...a friend has a poly hive from P****S and she said she is having trouble with condensation under the clear plastic crown board they supplied with the hive.
Not knowing the hive I suggested some matchsticks - sorry if have offended someone by saying that - but is this an inherent problem with the poly hives?
I presume that this could further problems when the cold weather arrives?
Its not a problem.
With a clear and not moisture-permeable crownboard, you'll see
any condensation there might be.
A little, particularly round the edge is no problem at all, even in winter. Having access to a few drops of water can help the bees to access crystallised stores.
What you'd like to avoid is condensation dripping onto the clustered bees, chilling them.
At this time of the year, the nights are cool, but the bees are probably still hard at work evaporating down Ivy nectar for winter honey stores.
Consequently, with the coolth, the hive has even more of a moist 'fug' than usual - and condensation is likely. But not a bother.
And my personal opinion is that P's roof could be beneficially thicker (providing more insulation) and with more of an overlapping sidewall (it seems no more than inch of wrapover) - for example to cover a beespace-framed polycarb crownboard.
I think the roof should be thicker (better insulated) than the walls - it doesn't seem to be the case for P's national/14x12.
But even so, I don't think that they suffer from excessive condensation.
And certainly no need whatsoever for any top ventilation.