A also second Dick's excellent post and yes it largely mirrors my practice. Some thoughts;

We are discussing on two parallel tracts. The scientific/engeneering folks are trying to determine the optimine conditions for colony wintering. They site multipal studies and a lot of data but each study and data set is unique to the conditions specific to the case. The variables are overwelming and make it difficult to interpet the conclusions. Little is said about the health of the colonys before and after the trial. Things like mite load, stores, colony population, other deseases, and queen condition all are important and difficult to duplicate in a controlled study. We can not put much credence in the bees choise of cavitys. They take what is available and very often make a poor coices. In their defence I believe that the conventional Langstroth hive is probably not the optimun housing and carefully read the posts and encourage further study.

The other group are the practical beekeepers. Many with decads of experience and proven empirical knowledge. I am among them. This thred started with the "eco" part of friendly insulation refering to enviromentally friendly but equally important is "eco" meaning economic. We have a sizeable installed base and any improvement must also be cost effective. In the last few years I have included 1" of foil faced rigid insulation between the inner cover and telescoping lid. For around $25 I cut 14 20x16" boards and get a modest R6 advantage. Not a controlled study but it does prevent the frost melt on the lids. Years ago I did do a comparison of 30# felt wrap with 1" top insulation on 50 colonys, 50 with only top insulation and and the rest 100 +/- only double deeps on solid bottom and nothing more. Again not a publishable study. I detected no noticable difference in survivorship. I have never lost a colony to cold to my knowledge dispite long hard winters. I operate on the assumption that a couple or three frames of capped honey on each side of the cluster offer suficient insulation. That also relieves the need for any emergancy spring feeding and it all gets used for the spring build-up. 

As has been noted far more important is that the colony has been low mite (<1%) for the entire season, has ample stores inplace by late Aug, and has a healthy queen and is overall fit. With those conditions a colony will do just fine in a Langstroth double deep. 

Paul
46N 119W 2200'

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