Yes, it will allow any of the unwanted gases to still escape. And by 20 degrees, I hope you mean Celsius! Which is 68F.
Smick Daddy Brewing
Fermenter 1 - Scottish Nut Ale/80 Shilling
Fermenter 2 - Cascade Pale Ale
Fermenter 3 - Green Flash IPA Clone
Fermenter 4, 5 & 6 - Empty
Bottled - Kolsch