How to design “light” from comfort and avoid visual light traps?

Architects are increasingly aware of the impact on the happiness and health of project users. Natural light, and how it complements artificial lighting, is an important factor in considering the visual comfort of indoor spaces. But do we know how to handle it correctly?

There is no visual discomfort to measure a space that is successful. There are also blinking frequencies, glare levels or light blind spots to help determine the environmental quality of the room. Other important considerations include color representation, low reflection, and even distribution of light. In order for people to see the clear view outside, it is also important to control the amount and location of the openings in the building envelope to control the intensity of natural light. Too little or too much light can cause visual discomfort. Important changes in light levels or strong contrasts (called glare) can cause stress and fatigue because the human eye is permanently adapted to light levels.

Therefore, all things that enter our eyes affect our physical and mental health, affect our biological clocks (sleep and wakefulness), our heart rate, organ function, and mental state. The versatile and dynamic nature of natural daylighting provides an opportunity for architecture to make a positive contribution to the overall well-being of the occupants.


Give priority to natural light

Natural light is always the most comfortable for humans because it is the natural source of light for our eyes. Not only does it have a proven impact on health and well-being – raising awareness during the day, improving sleep patterns, reducing the risk of depression, and many other things – it also saves a lot of energy and avoids the use of artificial light sources.

When designing a new project, make full use of the orientation of the site and provide the best possible natural light to the user through the correct opening design. Depending on the specific use of each room, consideration should also be given to the use of a space at different times or on different dates.

Illuminance, expressed as lux (lux), is the optical power from all sides and reaching the completion point of a particular task. When measuring on a certain surface, such as on an office desk, ensure that the illuminance reaches 500 lux. A value that is too high or too low can cause discomfort. This is effective for artificial lighting in offices and workplaces, but in order to take into account the natural variations in daylight, it is best to refer to the new European lighting standards outlined below.

Brightness, expressed as (cd/m2, Kandalay per square meter), corresponds to a unit of light, different luminous intensity emitted or reflected by the light source and the surface around us. [1] It basically describes the brightness of light from the perspective of visual perception and psychological perception. By measuring it, we can identify the contrast between light and glare and see if the light is evenly distributed or from a particular source.

A photometer must be used in both cases. The measured illuminance (lx) is called a Lu Meter, and the measured brightness (cd/m2) is called a Luminance Meter.

In order to assess the amount of light, the distribution and illuminance of light in space should be measured at specific and relevant points in the room performing functions.

To measure the quality of light, UDI must be modeled first, integrating the evaluation of daylight levels and glare, setting the value of the movement between 100 and 2000 lux to an acceptable range. [2] Then calculate the daylight autonomous (DA), the percentage of the total daytime time that is maintained above a certain level of light by a particular point in the space set by the user. The new European lighting standard EN17037 states that the following guidelines (minimum requirements for space sunlight autonomous) should be met: over half of the day, 50% of the space reaches 300 lux and more than half a day, 100% space reaches 100 lux.

Sunlight autonomy is determined by the position, orientation of the glass, the shadow and position of the window, and the ratio of window to floor and visible light transmission. To achieve an effective balance between all these variables, the following aspects are basic:


Consider the relationship between opening and space: window to floor ratio

The ratio calculation of the open area to the spatial area is referred to as the window-to-ground ratio (WFR), which is obtained by dividing the total area of ​​the opening by the total area of ​​the space associated therewith. This factor helps define the number of openings that will be effectively executed in each space of our project. It also guides the size, position and glass type of the opening. In some countries, such as France, it is mandatory to have a WFR of at least 17% for all new homes.

The WFR value must be multiplied by the visible light transmission (VLT) of the selected glass, as described below, to ensure that the design moves within a threshold range of certain visual comfort (typically above 0.15). Determine the amount of light passing through the glass: visible light transmission.

According to the above description, the relationship between the opening and the space must be supplemented by the visible light transmittance (VLT), that is, the amount of visible light passing through the glass. 50% glass with a VLT allows 50% of the light to pass through and blocks the remaining 50%. With it, we can combine large openings in the project while controlling the amount of light passing through it, increasing the protection of UV and glare.

In order to obtain valid results, all of these analyses must be combined with calculations of other relevant factors, such as the solar heat gain factor and the U value. Local regulations must be considered, as well as technical specifications for the type of window selected.


In addition to this, it is important to assess the outside world’s vision, such as urban or natural landscapes, or other elements that can be observed from each transparent surface. Also consider other methods that combine solar control systems or that affect the visual comfort inside a building project.


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