I posted a thread about insulating my hive, had some positive comments and negative ones too!
with that said, I experimented this weekend, the temperatures in Indiana were lows in the lower 30's and the highs in the upper 60's
I am top feeding both hives until they won't feed anymore.
I have two hives, both have top feeders and both have the heavy plastic top the Walter Kelly sells.
I did an experiment I placed a two inch foam insulation cover over one of the hives, the other one I left alone.

I wrapped the hive with the foam cover with Double Bubble insulation, then placed a 4 mil, plastic bag over the hive at night.
The sun radiant heat warmed the covered hive to a temperature of 79 degrees F.
The syrup was 57 degrees F.
The bees were buzzing in this hive, when I opened it the bees were taking the syrup like always.

The hive I didn't do anything too, had an internal temperature of 52 all day yesterday, bees were slow, only a few bees were eating the syrup.
As the temperature rises, I can take off the plastic bag and the insulation.
I've reduced my lower entrance on both hives, to keep the mice out.
The only thing I"m concerned with is moisture within the hive, I need to keep the moisture level down, that's why I'm removing the plastic and the insulation during
the daytime.

I'm kind of a newbee, here, but I've worked for years in the energy management field, trying to see if the EMS, (Energy Management System) work for raising bees!