permaculture

[S P SHERMAN <spsherm@msn.com>]

I had a question on ventilation for a quasi root cellar I am building. 
It is a 6'x8' "room" in the NW corner of the basement level of a barn. 
Two of the walls are below soil level with concrete walls in direct soil 
contact, with the other two walls being framed 2x6 and insulated. 
Ceiling is 2x8 with insulation. The climate here is rather cold, US ag 
zone 5a, min winter temps of -20F and quite windy.

I have read several books and article on venting root cellars, and plan 
on an intake vent in the NE corner at the floor level, and an exhaust 
vent in the SW corner of the ceiling. This should provide decent 
circulation inside the room, the question I have is on the sizing of 
these vents.

Most sources recommend 3 or 4" diameter vents for a storage room of 
about this size. I am considering whether smaller diameter vents might 
be a better choice. My thoughts are that the 3-4" size would be good for 
purely passive ventilation in a less windy and milder climate, but with 
our winds and cold winter temps, smaller vents might be more 
appropriate. Less apt to freeze things if someone forgets to block them 
off during the cold/windy spells. The smaller diameter vents would tend 
to slow the cool down during the fall, but I am thinking that might be 
overcome with a few choice nights of venting possibly with the help of a 
fan.

What do folks think? Anyone with root cellar ventilation experience have 
any thoughts?

TIA