attic grow - insulating box

[stinkhairs]

Going to try and convert an attic for a grow. It has a nice floor space, about 4 foot square, but limited height due to the triangular angle of the gables. The light can be about 5 foot off the floor. Not so much a problem as i'm going to lst them and keep them short and wide. I have intake (100mm) and exhaust (150mm) coming in and going out of two seperate roof flumes, so fresh air in and exhaust out is not a problem.

Anyway, i'm going to build a box around a section of frame of the gables, and was wondering how much insulation i'd need to keep the temps isolated from the rest of the attic. I bought two rolls of the yellow furry loft insulator, and plan to sandwich it between two boards of 3mm plywood, to make "insulated boards" that i can then screw to the gable frame. How thick would i need the insulation to be?

 

[guyyug]

That stuff is meant to be used between 2x4 or 2x6 studs, so 3.5 or 5.5" thick. Building 2x4 walls will make everything much easier anyway. I would use sheetrock as the inside surface instead of the plywood, easier to seal and paint, use the plywood as the outside if you want though. There just needs to be a solid surface on the outside of the insulation (if using fiberglass "pink" stuff) and the inside so that the insulation can work properly.

 

[GP73LPC]

a couple of things.

maybe i misunderstood, but sandwiching insulation does not work. the stuff is not meant to be compressed. but like i said i may have misunderstood.

on the intake and outake, my concern is with your intake. are you intaking through a roof pipe designed to exhaust menthane? if so, i would definitely consider an alternate source for intake.

peace

 

[RM - aquagrower]

on the intake and outake, my concern is with your intake. are you intaking through a roof pipe designed to exhaust menthane? if so, i would definitely consider an alternate source for intake.

peace

Nice catch. The 100mm (4") pipe is probably a soil pipe (plumbing vent) also known as a stink pipe (for good reason). Another thing to concider is that roof deck temps can reach 170 degrees on a 90 degree day in the full sun. This means that even if you are pulling fresh air in threw a brand new, freshly installed pipe, it will be pulling in very hot air.

Better solution for the intake is to pull in from a soffit vent.

 

[stinkhairs]

Thanks for the replies.

a couple of things.

maybe i misunderstood, but sandwiching insulation does not work. the stuff is not meant to be compressed. but like i said i may have misunderstood.

on the intake and outake, my concern is with your intake. are you intaking through a roof pipe designed to exhaust menthane? if so, i would definitely consider an alternate source for intake.

peace

I was not going to be compressing the insulation between the boards, but sort of leave it fluffed up. I can't remember where but i'm sure i read that there actually needs to be some space around the insulation or it will invite damp.

The roof vent does not exhaust anything, it was an old central heating flume that no longer has any pipe work connected to it. Seems like it was placed there just for me

 

[GP73LPC]

cool

just didn't want you pumping deadly methane gas into your grow room...

 

[fungzyme]

Another thing to concider is that roof deck temps can reach 170 degrees on a 90 degree day in the full sun. This means that even if you are pulling fresh air in threw a brand new, freshly installed pipe, it will be pulling in very hot air.

Better solution for the intake is to pull in from a soffit vent.

I second that. It's hard enough to control attic temps (even if your growspace is insulated) without bringing in intake air from off the roof.
Your intake air temps are going to vary widely and wildly from season to season and from day to night. (Maybe as much as 50 degrees or more. Just picture the heat shimmering off a rooftop in summer) And no matter how good your ventilation is, your ambient temps are never going to be cooler than your intake air.
Is there any way you can get your intake air from inside the house, and then exhaust to your roof vent? That's going to make having controllable temps possible.

 

[DankDork]

Hi from Finland! i made my attic space almost solely of urethane insulation boards.
its handy couse you dont need a thick layer and you can build the walls from it on wood frame, easy to cut and saw too.

 

[DankDork]

urethane foamed sheet seems to be the propper english name to it