I cannot say whether the D.E. hives successfully address the ventilation
problem, but can vouch for the fact that the usual arrangement does not.
This Fall, with the colonies populous and finishing off their Fumidil syrup,
the top shavings in the shavings boxes got quite wet.  I tried spacing the
outer covers up 1/2", then 1", using drywall screws.  Despite 1/2" clearance
horizontally all around between the box and the outer cover, and the new
vertical clearance made above the box edges, things were still too wet.  I
made new outer covers which greatly increased ventilation above the shavings
box, and succeeded in getting things dried out.  Now with the syrup gone,
and temperatures between 20 and 40 F, the bees have settled down, and just
for a test I tried a regular cover, which now seems to work, but you can bet
that once Spring feeding starts and the willow and maple yield nectar, that
regular outer cover will make things wet again.  It is deceptive to check
the dryness out in mildly cool weather when the bees' metabolic rates are
low.  My guess is that in this climate, any detectable moisture now is too
much.  It's no wonder that I saw a little chalkbrood in some colonies early
last Spring.

Furthermore, last season when the bees were curing honey, things got too
moist and some bees started gnawing wood at cracks to get more ventilation.
(The outer covers were already spaced up about 3/8".)  I made a 5" diameter
hole in each inner cover and screened it with metal screen.  Had the bees
found this excessive they easily could have propolized it, but did not.
Perhaps larger holes were needed.  I suspect that despite all this, plus a
2" high entrance with Killion slatted boards, my bees' ventilation was
marginal.  If the bees bring in 15# of nectar in a day and cure it, much
water must come out of the hive.  It is further questionable whether my
central location of the screened hole was good, as the bees tend to block
off the lower central combs containing brood with their bodies when fanning
and direct their fanning to pull air down at the sides of the hive.  Perhaps
the bees' propensity to fill central combs more willingly relates to the
difficulty in establishing good airflow in corners.  Do we humans have an
inkling of 10% of what would be optimal?

The season's end frustrated further learning, but what was learned made the
need for something like the D.E. hive seem very real.

Bill Morong