[hvatum]

Neat idea.

Remember though, if you use electric heat then you won't be gaining anything by doing this. The refrigerator is basically a large heating element when the thermal system of the entire house is taken into account. All the coolness of the inside of the refrigerator is offset by heat it dumps in the house, plus a little bit (since it's not 100% efficient).

Actually you would be coming out slightly behind since the box might increase heat losses to the outside.

It might be interesting to run a heat pipe outside though, attaching it to a normal refrigerator's cooling coil. That would be mainly useful in the summer, so the fridge is not dumping heat into your kitchen. But in the winter it would keep it cool. Again though, that's only desirable if you heat your house with gas.