5.1 Spatial ergonomics

An activity study examines the activities that will take place in the proposed building, the people who will carry them out and the furniture and space they need. Spatial ergonomics is the part of the study that fits spaces, furniture and environment to the human body and its movements, so that users can work and live comfortably, safely and efficiently. It draws on anthropometric data (body dimensions) and ergonomic principles to size furniture, clearances and rooms. Example: a student designing a county library in Butere studies how readers sit, reach shelves and move with trolleys, and sizes her reading areas and aisles from those measurements.

Why spatial ergonomics matters

• Comfort: reduces fatigue and back, neck and eye strain.
• Safety: clearances and heights prevent trips, collisions and falls.
• Efficiency: tools and spaces placed within easy reach shorten movement.
• Inclusiveness: spaces work for children, the elderly and persons with disabilities.
• Economy: rooms are neither too small to use nor wastefully large.

5.1.1 Anthropometric and Ergonomics Analysis

Anthropometry is the measurement of the human body: heights, reach, sitting dimensions and the space taken by the body in different positions. Ergonomics applies these measurements and knowledge of human abilities to the design of furniture, equipment and spaces. Designers use percentile data: the 5th percentile (smaller users) for reach and controls, and the 95th percentile (larger users) for clearances and headroom, so that most people are accommodated. Standard references include Neufert's Architects' Data and Panero and Zelnik's Human Dimension and Interior Space.

Key anthropometric dimensions

• Standing height and eye level: set door heights, shelf heights and display positions.
• Sitting height and knee height: set chair and table heights.
• Arm reach (forward and vertical): set worktop depths and the highest usable shelf.
• Shoulder and hip width: set seat widths and passage widths.
• Wheelchair dimensions: a turning circle of about 1,500 mm diameter and reach ranges for wheelchair users.

5.1.1.1 Desk and Chair Analysis

Desk and chair analysis sets the dimensions of seating and work surfaces for the users of each activity.

• Chair seat height: about 400 to 450 mm for adults, so feet rest flat on the floor with knees at about 90 degrees.
• Seat depth and width: about 400 to 450 mm, with back support for the lower back.
• Desk height: about 720 to 750 mm for adults; lower for children.
• Knee clearance: at least about 600 mm high and 450 mm deep under the desk.
• Work surface depth: about 600 to 800 mm to allow a screen at arm's length.
• Space behind the chair: about 750 to 900 mm to pull out the chair and pass.

These figures are combined into an activity space for each workstation, which is used to size offices, classrooms and libraries.

5.1.1.2 Lighting and ventilation

Lighting and ventilation are analysed for each activity so that users can see well and breathe fresh, comfortable air.

• Daylight: windows sized and placed to give even light; a common rule of thumb is a window area of at least about 10 to 15 percent of the floor area for habitable rooms.
• Glare control: desks placed so light falls from the side, with shading to cut direct sun.
• Artificial lighting: illumination levels matched to the task, for example higher for drawing offices and workshops than for corridors.
• Natural ventilation: openable windows of adequate size, cross ventilation through opposite openings, and high-level vents to let warm air out.
• Mechanical ventilation: extract fans for kitchens, toilets and laboratories.

5.1.1.3 Spatial design

Spatial design combines the activity spaces, clearances and environmental needs into rooms and circulation of the right size and shape.

• Activity zones: each room is planned as zones for its activities, with furniture spaces and use spaces.
• Circulation widths: corridors and aisles sized for the expected flow, wheelchair users and trolleys.
• Clearances: around doors, in front of cabinets and between furniture.
• Headroom: ceiling heights for comfort, air volume and equipment.
• Flexibility: spaces that allow furniture to be rearranged.
• Accessibility: step-free routes, ramps and accessible toilets in line with the building code.