geospyder wrote:After doing some reading I think I'm going to use the space blanket to line the inside of the cooler.
Silvering the insides of containers is what you do to trap radiant heat inside
the container. Think of a silvered vacuum bottle. It does little good for keeping things cool on the interior as there is little radiant heat to trap inside (see the heating/cooling distinction GreyCoyote made).
GreyCoyote wrote:A disenting opinion: bbadger hit the nail on the head regarding conduction being the dominate heat transfer mechanism,but he didnt take it far enough. Conduction gets the heat into the cooler, but it has to be there in the first place. Block it from the surface of the cooler and there isnt anything to conduct. The paradigm is this: the "cold" doesnt "leak out". Instead, the heat leaks in. This is not a distinction without a difference.
The real problem I see here is that the coolers people buy are just not well-insulated in the first place. The day coolers you sit on around the camp fire are not going to keep your ice cold for very long because they're not designed for it. What this elevation and covering is really doing is just adding additional layers of insulation to the cooler -- layers that really should be unnecessary in a good cooler.
Most coolers found in stores are insulated with thin continuous air pockets between the two linings. The air does act as an insulator, but it's not a vacuum and still facilitates the transfer of heat. The air in such coolers is also free to move about; any surface touching anything, creating a conduction path, will warm the entire insulated air pocket.
The size of the coolers matter too. The greater the volume, the more the contents insulate each other in addition to less surface area exposed per unit volume. My friends and I brought just a single Igloo Maxcold 165-qt 7-day cooler I bought at Costco for like $90. It uses foam-based insulation and is white on the surface to help reflect heat. Sure, we bought ice mid-week, but that was also because we were using that as the primary cooler for drinks, food, etc. I think most people would have more ice at the end of the day if they just bought better -- insulated -- coolers rather than coolers that serve better as reinforced storage chests (forget those Rubbermaid bins, coolers are great for storage).
We did an experiment a few years ago. Two Coleman coolers placed next to each other. Both contained 80 lbs of ice and equal drinks. We put one under a silver tarp, and the other was exposed. Both were placed on a sheet of R-panel ala monkey hut materials. After 5 days, the one exposed was completely awash and devoid of ice. The one covered by the tarp still had quite a bit of ice. Identical coolers.
But there are key pieces of information missing here: What specific models of cooler? Was the exposed cooler accessed more than the other, or were both allowed to remain unused those whole five days?
In the end though, if putting a cooler under a tarp works, by all means go for it. A solution like that is cheap and easy. Buying a better cooler, however, may go a bit farther.