Casement windows and double hung windows are both popular choices for residential homes. The simple answer to the question of which costs more is that casement windows tend to be more expensive. You should compare the differences in the windows, however, to determine if the casement windows offer other advantages to offset their increased price.
Casement windows are hinged to open like a door. This means that the full area of the window can be utilized to allow air flow. A double hung window will, at best, allow 50 percent of open area as the sashes overlap each other; double hung windows have a bottom sash that slides up and an upper sash that slides down. Casement windows are generally considered to seal better, as well, when closed. This means less unwanted air infiltration and reduced energy costs which can offset some of the initial cost of the windows.
It is typically easier to replace double hung windows than it is to replace casements. Often, double hung windows can be retro-fitted with new sashes rather than replacing the whole frame. Casement windows usually required removal of the entire window. This can increase the installation costs.
Double hung windows require very little maintenance as they have a limited amount of mechanical parts. Casements have cranks and hinges that can wear out or break and may need replacement. Cleaning a casement window is typically more difficult as well since it can be hard to reach the outside of the window. Double hung windows tilt inward so that all cleaning can be done on the inside and, if necessary, it is much easier to remove a sash from a double hung window than it is from a casement.
Casement windows have a locking mechanism that is stronger and more secure than that of double hung windows. Without breaking the glass of the window, casement windows are more difficult to break into. Some consideration should be giving to the price of peace of mind.