I have looked in some of my books and there is no reference to leaving the porter bee escape holes open. Crownboards are also known as coverboards and that seems to indicate 'covered', as in 'no spaces'.
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I looked on the Th*rne website and extracted these descriptions for their crownboards.
Glass QuiltIdeally it should be removed in the winter, as its insulation qualities are poor.
National Crownboard/Clearer Board with two plastic porter bee escapesThis board provides good insulation when in its usual position above the top super and below the roof.
Both those descriptions are fairly self evident re the holes. They are there for fitting porter bee escapes when using them as a clearer board.
They do not advocate, in any way, leaving the holes open and specifically refer to the insulating properties of the two types. It must be clear to most that there will be no insulating properties at all if large holes are left in them (both sides would be the same temperature; thermal energy would not need to pass through the material). In house terms that would be the equivalent of insulating your loft door and then leaving it open!
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Wedmore (back in the1930s) in para. 648 considers warm and cold way frames. He says, with a full entrance, the cold way is better for ventilating in hot weather. That would not be a logical consideration if there were a large hole at the top of the hive.
In the I930s top packing (insulation) was often a porous quilt of some description for moisture control ( no gaping holes) and reference is made (para. 716 of my revised edition reprinted 1948) and it says quote "The feed hole may be covered with porous material and soft packing used above...."
So even then they knew that top ventilation was always through a porous material and not large holes.
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I checked out Hooper, too.
Page 91 shows a piece of wood on the crownboard - presumaby covering the second porter escape hole while using the other for a feeder.
Page 100: he refers to raising the crown board by 1/4 inch so that ventilation is around the sides without draughts affecting the cluster.
Page105: he covers the entire box wit a polythene sheet -so no holes in use there
Page 120: exactly the same - no holes in his crownboard!
Nowhere is there a drawing, or reference, to a gaping hole at any time of the year.
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If anyone could supply me with a categoric reference to leaving a gaping hole in a crownboard (from any of the books accepted as a good reference material), I would be very grateful.
RAB
-----
I looked on the Th*rne website and extracted these descriptions for their crownboards.
Glass QuiltIdeally it should be removed in the winter, as its insulation qualities are poor.
National Crownboard/Clearer Board with two plastic porter bee escapesThis board provides good insulation when in its usual position above the top super and below the roof.
Both those descriptions are fairly self evident re the holes. They are there for fitting porter bee escapes when using them as a clearer board.
They do not advocate, in any way, leaving the holes open and specifically refer to the insulating properties of the two types. It must be clear to most that there will be no insulating properties at all if large holes are left in them (both sides would be the same temperature; thermal energy would not need to pass through the material). In house terms that would be the equivalent of insulating your loft door and then leaving it open!
-----
Wedmore (back in the1930s) in para. 648 considers warm and cold way frames. He says, with a full entrance, the cold way is better for ventilating in hot weather. That would not be a logical consideration if there were a large hole at the top of the hive.
In the I930s top packing (insulation) was often a porous quilt of some description for moisture control ( no gaping holes) and reference is made (para. 716 of my revised edition reprinted 1948) and it says quote "The feed hole may be covered with porous material and soft packing used above...."
So even then they knew that top ventilation was always through a porous material and not large holes.
----
I checked out Hooper, too.
Page 91 shows a piece of wood on the crownboard - presumaby covering the second porter escape hole while using the other for a feeder.
Page 100: he refers to raising the crown board by 1/4 inch so that ventilation is around the sides without draughts affecting the cluster.
Page105: he covers the entire box wit a polythene sheet -so no holes in use there
Page 120: exactly the same - no holes in his crownboard!
Nowhere is there a drawing, or reference, to a gaping hole at any time of the year.
-------
If anyone could supply me with a categoric reference to leaving a gaping hole in a crownboard (from any of the books accepted as a good reference material), I would be very grateful.
RAB