No doubt, but the real benefit of the black paper is solar gain. We make no attempt to insulate our hives...except for above the crown board. The colonies come through the winter with nice clusters despite the very cold temperatures and months with no cleansing flights. Surely we leave more honey on for winter than you, but they made it, and through proper management, that feed is in the broodnest anyway.
I'm sure our management systems are different, but so is our climate. We do what we have to and we learn what works best over time. Over insulated colonies don't do well here because of moisture issues, and are usually soaking wet and moldy come spring. Letting them cool off and giving them plenty of ventilation promotes quiet clusters, and yields healthy, dry bees.
Just an honest question...Why do your bees require such extra insulation, when your climate is no where nearly severe as mine?
The tar paper will feel warm in the sun but unless you make the top of tar paper air tight the heat will be lost in convection through the holes. The tar paper is not in good thermal contact with the hive(unless you glue it on) so there is not going to be any significant conduction. Any heat that gets in will then be lost by convection through the top vent.
The problems you get with insulation are probably because you putting far too little on and it isn't sealed at the top. It needs to be 2 to 3 inches of styrofoam, top and sides, sealed with no top vent or entrance.
Insulating with a top vent/entrance open is counterproductive nearly all the heat is lost and the condensation will occur inside and the heat of condensation lost as well.
Bees survive in trees in Vermont? Well they have highly insulated nests and bottom entrances and no top vent . And they probably need less than 20pounds of honey to do it.
The tradition here is not to insulate despite research showing increased spring development and honey yield, increased survival of smaller colonies. The use of polystyrene hives is increasing with some bee farmers. The traditional use of bottom entrance only and mesh floors has meant the insulation has been effective. Note although its not very low temperature it is very high heat loss (windy wet).
As regards bees the research show bees survive best in warm humid nest conditions, then cold dry, then cold humid and warm dry.
Btw I do talks on the experimental research I do on this subject. The furthest west enquiry for a talk (so far) has been Cornwall
Why did North American bee keepers go away from insulation, it was fashionable there in the early 20th century
and Why did you adopt top vents/entrances? were the two events connected?
(btw i can supply the citations for research if you are interested)
