Betting on Styrofoam: My Winter Insulation Experiment

Last winter I lost both hives. This winter I am changing my whole approach to insulation — and making a small bet that runs against what my mentor uses.

If you read my earlier post about the hard first winter, you know I went in underprepared. Quilts on top, no mouse guards, and a lot of hope. This year I am being far more deliberate, especially about heat and condensation, which are the two things that quietly kill overwintering colonies in a cold climate.

The plan for the Layens hives

My core plan is to insulate the top of each Layens hive, right under the lid.

Dr. Leo, whose plans and philosophy got me into horizontal beekeeping, uses wool pillows for this essentially cushions stuffed with wool fiber that sit over the bars and hold the colony's heat in. It is a proven, natural approach and it works well for a lot of people.

I am going to try something a bit different: styrofoam. Specifically, I plan to cut rigid foam board to fit and jam it into the lid space above the bars.

Why foam over wool

My reasoning is practical. I can cut styrofoam to the exact size I need and wedge it in tightly, so it fills the space cleanly and stays put. Wool pillows are great, but the precision of a cut-to-fit foam panel appeals to the part of me that wants a snug, deliberate fit rather than something I am stuffing in and hoping settles right.

I will be honest that I am not certain how much foam I will be able to get in there, and I am not claiming foam is better than wool. This is a genuine experiment. But between the two, cut foam is the one I think I can install most reliably.

The real goal: no airspace, no condensation

Here is the takeaway, and it matters more than foam-versus-wool.

I want no airspace between the insulation and the tops of the horizontal bars.

That gap is the enemy. In a cold hive, warm moist air rises off the cluster, hits a cold surface above it, and condenses. Cold water dripping back down onto your bees is a killer — often more dangerous than the cold itself. If I leave an open, cold pocket between the bars and the lid, that pocket becomes a condensation trap. By packing the insulation tight against the bars with no void above them, I am trying to eliminate the cold surface where that moisture would form in the first place.

Warm, dry, and snug is the goal. Cold and damp is what took my bees last year.

We will see

That is the plan going into this winter. I will be running it across different Layens hive types — the wool-insulated builds from Dr. Leo and the thick pine builds — so I will get to see how the whole package performs. Come spring, I will report back honestly on what worked and what did not.

If you are overwintering in a cold climate, do not overlook the top of the hive and the moisture problem. It is the detail I underestimated most, and I paid for it.

— Craig, Bloom-N-Hive