The tiniest gaps, cracks, seams or even pin-sized holes can have an effect on how well your cooler runs.
Using caulk we should seal up every seam along the panels. For the larger cracks, use spray foam like Great Stuff.
By staggering the rigid foam panels we can eliminate channels for air to pass through as well.
Common areas for leakage are around the a/c and the door.
-To seal around the a/c, we recommend using insulating sleeves for pipes. They come in various sizes and you can shove them into the cracks to seal up any weak points.
*We don't recommend using Great Stuff or spray foam around the a/c in the case of having to pull the unit it. That is a long afternoon of carving out foam to free that a/c.
Folks have even used pool noodles cut down to shove into the cracks to seal large gaps and others have even installed gaskets which makes for a very clean looking installation.
-For the door, we recommend buying a standard, pre-hung, exterior, insulated door. Doors are hard to get right and it takes a master craftsman to build one with a snug fit.
If the gasket seams weak, replace it.
Some folks have even used foam stapled along the jam to make for a tight seal too.
In addition to air tight, we want to make sure we are eliminating any sort of thermal bridging. This means we need to cover any studs with a layer of rigid foam. Studs have an R value of maybe 1, which is way less than we want. Even if we are only up to R7 with that one layer, it is stopping the cold air from having a point of easy passage.
A good way to make sure your cooler is airtight is to go in there with all the lights off. Do you see any slivers of light coming in? If so seal 'em up.