1. Insulate Your Room
Use Insulation of at least R25 Insulation Value
The current industry standard for insulation is a minimum of R25 waterproof insulation. Different insulation products have varying “r-values” per inch; this will be printed on the insulation you purchase. Instead of thinking about insulation in terms of inches, think about insulation in terms of r-value. The higher the r-value the better. When purchasing insulation, remember that the insulation you choose will impact your electricity bill; you only purchase insulation once, while electricity is an ongoing expense.
Check out our Insulation Information section for details on the best insulation options for your cooler.
NOTE: We do not recommend using fiberglass insulation for your cooler. This particular insulation can get soggy, sag, and mold within 1 year of full time use of your cooler.
Create an Air-Tight Cooler
Making sure your cooler is air-tight is just as important as the amount of insulation you put in it! Keeping your cooler air tight will allow you to cool down faster to lower temperatures and keep your monthly bill lower by preventing the cold air from escaping your cooler.
Use several bottles of spray foam and caulk to seal the following:
- Seams between insulation sheets
- Under the door (use a door sweep as well for extra seal)
- Around the air conditioner
- Every corner
Around the air conditioner is a common place where hot air can sneak in. Instead of spray foam, use pipe insulation, readily available at hardware stores. It comes in 6 foot long strips and you can cut it to the size you need before stuffing it in the gap between the wall and the air conditioner. It is soft and pliable but still “closed cell” in structure, so water doesn’t get into it and air can’t pass through. This way if you ever need to pull the A/C out, you don’t have to carve away your spray foam.
Attach Insulation Over the Studs, Not In Between:
Tack the rigid foam up on the outside of the studs. Cutting up your insulation to go in between studs will not only leave a few gaps and holes, but no matter how careful you are, polyisocyanurate and polyurethane will shrink a bit over time, exposing your cooler even more.
Overlap The Seams on Multiple Layers of Insulation:
If you are using multiple layers of insulation (e.g. 2″ x 2″ layers) to achieve your target r-value, stagger the seam locations and overlap the insulation. This will create a more effective barrier versus having all the seams lined up on top of each other.
Now that you know where you want to put the cooler, it is time to consider the foundation. Insulating your floor is just as important as insulating your walls.
Coolers built on a deck need at least as much (preferably more) insulation in the floor as in the walls. If you build on a deck instead of a slab, you need to insulate the floor to at least R25 (and R30 would be even better).
If you have an untreated wood floor under your cooler, you will need to put in a vapor barrier. This is how we did ours on the farm:
1. We put three layers of carpenter plastic between the styrofoam and our top layer of plywood. Some people happily report using single pond liners instead.
2. We stretched the plastic out into a “bathtub floor” that goes up the walls a couple inches
3. There it is gathered under “Roof Edge”* that is screwed about 3 inches up from the floor all the way around the wall like metal baseboard trim.
4. We caulked the entire top of the Roof Edge so the water dripping off the walls won’t slip between the plastic and the wall, and pool up under the floor.
*Roof Edge is cheap and available in the flashing and roofing sections of all the big box grocery stores.
Concrete Slab & Dirt Floors:
Since cold air falls, insulating the floor of your cooler traps the cold air – keeping your electricity bill lower and reducing the load on your A/C. Whether or not it makes sense to insulate the floor depends on your targeted cooler temperature:
- Above 45°F / 7.2°C — insulating the floor is not worth the investment.
- Down to 38°F / 3.3°C — customers in hotter regions might want to insulate the floor, but typically you can still reach 38°F / 3.3°C without it.
- Below 38°F / 3.3°C — floor insulation is required. Even just 2 inches of insulation makes a big difference.
If the concrete pad extends beyond the cooler, the pad can absorb radiant heat. In this case, you’ll need to insulate the floor.
Haven’t poured the concrete yet?
1. Use gravel for the first layer.
2. Second, put down a plastic vapor barrier.
3. Then place a layer of below-grade rigid foam insulation; 2 inches is fine, and 4 inches is fantastic.
4. Rebar or mesh comes next.
5. Lastly, pour! We mix in fibers to make it stronger.
How To Insulate the Floor:
Whether you’re building up on an existing trailer deck, above a basement or on a slab, you do not need to frame out a floor.
1. Place rigid foam directly on the floor.
2. Lay 3/4″ plywood painted with porch paint (or any exterior paint) directly on top of the rigid foam.
The plywood spreads the load out enough over the rigid foam; even after 10 years, our foam still looks fine.
In fact, if you were to stud out your floor, you actually risk decreasing the effectiveness of the insulation, because the studs can create thermal bridges where the cool air flows out through the less-insulated studs, between small gaps in your insulation.
Tilt the floor towards the door so that any water that gathers (due to condensation or dripping veggies) can naturally drain out. Don’t forget to site your structure so the water has someplace to go once it leaves the front door.
If you’re building on a trailer or a deck-type floor, this is easy to do. If you’re pouring a new slab, just build it above grade a bit and put your form-work a barely noticeable “off-level” towards the door.
The only people maybe needing drains are folks who do meat processing (see our specific recommendations on the Hunting & Meat page) and regularly spray down the cooler. Otherwise, it’s more trouble than it’s worth. If using a drain, make an airtight plug for it, so you won’t lose cool air when you are not draining fluids.
There isn’t enough water accumulating to necessitate a drain, and putting one in would just compromise the integrity of the cooler. The only thing the drain will really be letting leak out is cold air.
Inner and Outer Sheathing
The safest option is to put interior and exterior sheathing on your cooler, over the insulation. If you’re careful (and don’t have employees carrying boxes in and out that could bang the walls), you should be fine with just the exposed solid styrofoam insulation.
Our inner walls are sheathed with $7/sheets of “OSB board.” We could have used plywood, but it was just more expensive. Many restaurants and meat processors will use FRP panels which are great! They are easy to clean and durable. OSB board (or untreated plywood) should be sealed before installation.
If your cooler is built inside an existing structure, you don’t need to sheath it. If it’s outside, it has to be protected from the sun or the insulation will start to break down.
We did this by ripping cheap half-inch 4×8 sheets of “CDX” plywood into 1×8 foot strips to make home-grown overlapped siding.
2. Seal Your Cooler Properly
Sealing your cooler properly is essential for your cooler to function efficiently. This includes sealing joints between walls, floor, and ceiling. In addition, it is important that you regularly check the gaskets on your door as well. For sealing insulation, we recommend using spray foam. Weather stripping or a rubber gasket is helpful if the door doesn’t have a nice tight seal as well. Other options for insulation include pool toy floaties or the soft foam pipe insulation to insulate between the air conditioner cabinet and the walls.
NOTE: It is important to take your time sealing your room, as missing even the smallest hole can have a large impact on the energy efficiency of your cooler. These energy inefficiencies can be avoided by using inexpensive cans of spray foam (like “Great Stuff”) or caulking [this typically costs around $5.00 a can]. This step must be completed before turning on your cooling system for the first time.
WHEN USING FIBERGLASS INSULATION: Again, we do not recommend using fiberglass insulation. If you do decide to use fiberglass insulation, you will want to ensure you seal every crack and joint on the OUTSIDE of your cooler. Fiberglass coolers without an impermeable barrier on the outside fail within 1-2 seasons. Skipping this step will result in a moldy, mildew-ridden cooler walls regardless of location – we have seen this scenario even in Phoenix, AZ. If using fiberglass (which you shouldn’t), there must be a layer of rigid foam as well. This is always difficult for our team because we want to set up all of our clients for success.
Selecting Your Door
Pre-Hung Insulated Exterior Door:
Unless you’re a carpenter, we recommend using a pre-hung insulated exterior door without windows. This is because this particular door seals up tight, and it’s difficult to achieve a tight seal if you’re building your own door for your cooler. Even the smallest gap in your door can negate much of the work you have previously done when insulating and sealing your cooler.
Customize Your Door:
Here are a few tips to get the most out of your door:
- Make sure your door opens to the outside of the cooler. Ensure that as you build your cooler, it is slightly above the surrounding ground level so the door can swing freely.
- Glue another layer of 2″ rigid foam to the inside of the door, as most doors are only about R18.
- If you plan on hosing down your cooler – remove the bottom metal piece of the pre-hung door so it doesn’t create a dam for the water inside your cooler. This means you have to cut the sides of the door down so the bottom stays flush against the floor. This is only important if you plan on hosing out the cooler, otherwise, keep the threshold in place and clean with a mop and a bucket.
- Various home improvement stores sell door sweeps which can help seal any drafts which may be sneaking in at the bottom of the door. For an example please click here.
3. Electrical and Lighting
Due to the moist environment, we recommend using exterior rated light sockets and outlets.
This is less about the fixture and more about the perforations that wires coming into the cooler make. A vacuum effect can be caused by the warm outside air being sucked in through the back of the outlet box by the cold cooler air. This can result in moisture gathering and could cause the circuit to trip.
1. Take the cover off the outlet.
2. Find where the wire enters the back of the outlet box.
3. If there are any gaps where the wires enter the box, seal them using silicone caulk seal so no air can move through.
4. Replace the cover.
NOTE: Besides silicone caulk, clay or feldspar can be used to seal up the gap
4. Choose the Right A/C for your Cooler
What size of A/C you need depends on:
- The size of your cooler
- Your desired temperature range
- What temperature your product is coming in at and how quickly you need to get it down to your target temperature
Please see our Air Conditioner Selection Guide for our recommendations on choosing the proper A/C.
For the majority of our customers who are keeping their cooler 38°F – 41°F (3.3°C – 4.3°C) and opening their coolers less than six times per hour, the below table is a general outline of A/C sizing needs.
Dimensions of Walk-In Cooler
|Size of Air Conditioner|
|6’ x 8’ x 8′||10,000 BTU|
|8’ x 8’ x 8′||12,000 BTU|
|8’ x 10’ x 8′||15,000 BTU|
|8’ x 12’ x 8′||18,000 BTU|
|10’ x 14’ x 8′||24,000 BTU|
Our favorite brand is LG – we have the most experience and best results working with their window units. We do not carry AC units directly, but you can purchase them through our Amazon Associate links here:
Have you reviewed the Air Conditioner Selection Guide and are still not sure about your set up? Fill out our Cooler Construction Advice Form, and we’ll help you out with the details.
5. Installing your Air Conditioner
Once you have chosen your air conditioner (with help from our Air Conditioner Selection Guide), you need to mount it properly within your cooler.
A/C and CoolBot Placement:
If you build a rectangular cooler, you need to make sure your A/C is blowing air down the longest portion of the room. For example, if you build a 4′ x 6′ cooler, you want to blow the air down the 6 foot direction, not across the shorter 4 foot section. If you have a 6′ x10′ foot cooler, you would want to blow down the 10 foot direction. If you have a 6′ x 20′ cooler, you need to buy 2 air conditioners and put them on either end (with 2 CoolBots).
Here are a few tips for ensuring best A/C placement:
|Eye Level:||The A/C will preform at its best when installed so the bottom of the A/C is at eye level. Cold sinks, so the higher up the A/C is installed the better. This also makes maintenance a lot easier.|
|Longest Way:||If you have a space that is less square and more rectangular in shape, then the A/C should be mounted on the small wall so that it is blowing the longest way possible. For example, on a 5’ x 10’ room, the A/C should be mounted on one of the 5 foot walls.|
|Side By Side:||The CoolBot should be mounted inside the cooler next to the A/C unit. For troubleshooting purposes, the CoolBot and air conditioner must be right next to each other.|
|Slight Tilt:||Be sure your air conditioner is lower in the back, on the outside, than it is inside of the cooler. A whole inch lower is good, it’s important that the condensation pulled out of the air by the air conditioner be able to drip out the back before it freezes inside of the AC unit. Most air conditioners will keep a little water at the back of the pan to help cool the compressor and extend it’s life, but the tilt is important so the water doesn’t get too far forward where it will freeze. An LG air conditioner must be level left to right because of it’s design with a trough for the water inside.|
6. Protect Your Cooler from the Sun
You know how in the middle of summer it’s much more comfortable in the shade rather than out in the hot sun? It’s the same with your cooler, except instead of dripping sweat, a cooler sitting out in the sun drips dollars!
It is important to keep your cooler out of direct sunlight. This is critical for energy cost savings. Coolers in direct sunlight require approximately 70% more electricity, nearly double what your cooler would typically require in the shade! For the most efficient performance, place your cooler:
- Inside an existing building
- Under a tree
- On the north-side of a barn
- Build a shading overhang onto an existing structure
If you build an overhang for your cooler, be sure to build an openly vented roof that keeps the sun off the insulated ceiling of the cooler.
Flat roofs on a small cooler may still be structurally sound in wind, rain and snow loads, but they don’t protect from sun exposure. Building a standard peaked roof with ventilation over the insulated cooler ceiling will shade the cooler and provide passive ventilation that will keep air circulation over your cooler and save money on cooling costs.
Note: In a house, heat rises and that’s why we put twice as much insulation in the roof as the walls. In a cooler it’s the opposite, we’re building a box to keep cold in, and cold air sinks. Keep your cooler roof out of direct sunlight and you can put the same insulation in the roof as you did in the walls and you’ll save money both in construction and long-term operating costs.
7. Allow Your A/C to Breathe
Air conditioners need at least 2 feet of clearance overhead on the back side to vent properly. If there is not enough room, they will overheat and fail prematurely. Check your particular A/C’s specifications to determine the exact setback required for your model.