8 common lighting design mistakes

Besides functions, colours, materials and shapes, light plays a particularly important role and is the main component that creates aesthetic and emotional quality for architectural and interior works. Along with architectural-interior design, lighting design is increasingly asserting its role in the completion of a beautiful, emotional project while ensuring functionality. However, lighting design has never been easy, and many people have encountered basic lighting design errors, making the house less luxurious, costly but also harmful to the eyes.

Here are the common lighting design mistakes, let’s look over them with Lumi Lighting and avoid applying these to the project!

Forget natural light

Louis Kahn – The famous Jewish architect once said: “A room without natural light is simply a dead room”. In any interior architecture, light is the main link, creating the interaction between the interior space and the surrounding environment. In particular, sunlight is the ideal source to create unique interwoven light effects in space. At the same time, it also helps to reflect the beauty of each object, highlighting each line, architectural detail and interior in the overall space.

Also, a space that receives a lot of natural light will always be lively. In many studies, it is also shown that sunlight has a positive effect on mood, circadian rhythm and human health. Therefore, today artificial light is being studied to emit the light source most similar to sunlight. Specifically, Lumi’s smart lighting solution, which allows artificial light to change colour temperature corresponding to the rising and setting cycle of the sun. Thereby creating a light source compatible with the natural human circadian rhythm.

Although there are many positive effects on interior space and human health, many people still encounter this lighting design error. In particular, many people forget this when building houses, dividing closed rooms, without windows, skylights, etc., and then have to light the lights in the middle of the day, which is costly.

Choosing the wrong light source is harmful to your eyes

The next lighting design mistake is choosing the wrong light source/ lighting device. Lighting devices or lamps are considered the main light source for areas where natural light cannot reach or illuminate at night. However, not all lights are suitable for the eyes. Specifically the blue light from the LED. Prolonged exposure to blue light increases the risk of macular degeneration of the eyes. Because the cells inside the retina are susceptible to harmful light sources.

Besides, using lamps without anti-glare or too wide reflectors also negatively impacts our eyes. Because these lines of lights will emit light in the direction directly into the human eye and cause a feeling of tension and very uncomfortable glare. Therefore, when designing lighting, it is advisable to choose ceiling lights with a depth of hole larger than the width of the reflector to eliminate light sources and not harm the eyes.

Wrong lighting angle design

Lighting angle is the angle between two faces with a minimum luminous intensity equal to 50% of the strongest luminous intensity in the central bright area. Lighting devices that are the same, but with different beam angles, will produce different areas of light. The larger the lighting angle (the more radiant), the smaller the center light intensity and the wider the light area.

However, when designing lighting, many people are confused about the projection angle that the installation location is not suitable for the object and space to be illuminated. Thereby reducing the lighting efficiency and not showing the hidden intention that the architect wants to show.

Here are the interior lighting angles recommended by experts:

  • Lighting with a beam angle of 5°-15° is considered accent lighting. Such lamps with such a small angle are often used to project small objects in space or strongly illuminate a small area.
  • Light with a beam angle of 20°-30° is spot light. Lights with such an angle are often used to project pictures and display objects of medium size; or mat for a fairly large area.
  • Light with a beam angle of 32°-45° is phased light. Light with such an angle is used to illuminate large objects, wide areas.
  • Light with a beam angle of 45°-60° is considered wide-phase illumination and is often used for general lighting or illuminating very large objects.
  • Light with a beam angle >60° is considered an ultra-wide floodlight and is often used for general lighting, street lights, security lighting,…

Incorrect light frequency calculation

Next is a lighting design error that harms the eyes, nerves and makes the house less luxurious that designing lighting we need to pay attention to. Many people think that the more lights are arranged, the more beautiful the living space will be. This is a very wrong notion. Excess light not only destroys the design language of the house, but also costs money and wastes electricity.

In particular, light also has a strong impact on the psychology and feelings of people. Living in an environment with excess light will cause stress and inhibit the nervous system. Therefore, it is recommended to arrange the light intensity just enough to bring a feeling of comfort and convenience as well as to ensure that daily activities take place conveniently. In addition, the frequency of lights should also be carefully calculated based on the actual clearance area of the space to ensure the lighting function and increase the emotion and aesthetics of the space.

The formula for calculating illuminance and number of reference lamps:

  • E= (F1*N1+F2N2+..fn*Nn)*LLF*UF/S
  • N= E*S/F*LLF*UF


  • E: Calculated illuminance (target illuminance)
  • F: Luminous flux of a light bulb
  • N: Number of bulbs
  • LLF*UF: Coefficient related to light loss through shackles, shutters, maintenance factor, absorption coefficient by the wall. Take the approximate value 0.6~0.8
  • S: Room size

For example: The baby’s bedroom has an area of ​​20m2, using a 10w lumen 850 downlight bulb.
Target illuminance: 300 lux
Number of bulbs: N= 300*20/(850*0.8) = 8.8 ~ 9 bulbs

Light distribution is not optimal

Occupying an important role in architecture-interior, lighting has always been focused and carefully calculated in recent years. Instead of using only one light with one type of light to illuminate the entire space and in all circumstances as before, today the light is divided and used a specialised light source for each lighting purpose and achieves high efficiency in terms of aesthetics and feelings of space.

However, when dividing the lights, it is necessary to note the appropriate division of control switches according to each cluster and science, for convenience during use. With traditional mechanical switches, it will be a bit difficult to divide the lights and after dividing them, it will be difficult to change later. If you want different lighting scenarios and easily change the lighting schedule or combine the lights, you can integrate the light system into the smart home electrical system. With a smart home, you can not only divide the lights, flexible lighting scenarios, but also control the power on/off status from anywhere via smartphone. This both saves energy and avoids unexpected electrical fires.

Wrong design of light’s dropping point

Another lighting design mistake that we should note when arranging lights is the wrong design of the light drop point. In each space, there will need to be a point of light falling, or simply the brightest point, where the light rays interfere and create a special highlight. Note that the light source should not be scattered and there are no highlights or wrong lighting. This not only does not enhance the aesthetics of the space, but also brings back the opposite reaction, making the space boring.

The dropping point of the light highlights the object that needs to be highlighted in the space. For example, in the living room, where guests are received, the drop point is the point of connection and direction of the conversation. The projection angle of the light drop point should not be too wide, it will distract the focus, and should only be limited to a certain area such as a tea table for maximum effect.

The arrangement of lights is not suitable for the position

Before designing the lighting system, we need to calculate and consider carefully the space and furniture, electronic items available or will be in the house to avoid the case of being obscured, leading to a shortage of light, does not guarantee light for the whole space. The optimal way to avoid this situation is to design the lighting based on the 2D interior design of the space. Because through the 2D interior design, we know the exact location of the furniture in the house. Or you can perform lighting design in parallel with 2D interior design to have appropriate calculations.

Colour rendering is not guaranteed

Colour rendering is simply a measure of how faithfully the colour of an object or space is compared under the light of a light bulb compared to under natural light from the sun. This quantity is represented by a colour rendering index (CRI) that ranges from 0 to 100.

The higher the colour rendering index of the light source, the sharper and more realistic the image of the object and space under the light. The highest colour rendering index CRI 100 is measured in sunlight and no artificial light source has yet reached this threshold. Therefore, it is not recommended to install CRI bulbs that are too low, to avoid affecting the aesthetics of the space. The recommended colour rendering index is above 80. You can check out some of the lights with a CRI >90 here.

Above are 9 common lighting design errors that not only affect the aesthetic quality of the building but also adversely affect the eyes and psychology and emotions of the people living in it. Hopefully, the information shared from Lumi Lighting can help customers understand more about lighting designs for proper and effective application for their homes. If you need advice on lighting installation and lighting design for your home, do not hesitate to contact the hotline (+84) 904 665 965 for the fastest support.

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