Can I Build a Free Cooler from Scrap Styrofoam?

No, definitely not.

Not free anyway. I did build a cooler (my second, here's a post about the first one) using scrap Styrofoam as the insulating material but spent about $85 on additional materials. 

Below I'll describe the build process, list the materials and costs, and offer thoughts about building one more economically. You can also watch the video. Note that this post may read like a "how to", but to quote the esteemed Mr. Savage, it is more of a "here's what happened" and you would be exceptionally foolish to attempt such an endeavor. 

TOOLS & SUPPLIES

• Utility knife with breakoff blades - The blade can be extended to make fairly clean cuts through the Styrofoam.
• Gorilla glue (original formula) - This works well for gluing Styrofoam together.
• Clamps and weights - Used to hold pieces firmly together as the glue sets.
• Masking tape - Also useful for clamping pieces together as glue sets.
• Miter box - This is a handy and economical way to accurately cut the trim pieces for the exterior shell. 
• Measuring tape & ruler
• Straight edge

BUILD PROCESS

1. Cut Styrofoam sheets to size. A wall thickness of 1.5 to 2 inches should provide good insulation and sturdiness. Thinner sheets can be glued together to achieve the desired thickness. 

2. Glue sheets together to form the box. Plan carefully how the pieces will be clamped together, as Gorilla glue has a working time of about 10 minutes and the box bottom and sides will need to come together in one operation.

Vinyl tile

3. Apply exterior shell. For the sides I used vinyl flooring tiles, attached with Gorilla Glue. I removed the adhesive from the tiles with Goo Gone, but I'm not sure that was necessary. I am sure that it was a pain in the ass. I think a better choice would be polywall, which is a PVC sheet material used on walls in wet environments (e.g. bathrooms and kitchens). I glued a sheet of Luan plywood, covered with epoxy, to the bottom.

4. Apply trim to exterior corners/edges. I used epoxy. Gorilla Glue might work. I painted the trim before attaching. Note that in my actual build I reversed steps 3 and 4, which made sense to me at the time but doesn't make sense in retrospect. 

Corner/edge trim

5. Apply interior lining. For my previous cooler, made of foam board, I used foil tape which worked well and has proven to be durable. Alas, it doesn't stick well to Styrofoam or provide adequate protection against damage. Thus, I used cardboard covered on one side with sheets of adhesive backed vinyl, then glued the cardboard panels in place with Gorilla Glue. This proved to be plenty strong as well as economical. I used a piece of epoxy covered luan plywood for the interior bottom plate for extra durability. I then caulked all the corners and seams.

Vinyl covered cardboard

6. Create a lid. I started with a Styrofoam sheet, cut to fully cover the top of the cooler box. I then cut a second sheet sized to fit snugly between the interior walls, and then glued the two sheets together (paying close attention to alignment). Next I cut a piece of luan plywood to cover the top. I painted the luan top with spray paint.

7. Trim out the lid. I epoxied 3/4 inch trim to the perimeter of the lid, and glued vinyl-wrapped cardboard to the undersides. 

8. Make a gasket for the lid. I used an inexpensive foam gasket plus double-sided foam tape, covered with the adhesive backed vinyl.

Lid detail

9. Attach handles. I printed this 3D model, bolted it to a "mounting plate" and then epoxied the assembly to the cooler. Depending on the size of the cooler and the weight to be carried, I'm not sure that epoxy alone will create a strong enough attachment. I may add bolts that go all the way through, with large fender washers on the inside to distribute the force.

10. Install lid attachments. I created hinges out of nylon webbing and added d-rings plus paracord to keep the lid from falling back when open. I modified wiring clamps to attach the d-rings to the cooler. 

11. Attach a latch. I used this 3D model. 

12. Apply corner protectors. I used this 3D model and attached them with epoxy. 

13. Apply stickers. You might think this step is optional. It is not and if you fail to do so there will be consequences. You'll have a cooler without stickers. I guess that's just one consequence, but it's a bad one. 

MATERIALS & COSTS

In calculating the total, I didn't count the cost of supplies and scrap materials I had on hand. If I'd had to buy everything, the total would be significantly higher.

• Trim (5 pieces) - $19
• Epoxy adhesive - $7
• Vinyl floor tiles (5 pieces) - $11
• Adhesive backed vinyl sheet (2 rolls) - $8
• Gorilla glue - $15
• Spray paint - $6
• Masking tape - $5
• Goo Gone - $6
• Fasteners - $5
• Foam gasket - $3
• Spray paint primer and clear coat - On-hand
• Double sided foam tape - On-hand
• Epoxy coating - On-hand
• Cardboard - On-hand
• Plywood (luan) - On-hand
• Caulk - On-hand
• Foil tape - On-hand
• Nylon webbing - On-hand
• Filament for 3D printer - On-hand

APPROXIMATE DIMENSIONS

Weight = 12 pounds

External length X depth X height = 20.75 X 17 X 15 inches

Internal length X depth X height = 16.75 X 13.125 X 10.5 inches

Volume = 2300 cubic inches = 40 quarts

A MORE ECONOMICAL OPTION

Assuming that Styrofoam and cardboard were available for free, I think it would be possible to build a reasonably durable and well-insulated cooler of a similar size for about $40. The vinyl covered cardboard would be an economical method for both the liner and exterior shell. The edges and corners could be reinforced with extra layers of cardboard. The hinges and latch for the lid are not strictly necessary. The handles would require a creative solution that is not immediately apparent to me. The main expense would be glue, vinyl and a gasket. 

BUT WHY?

Given that a wide variety of inexpensive manufactured coolers are available, I can think of few good reasons to build one, aside from these:

• The need for a non-standard size or shape
• The pleasure of making something