casement windows;
awning and hopper windows

Hopper, awning and casement windows are three variations of the same window frame design, based on hinges and on compression seals.

Casement windows (image at right) have hinges at one of their sides; awning windows have their hinges located at the top, while hopper windows are an inverted version of the awning windows: they have their hinges located at the bottom.

These models are also based on compression seals (crank outs) to provide an higher airtight and energy-efficiency. They allow less air leakage than that of other window designs.

Casement window advantages

Casement windows are one of the most common and time-tested window designs.

They are particularly energy-efficient - the most efficient window design, if we don't consider the fixed-pane windows... - and provide excellent ventilation possibilities.

Due to the window sash pressing against the frame on closing, they are very effective in blocking air-leakage.

Disadvantages of casement windows

Casement windows can be relatively obstructive - when compared with fixed-pane or gliding windows - in some locations, and can be less easy to clean on the outside.

Their design also poses some limitations in terms of larger sizes.

Casement windows Ventilation

Casement windows open outward fully (or inward, in some models), providing great natural ventilation.

Awning windows

Awning window Awning windows are hinged at the top and swing outward instead of being hinged at the side like the casement windows.

They share the advantages and disadvantages of casement windows.

They are energy-efficient and a good option for controlled natural ventilation; they can be located in many places, and arranged next to other windows: they are commonly used above large patio doors for natural lighting and ventilation.

Awning windows allow full and controlled ventilation (the window can be entirely opened, or just partially).

On the other hand, awning windows do not combine well with exterior storm windows (if you have to use them any time) and their opening and closing can be slightly more difficult than that of other windows.

Hopper windows

A hopper window is an inverted awning window, opening inwards… with the sash hinged at the bottom.