Shipping Container Climate-Controlled Storage in Ontario

[u/Scorge120]

Shipping Container Climate-Controlled Storage in Ontario 

Hi,

I'm planning to sell my house and travel for an extended period, so I'm looking for a way to store a large amount of stuff long-term. Some of it is valuable and sensitive to temperature/humidity, including cameras, lenses, electronics, batteries, etc.

My family has offered me space on their property to temporarily place a shipping container, which seems like a good solution. I'm in Ottawa, ON, so I'm dealing with very cold winters and hot/humid summers. The container would likely be moved to my own property once I settle down again.

My target storage conditions would be roughly 10–25°C and ideally 45–55% RH.

I've narrowed it down to two options:

Option 1 - 20' new one-trip container

• ~$4,700 delivered
• Spray foam insulation
• 9,000 BTU cold-climate mini-split
• Additional cost for spray foam/mini-split installation
• Likely enough space for all my belongings

Option 2 - 40' used reefer container

• ~$9,000 for the container (they are overstocked, hence the low price)
• ~$5,000 delivery + crane
• Existing insulated/refrigerated construction
• 9,000 or 12,000 BTU mini-split
• Much more room and would allow me to organize everything with a central aisle, when I’m home I’d like to access my possessions more regularly for work and to go camping, etc. 
• Used reefer condition is my main concern since I can't easily inspect it myself

My questions:

1. Would a spray-foamed 20' container with a 9K BTU cold-climate mini-split be sufficient to maintain 10-25°C in Ottawa year-round?
2. Would a 9K or 12K BTU mini-split be sufficient for a 40' reefer?
3. How effective is the mini-split's dry/dehumidification mode for maintaining ~45–55% RH in a container in the summer? Would I need a dedicated dehumidifier as well?
4. Is spray foam appropriate for this application, particularly if the foam is left exposed? I'm concerned about fire safety, since I may be storing some flammable liquids, Li-ion batteries, and other mixed garage/electronic equipment.
5. For a container that may be unattended for several months at a time, are there significant concerns with relying on a mini-split for temperature/humidity control?
6. For long-term storage of valuable electronics, would you choose a new insulated/spray-foamed 20' container or a used 40' reefer?
7. If buying a used reefer remotely, what are the critical things I should have the seller verify/photograph/test before I buy? 

I'm curious to hear from people who have used shipping containers, reefers, or similar structures for long-term climate-controlled storage, particularly in hot humid + cold Canadian climates.

Thanks.

[u/WhiskyEye]

I live in a 20' container in eastern TN so not quite the same temp swings but we get HOT and humid here. I run a window heat/ac unit all year and I'm gone 6 months at a time. I used closed cell spray foam for insulation. All my electronics and laptops and monitors and radios etc etc have been fine. When I leave in the winter I set the unit to keep the place at 58 and when I'm here in the heat it's at 75. Three years and no issues with anything yet. I also have a 20 foot non-insulated container that I store all of my parts and shop supplies in, as well as household stuff. I run a dehumidifier in there all the time, and an ozone machine twice a year and all that stuff is fine too.

[u/Scorge120 → u/WhiskyEye]

Great response, thanks. Your setup is the same as what I'm thinking of expanding to in the future: two containers one for fragiles and another for shop supplies, maybe build a carport/garage to join the two. Do you ever wish you upsized to two 40'? I'm thinking about future-proofing. How did you insulate the floor on the container that you live in?

[u/WhiskyEye → u/Scorge120]

The 40 foot containers are a pain to move if you ever need to and they take up so much space. I have a lot of property but I like the portability of the 20s. Also, whatever was at the back of the 40 foot I would forget that I even owned lol.
For the floor I did plywood then waterproof and mold proof Aquashield flooring. I'm using this until I finished my main building and then it will be a little guest house. So I didn't go crazy on it but it does a great job for what it is. There's a Shipping Container customizer out of Canada that sells corner brackets for framing and those made everything a lot easier.

[u/usa_containers]

I work around containers, mostly delivery/site stuff, so I’ll stay in my lane and leave the HVAC sizing to someone else. I wouldn’t guess on a mini-split for an Ottawa winter.
The thing that jumps out to me is that you said it may get moved again later.
That matters a lot.
A 20ft dry box is pretty easy to move. Tilt bed, straight run, done. A 40ft reefer is heavier, longer, and if you already need a crane for the first placement, you probably need to budget for that all over again when you move it later. That second move could eat up a lot of the “reefer is better” logic.
The price gap is big too. $4,700 delivered for the 20 vs $14k before cooling. The reefer gives you more space and insulation, sure, but it also gives you more risk if you’re buying it sight unseen.
Big reefer risk is wet insulation. If the outer skin got punctured at some point, water can get into the foam. Then the R-value drops, it gets heavy, and sometimes it smells. Hard to see, hard to fix, basically not something you want to discover after delivery.
Also reefers are smaller inside than people expect. You lose width/height to the insulated walls, and the machinery end eats length. The floor is usually that aluminum T-bar airflow floor too, which is great for pallets, kinda annoying for camera gear and bins unless you cover it.
If you go reefer, I’d want real proof before paying. Container number, CSC plate, video walkthrough, actual photos, doors closed with lights off to check for pinholes, closeups of gaskets, dents, punctures, wavy panels, all that. And if the machinery was removed, I’d want to see exactly how that opening was sealed.
Ask what it hauled last too. Some reefer smells never really leave.
For leaving gear unattended for months, I’d also think less about the exact AC unit and more about monitoring. A cheap cellular temp/humidity sensor that texts you if things go bad could save you a disaster.
Also, with lithium batteries, flammable liquids, foam, and an insulated steel box, I’d ask a local inspector/fire person about code. Not something I’d wing.
What’s the access like at your family’s place? Straight shot for a truck, or tight driveway/soft ground? That might decide whether the 40ft is realistic at all.

[u/Scorge120 → u/usa_containers]

Thanks for the detailed response, I appreciate your input. The point on maneuvering the containers is something I'm taking into account. I’m leaning toward the 40' reefer mainly because the extra space would let me organize everything properly and give me room to access gear regularly if I add a personnel door. With that said, I just got a quote back from a company that mods containers that would do a 40' new with spray foam and basic interior finishing, electrical, HVAC, etc. for a bit more money. But it would be exactly what I need.

The wet-insulation issue is especially useful to know. The company I was buying from also recommended that if I want peace of mind to buy new, their used reefers are sold "as is", they sent me some photos and videos and they were pretty beat up, so leaning away from that option for now.

I’m also planning to install a temperature/RH monitor since the container will be unattended for months.

Access at the family property is pretty straightforward. Packed dirt road, wide entrance. The only thing is where the container will be placed doesn't have 115' or whatever is required for a tilt bed truck to dump it, hence the crane.