What is a Single Double Hung Window?

Identification

• Double hung windows can be installed as a single unit, mullion arrangement or grouped unit consisting of three or more windows. These are different from single hung windows, which are generally cheaper than the double hung window type. Single hung windows slide vertically like their double hung counterparts, but only feature one sliding sash. Unlike double hung windows, where both sashes move and can overlap, the top sash in single hung windows remains stationary. Only the bottom sash moves up and down.

Materials

• Single double hung window units are made from wood, steel, vinyl, fiberglass or aluminum. Each type of material has its own benefits and drawbacks. For example, steel double hung windows are strong and durable, but also require continual maintenance. Vinyl windows are low maintenance, but also weak. Aluminum provides high quality results, but can be expensive and less energy efficient than other materials.

Features

• Besides containing upper and lower window panes that move separately, single double hung window units feature removable or permanent grill bars. Installed between the window’s glass panes, grills come in multiple finishes, and standard and custom patterns. Since double hung window units are susceptible to moisture and air leaks, some models possess high R-values, which is a measurement of resistance to heat transfer, for optimal energy efficiency. Glazing materials coat and treat glass for heat absorption, low heat transfer and protection against strong shocks and vibrations. Common glazing materials for windows include polyester, polycarbonate, acrylic or polyethylene. Additionally, some double hung windows can tilt inward for greater flexibility during cleaning and maintenance.

Considerations

• Double hung windows tend to be less energy efficient than single hung windows, since both sashes move along the frame. Areas between the fixed and movable parts the window create air pathways into and out of the building, and disrupt heat flow. Replace or install high quality caulking or weatherstripping to fill in any cracks and holes, as well as seal gaps at window joints along the frame. Weatherstripping materials including rubber, metal, felt and foam, which can be used to prevent air leaks in double hung windows without impeding operation of the window. Look at the type and quality of the window frame can also affect air infiltration and energy efficiency.