Carefully consider window position and size to optimise daylight and solar gain, taking into account:

• Function - living areas tend to need more daylight than bedrooms.
• Size - room too big or deep for window size and window size too big for room.

Glazing below 800mm provides little benefit to internal daylight levels and is typically for view and enjoyment. When designing windows, keep the room proportion and layout of the room in mind. Note: upper floor windows (floor heigh 600mm above outside) can only be modelled as openable if guarding is at a minimum of 1.1m.

Horizontal windows are more effective than vertical windows in terms of improving daylight distribution and increasing the amount of openable area available for ventilation. They are typically easier to shade, lowering the risk of overheating. Horizontal windows in bedrooms also provide privacy and space for furniture. It is understood that due to local context or other design factors, this optimal approach may not always be possible.

Where possible windows should be installed in the insulation line, to reduce thermal bridging.

Window openings

Consider how the windows open for effective ventilation. Side hung windows have a larger opening area than top hung windows. Consider potential conflicts with internal or external shading devices. Place windows on opposing sides of the room or at 90° to help with cross ventilation.

Design Actions

• Consider what portion of the window is useful for daylight, solar gain, ventilation, privacy and views.
• Favour horizontal windows over vertical glazing
• Favour side-hung over top-hung windows