The short answer
- A casement window cranks the entire sash outward on a side hinge, while a double-hung has two sashes that slide vertically; that difference decides airflow, sightline, cleaning, and weather seal.
- Casement wins on airflow, opening the full sash area for roughly double the peak ventilation of a double-hung with both sashes open.
- Double-hung matches existing openings in most pre-2000 homes without recutting the framing, and its check rail lets you crack the top sash for night air while the bottom stays locked.
- Casement seals tighter because closing the crank compresses the gasket around the full perimeter, making it the better pick for high-wind locations; double-hung relies on sliding tracks that are harder to seal fully.
What changes between them.
A casement opens the whole sash, so airflow is the full window area when cranked wide. A double-hung opens at most half the window at a time, top sash or bottom sash, so airflow is capped at half the area even with both open. For ventilation alone, casement wins.
Sightline is thinner on casement because the sash sits inside the frame as one piece. Double-hung needs a check rail across the middle where the two sashes meet, which reads as a horizontal bar through the glass. If the design wants the largest uninterrupted pane, casement wins on that too.
Where double-hung wins.
Double-hung is the classic US single-family profile. It matches existing window openings on most pre-2000 homes without recutting the framing, which is the whole reason it stays popular in replacement projects. The check rail also lets you crack the top sash for night ventilation while keeping the bottom locked for security.
Casement needs clearance to swing outward, so it does not fit cleanly above kitchen sinks under upper cabinets, behind a deck rail, or under a low awning. Double-hung opens within the plane of the wall, so those obstructions do not matter.
Common questions.
- Which is better for airflow, casement or double-hung?
- Casement is better for airflow. It opens the full sash area, so peak ventilation is roughly double what a double-hung delivers with both sashes open. The cranked sash also catches wind and funnels it inward, which double-hung cannot do.
- Are casement windows more expensive than double-hung?
- Casement and double-hung are similar in cost at the same size, material, and glass. Hardware differs (crank versus balance system) but neither is meaningfully more expensive than the other on a thermally-broken aluminum frame.
- Which seals better against weather?
- Casement seals tighter. Closing the crank compresses the gasket around the full perimeter. Double-hung seals at the check rail and sill but relies on sliding tracks at the sides, which are harder to seal as completely. Casement is the better choice for high-wind locations.
Keep reading.
Project in motion
Specifying casement or double-hung?
Send your openings and we will quote both in thermally-broken aluminum so you can compare on the same spec.