15/05/2013 - nZEB

Designing for Daylight


When is a building sustainable?

A building is not only sustainable in itself. What should also be sustainable is the relationship between the building and the ever-evolving activities carried out within it. The building as such requires flexibility to allow it to adapt to varying functions over the course of its life. A sustainable building, therefore, is more like a natural environment which responds to the flow of life as opposed to an object frozen in time. This brings us to the question of how we relate to our natural environment. Do we shut it out and protect ourselves from it? Or do we actively engage with it?

Daylight from our sun is one of the most beautiful and powerful elements available to architects. Unlike wood or steel its supply is free and boundless. Daylight provides building users with superior visual acuity, dramatic energy savings, and a sense of psychological and emotional well being. Naturally lit buildings help people to relate to daily and diurnal rhythms of light and darkness, providing awareness of the world outside and a sense of belonging in one’s environment. Exposure to natural daylight helps people to work and live more comfortably, safely and happily.

According to the British Standards Institution, BS 8206 Part 2 CIBSE, a space with a mean daylight factor between 2% and 5% is considered well lit and requires little or no additional lighting during daytime. A space with a daylight factor of less than 2% appears dimly lit. Effective daylighting design needs to be considered from the earliest stages onwards, as the level and distribution of daylight within a building depends on many factors such as the geometry of the space, the shape and orientation of openings and the characteristics of the internal surfaces. Many of these factors cannot be retrospectively applied.

Some of the key aspects to be considered from the earliest stages of design are:

• What is the proposed building form?
• What is the building’s orientation?
• Does the building form and orientation maximise the use of daylight?
• Where are windows proposed to be positioned?
• Is there adequate daylight penetration into rooms?
• Is the amount of daylight in the building controllable / flexible for different uses?
• Has energy efficiency / passive design / overheating been considered?

It is the responsibility of the lead designer / architect to ensure that daylighting is appropriately considered at all stages of design from the conceptual right through to picking appropriate materials and finishes. When we design without putting daylight high on the agenda we leave a legacy of mediocre buildings behind us. When we design for daylight we provide our contemporaries and future generations with buildings which are energy efficient, health promoting and sustainable.

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