly from outside and heating it up... In fact, I've never taken it directly from outside and heated it, it's always come from within a house or loft space (although the loft space was blooooody cold and I had to heat it with a couple of 500w heaters to keep it warm!) Still, my RH never dropped below 35%.

hi m8

i only have a very small wardrobe growroom you can see what i use in my profile but to answer your questions,, i use passive intake and 4" extraction,, like i say its only a small grow for about 3 plants and i pull and push the air from the same room which i know isnt ideal and is one of the reasons i end up with RH problems.

No idea on wattage of my humidifier m8 i didnt know thats how they where measured, its just a bog standard chepo one that does the job well imo

hope that helps

the cooling effect comes from the heat that is absorbed by the water as it evaporates...... tbh they're shit for cooling, but brilliant for creating humidity. and they're pretty cheap, look on fleaby, prolly about 20-30 quid if i remembers correctly. they're pretty big, maybe take up a foot n half square, dunno if they do mini ones? probably

I had a 5-head mister,but had good and bad experiences.

Firstly the cons,Power- (and think of running cost) The transformer (24v ac) pulled around 4.2 amps (according to it's labelling)

Next,You wouldn't believe the amount of crap that is in 0.4 tap water! I used a gorrilla type bucket to float the mister (30l?) and aimed a small fan near,to disperse the mist aroung the tent instead of it just looking pretty. My set up consisted of 2 tents with the air pulling out through one..into the intake of the other-cooltube style. I noticed,as my mate and missus did that there was a fine white/grey dust over everything in the 2nd tent (just moved from veg tent a week earlier where the mister was)...puzzled. I put a filter in the intake duct of the second tent .........and in 12 hrs (10 litres (ish) of mister water) I shook the filter gently,and got 1/4 eggcupfull of powder!!!! I tried testing again,and the eggcup was nearly 2/3 full...was totally shocked.
As laborious as it was constantly filling the bucket,I just used RO water instead with 0% dust
Watch out for this in hard water areas.

Next,If you fan too much you can simulate a rainforest within your tent...complete with 150% humidity with droplets dripping from leaves,branches,lights,sockets ect!!! Watch out!!

Pros...
Does what it says on the tin!!

Harder to find,but for a grow tent a 3-head mister is about right and without the risk.

With misters,you face the same problem as with co2, in so much that the fans,unless powered by a control system will just constantly be pulling the stuff out through the ducting....which is why I tried the 5 head version in the first place.

it's a semi myth, if there's such a thing. as has been said, RH is merely a function of the volume of water contained in the air, against the total volume of water that the air could possibly hold. as the temperature goes up, the total volume of water the air can hold also goes up. the actual volume of water of course stays the same unless more water is added. so because the actual amount of water present stays the same, RH goes down.

a temperature rise of 10'c is a rise of 10'c, doesn't make a shit of difference how the heat is delivered, it's still the same heat. so the only overall effect on humidity a fan heater will have, is the temperature rise it creates affecting RH. exactly the same as with an oil heater. the thing is, a fan heater blows out air much hotter than the average temp of the room, and as we know, the hotter the air for a given amount of water, the lower the RH, so the air in the stream of hot air from the fan heater is very low, but the overall RH in the room will be no different than if you used an oil heater to bring the same temp rise.

basically what it means, is don't do the obvious and point a fan heater directly at your plants!

so you probably had a drop in temperature when you airflow increased? if you had to use heaters to bring temps up, then i'd say that temps were just a bit lower, it only takes a small change in temp for a large change in RH. like i said before, a 10'c change, will either half, or double the RH!

Yeah, my temps went down about 5 degrees, but that was desirable as my average was around 30-32

Cheers StripeyMoon, Its only because there wasn't a five membrane version for sale on ebay i got the one membrane version. I had seen the 5 version on other sites but wanted to pay with paypal.

I'm in a pretty soft water area so hopefully not as many problems there. I'll try it with tap water and keep an eye on it. Thanks for the warning.



Hey Scoob, I just wanted to know the wattage to guestimate the damage to my wallet in electric bills. No worries, I'm going to give this mist maker a go and see how I get on anyway.

TTF

Well 3 days in and all seemed to be going well. It kept the humidity higher after lights off for longr but it still went down to 20% (or less) throughout most the lights on period. I started to use nutrient water as suggested by someone in another thread. Sorry I cant be arsed to look who it was right now. The plants did love this through, you could tell within 24 hours.

Downsides

As stripeymoon said I have found a lining of white dust forming everywhere. On buckets and leaves. The unit seemed to work great for three days then on the fourth day of use the unit was hardly working. I read the instructions which said this was normal and it meant that the unit needed cleaning. I took the plate out and cleaned it as best as I could. I let the unit dry out fully before putting it back together but non of this made a blind bit of difference. It no longer works - Off to complain to the ebay seller now, see where that gets me. Its a shame because the plants really seemed to have thrived the last few days.

look on ebay for humidifier and they sell evaporative ones for about 20-40 quid. they basically make steam (different to the swamp coolers i suggested earlier, and a lot smaller, use much more power though, but it should be intermittent)