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Growing in a converted attic (ventilation)

Looks like I'm going to have to venture into my loft space in the near future.  Not really ideal but needs must.  And if done properly there will be an extra room in the house.


My grows will be very small and in soil.


The environment is my biggest concern. If the loft is fully insulated that should go some way to steady the temperature somewhat??


As for fresh air, I wondered if a velux window with balanced ventilation would be sufficient?  It's kind of the same way I'm ventilating my current grow room.  The window is slightly cracked open, just enough so there is fresh being drawn in and extraction into the room at ceiling level. Works so far.


I don't want ducting running here or there in the attic space just want to run the extraction into the loft space, (all be it into the other half of the loft) mimicking my current grow essentially.


If anyone has experience of this I would very much appreciate your input.





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I have a tent in the loft and just vent into the loft space. However I had some fancy new soffitts fitted that allow good ventilation to the loft. Sometimes it's blowing a hooley up there!

I've found that I need a good carbon filter and replace it every 4-6 months. My neighbours are cool but they let me know when they can smell it. If you are in a detached house  then you're fine, terraces, semis and flats throw up their own issues

Venting out of a Velux should be fine. My concern would be more about light leaks during the dark period,

As you say lofts are not ideal. They are too cold in winter and too hot in summer. Saying that I have muddled through and produce crops all year round for over 15 years. They may not be the biggest grows but I fill my jars with decent bud every time.

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I have a loft setup. 2 rooms actually, flower and veg. 

It's a previously unused space though so isn't plasterboards or anything, no windows etc. 

I have DIY tents in the centre around 8 foot wide and 8 foot long with a high centre down to around 5.5ft at the edges. 

There is a gap between the roof and the tent material which stops it warming up the roof, yes snow stays put. 


My intake ductings run in one side of each room and the extraction out of the other, with the filters sat in the tops of each room of course. 


I pull air in from the eaves and push it out the eaves on the other side. With sufficient sized intake and outakes I have no problems with temps even at the height of summer :)


I cannot put the outakes right up to the soffits as it's far too loud outside but them just pointed at them with around a 12 inch gap works perfectly. I'm lucky in that the house is next to a busy bypass so road noise covers any sound even at night mostly but as a second bonus my neighbor has a fancy fish pond with fountains and whatnot so the water sound covers any unwanted noise also 

Edited by Pecunia Arbor
Adding info

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Oh yeah in winter in the veg room running the lights 24/7 is an easy solution to heating although a fan heater sat at the eaves end of your intake ducting, pointing into the ducting, that comes on when lights go off is a very effective way of maintaining night time temps

Edited by Pecunia Arbor

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Lots to think about there.  If the insulation can help with temperatures, especially summer, but I guess it's still going to get hot up there.  Will look into a/c unit.  For the large majority of the year I just need to keep temperature up with a radiator and I think that will be achievable.

My current 160cm tent wont fit up there though.  Can't seem to find attic tents as small as 140.  I will probably get away with not using a tent and just use the room its self.  I'll be growing autos so no worries about light leaks from the velux but I can always black that out somehow.

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I recently moved into the loft so can share what I have experienced so far


Setup my old DR60 tent with my 250w around Sep last year but found that the temps were just too low and had issues getting them to grow. Ended up getting an oil rad eventually but it was too late and had no root mass come the end of the grow. Got a bit to tide me over but had to rethink the plan.


I had planned to get a 1.2M tent and put insulation boards around the tent to insulate but after looking couldn't find any that had the socks in the right place so went DIY.


I've now got a 1.2x1.1m room with 50mm insulation board. This so far has kept temps pretty nice. I ran a 250w for the first couple of weeks and with lights on I had to run a 60w tube heater as well to keep temps around 24c. Once I swapped to 400W I've turned off tube heater and temps are holding around 25c. I haven't tested the 600w yet but think I might be too warm! My intake was being taken from the loft at temps between 5-10c. I've since cut a hole in ceiling to bedroom and intake temps have increased to around 15c. Temps in room are now around 26c and the fans are working a bit harder.  Lights off, my intake fan is in a box with an oil rad, this comes on when temps get to 21c and heats the air up being pumped into room. Logs today say it came on 4 times with lights off. This is helped by the warmer air coming from downstairs, before I had the intake coming from downstairs it would be on a lot more often.


My loft isn't converted or anything and is breezy around the eave, I just extract to the eaves as it seems breezy around there anyway.


 Here's my setup


If you are OK at DIY I would suggest that route as you can tailor the room to what you want. If not then a tent with an insulation wall built around it will be needed. I haven't tested mine in the summer but I think I'll either need to stop or use the 400w max if I can get cool enough temps for the intake.



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Warming a room is an easy problem to have. Its cooling in summer thats the art. Just drastically over spec your intake and outake and problem solved though. Doesn't need to cost the earth ive had some epic bargains through ebay and gumtree over the years. 

Massive box fans arnt always as loud as youd imagine. As an example i use a tornado 12 inch box fan for my flower room (room isnt that big really) with acoustic ducting and a massive 10 inch mountain air filter. 

That setup is much much much quieter than the previous centrifugal fans ive used before. 6 8 and 10 inch.

For added benefit i wrap my box fans in a double duvet but thats more to stop the vibrational hum resonance as my box fans sit on the floor rather than being hung.


The majority of the time the fans just tick away at around 25% but soon bring temps down and control them when the controller goes over 25. Basically a silent setup once your back down out of the loft even when the house is quiet 

Edited by Pecunia Arbor
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Just to throw in if you were looking to use a tent up there, hydrolab do a couple of shorter tents, a 60 x 60 x 140 and a 120 x 60 x 120

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@Autobud thanks for the tent info, that helps a lot.  


It's a shame really that I will have to go into the loft.  The room I'm using is perfect.  But as you guys have demonstrated, loft growing is possible with the right gear and know how.

The biggest issue is keeping temps down.


Any links for reasonably priced a/c units is appreciated.

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It's a roller coaster for sure.


Intake from our bedroom, extract to chimney...

Loft been thermal bubbled and has fibre wool on floor and boards..

both tents double wrapped in thermal bubble..

veg = ds 60..5"l, passive intake.. 2 x 2ft 60w tube heater under a pallet with 400w 24/7.. just ok but dips and peaks. 250w in summer.

flower - dr100..6"l, passive intake, 2x 315w cmh..2 x habistat 70cm heat matts, 450w oil rad, 1x 2ft 60w tube heater in duct... gotta be on the thermostat temps to keep it semi stable.

all on digital thermostats and root it probe thermostats...


even with water trays humidity can be a real problem.


good fortunes :)



Edited by Ital

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Would venting through a slate/tile vent work better than the eves?

just an idea as no one has mentioned it.


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