Venting from basement to roof cavity. A few questions

[lightsout]

Hey guys, I have a basement that has a hole in the wall for access to underneath the house. I've been in there doing a bit of digging and have created the perfect spot for a little 2 plant grow. I live with my parents so this has to be an ultra stealthy set up, smell and sound wise.

 

One of the walls of my chamber is the outside wall of the house, which is double brick. I removed a bit of rubble from this small opening that was blocked up and am now able to get my arm into the cavity between the two walls. Convieniently there happens to be one of those old cement vents (about 17 x 12 cm in size) on the outside wall pretty much opposite my opening.

 

So my post (sorry bit of an essay) has two parts.

 

INTAKE

 

I am thinking of drawing my clean air through the vent with a normal inline fan, as it only has to travel about half a meter. my question is will it make a noticable noise? either the air rushing through the vents or the sound of the fan in operation (is there a way to muffle the noise?).

 

Also the vent only has 15 2x2cm gaps in it. Do you think this will provide enough airflow? especially with only a standard inline fan pulling the air.

 

EXHAUST

 

My second problem is outgoing air, for which i have a bit more of an eloborate plan. I want to vent to my roof cavity into a carbon filter as i have heard this is the best way to eliminate smell. My problem is that:

1) the roof space is about 5-6 meters away as i am already under the house

2) I only have the cavity between the two brick walls to work with.

 

Say i were to split the out going ducting so that it diverged into 4 (or however many are necessary) lengths of PVC pipe that ran up the cavity and then converged back into a single ducting tube in the roof space which contained a centrifugal fan followed by the carbon filter. I assume i would need a pretty powerful fan to move all that air over that distance.

 

My question is how powerful? or would i need two fans? one pushing one pulling?

Also, with greater power obviously comes increased noise. Is there an efficient way to muffle the sound at all? I have read threads on here about people building boxes around them and stuffing them with rugs etc. but all seem to be based on word of mouth. has anyone had any first hand success with this?

 

I have a 600w kroplight that i bought ages ago. I am hoping to build a pretty well seeled little area within the chamber, roughly 1m wide, 2m tall and 1.5m long (so about 3 cupic meters of space i need ventillation for).

 

Sorry for the lengthy post.

Hopefully you guys can answer some of my questions

 

Thanks in advance,

Sam

 

PS. The only entry into the chamber is through a 35x35cm hole in the wall. So on the plus theres no chance my parents could get in there, but at the same time i can only use building materials that will fit through this hole.

[jimbojones5678]

Hi lightsout ,

 

Firstly a drawing of the area would be good.

 

I am thinking of drawing my clean air through the vent with a normal inline fan, as it only has to travel about half a meter. my question is will it make a noticeable noise? either the air rushing through the vents or the sound of the fan in operation (is there a way to muffle the noise?).

 

Also the vent only has 15 2x2cm gaps in it. Do you think this will provide enough airflow? especially with only a standard inline fan pulling the air.

I think that passive venting or an inline for the intake would be do-able, they do make a noise (and the cheap one's can be quite loud actually) so if you can get away without an intake fan - do it. The vent size is fine.

 

I want to vent to my roof cavity into a carbon filter as i have heard this is the best way to eliminate smell.

you have the order of things wrong here - you want the fan pulling the air through the CF

The roofspace is probably a good exhaust spot because no-one sticks their head up there very often - but as long as your CF is new then you shouldn't have any odor problems, enabling you to pick a better exhaust point closer to the growroom

 

Say i were to split the out going ducting so that it diverged into 4 (or however many are necessary) lengths of PVC pipe that ran up the cavity and then converged back into a single ducting tube in the roof space which contained a centrifugal fan followed by the carbon filter

rubbish...there's got to be a simpler way

 

But as I said - do a mudmap of the room so we can see what you mean better

 

Jimbo

[lightsout]

Thanks for the reply Jimbo

 

I knocked this up in paint for now. Might take some photos next time i get in there so you can see what i mean.

 

I've been in there all day today with a mate building a retaining wall and compacting the sand. We also ran a new power lead up the wall cavity, through the roof space and straight into the meter box and put it on its own breaker.

 

I think your spot on with the no intake fan idea, even without any fan in there i can feel the fresh air coming through the vent now that i've cleared it all out.

 

Having the exhaust fan in the room would make things alot easier, then i could just vent straight into the wall cavity. I'll just have to make sure i do a good job of muffling the sound. Cheers!

 

 

[lightsout]

Ok, grow room is well under-way. I've cut all the wood for the frame so i know the exact dimensions now (1.1x1.24x1.8m, so 2.46m3). At the moment i cant afford to buy a centrifugal fan but i have access to 4 25w inline fans. There all HPM Heavy duty exhaust wall fans (R621/8A), which according to the HPM site have a flow rating of 245m3/hr.

 

The intake fan only has to draw the air down ~1.5m of ducting to the base of the plants. I think this should be sweet. For out-going I could have the fan sitting about half way up the frame and venting directly into the wall cavity (air would only have to travel about a foot). But I have heard its best to have your exhaust fan at the top of your room as hot air rises, i could do this, but it would add a couple of meters to the distance the air would have to travel. worth the trade off?

 

I could also have two exhaust fans if one isnt enough.

 

This is all well and good whilst the girls are in veg but come flowering time i might have odor issues. Are there carbon filters that these little fans can handle? Even a low efficiency one that could reduce the smell a little bit? or will i just need to bite the bullet and get a centrifugal to solve my odor problems?