Ventilation Q

[skilledmonkey]

hi os',

 

setting up a room at the moment + wanted to run some ventilation ideas by you guys for some advice.

 

room is approx 4m x 3m with a 2.7m ceiling. (33 cubic mtrs)

 

exhaust will be by way of a 700 l/s (1500 cfm) centrifugal pulling through a carbon filter. i plan to vent directly into the ceiling. this leads me to my first queries:

 

the roof is a flat-type roof. the cavity from ceiling to steel corrugated roofing is about 300mm. will ducting directly into the ceiling create excess pressure + heat in the roof cavity?? i'm guessing there is space between the roof beams for air to move + eventually find its way out of vents/gaps but not sure....

 

 

as for intake...

 

i have 2 options as far as i can see.

 

1. go up through the ceiling again and through the roof to outside + duct back into floor level of grow room. if i did this would leaving it passive (no fan) be enough? i'm thinking that a room this size + a fan of 1500 cfm capacity will need maybe a 500x500mm passive intake hole at least?? (btw i'm on the 2nd floor so cannot intake from floor)

 

 

2. there is 1 window in the room. it is the type that is hinged at the top + when u wind the handle the bottom part of the window opens + flares out. if i go with this option i can build a light trap as per this old overgow thread:

 

http://www.overgrow.com/edge/showthread.php?threadid=45055

 

this would allow me to probably have more fresh air than i need + i could effectively control intake to suit fan speed. i feel ducting coming from the ceiling will not allow enough air flow unless i use huge ducting (is there such thing as 500mm ducting?) or muliple ducting (want to limit craters in the roof!). :reallyexcited:

 

am i right in thinking that even by installing a fan in your intake that it will not increase air flow to the grow room? that basically your exhaust fan combined with the size of your intake hole will determine how much fresh air makes it in b4 it gets sucked out??

 

 

the main negative re the window option is that the window is in full view of neighbours so leaving it open all year round may attract some interest.

 

have access to a portable a/c unit for the summer months.

 

 

any tips, pointers, advice or even abuse will be welcomed. :thumbsup

 

cheers,

monkey

[Tom]

You could vent into the roof space close to the outside wall and then fit a vent into the roof space from under the overhang or the side of the roof outside.

 

[skilledmonkey]

g'day Tom + thanks for the quick reply.

 

the entire roof perimeter has a protruding brick firewall around it. picture 2 storey townhouses all abutting side by side.

 

have pretty much settled on the roof idea for the intake so figure what the hell if i'm gonna cut 1 hole may aswell cut 2. think i will definitely need some venting through the steel roofing though as concerned about pressure problems as theres not heaps of space up there.

 

so if i go down that road - as far as intake is concerned do you think a 350mm diameter length of duct with a cpl of slight (35 degree) bends finding its way to floor level be sufficient for that set up(passively)? i would run the exhaust fan on a speed controller at reduced speed.

 

how do you know when you are drawing in enough air? is your fan labouring if it is struggling to draw in new air - considering the room is really well sealed.

 

i plan to run about 3000w in there if that helps.

 

many thanks,

monkey

[everest]

hi monkey , love to help here , any chance of a diagram of what you propose ..... ta

 

ev

[skilledmonkey]

hey everest,

 

thanks for the interest. now don't laugh at my diagram! it was supposed to be so much more but with just ms paint to work with this is the best i could come up without throwing the mouse out the window. it's a side view of the room - its not to scale + just imagine the filter has a fan attached in there as well.

 

the intake has a dog leg in it as i want to cut through the ceiling from inside a built in wardrobe. this is also why i want to have my intake + exhaust holes close together - when i cut into the ceiling i want to do so through the built in robe so i have a ceiling (inside the wardrobe) of about 450x1120mm.

 

outside i was thinking to rise the exhaust up about 600mm or so so i don't just suck the exhausted air back down.

 

cheers,

monkey

 

 

 

[skilledmonkey]

would also move the filter further towards the other side of the room too (left of screen). i believe having a reasonable length of ducting completely straight before any bends is good for airflow + noise? sound right?

[thc24]

hi skilledmonkey i have seen the odd set up ducted through corvon filter through roof and into a wirlybird vent does not look sus atall as every second house has one now.

[Ozzy420]

Venting the hot out of the roof would be ok but i wouldent be getting my freash air from there, i have lived in a place with a flat tin roof and when the sun heats it up the space between the tin and ya roof gets bloody hot and the air that is traped up there gets real hot it is like a sweet box, so imo i woul;d find another way of getting freash air in...

[everest]

hey monkey , i can see your dilema :scratchin

 

i'd defo use the window for yor fresh air , wouldn't worry about the neighbours no one ever reports an open window , as for exhaust suck it out through your filter and into roof cavity , you will have a bit of temp rise , but nowt to worry about , air especially hot will find all the escape avenues .....

 

you will need a good fan to suck air into the room and probs another fan oscilating , it's a big room ..... :smoke

[skilledmonkey]

thanks for the replies guys.

 

thc24 - i like the whirlybird idea. just venting into the roof cavity has me thinking pressure will build + the fan will not be as effective as it should. the cavity is only 400mm high + it seems like there are 400mm high beams about 600mm apart. i'm sure there will be space at the ends but it seems to me pressure will build. the whirl bird should also help with heat i guess.

 

g'day ozmade + everest - it gets bloody hot up there. galvanized steel. doesn't have to be a hot day to roast up there. looks like the window will be the go. i am more confident with drawing in enough air that way too. 350mm ducting with bends from the roof had me worried i would never draw in enuf air not too mention the heat + the chance of cycling in the same air i just exhausted. :smoke

 

so thanks heaps guys. should be up + running in 3-4 weeks so will keep you posted + will probably do a diary thread.

 

all the best,

monkey