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WINDOWS Window Types Many types of windows have different characteristics (Figure 128) along with their own advantages and disadvantages. Common window terms are shown in Figure 129. Fixed windows cannot be opened and are generally the least expensive. Though they usually offer the best level of energy efficiency and resistance to forced entry, fixed windows do not provide natural ventilation and cannot serve as a means of egress in case of fire. Single- or double-hung windows open vertically. A single-hung window has only one operable sash (usually the bottom unit) and a 128 Common window types
double-hung window has both sashes operable. Because of their design, only half the window area can open for ventilation. Older hung windows were difficult to open or close and were prone to air leakage. Modern hung windows are much improved and provide good resistance to forced entry. Horizontal and vertical slider windows are easy to operate and do not swing into or obscure living space. Similar to singleand double-hung windows, only half the window area of a slider can open for ventilation. Sliders tend to be less airtight than casement windows, awning and tilt-and-turn windows because their weatherstripping is subject to wear.
129 Window terminology
Interior
Casement
Slider
Hopper
Exterior
edge seal or spacer glazing gas fill low-emissivity coating
sash Awning
Tilt-and-turn insulating glass unit (glazing)
sill Single-hung or Double-hung