Wintering question: entrance reducers and ventilation

I've been in the habit of putting on entrance reducers in the fall and leaving them on until spring. My thinking was to help the hive defend against yellow jackets and to reduce the amount of cold air entering the hive.
I'm reconsidering: here in the PNW, moisture is a bigger problem than cold. So maintaining good airflow is critical to preventing condensation in the hive. This year I'm thinking of removing reducers once the yellow jacket pressure subsides in fall.
What do you guys think?

I live in a northern continental climate where it doesn't get warmer than -15C for about 6 weeks at the coldest time of year and gets to -40 C overnight.

Is there anything specific that needs to be done to assist the bees through the winter (6 months)? Is insulating the hive with bales of hay etc beneficial or detrimental?

Thanks.

A strong colony should be able to defend itself against wasps. However, a colony that is slow building up may indeed need help by fitting an entrance restrictor. As this could impair ventilation I use a wasp-proof mesh over part of the entrance leaving enough entrance area so as not to restrict foraging traffic, while making it easier for the guard bees to defend the entrance. In the winter, the hive should be fitted with mouse guards. Mine give the recommended 7.5 mm maximum aperture width. However, yesterday, when cleaning hive floors after the winter, I found a dead pygmy shrew on one floor. Perhaps it managed to squeeze under the mouse guard but, once it was fat with bees, could not get out. Either that or the bees stung it to death.

Wintering bees in the far north is certainly not an easy task. John Moerschbacher has succeeded in Alberta at about 4,000 ft omsl. Your climate, Nick, sounds much the same as his. I have put a page on his modification of the Warré hive at

http://warre.biobees.com/alberta_warres.htm .

Basically he uses much thicker wood than the minimum 20 mm that Warré recommended and he wraps his hives with tarred building paper in the autumn/fall. He has also substituted for the quilt a condensation trap that doubles as a feeder. He says a small upper entrance should be added.

Surrounding the hives with bales or anything that could screen it from solar heat gain is not a good idea. However, a good prevailing wind break far enough away not to restrict sunshine when the sun is at a low angle might be worth considering.

I've been debating this myself, Patrick. I live in Northeast Ohio, barely zone 6. My hives have mouse guards all year because they are in an Oldfield mosaic where mice are prolific. This is only my 3rd spring going into beekeeping but so far my two hives have done very well keeping the reducers in place all winter. Yellowjackets and moisture are an issue here too. I made my Reducers out of two pieces of wood and 3 drywall screws. The first piece of wood leaves a gap like the standard reversible entrance reducers, but is only approx half as thick. The bees can still squeeze out the entire width of the hive if they want to and seem to guard that little sliver of horizontal entrance space. I just screw another little strip of wood on top of the first piece to fully reduce the entrance as usual. It was just something I came up because I felt in late summer I wanted the bees to be as unrestricted as possible at the hive entrance but still be able to defend the Yellowjackets. As it gets colder I add the second piece of wood. I have small upper entrances for ventilation on the inner covers. In Montana last year Sepp Holzer mentioned upper hive entrances let out the air that has been naturally disinfected by the bees. Perhaps the need for moisture to escape is more important in our climates? I did notice the bees sealed my two piece reducers with a bit of propolis where it rests on the bottom board. I don't think they would seal this small gap if they felt the need for more entrance space or ventilation.