Hello. I sectioned off a vegging chamber yesterday, sealing part of my room off - the area is about 1m x 1.4m sq, with a height of 2.3m, under a 400 watt MH lamp. Problems with it are the temperature and humidity. Both are in the early 30s - not great - may be cooking the plants in a dry heat without fresh air, so I'm determined to get a fan in there asap. Given the size of the chamber, would a 4" fan be enough? I've hooked up an intake duct through the window using 6" ducting. I figure I can maybe scrape the money together for a fan and some ducting, adding a filter at a later date to reduce the initial costs - the plants are only seedlings at the minute, so no smell for a while. I was thinking I could pump the old air out through a hole in the lightite into the main room it's in?

Also, in the case of humidity, would a heated propagator work, if say I added boiling water to the tray, or wet soil, or something, opening the vents to let the steam out? (Try it and see I suppose?).

Hope someone can help - many thanks again UK420.

NG

hi temps need extraction fans to exhaust more air from your grow space. If you vent into the room your cabinet is in and take air in from the same area it will increase temps by a lot. you should be exhausting out a window or the like and intaking from outside as well. as for the humidity you should get a humidifier.

GNF

Hi GNF - thanks for the reply. I am intaking from outside, but thought, to forgo the need/expense of a carbon filter for a while, I could pump the old air into the house - may take it up into the roof space instead (bit wary of putting holes in other peoples' property though tbh)? Money's a bit tight at the minute (isn't it always?), so not sure if I could afford a humidifier, or anywhere round here I can get one ftm. Not even sure I can afford a fan, but needs must when the devil drives, eh?

yeah you really need to get the hot air out of the room, make you should use your intake fan as exhaust, once you get the temps down the humidity should raise naturally anyway

Thanks Established - problem there is I don't have an intake fan either - just passive intake - 2m of 6" ducting attached at one end through a board, behind a perforated blind and secured to the window frame with the wee top window open, the other end into the chamber. There are 2 oscillating fans in there at the minute, but apart from that, there's sweet FA. Thinking low budget (ie flat broke), do you think a 4" fan would be big enough for an area that size (given the above dimensions) - I thought, since it's not going to get much warmer round here for a while, I don't want it getting too cold in there either.

You profile says your going to be using a 600w HPS eventually, that would require a 5" or 6" or even 8" extract really, im not sure about 400w MH and the bigger your extract fan is the less likely your going to need a intake as well, if you get a great big extract fan then you can rely on passive intake more. You could always get a 4" for extract for now and then eventually use it for intake and get a bigger extract later on, I think I paid £55 for my 4" rvk and £60 for the 5"

Thanks again Established - yeah the 600 HPS I plan to start a seperate flowering chamber with that. I'll have to price fans locally today, see if there's much difference in price - they seem to go up about 15-20 quid an inch though, from what I've seen. I figure locally coz I get my dole today and don't think I could wait for the postie to lug it round/steal it, with the situation as it is atm. The chamber I have at the minute will probably be used to flower this grow as well, possibly under a 400 HPS till I get more cash - which, given my current run of luck at the bookies, isn't going to happen any time soon.

ok well dont forget to ask them to price match, the scabby shop near me wont ... but 15 miles away in the next town they do! you find the cheap price online and buy in store for same

Will do Established - cheers! Local hydro guy doesn't open till sometime between 10am and 12pm, or whenever he gets round to it, not sure if he'll be up for a bit of haggling, but I'll give it a shot. Next nearest town that sells it is Belfast, about 60 miles away - 1 and 1/2 hour train journey to get there - bit over priced too if you ask me - UK420store seems well priced - not sure how the postage works though and given that it's an emergency, I'm afraid it'll have to be a local purchase. he already (local guy) quoted me £135 for a 5" fan and filter, so I'll have to see how much of that was for the filter. Thanks for all the advice - appreciate it.

any luck with the fan m8?

Hello again Established - I'm just back online - ended up having to install linux to get here, but I made it Anyway, I got a 5" fan and 3m of ducting this morning - cost me £85 all in - bit tight but I hung it in the chamber, after I had to go out again to get a length of cable for the flamin' thing - all that money and not even a plug ffs. As it is, passive intake doesn't seem to be working - the fan's blowing out cold air, but little if any fresh intake - I'll wait till later then perforate the blind a bit more, but I may need an intake fan - expensive hobby this, innit? As it stands the temp's still around 30-31 and the humidity has actually dropped to about 24 - not my day is it I was searching to see if anyone else had posted something on fan height - hopefully you or someone else can please answer this for me.

The chamber is 2.3m high, 1.4m long and 1m wide, the 400MH lamp is suspended at about 3.5 feet. What would be the best height to set the fan at, to maximise air flow and extract the heat? As it is, having started at lamp height, it's now in the top corner, creating a bit of a vacuum in the chamber, so I'm thinking it's the intake's the main problem now - am I right? BTW, I slotted the outlet ducting through the cover sheeting and gaffer taped it. Also thinking I may have to get another board, some more ducting and open another window. My empire is taking a hell of a long time to get started...

a couple of suggestions, put your fan high up as hot air rises and extracting from the hottest point in the area is going to most effective, passive intakes need to be about 5 times the size of the exhaust so your gonna need five 5" holes for passive, I believe you got ducting on your passive inlet to the window or something, well I dont think its a good idea to have ducting on passive inlets, it restricts the airflow enough with a rvk .. never mind passive

edit : where you exhausting the hot air to? a pic would be good, you need to exhaust out of the room maybe the loft, then get rid of ducting on passives, make them 5 times bigger and let the cool air come naturally from the window into the room, when you get an intake rvk that when you can put the ducting to the window again.

Cheers Established - the room's coming down again tomorrow for a re-fit, to measure 1m long x 1m wide x 2.3 high - about right for a 400 watt lamp, isn't it? At the minute, I have the 5" extractor in the top corner and, God forgive me, I put a hole in the ceiling to pump the hot air into the roof space. Seems to be working ok, but the plastic sheeting needs secured a bit better, so tomorrow, I'm off to get some more timber from B&Q and building a proper ceiling to floor frame to fasten it to. For intake at the minute, I've got some 6" ducting fed through the sheeting with the outside end facing a 12" fan that's on full power to blow air in at the bottom of the chamber, directly at the plants - there's a 9" oscillating fan inside the growspace as well for circulation - both windows are now open, but I can access them again if needs be. The temp's dropped now to around 27 degrees, which isn't as bad as yesterday when it was over 31.

However as one problem gets solved, another arises - or in this case, decreases - the humidity's dropped to about 19 RH. I've been informed that, as I pot up, the humidity should rise too, so was thinking - what if I added 2 large basins of wet soil to the chamber - would that raise the humidity? Have to try it and see, but hopefully by this time tomorrow, my crop'll be in a nice new vegging chamber. Next I have to build a flowering room and then see if I've enough space left for a mother and cloning area. Thought did occur for venting the flowering chamber (if/when it goes up) - rather than use 2 fans for extraction, run 2 lengths of ducting from both chambers to a Y connector, then connect that to the extractor - any idea if it'd work? Probably need a bigger fan huh? Boys, this is getting out of hand hi...

Yes 1m2 is better for a 400w, 27c is good you just got to try and keep it from going over that and it can only get easier as winter gets closer.

I wouldnt want soggy compost sitting in my growroom, try a wet towel instead. Or a humidifier or a mini-fogger (maplins)

B&Q don't do humidifiers round here - just the de-humidifiers for some reason - probably all the damp weather we have The nearest Maplins is miles away, but I think they do a mini fogger for about £15 quid - I've 1 or 2 mates that go to it now and again - I'll ask one of them to pick 1 up for me next time they're there - the temp dropped to 22 last night in the growspace, the humidity went back up from 19 to 30 (it reaches about 50 RH during lights out). I've closed one of the windows to see how it affects the temp - at least I know I can drop the humidity later if I need to - just have to find a way to get it up first - you reckon the damp soil's a nono then Established? What if I boiled a kettle in there a few times - think that'd work or is that too dodgy given the light's electrical? Thanks again for all the advice, I really appreciate it.

its up to you but one of the reasons for potting up is so you aint got unused soggy soil sitting around you plant, so I wouldnt do it intentionally (plant or no plant in it) especially if you intended to use the soil in future, a wet towel is much more hygienic way.

Soggy towels it is then - cheers Mr E!