The short answer
Double-hung sashes slide vertically; casement sashes hinge at the side and commonly project outward. Compare room and exterior clearance, ventilation, screens, cleaning access, hardware, clear opening, exact NFRC ratings, and installation implications.
| Compare | Double hung | Casement |
|---|---|---|
| Movement | Vertical sliding sashes | Side-hinged projecting sash |
| Clearance | No exterior projection | Exterior swing area required |
Sources
Sources
- Window Types and Technologies — U.S. Department of Energy
- Window Energy Performance Ratings — National Fenestration Rating Council