Polystyrene (foam-board) insulation. Extruded vs Expanded

[rickymac21]

So here's the situation. The grow room is in an attic above the garage, and neither the garage or attic portion is insulated. It makes it extremely susceptible to temperature fluctuations. So the grow box is going to need some insulation and a/c. Especially with a 400w mh for veg and 600w for flower. It already reaches 85 f without any lights on and the temp outside is only 65-70.

I've been looking at the polystyrene boards because they seem to be the cheapest option.
My question is does it matter whic type of polystyrene I use?
Expanded polystyrene is SLIGHTLY cheaper and offers an R-4.5 rating.
Extruded polystyrene offers slightly better insulation at R-5 or so. But it also is made with gas molecules? And the gases diminish over time eventually losing its insulating strength. I have also read that the gases may be harmful to plants.

It seems like expanded polystyrene is the safest way to go, but I'd just like to hear opinions from people who have used the foam board style insulation.

 

[computergroove]

Take a look at the plants then notice the walls.

I use vertical lighting and a ductless mini split AC unit and it failed just after these pics were taken. The room is sealed and the water in all the buckets and the 55 gallon drum I have in the room reached 120 degrees so I assume that the room was 120+ degrees for over 24 hours and the person who watches my house could not feel any additional heat. I use 2 " foam and seal the seams with silicon calk and I have an exterior door with magnetic weather stripping. I highly recommend using this stuff. I also recommend buying a $20 baseboard heater thermostat to be wired before the electricity going to your ballasts so the electricity will automatically shut off in the event of a high temperature situation.

 

[rickymac21]

Man that's super $hitty. Sorry to hear about the a/c failure, I'm sure the ladies weren't to happy about that. But yea if the room is able to keep that amount of heat in with only 2" board then I'm sold.
Although ill probably only use the 1" boards (still not sure if I need expanded or extruded). I'm really not concerned with the winter conditions as I can just "un-duct" my lights and allow the heat to stay in the box. With ambient temperature of 20 f (outside) the attic temp is usually 10 degrees hotter. So 30f plus my 1000w of light should provide enough heat (except when lights are off of course.).

Regardless it looks like the boards will work.

 

[rickymac21]

I found a nice little website that helps you calculate how many BTU's needed to cool/heat your room.
http://blogs.howstuffworks.com/2010...ow-to-calculate-heat-lossgain-for-your-house/

basically you find the total sq ft of your room (walls, floor and ceiling). Mine is 180 sq ft.
Then determine the temp you want in your grow room (75 on average).
Next, determine the outside temperature (say 90 f for example). But must account for the hid lights that emit a lot of heat. So lets bump it to 110f. (This is all a rough estimate)
so the temperature difference is 35 degrees.
With foam board having a thermal resistance of 5.

Now that you have the factors you can do the math.

180sq ft • 35f= 6300.

6300/thermal resistance R-5= 1260btu.

So I would need ROUGHLY 1260 btu to cool my room. This would be highly ineffeciant as 1260 btu would have to run continuously to keep the room at desired temp. So a bigger a/c would be worth it.

 

[computergroove]

A bigger AC is always worth it (within reason). Never get an AC that just barely covers what you need. You need to take into account the amount of heat the sun will produce in your room. If you insulate the hell out of it then the sun wont be a problem.

 

[ButchyBoy]

I have my room above my garage also. I use the 1" rigid insulation from Homey depot. It does not do much for insulating the area but the reflective side is a nice touch. I run a cool tube without a reflector. The light reflects off of the ceiling as well as the walls and covers pretty well. This summer at 90+ outside, It was hard to keep it under 85 inside with a 6000 btu window A/C on 24 hours a day. That was with a 600 watt mh/hps setup in a 6x8 vented area. I plan on more insulation real soon.

 

[rickymac21]

I have my room above my garage also. I use the 1" rigid insulation from Homey depot. It does not do much for insulating the area but the reflective side is a nice touch. I run a cool tube without a reflector. The light reflects off of the ceiling as well as the walls and covers pretty well. This summer at 90+ outside, It was hard to keep it under 85 inside with a 6000 btu window A/C on 24 hours a day. That was with a 600 watt mh/hps setup in a 6x8 vented area. I plan on more insulation real soon.

View attachment 2850359

im not sure the difference between the foil material lined insulation vs the regular white polystyrene insulation, but I plan on using the regular kind without reflective material on it. I have Mylar that ill use for reflective purposes.

But that kind of scary hearing you say that it's tough to keep the temp down to 85. I might have to go a little more heavy on the insulation.

Its about to be winter time though and my region usually settles around 15-35 f in the cold months. So for the time being keeping the room cool won't be an issue. But come summer time I might just insulate the whole garage attic portion along with insulation of the grow box itself. If the money permits ill probably buy a mini split AC system as that seems the best way to keep a controlled environment.

 

[rickymac21]

http://m.ebay.com/itm/221198861959?cmd=VIDESC

what do you guys think of this mini split? I have no experience with these systems so I'm not sure which is good or not. I do know that 9000 BTU's should be plenty for my room (4'D x 7'W x 5'H). With 2 600w hps. The seer rating is 14 which seems to be slightly more effecient than other units like this one. And its a good price.

I do have a question about positive pressure in the grow room though. With a mini split and aircooled hoods( ducted from outside box to outside box) there's no need for intake air or exhaust (with co2). But pushing cold air in through the mini split would cause positive pressure in the room causin insulation to be less effiecient and the smell to escape. Is this right? If so how do I avoid this without losing co2 or AC.

 

[computergroove]

I just bought a 45000 btu heat pump -> http://www.thermospace.com/ductless_split/ymgi/tri-zone-45000-btu-18000-9000.php and I have had no problems with it (other then I did some electrical work and didn't turn the thing back on). This one is a bit cheaper than the one you are looking at ion ebay -> http://www.thermospace.com/ductless_split/aircon-9000-btu-ductless-split-heat-pump.php. You will need a professional hvac guy do the installation and give you some paperwork to satisfy the warranty.

The minisplit is a sealed unit for in the room. It does not take in air from outside. It has a compressor outside and it has freon tubes going through your wall and into a wall unit that takes air from inside the room and cools it and circulated the air in the room. You need to seal the seams so there is no air leaks for smell and temperature control. Hoods will work fine with this because they to are a sealed system. There will be no issue with positive pressure. Watch this to get a better idea of what I'm talking about. http://www.youtube.com/watch?v=nVNESfc1GKU