How Many Downlights Do We Need? | Downlight Manufacturers | Mihouse

How To Confirm Downlights Quantity Needed For The Applications


Downlights are the main lightings for various commercial architectural applications,such as hotel indoor wall, ceilings and room design projects,but many people do not know what downlight quantity needed for the scenarios. Hope be of help to you hereof reading this article.


1.Room and its respective lightings

The normal downlight installation way for recessed downlight is cutting a hole in the ceiling then embed downlight inside ceiling. Room ambiance vary to fixtures cutout sizes. Bigger cutout downlight can enhance lighting feeling of existence, with small size cutout downlight need to increase light quantity and make ceiling looks like sky with full stars. In general, 100-150mm cutout downlights are suggested to use for ceiling height of 2500mm.hence, lighting quantity, luminaires lumen and fixture cutout size must be take into account for lighting design.

According to the following suggested illuminance indices, lightings quantity in need can be count as following formula.


N: Lighting quantity

E: Lux In Need(As the following table)

S: Space area

φ : Luminous Flux

U: Utility coefficient

K : Maintenance coefficient

Room or space Reference Surface or HeightStandard Lux Value UGR Ra
Standard Office 0.75m Surface 300 19 0.680
Luxury Office 0.75m Surface 500 19 0.6 80
Meeting Room 0.75m Surface 300 19 0.6 80
Video Meeting Room 0.75m Surface 750 19 0.6 80
Reception Room/Desk 0.75m Surface 200 __0.4 80
Service / Business Hall 0.75m Surface 300 22 0.4 80
Design office Actual working surface 500 19 0.6 80
Doc Sort Copy and Issue Room 0.75m Surface 300 __ 0.4 80
Archive Room 0.75m Surface 200 __ 0.4 80

The above indices are fit for the room with wall length is four times the size of width, which can bring about homogenous light. Utility coefficient must be accurate and can acquired in lighting specifications sheet. Generally utility coefficient is 0.6. the aboved indices are not suitable for the applications with complicated conditions or need special lighting distribution.


2. Attentive matters for downlight installation

1. Luminaire fixture cutout size according to room size. In general, 100-125mm cutout size downlight for 10㎡ room.

2. White wall relative to dim wall or glass material scenario with higher reflective index, even for the same application, the former required less lightings than the latter.

3. Lightings color need to confirm whether match ceiling color or not.

4. Take note of downlights category and beam angle.

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