Erichalfbee,
As long as the roof is vented above the Kingspan, it will be alright. That is presuming you do not require any top ventilation for the bees (eg on OMF).
You are losing the thickness of your battens in the height of your roof as an air space?
In those I made recently, I inserted 25mm EPS in the roof to fill flush with the 25mm battens and I have enough overlap for another 25 mm EPS or other insulation if needed. At the moment the colony could be top vented but in winter I may put a membrane, or insulation, between the crownboard and the current insulation. I look at it like this - a crownboard rotted is easy to replace, but a rotted roof is a far larger investment in materials and time.
The EPS sheet cost less than 50p a roof - a kg of sugar saved will pay for it and then it will make a positive saving for as long as it lasts.
I think of houses - air bricks for under-floorboard ventilation are so very important to prevent rot, as is some ventilation (air flow) over any insulation fitted, unless a breathable membrane is included as part of the system design.
If I have to use any solid floors, I will not be using any top ventilation for over-wintering;the brood boxes will be raised by 3-4 mm from the floor when the bees start to cluster, and lowered back onto the floor in the spring. Frames would be cold way and the hive would have a definite slope towards the entrance to avoid any risk of driven rain accumulating in the hive. My hives are not in an exposed site, so little trouble would be anticipated with them like this.
Regards, RAB
