no we dont normaly insulate a hive over winter its only recently that in england we have started to do this, our winters are mild enough down south but up north it would be better, most hive kills over winter is , and i am sure to get shot for this , is because the ladies were in poor shape before the start and were unable to suffer the food shortages or disease had taken avantage of there weekend state
What Pete says is probably not quite correct Some hives have been insulated by construction and/or by some beekeepers for many a year.
Usually a WBC, double skinned, was the way with carpet squares, or similar, placed over the crownboard. job done. That was enough.
Some broods were made with a cavity - so again built in insulation. But only on two sides. So the frames were arranged for the max insulation of the brood, if the beekeeper thought about it.
Nationals were not generally insulated - apart from the carpet squares. Maybe someone can remember if there were any serious problems back in the winter of '63? It is also a matter of how sheltered the site is - a hive stood on the top of a hill with no shelter would not be recommended.
So really it comes down to where your bees are, how many colonies you have, and type of accommodation.
Pete is right about lost colonies over winter.
Too much top ventilation (warm air rises and too much heat is lost), too little ventilation (damp in the hive).
Too small a colony is another but we can get nucs through, so just needs some thought - like is the box too big? How can I effectively make it smaller? Making it smaller automatically introduces extra insulation between the colony and the exterior, possibly a couple of dummies, one each side, but a couple of dividers would be much better (no bee space for heat loss) and insulation in the gap can be even better.
If so what is the normal way to do this?
Open mesh floors are all the ventilation I give my colonies. I do reduce it if the weather becomes particularly cold. No top ventilationat at all. Polystyrene sheet above.
One can put an empty super under the brood to raise the brood further away from the draughts, but put another mesh in, or beware, as they may be building comb under the brood before you get the opportunity to remove it in the spring!
A tight fitting block of poystyrene in a super is a good way to insulate above.
Some of my nucs are made with 6mm ply sides. These are most definitely insulated if they were expected to keep a mini-colony comfortable in the winter!
Expanded polystyrene sheets and carpet tiles for tops.
Expanded polystyrene sheets on the sides as necessary.
Retention is either by battens or ratchet straps.
Having said all that, just consider your house - more/better insulation means lower energy bills to heat it in winter. Bees are the same, except their only energy source is the stored honey. So, if less heat is lost, then less food needs to be consumed to retain the nest temperature. Simple energy balance.
That food and extra warmth can be converted into earlier brood development, so they can be better prepared for the first nectar flows. Beware that too much winter stores left over in the spring can slow brood expansion due to lack of laying space.
I have lost colonies with plenty of stores and strong in numbers - an eg. a late and lengthy very cold spell got the bees isolated from their stores and they died of starvation. They may have fared better (well, survived!) if the hive had been heavily insulated.
It is doesn't help the bees after they have died by saying they could have survived if.....
It will be experience and you will take better precautions in the future.
With only 2 hives, like you, I would insulate, especially if a new starter. With 200, probably the minimum extra, but that is why bee farmers keep a large number of over-wintering nucs (they would get extra attention, as necessary).
Of course, some don't need to insulate at all - those with poly hives will perhaps pass on details of how much less stores is needed and how much earlier the spring brood development occurs (probably answers the first part of your question).
My hives homemade are walls 1" polystyrene sandwitched between plywood with heavier poly on lid these outperform basic nationals by miles, Brood is common on outer frames in these hives where under the same conditions nationals had empty combs. Cosy bees have less stress.
Insulation reduces winter food consumption, but the most important is that early spring brooding needs warm hives. When the hive is warm, brood area's radius is bigger than in chilly hive. The hive becomes faster in foraging condition.
The surprise is that biggest hives get biggest advantage from warm hive.