Bees need venting in the hive, all year long. The current hive design does not offer much, if any. The inner cover has a nice hole in the middle, but there isn't any air gap between the inner cover and the outer cover. No place for air to get out. Since hot air rises, the beehive is a natural chimney with all of the hot and humid air rising up to the top.
In winter the high humidity condensates on the inner cover, causing droplets to rain down on the bees.
In the summer, the solar load on the top cover is stifling hot, and the bees spend a lot of extra energy (= less honey and brood) to keep the box cool enough. Also, as they are trying to dehydrate nectar into honey (90% --> ~17% water content) it seems a very difficult trick of physics that they can do this with the inside of the hive being close to 90% humidity all the time. We need to add some venting to hive. Not a lot, just some.
There are several concepts of top ventilation floating around. Serge Labesque is a big fan of ventilation, and his custom hardware has a 2 square inch screened port on his inner covers to let air out. He also recommends using follower boards on the sides to allow the cool air to flow around the brood chamber to let the bees manage their environment better. Many of our members put a pebble, or stick in between the inner cover and the outer cover. Many inner covers now come with a notch in them for ventilation, or a top entrance. I have converted some winter inner covers to year around inner covers with vents in them. (they are just tall inner covers) There is also a nifty device called a Vivaldi Board, which is very similar to winter inner covers with vents. https://www.youtube.com/watch?v=xKL46LKVqHs
I have a new idea for venting that is cheap, durable, simple to add, and does't require you to keep track of sticks or pebbles. Its Coroplast. The corrugated plastic that is used for signs (mostly campaign signs) Its Tough, durable, cheap. Cut some 2" wide strips and staple them to the inside of your telescoping outer cover. Make sure the channels go from the inside to the outside. Leave a 1/2" around the outside for air flow. Staple or glue in place. (use a glue that remains compliant, like silicone. Wood glue and Gorilla glue are too rigid and will fail shortly as it doesn't bond well to polypropylene)
You could also do this to your inner covers if you like. Just put the coroplast on the top side, as the bottom side will get propolized in week.
Its not a lot of air flow, but it is certainly more than you had before. The bees will then be able to adjust the temperature
and humidity much better now they have the added benefit of getting the hot and humid air out of the top of the hive. Happier bees. Less stress.
Phil in Fremont