How to Insulate Your Walk-In Cooler

Excellent insulation is critical to your walk in cooler, for keeping both temperatures and electricity bills low. Insulation is measured by its “R value” per square inch – the higher the value, the more effective the insulation. The industry standard for walk-in coolers is an R value of 25. Going up to R30 will save you even more money, especially if you are keeping your cooler at 40°F or below. We recommend using either spray foam or rigid foam insulation.

For spray foam, we recommend the spray foam kits which you can buy from our friends at Energy Efficient Solutions. Use the coupon code COOLBOT_FOAM for 3% off your spray foam kit purchase. For rigid foam, we recommend polyisocyanurate on the walls and ceiling, and extruded polystyrene (XPS) on the floor.

Rigid Foam

R Values can vary based on the different kinds of foam as well as the age of the foam. No vapor barriers are required with the use of rigid foam.

3 Types of Rigid Foam Insulation:

Polyisocyanurate – best choice for walls and ceiling:

Grey or yellow
R Value of ~6.8 per inch (can vary among brands)
After 5-10 years: R Value of 5.5 per inch (where it stays)
Comes in 4′ x 8′ sheets
Available at Lowe’s and Home Depot

**Use at least 4 inches. If it has foil backing, be sure to face that towards the outside. This product can be irritating to skin, so be sure to wear long sleeves.**

Extruded Polystyrene (XPS) – best choice for the floor:

Pink or blue
After 5-10 years: R Value of ~6 per inch (where it stays)
Comes in 4’ x 8’ sheets
Available at Lowe’s and Home Depot

**Use at least 4 inches in the walls, floor and ceiling, and you’ll be fine.**

Expanded Polystyrene (EPS):

White beaded
R Value of ~4 per inch
Comes in 4’ x 8′ sheets
Available at Lowe’s and Home Depot

**EPS has the lowest R Value, so be sure to use 5-6 inches.**

Spray In Place Foam

This is a professionally applied polyurethane product that can turn leaky barns or sheds into well-insulated walk-in coolers in a short amount of time. R Value and cost can vary drastically. Depending on your location, this may be a practical solution for you; check with your local installer for costs. Four full inches are necessary to keep your cooler below 40°F (4.4°C). Spray foam is generally more expensive than rigid foam options, but can also be easier to install.

We recommend the spray foam kits which you can buy from our friends at Energy Efficient Solutions. Use the coupon code COOLBOT_FOAM for 3% off your spray foam kit purchase (~$17 off per spray foam kit)!

Roxul Mineral Wool

Roxul is a rock-based mineral fiber insulation. Because of its moisture resistant and mildew resistant properties, its high R value, and the fact that it generates zero off-gases, it makes a great material for insulating coolers. Since it is not vapor resistant, you do need to add some rigid foam to the cooler. This rigid foam layer will also help stop thermal bridging, so it needs to be on the edge of the stud. You would probably be fine with 3/4 inch, but going up to 1 or 1.5 inches would be even better.

Cellulose

Cellulose insulation can be an option if it’s properly layered with styrofoam on both sides (like a sandwich) to create a waterproof barrier. Otherwise, the cellulose can retain moisture it is exposed to. On the inside of the cooler, add the rigid foam insulation before the plywood or FRP; this will help with both the moisture retention and with thermal bridging. There is loose pack cellulose and dense pack cellulose; loose pack is much more common. Take extra care to caulk or spray foam all corners and cracks.

Fiberglass Batt

DO NOT USE FIBERGLASS BATT INSULATION! Regardless of whether or not you have a vapor barrier, moisture seeps into the fiberglass insulation. This moisture creates a moldy nightmare and also decreases your insulation value. The decreased insulation value results in higher electricity bills; your A/C now has to work constantly to cool the cooler, since the cold air is leaking out through the now uninsulated walls. Please do not use this!

Basement Builds

A concrete block has a ~.2 R value per inch (so ~.8 R value per 4” block). If your average underground temperature is 52-62°F (11-16°C) and you want to be within that range (for a wine cellar for example), then you don’t need insulation. If you want to be lower than that though, you will need some sort of insulation, otherwise, you’ll be spilling out all the “cold” through the walls and into the ground.