Ive moved my setup into my shed 2 weeks ago and am struggling to keep up temps when lights off and im also suffering from low humidity
Ive just upgraded to a 600 hps diamond reflecter and only got a 4" exctraction with passive intake
should be getting 5" end of month

Light times are 12 am to 6 am - on
6 am to 12 pm - off

lights are on over night so night temps are bout 25-27
But as soon as the lights go off the temps reach as low as 9 deg
Would a 180 w tube heater be enough for a 1.2 x 1.2 x 2 room (shed)
Also is low humidity bad to plants health

Dam this British weather

I'm in a shed too - well a brick outhouse - the 180w tube will help, but I reckon you need a 700w + oil rad do keep temps up properly at lights out. Re your timings warmest part of the day anytime of year is normally the late afternoon. My lights off is noon to 6pm, lights on 6pm to noon. 12/12 I run lights on 7pm to 7am.

Low relative humidity goes with the territory of heating the (cold + humid) outdoors air up to growroom temps. Low RH is what you want late in flower, but it's better if it's a little higher in veg (at least 50% light's on). It's not a big deal imho as long as humidty isn't sub 30%.

If concerned I think peeps rate mini-foggers (Maplins), or simply try a few wet towels in a bucket in the corner with a fan blowing over them. Let them dry thoroughly between adding more water or replace regularly with fresh wet towels. Don't want moldy wet towels in a bucket in the corner.

Cheers for the help Bp with regards to light times can i just switch them over to turn off at noon or should i change by 1 hour each day
i was thinking bout oil rad but i didnt want to buy 1 as i had one in my shed and its dissapeared.... i blame those fooking garden gnomes aaaaaahhhhhhh bastards

Hi mate,

This is a tricky one, I have a similar space and problem to you...

I have a 180w heater and it keeps temps at around 17 lights off (although I've just started running my lights at night so that may improve).
and also
Most would tell you to get a 6" fan as would I but with a note of caution that it will bring down temps and you may need a fan controller with it too to reduce noise and also seed for the sake of temps.

I'd go for one of these two options re the heater...

Get a 180w heater and line your grow space with that bubble foilwrap to insulate it (the foil will costs £20 total at b&q), this'll keep temps acceptable and also help you to avoid detection somewhat.

Get a oil filled rad with a thermostat which will prob do the job alone, but take up more room and cost a bit to run.

Howdy Elbows thanks for stopping by, are those tube heaters any good/do they get hot if so would 2 be ok for size of shed as only 180 w x 2 = 360 w its gotta be cheaper to run than a 700 w oil rad or am i way off the mark

if the heaters are on a thermostat, then it should make no difference, if the 360watts are adequate then the 700w will be and will just switch off when the rooms up to temperature, whereas the 360watts of tube heaters will just have to stay on longer, it will still take the same amount of energy to heat the room to the required temperature, if the 360watts aren't up to the job, they'll never switch off, you may end up using less power, but your room will never get up to the temp you want. better to get a heater that's more than up to the job, and then just have a thermostat switch it off at your desired temp. you can also get away with turning your fan down a bit at night to help with temps

Thanks scraglor what ur saying makes total sense if the tube heaters aint up to it and cant get the temps up then they will always be running and i would only have to find another solution

This is the real use for this forum. people sharing info about a mutual hobby
I find it hard talking to people about products and verious problems as i have to hide the truth about what im really upto

Have a good week end everybody

As other poster said, I would insulate the growspace as a matter urgency. I have used rockwool wrapped in plastic and it works well. 100mm rockwool is much better than bubble insulation.

I use a thermostatic fan heater on low power setting. Blows slightly warm air and switches off automatically. Responds to temp changes faster than an oil rad or tube and creates air movement.

If you can get sealed up water containers in there(black or dark coloured preferably) these will take in heat when lights are on and give it out when lights are off.(Passive heating-free!!) Anything that will store heat will do-concrete blocks are good too- but you must insulate from cold ground.This is done in commercial polytunnels with massive water butts. You may still need heaters.But heater will run less.

Make sure you insulate floor first whatever heating option you go for would be my main advice.Turn fan speed down at lights off also.

Hope this helps.

Cheers
Papa.

PS Kingspan 50mm sandwiched between two bits of pond liner in the best growroom floor I have ever had. Warm as toast and one million per cent water proof.

If you're going to get a heater, get it TODAY - NOW...before 4pm....there a high chance of frost tonight, at least down south here in the smoke.

GN

If you can't get a heater today you could always consider 24/0 lighting until you can I assume you're in veg.

I haven't got mine yet and we're 4 weeks in flower, luckily my temps will only drop to 15C lights off even in the harshest winter but that's 100mm celotex for you.

I've set my fan to 15 minutes on/off (When they're in the dark) on the intake side (Which draws from outside) and I fire the air straight at the the reflector which takes the chill off.

I might be wrong but I'm sure they need less fresh air when they're in the dark.

I would insulate you shed roof if you haven't already in freezing conditions it will glow like a fire cracker to any police helicopters.

Yes. Fresh air not needed at all by plants when lights out.
Turn fans down to a trickle just to dehumidify air. Otherwise you are just wasting electricity by trying to heat a constantly changing airflow.

I have found that in certain conditions turning off fans and putting on a dehumidifier at night works great. Dehumidifier heats and dehums.No cold air coming in so temps stay up. This is a good option in wet weather/late flowering as sucking in the wet air from outside does nothing to control humidity.
P

Plants may not be photosynthesising but they are still respiring in the dark - so need plenty of ventilation light on or off imho.

Get an electric blanket, fold it over atleast twice and stick it under your plants

Mine are looking ace, 10C the other night in the room and roots were kept @ 25C, they looked better than they did on the warmer nights! Same last night but just 14C.

The pic was taken just after lights on, that plant had been chilled for 6hrs at 10C with nice warm roots!

mmm......Leccy Blanket and water.......is that really a good idea?

hence the dehumidifier

I made a bag to stick mine in. To keep it clean, some 3M floorseal and ducktape.

Blanket is washable, it has waterproof connections...

Personally I am not cackhanded, I can control my limbs so I have no issues with water and electrics, rather like being in the kitchen etc

Its a quick fix before the underfloor heating goes in, this guy needs a quick fix, lot of people have blankets.

How does a dehumidifier provide the O² needed for respiration?

Fair enough, i haven't come accross a leccy blanket in years, just remember tales as a kid of peeps pissing the bed and electrocuting themselves........

I think ur plants do need fresh air when lights are out mate but leave it too u to find out.also I would be cautious folding electric blankets over a couple of times get a oil filled radiator iv got a 2 kw heater. I'm in outbuildings and it's starting to turn cold at night know.but I would insulate it I used celotex not cheap but does the job 100mm.if ur gonna by a heater buy a decent one that's maybe a bit more powerfull than u need.my mate bought one that was the right size for his room but when it went realy cold it was not powerfull enough always better to have more heat that can be controlled than not enough.

the air is 20% (200,000 ppm) oxygen. there is 100's if not 1000's of times more than that needed for lights off, unless your room is totally sealed (which if you have a fan it of course wont be) then the o2 concentrations in the room will barely drop a few ppm

e2@: people running co2 and aircon, of course often do have sealed rooms, and again, no ventilation, just dehumidification and temp control, used to run co2 myself

Fair enough, I have always wondered if you could suffocate a plant in a sealed room for lack of O². Obviosly not. Still prefer to run fans full whack all of the time, and suffer slightly higher humidity. Not enough air movement has caused me fungal problems in the past (with low humidities).

true, you need good air movement, but this can be achieved by oscillating fans, which is imo a necessity in every growroom anyway, and there's nothing fungal infections like more than high humidity. but anyway, it's not the only solution, and a large enough dehumidifier, in a lot of growroom's is just wasting valuable grow space.

Thanks all for your help,
ive been keeping a eye on temps last nite/this morning and it only dropped as low as 14c
Im not sure as it was quite mild last nite
I should be getting a Frost watch heater as this sounds like is should do the job nicely

Hi Bushmaster

I had a similar problem growing in a tent of the same size. I solved it by buying a thermostat from Screwfix and wiring it up to a cheapo fan heater set on the 1kw low setting. The thermostat that people here recomended was a Honeywell T6360B. Its good enough to switch the mainly resistive load of a fan heater. You need to be a bit of a DIY er but its a cheap and effective solution, although I like the idea of an electric blanket.

Best Wishes - Jak

Plants looking SWEET this morning, all puffed up and ready as the lights came on.

10C in the room all of lights off, roots @ 23C They look better now than when it warmer...

I use a T6360B to trigger my fan from high to low variac controllers. I'll soon be getting a box of them for other things!

i also suffer from low temps in a shed found that strains that are more indica dominant cope better than tropical sativas,where their natural enviroment stays hot in the dark.

i find sats usually cope better with cold temps, a lot of 'sats' grow in high places, i.e foothills of mountains etc, where it gets very cold at night. 'most' sats ime will suffer a good frost better than 'most' indicas

Hi all thanx for all the help,
i managed to get hold of a little 500w heater that ive put in my shed not gr and im going to have to wait till 2mora to find out if temps get above 15c otherwise i will have to move it into th gr and that may not be such a good idea

I grow outside in a garage and in a shed, I made for growing, this year I am lifting the plants of the ground 200mm and have put a small tube heater under an alu plate, keeps temps ok not ideal as I have lost 200 mm grow hieght I now only have 1350mm between floor and grow star reflector I have another 2 3ft tube heaters conected to a room thermostat, keeps the room nice and warm lights out I also have a 6 inch ruck high power also conected to a themostat then into a variac, keeps temps down but not sure if I like the freezing air blowing over the plants, growing outside in a shed is a real pain dont do it if you can should of just got a tent to start of with gonna end up getting a tent for the garage to replace my make shift veg room that way I will be able to lift tent of the ground put heater under it without loosing grow room

sheds are fine, as long as they're well insulated, and you grow in a sectioned off area, so the air can come into the shed to be warmed before actually entering the growing area...... works for me anyway, lights off temp 18-20'c lights on 26-27'c. just a little greenhouse fan heater inside the grow working off it's own thermostat. because i'm doing a scrog i have the heater sat under the canopy right at the air intake, the heater just switches on and off at around 20'c, so under the canopy stays a constant 20'c and when the lights are on, top side of the canopy gets to 27'c. lights off the whole area is a steady 18-20'. spot on

Instead of an electric blanket wouldnt a spider mat be safer i used to use one when i had a pet lizard not sure of the price but should keep your roots toasty