The Updated Hayloft mod adds an updated version of the hay barn with improved design and increased capacity:

Increased capacity: now up to 500,000 liters (twice as much as the base version)
New design: old style with weather roofs and whitewashed walls for a more attractive appearance
Additional feature: now added grass storage option
Retains all the basic barn features from the game, but with improved style and functionality

Credits:
MonsterModding