Attic grow room advice

Hello all, before i start ill let everyone know im pretty new to growing. Ive got one outdoor and one indoor grow under my belt. But ive done loads of research just need a little advice.

Im thinking about an attic grow over the winter. Im planning on setting up a perpetual sog grow with a growth area of 3x3 ft for flowering and another small area for two bonsai moms and rooting clones. I have an unfinished attic about 5 ft tall at peak stretching 9 ft in length down to about 6 in in height. The space is about 90 cubic feet with a 4 ft width. I want to use a 400 watt hps for flowering and flouros for mothers and clones. The grow area will be sealed off from the rest of the attic. With styrofoam insulation.

In my area our winter temps are about 24-55F. Im wondering about heat/cold issues. I know attic grows are tough because of the heat thats why i want to start in the winter. Im wondering how hot a 400 hps would make an area of ~ 64 cubic feet? I have a few options for temp control and ventilation. I could pull air from a bathroom under the grow area through a broken fan or i could tap directly into the hvac. Id rather not tap the hvac but will if i have to. I may want to coninue the grow into the summer if it works but we regularly get 90 plus in the summer.

Anyway my question is to what extent do i need to prepare for heat/cold issues from a 400 watt hps in a 60ft3 area? With both intake and exhaust fans most likely 3-4 inch inline. Would the humidity from showers cause an issue if i pull air from bathroom?

Ohh and the light will likely be at a height of 3 feet or so above the soil. Ill probably start flowering clones at around 6-8 inches and this strain usually doubles height during flowering to 12-16 inches leaving about 2 feet between tops of plants and the light. I read 3 ft is the penetration depth for 400 watters. Then therell be a triangular space of about 2 ft above the light to the ceiling.

Hello there minutemaid,I am new to Roll It Up but have several attic grows under my belt,i have found that it is best to build a room in the attic to stop the light from your hps warming up the roof itself,this is how people get caught out by Flir.You are doing the right thing by insulating with styrofoam. As for temps its quite simple in winter months if it gets too cold,add more lights cfl's, hps whatever your budget allows.Now in summer, i find extra air being brought in will sort your temps out as will an extra rotating fan blowing the cool air around the grow room. As for humidity,although its a factor in growing i have experienced that its not a major issue at all. Keep it simple,air in and air out and temps around 80,add light for temps up and add more fans and air for temps down.All the best brother.

dirtydaztrundell said:

Hello there minutemaid,I am new to Roll It Up but have several attic grows under my belt,i have found that it is best to build a room in the attic to stop the light from your hps warming up the roof itself,this is how people get caught out by Flir.You are doing the right thing by insulating with styrofoam. As for temps its quite simple in winter months if it gets too cold,add more lights cfl's, hps whatever your budget allows.Now in summer, i find extra air being brought in will sort your temps out as will an extra rotating fan blowing the cool air around the grow room. As for humidity,although its a factor in growing i have experienced that its not a major issue at all. Keep it simple,air in and air out and temps around 80,add light for temps up and add more fans and air for temps down.All the best brother.

Click to expand...

What about when the lights go out and temps plummet????

I try and not rely on ambient temperature to get my room where I want.. I have never had to heat anything at lights off, but a nice 10-12 degree drop in temps is ideall......

imo, make sure you plan for good ventilation (and insulate the roof if it snows in your area ever, snow melting fast is a pretty good sign of an attic grow). It's much easier to heat a space than to cool it. If it starts to get cold in the winter (get a digital thermometer that will record hi/low), increase circulation or add a heater.

I have many attic grows under my belt and the number 1 thing you need to do is insulate as well as possible. Also in winter you probably want to pull air from your bathroom like you said but if you want to continue it in the summer you should really tap into your central air. Here are a couple pics of 1 of my attic rooms < I have 2 attic rooms running 1200 watts a piece and I have very little temp fluctuation in the summer or winter it stays pretty much the same temp as the rest of my house.
View attachment 1113828View attachment 1113831View attachment 1113832

Also its a good idea to add some sort of water source up there so you are not lugging up water all the time and its also a good idea to add pond liner on your floor to make sure you never have to worry about water leaking from your room from overflow when you water. Just straight plastic will get holes in to easily but pond liner has a lot of give and will not puncture/tear as easily. Some tarp zip-ups are also good to have to make a door so your room is fully enclosed and they are cheap and easy to install, you will need 2. http://www.plantlightinghydroponics.com/tarp-zipup-peel-and-stick-zipper-p-1713.html

If you have any other questions feel free to ask.

Thanks for all the replies guys. I decided to double the width of my room for more work space and ventilation. Im going to pull climate controlled air from the bathroom by using an exhaust fan with about twice the cfm i need in order to create a decent vacuum in the grow room vented directly through the vent in my roof that the bathroom fan blows out of. Ill position the light directly under the vent and fan to hopefully control the heat.

As for insulation i was thinking 1 inch thick styro foam boards glued directly to the roof, then ~2.5 inches of air between the styrofoam and bottom of 2x4s where a layer of reflectix insulation stapled to the 2x4s. Is this sufficient for the roof?

Then i was hoping i could get away with 3/8 inch drywall lined with refectix insulation for the walls. Maybe with a layer of air between the two for added insulation.

All reflectix insulation will be connected and hopefully sealed with that silver hvac foil duct tape.

Im also thinking im not going to insulate the floor at all since its to the inside of my house and can only help heat/cool the grow room.

Does this all sound sufficient? Do i need to add to anything? Thanks in advance.

I would attach the vent from the bathroom to your grow room and then exhaust your room through your lights and then out the roof, the suction should pull the air from your bathroom into the room and since most of your heat is going to be coming from lights its best to exhaust those directly. I also think regular insulation attached to your roof and then the foam board on top of that would be the better option. You can then use the foam board as your walls which is much easier to attach then drywall and then add the reflectivex on the inside of your walls to make it more insulated and more air tight. Also you can then add a carbon filter to your lights so all the air being pulled out your room is being scrubbed first. Make sense? And don't forget to put something on your floor to keep water from getting in your ceiling you don't want wet spots on your ceiling and you don't want any electrical wiring getting wet or any mold forming in between your floor and ceiling. 1 more thing when you place your vent from your bathroom try and place it on the opposite side from where you are exhausting so the cool air is being pulled over your plants this will help maximize your air flow and keep you from having hot spots.

From my research i found that a radiant barrier is more effective, especially in an attic grow, at keeping heat where it belongs whether in or out depending on the season. It may have just been an advertising tactic but something like 95% of heat is transfered radiantly rather than through convection or conduction. Anyway ill probably use some r-13 fiberglass instead of the styrofoam its about the same price. That way i cant go wrong. Thanks for the input.

Not sure if this is the appropriate place to ask but im also looking to build a custom light reflector and am wondering what the best design is. Im looking to get the most square footage out of my one light and maximize heat dissipation/ventilation. Would holes drilled above the bulb be effective? Could i get a good 4x4 area with a 400 watter and good reflector?

Again thanks for the help and any and all input is welcome.

Well there are a lot of different answers to that question about the light. You can get more grams per watt going vertical with no hood but you also have to have the correct space for that and the correct design... You could get a bat wing reflector and those do a decent job and those have the ability to concentrate light or spread it out depending on how you position it and get very good air flow. I personally like the Super Sun 2 reflector because it is cheap (just over 100$) and is a good design and has very even light dispersal. But most hoods are made for 600-1000 watt bulbs so they all are going to have slightly uneven light foot print for you because the 400 watt bulb won't be as centered. If you are designing your own hood I would get a light meter so you can adjust things to your own needs. Anyways, here is a good thread on another site that test different hoods to see there effectiveness but it just tests air cooled reflectors not all reflectors but is still a good read.
http://www.icmag.com/ic/showthread.php?t=51325

bad idea unless you know what your doing. I tried setting up in my attic and i wasnt too succesfull. even tough it would be easier in the winter

Attics just seem to hot in summer but like said if insulated well, its ok....I mean who can argue with results.