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 Company
Primary - American Red Ale
Secondary - Smashing Pumpkins Ale & Great Minds Drink Alike
Bottled - Laurens Pale Ale
On deck - 15min Cascade Pale Ale, Winter Ale, Porter, Scottish 80 Shilling