Advice needed - 7x13 sealed - garage build - walls and insulation

[LowlyWorm]

Hey all,

I'm framing out a room in a detached garage and can use some advice on the construction. My goal is to have a 2-3 1000w setup with maximum efficiency and low maintenance, quality being a big thing to me. I'm leaning towards a sealed room based on the premise that if I make it as insulated as possible I can run it cheaper (with better yield) on an AC/dehumidifier; over fans with intakes and a dehumidifier to handle night sweats and condensation (which my tent currently struggles with). My hoods are 8" vented so it would be an exterior to lights back to exterior vent for their cooling. I have 9'6 ceiling joists to work with as its an unfinished garage.

The plan is currently as follows:
* 2x6 framing - 16" on center
* R-19 rolls walls
* R -30 rolls ceiling
* Steel security door 32x80
* sheathing - ???? - I originally was thinking of radiant barrier OSB for the walls but heard it's not nearly as reflective as it looks. That and you still have to moisture proof it. Now I'm wondering if I should use CDX, 1/8 underlayment, rigid foam board, cement board, bathroom drywall?
* reflection - ???? - I could put Prodex over the 1/8 underlayment and get both reflection and insulation. I could get a ton more R value and solve the reflection with Prodex but is it worth the cost?With the cost of Killz and other paints I'm shying away from painting if I dont have to.

Its the wall covering and whether or not to use Prodex that I'm struggling with the most. I've read a lot but can't find anything weighing each of these pieces together. I'm new to the forum but y'all have already helped a ton. Any expertise/thoughts/opinions would be much appreciated, thanks!

 

[LowlyWorm]

One thing I forgot to add. Part of my hopes with a sealed set up is to be able to run Co2.

 

[JointOperation]

one thing I will say is ORCA FILM.. .. I just bought a 100 foot roll.. and this shit fucking is way better then reflectix.. way better then panda.. and way better then paint..

im putting in another order for another 100 feet. we got a new place so new rooms going up.. so excited to be able to setup a new room the way I want to ..

 

[LowlyWorm]

Orca is most definitely on the list of possibilities. I think it's even more reflective than Prodex but is the extra insulation worth the slight compromise in reflection?

 

[queequeg152]

your plan sounds legit, and very reasonable.
regarding your vapor barrier, i suggest that you spend a chunk of time reading about vapor barriers/ membranes prior to building anything.

check out building science. youre wall construction should foremost, reflect your climate and the environment you are going to create in this space.

If your climate is predominately hot and humid, like mine,you are in a "cooling" climate.

if you climate is cold and dry, you are in a heating climate.

understanding all this will prevent unfortunate problems like mold growing inside your walls.

also, steel studs are probably the most under rated building material. if you are working by your self, and a few extra bucks does not bother you, building from steel studs cannot be beat... sooo much lighter, so much easier on your back... just need some decent shears and a nice power drill(not a driver!)

you can carry like 5 2x4 steel studs on your shoulder no problems. try that with 2x4's =)

unfortunatly steel studs conduct heat like a beast, so you should include an outside cladding of foam board to minimize thermal bridging. that cladding though, can act as your air barrier though. steel c channel studs also WILL NOT cooperate well with bats of roxxul or fiber glass etc. imo steel stud construction should be done with blown in blankets.

anyway what ever, your proposed construction as is sounds pretty good already, though i do not like the idea of adding the metallized films to the interior personally, as they present and additional fire,smoke hazards, but its up to you not me.

http://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall

http://www.buildingscience.com/docu...walls-pacific-northwest-hygrothermal-analysis

 

[Grow4Flow]

Orca is cool if you are going to stuff batting in the walls as the insulation part would already be taken care of, thus no need for foam board.

You could save yourself some money and go 2x4's on 24" centers, OSB, and 3/4"-1" foam board. This will give you not only the R12 insulation and hold in temps very well, but it will also remove any heat signatures which can be of importance depending on your location since it will be in your garage.

I have 4 rooms 9x15 built this way each running 6kw and 18000BTU splits, it is always cool in there.

 

[queequeg152]

your wall should be closer to r15-19 no?

1" foam is like r4 to r5 maby, and 2x4 cavities will take a reg 13 fiberglass bat or r15 roxxul bat.

 

[Granger2]

Prodex with air space between layers. Nothing better. Check Gnome's Room Build Thread in this section. Reflects near the top of the list. The difference in reflection between Prodex, and paint or other films is tiny. Good luck. -granger

 

[queequeg152]

sorry but prodex is bullshit. utterly bullshit. the r16 claim they make w/ the 2.64 air gap is an insanely dishonest value for a number of reasons.

hate to get up into folks noses about this, but i cant stand seeing people waste good money on bullshit products peddled by shitty companies.

ive written a bit, in the off gassing sealant thread on this subject if you care to check it out.

 

[EclipseFour20]

Don't laugh but I used "door slabs" for part of my "room within my garage". Hollow core doors for the walls and ceiling, solid core doors for the flooring elevated 4" off the concrete floor. The door slabs (unfinished door blanks without hole for door knob or cutout for hinges) do have some insulation properties and come already "primed". I used a mixture of 24", 30", 32" and 36" size doors and all are 80" tall; hollow core are 1 3/8" thick, with the solid 1 1/2" & 1 3/4" thick. And, everything is painted "hi gloss" white.

The ceiling is reinforced with 2x4s to support the big CAN150 filter+14" fan (jumbo scrubber) hanging inside the closed environment. It did take some planning, but in less than a week, I assembled it and painted everything...a week later (let the paint cure and fumes to dissipate) it was fully operational.

 

[Jhhnn]

Dunno where you live, but following the best construction practices/ code requirements wrt framing & insulation for your area is never a bad idea. I'd use water resistant sheetrock (usually green) & dry mix setting-type mud w/ fiberglas tape. Cement board, fiberglas tape & thinset mortar is an upgrade from there. Poly vapor barrier first, if that's usual where you live. Then primer & a good grade of flat white paint. Paint seals the walls in ways that roll goods won't. Add 'em if you want- I don't. Flat white works fine. Sheetrock or cement board serves as a fire barrier, as well.

Might consider using the garage as a lung room for the light ventilator & HVAC, use a thermostatically controlled gable fan & gravity louver at the other end. Excellent stealth & a heated garage in the winter.

 

[LowlyWorm]

Thanks for the clarification on the reflectivity. I wondered how big a difference it really makes. Gnomes build thread turned me onto the idea of the prodex. I wasn't clear if he went with the full airspace though.

Prodex with air space between layers. Nothing better. Check Gnome's Room Build Thread in this section. Reflects near the top of the list. The difference in reflection between Prodex, and paint or other films is tiny. Good luck. -granger

Thanks for weighing in on the quality of prodex. Online about it and to be honest was pretty skeptical of the r value claims. If nothing price is a pretty tough one.

sorry but prodex is bullshit. utterly bullshit. the r16 claim they make w/ the 2.64 air gap is an insanely dishonest value for a number of reasons.

hate to get up into folks noses about this, but i cant stand seeing people waste good money on bullshit products peddled by shitty companies.

ive written a bit, in the off gassing sealant thread on this subject if you care to check it out.

I'm still on the fence about whether to use drywall or plywood. I suppose if my paint is being primarily as the sealant I can still get sealed and still hang things on plywood. If I seal all the seams with caulking and paint it up I shouldn't need to worry about regular fiberglass insulation from a moisture standpoint right?

 

[queequeg152]

I'm still on the fence about whether to use drywall or plywood. I suppose if my paint is being primarily as the sealant I can still get sealed and still hang things on plywood. If I seal all the seams with caulking and paint it up I shouldn't need to worry about regular fiberglass insulation from a moisture standpoint right?

well... drywall is like 1/10 the cost of plywood. i would NOT use plywood on the inside of your structure...it costs too much!

regarding your question on moisture.

i would NOT rely on drywall and paint and caulk for your vapor barrier.

its impossible to tell you how to build your wall. you need to take into consideration the environmental conditions where this wall will go up. you should not skip the vapor barrier! its very cheap, much much cheaper than prodex, or drywall, etc. Just do it.

here is an ultra simplistic guideline for you to use. (if you are a professional builder or building scientist, please dont jump up into my ass.)

vapor barriers face the HOT HUMID SIDE of the wall. if you are building in a very cold not so humid climate, your vapor barrier will face the inside of your space. nailed to the wall just under the drywall.

in hot humid climates the vapor barrier is on the outside. nailed and taped up on the exterior studs or hopefully the exterior structural cladding( OSB panels usually).

WHY?
because water vapor, like heat is governed by the laws of entropy, and they diffuse from high energy states to low energy states.

in my climate HOT HUMID.
this means, when i run my ac down to 74 degrees, 50% humidity, hot as hell wet humid air wants to diffuse into my wall structure, through my brick veneer, into my insulation, and condense onto the inside face of my cold painted drywall.
if i had an impermeable polyethylene "diaper" type barrier on the inside, under the drywall, the wall would just collect hideous amounts of moisture... in some cases exterior walls will literally drip with this condensation, and you can get mold on the OUTSIDE, not just the inside of the wall.
this is called the INWARD moisture drive.

what is your case?

if i had to guess, you will probably have an OUTWARD moisture drive, meaning that your room will be loaded with heat and humidity from your plants, lightsd etc, and this hot and wet high energy air mass will want to diffuse through your wall, into your wall cavity, into your insulation, and exchange energy with the colder dryer outside air.

in the above case, you defiantly want the air barrier/vapor barrier on the inside of your wall structure, else you get condensation on the outside.

 

[IntelliGeneS]

Interesting information, thanks very much.

 

[Granger2]

Shit, get a dehumidifier. Good luck. -granger

 

[Jhhnn]

Drywall isn't cheap, at least not around here. I recently paid $11 per sheet at the Home Despot. Green rock is $14. Cement board & hardibacker are $23. 15/32" OSB is cheaper ($10) but I wouldn't use it for a grow because it's not flame retardant. Hard to paint, too.

 

[queequeg152]

Drywall isn't cheap, at least not around here. I recently paid $11 per sheet at the Home Despot. Green rock is $14. Cement board & hardibacker are $23. 15/32" OSB is cheaper ($10) but I wouldn't use it for a grow because it's not flame retardant. Hard to paint, too.

hm. round here you can get 10' and 12' panels for like 12-14 bucks on a sheet by sheet basis. i assume if one buys truckload quantities its far cheaper. the GP OSB is cheap, its like 12 bucks per 8x4.