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Need help with DIY cooler insulation Answered

Long time fan, first time poster. I'm looking to convert a cool-looking vintage toolbox into a heavy duty lunchbox. I'm currently prepping the metal for paint and looking into what I can use to insulate the box. I've thought of:

* spray foam insulation: Good coverage and thermal protection, but not water-resistant enough (think condensation)
* fiberglass insulation (pink stuff): Good, but unsure about how cold it will keep things
* styrofoam: probably the one inch sheets used for basement walls below grade. Best solution so far.

Before I do something that will likely mean stripping the box clean and starting over, I thought it best to see what others might have to say about this. Any and all help is greatly appreciated!


Expanded polystyrene sheet is probably best for insulation, if you add a food-grade plastic box and seal up the edges with e.g. silicone-sealant.


Although I had a thought of trimming the interior with some laminate flooring (more for looks than anything else), you make a sound argument for a food grade plastic interior. And since Good Stuff and board insulation are the same material (polystyrene) and about the same R value, this should go together pretty easily.

. I'd build a box inside your existing box and fill the gap with some type of expanding foam. Put good coats of primer and paint on everything and that should prevent any rust from condensation. YMMV