Designing a new shed build-out

Aheadatime

Aheadatime

Well-Known Member
What's up everyone. Designing a shed build-out for a friend, uninsulated, detached from house. Dimensions (after framing, insulation, drywall, etc) are 9.6 feet by 18.8 feet, 7 foot ceilings. Concrete floor in great shape. So far we've got the room framed with 2x6, insulated with roxul. Located somewhere out here in the midwest, the area has very cold, wet winters (0 degrees fahrenheit, good deal of snow) with hot, sometimes humid summers (up to 90 degrees).

Couple things I wanna poke your brains about; lighting, AC/heat, and vapor barrier. For such low ceilings, I'm thinking 8 open-bulb SE HPS with low-pro style hoods on ratchets. I've only got experience with HPS, both DE and SE, so I can't recommend LED or CMH due to lack of experience, not to mention the upfront cost with LED. What do you guys think? I'm open to suggestions. This is a production facility, so every watt matters and should be based around yield.

This will be a sealed room, so for the AC/heat, fresh air exchange isn't an option. Because the area gets cold in the winter, 5-ton central air/heat pump units have been on my mind, with a variable speed air handler to cut temp swings and save electricity, and a UV light for sanitation. I personally run a few mini splits at my own facility, but they accumulated mold in the past when the drain pan tilted a bit, and after talking to some HVAC friends, apparently mold in the handler is quite common with splits in general. Open to suggestions/discussion.

Vapor barriers. Do we need one? Inside temps will be 70-80, 50-60RH, while outside temps will be 0-90, 30-80RH. I'm no expert with construction, having only built out a few rooms, all of them being inside insulated buildings/homes. Obviously want to avoid mold/condensation at all costs, have a clean, dry, proper room. Is it a good idea to put a barrier between the drywall and the studs? Like this;

1.png

Let me hear your thoughts fellow farmers!
 
A vapor barrier would help with high winds penetrating the structure.

Aheadatime said:
Because the area gets cold in the winter, 5-ton central air/heat pump units have been on my mind, with a variable speed air handler to cut temp swings and save electricity,
Click to expand...
I run in a basement at nights and it gets cold here. I have to run my AC (minisplit) even when it's cold outside unless I switch to my venting system. My unit will run down to 5 degrees F according to the specs but it has run as cold at 0F. You would definitely need to run the AC when it's like 30 degrees outside so you will want a unit that can run low ambient. I would look at the 5 ton minisplit heatpump units as their inverter tech allows them to run only as hard as they have to, so the compressor and fans are all variable speed. This allows them to be very efficient and run when it's cold outside.
 
Also, if you have a 5 ton split unit that is not inverter technology it will likely freeze up the evaporator coil at times. If the fan slows down, humidity is in the 60's to maintain VPD, the compressor is running at full, thats likely to freeze the coil.

8 lights can be done with a good 3 ton unit but of course you have to handle the heat in the summer as well. If you oversize a unit that doesn't have inverter tech then it's likely to kick on and off a lot thus not dehumidify as much as it should, shortening the compressor life and reducing energy efficiency.

I would look at a good ductless minisplit, oversizing them is ok unless you get excessive with it. They can run at low ambient temperatures, most energy efficient.
 
Good points Renfro. I had thought about the outside temps, had a low ambient kit for that. The inverter tech is a great point, I hadn't thought of that. Myself and a few of my grower friends have all had trouble with eventual mold in mini splits, and that's something I can't get over. I've had patients comment on certain batches giving them anxiety/heart palpatations, which I assume is residual mold spores accumulating on the buds from air handlers that weren't cleaned thoroughly enough.

Cleaning mold thoroughly enough not to have recurring issues in a sealed environment is very difficult in my experience, because it's cause isn't known. I've had discussions with various HVAC guys on this, and noone has an explanation. The majority of them think it's that I'm not having any fresh air introduced to the room, so the air handler is accumulating mold spores over time, which gives them the chance to colonize. That doesn't solve the issue of the mold spores needing the proper environment in the first place, though. Perhaps due to how compact the mini split air handlers are designed, coupled with how ineffective/borderline-nonexistent their filtration systems are compared to convention central handlers, the environment inside the handler is wild enough for mold growth? I'm not sure, but I haven't heard of as many people having issues with conventional ducted style handlers. You have any experience with mold in mini splits?

I did some googling, and there are ducted compressors that have the inversion technology too; lennox, bosch, etc. Spent the morning calling around, and not many of my HVAC people are familiar with the units. They seem to think that there's not much difference between inverter tech and 2 or 3-stage tech. Yeesh. I'll have to call around a bit more.
 
Aheadatime said:
You have any experience with mold in mini splits?
Click to expand...
I have a lot of experience with them and I have never seen this mold. Is it brand specific? You could always put a few drops of bleach in the condensate tray once in a while.
 
It's a white mold, sometimes greyish if it's tinted with debris/dust. It cakes up on the blower wheel, and I've had mold grow on the coils as well. This is with a mold-free environment without any RH swings at night. I do recall though that the guy I had install them installed them with a tilted drain pan at first, and that initial leak may have had sparked all of this, but who knows. The units I'm using are Friedrich, both the cool-only single-zone splits, and the heat pump single-zones splits.
 
Instead of Sheetrock you could use poly iso insulation board. This will give you a vapor barrier and some extra r value (r6 for 1”) depending on thickness you choose. Also will reflect light. I used zip tape to tape all the seams, and taped it to the floor to make it 100% air sealed. 5 ton mini split? 60,000btu?
 
Aheadatime said:
It's a white mold, sometimes greyish if it's tinted with debris/dust. It cakes up on the blower wheel, and I've had mold grow on the coils as well. This is with a mold-free environment without any RH swings at night. I do recall though that the guy I had install them installed them with a tilted drain pan at first, and that initial leak may have had sparked all of this, but who knows. The units I'm using are Friedrich, both the cool-only single-zone splits, and the heat pump single-zones splits.
Click to expand...
Thats very odd. I have never seen anything like it in Missouri or Colorado.
 
Lund-o said:
Instead of Sheetrock you could use poly iso insulation board. This will give you a vapor barrier and some extra r value (r6 for 1”) depending on thickness you choose. Also will reflect light. I used zip tape to tape all the seams, and taped it to the floor to make it 100% air sealed. 5 ton mini split? 60,000btu?
Click to expand...

I've thought about that, and it sounds appealing not to have to mud/tape/sand. I'm not one of those guys who enjoys drywall work. You're talking about the R Max stuff you can get at home depot right? Hmm is 5 ton overkill for 8 lights, non-air cooled, ballasts in room, dehuey, etc. The shed will be baking in the sun in the summer too, gets up to 90 around here and it's not shaded by trees. In basement's I've gotten away with roughly a ton per 3 lights, but this is with lights on at night time. I believe this friend wants the lights on during the day, at least partially so, to make working easier on their schedule. You guys think I'm oversizing the ac?
 
Renfro said:
Thats very odd. I have never seen anything like it in Missouri or Colorado.
Click to expand...

I've never been able to unsee it. Whenever people show off their 30 light room with a mini split on each wall on social media, I wonder if any of them have mold lurking in the blower wheels. Here's a vid of someone power washing the blower wheel in a pretty bad case. My case wasn't quite this bad, but there was a lot of visible debris coming out when I washed mine too.

https://johncipollone.com/avoid-mold-in-your-ductless-air-conditioner/
 
Aheadatime said:
It's a white mold, sometimes greyish if it's tinted with debris/dust. It cakes up on the blower wheel, and I've had mold grow on the coils as well. This is with a mold-free environment without any RH swings at night. I do recall though that the guy I had install them installed them with a tilted drain pan at first, and that initial leak may have had sparked all of this, but who knows. The units I'm using are Friedrich, both the cool-only single-zone splits, and the heat pump single-zones splits.
Click to expand...
Mold is VERY common in minisplits. I suggest you look into a package unit with hot gas bypass or reheat capabilities.
 
Is it mold or just an accumulation of dust and crap in the air? I've seen similar on fans and other air moving equipment. Mold is everywhere but is that mold?
 
DarkWeb said:
Is it mold or just an accumulation of dust and crap in the air? I've seen similar on fans and other air moving equipment. Mold is everywhere but is that mold?
Click to expand...

Inside mini splits it's definitely mold. The grey dust on oscillating fans is just dust.
 
Well then, that's pretty nasty and will look at every one like it's a used jock strap from now on! LOL
 
DarkWeb said:
Well then, that's pretty nasty and will look at every one like it's a used jock strap from now on! LOL
Click to expand...

Haha I mean some people do a good job with them. You can get these cleaning bib kits and clean out the handler once every couple months to prevent/slow down the mold growth.
 
Aheadatime said:
What's up everyone. Designing a shed build-out for a friend, uninsulated, detached from house. Dimensions (after framing, insulation, drywall, etc) are 9.6 feet by 18.8 feet, 7 foot ceilings. Concrete floor in great shape. So far we've got the room framed with 2x6, insulated with roxul. Located somewhere out here in the midwest, the area has very cold, wet winters (0 degrees fahrenheit, good deal of snow) with hot, sometimes humid summers (up to 90 degrees).

Couple things I wanna poke your brains about; lighting, AC/heat, and vapor barrier. For such low ceilings, I'm thinking 8 open-bulb SE HPS with low-pro style hoods on ratchets. I've only got experience with HPS, both DE and SE, so I can't recommend LED or CMH due to lack of experience, not to mention the upfront cost with LED. What do you guys think? I'm open to suggestions. This is a production facility, so every watt matters and should be based around yield.

This will be a sealed room, so for the AC/heat, fresh air exchange isn't an option. Because the area gets cold in the winter, 5-ton central air/heat pump units have been on my mind, with a variable speed air handler to cut temp swings and save electricity, and a UV light for sanitation. I personally run a few mini splits at my own facility, but they accumulated mold in the past when the drain pan tilted a bit, and after talking to some HVAC friends, apparently mold in the handler is quite common with splits in general. Open to suggestions/discussion.

Vapor barriers. Do we need one? Inside temps will be 70-80, 50-60RH, while outside temps will be 0-90, 30-80RH. I'm no expert with construction, having only built out a few rooms, all of them being inside insulated buildings/homes. Obviously want to avoid mold/condensation at all costs, have a clean, dry, proper room. Is it a good idea to put a barrier between the drywall and the studs? Like this;

View attachment 4378846

Let me hear your thoughts fellow farmers!
Click to expand...


Kinda same setup as i have been running for a few yrs now. Went from hps to cmh now on led strips to cut down on electric and heat. In the summer when temps are 100 and lights on you also have dehumifiers running, pumps, fans, water chillers etc.

Add up your watts on everything and then add in what it would take to chill the room in your area. In wintertime you might have to add heat when temps get to 0 outside during lights off. Best bet is to have lights on when the sun goes down. I have 2 air units and they run all the time in the summer trying to keep up. Be prepared for $1000 electric bills in the summer and my electric is .12 cents a kw.

You will also need CO2 in your room with it bring sealed. I have a 100 lb tank and co2 burner i use titan with the atlas 1 with remote sensor. My room is like 12' x 30' and i run a home built rdwc.
 
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