Polytunnel vents

Hi,

I'm toying with the idea of buying a polytunnel and am trying to save money on the extras if I can do without.

The side vents cost a lot extra, especially with the roll up covers.  Now I know vents are very important but if I build my own double doors (1.2m wide in total) on both ends and use netting on them, would that be enough ventilation on a 12x10?  Or should I dig into my wallet and get side vents on atleast one side?

Cheers!
Carl