Right choice The level of illumination in a room is considered one of the conditions for a comfortable stay and is clearly standardized regulatory documents on labor protection, a number of GOSTs and, of course, a set of building codes and regulations No. 23-05-95. The calculation of room illumination in a house is carried out by specialists at the design stage, and during the acceptance of a new building, the indicator can be monitored by the selection committee. In fact, knowing the level of illumination in the house is also important because a person’s health and the state of his vision depend on it.
How to theoretically determine the lighting level
The method for calculating lighting comes down to obtaining the value of the required luminous flux of one lamp used to illuminate a room under specific conditions, with previously known characteristics. Simply put, they create a simplified model - a light bulb under the ceiling in an empty room. Based on the model, knowing from the recommendations of SNiP the level of illumination for a given category of premises, the luminous flux of the lamp and its power are determined.
To calculate lighting and luminous flux you will need to know:
- The standard of illumination for a specific type of premises, usually in reference books, illumination is indicated by the index E n, measured in lux, Lux;
- The total area of the room is S, unit of measurement in m2;
- Three correction factors - k - safety margin, z - correction for unevenness of the light source, n c - efficiency factor for using the light flux;
- The number of light fixtures is N, and the number of light bulbs in one fixture is n.
In order to correctly calculate the luminous flux of a lamp, it is necessary to take data from reference tables, use information about the geometry of the room and the characteristics of the light source, and substitute them into a well-known formula that determines the amount of luminous flux.
The luminous flux formula looks like this:
F l =(E n ∙S∙k∙z)/(N∙n∙n c).
Advice! When using old reference books, pay attention to the dimensions of the given values.
After calculating using the formula, we obtain the value of the luminous flux for one lamp in lumens. All that remains is to choose the right version of the light source. In a similar way, the inverse problem of calculating illumination is solved, namely, using known data on the luminous flux F l for a specific light bulb, knowing the other characteristics and coefficients, it is possible to calculate illumination for specific conditions using the formula:
E n =(F l ∙N∙n∙ n c)/(S∙k∙z).
Option for calculating indoor illumination
There is nothing complicated in how the amount of light and illumination is calculated; you just need to strictly follow the recommendations and correctly select the data from the reference tables. For example, let's take an ordinary room with an area of 20 m 2 with standard height a ceiling of 250 cm. To simplify, we will assume that the ceiling is white, matte, and the walls have a plain, non-glossy, beige coating. All this data is needed to calculate illumination or illumination.
The lighting fixture is a ceiling lamp consisting of five light bulbs, each of which is covered with a diffuse white shade. The plane of the lamps is at a height of 2.3 m.
To calculate lighting you will need the following reference data:
- Tabular information on the luminaire utilization factor;
- Calculation of luminous flux utilization factor;
- Correction for unevenness;
- Safety factor.
The first point when determining the amount of illumination will have to be taken from the table, the rest are obtained by correction or a simple calculation based on the characteristics of the room.
How to choose coefficients for calculating illumination
The simplest is to select a correction for unevenness and a safety factor. The last parameter is used to take into account the decrease in the luminous flux density of the lamp due to the settling of a layer of dust when calculating illumination. For residential premises with a dust content in the air of less than 1 mg per cubic meter of volume, a value of 1.2 for electrified fluorescent light bulbs is taken for calculation. For conventional incandescent lamps 1.1 and for the coldest low-voltage LED devices, the coefficient is taken equal to 1.
The unevenness correction is used to take into account the nature of the work in the room. For lamps with incandescent filament it is 1.15, for LEDs it is 1.1.
The flow efficiency coefficient is determined by calculating the index using the formula:
I=S/((a+b)∙h),
where S is the floor area of the room, a, b, h are the length, width and height, respectively. For our case, the calculation of the index gives a value of 0.9 units. Knowing the illumination index of the room, the percentage of reflection - for a white ceiling surface - 70%, for beige walls - 50% and a gray floor - 30%, the location of the lamp on the ceiling, we determine from the tables the flow efficiency coefficient n c = 0.51 required for calculation.
We will select a lamp for lighting
Knowing the necessary numerical values of the coefficients, we substitute them into the luminous flux formula for our case F l =(E n ∙S∙k∙z)/(N∙n∙n c)=(150 * 20.0 * 1 * 1.1)/(1 * 0.51 * 5)=3176.25/2, 55=1245 Lm. This means that for the room we have chosen, with an illumination standard of E n = 150 lux, the luminous flux of one LED lamp should be 1245 Lm. To complete the calculation, choose the right light source, you will need to compare several options for lighting fixtures with different light temperatures, from the warmest at 2750K to the coolest white at 4500K.
This stage of calculation is the most labor-intensive. There are four main types in the range of modern light sources:
- Halogen bulbs;
- Lamps with filament;
- Luminescent devices;
- LED light sources.
There are conditional tables of correspondence between light output or luminous flux density and power consumption. In our example, table data was used. The most common filament lamp produces a relatively soft, warm light, but has low luminous efficiency. According to the calculation of illumination, in order to provide a flux of 1245 Lm, you can take a 100 W light bulb, which produces a luminous flux of 1300 Lm. Among halogen light bulbs, the one with the closest characteristics of 75 W produces 1125 Lm, which is clearly not enough. A fluorescent lamp of 20 W and 1170 Lm, an LED lamp of 12 W and 1170 Lm have closer characteristics.
We choose the last option and calculate the illumination in the room using the above formula E n =(F l ∙N∙n∙n c)/(S∙k∙z). As a result, we obtain a value equal to 141 lux, which is allowed by SNiP standards. For the living room and bedroom, the illumination level should be from 100 to 200 lux, for the kitchen 200-300 lux, for the bathroom and toilet 50-150 lux. If desired, using the above methodology, you can recalculate a variety of illumination options for different light sources. The most economical was the LED option; with a consumption of 12x5 = 60 W, the lamp produced 5850 Lm, which corresponds to the power of 500 W of an incandescent lamp.
The most primitive calculation can be performed based on the rule - for 1 m 2 a lighting source with a power of 20 W is required. But such a determination of the power of a lighting device can only be made for a square room with white walls and a ceiling, with a ceiling-mounted lamp. For other cases, the error will be more than 20%.
Conclusion
The methodology for calculating lighting, specified in SNiP and based on statistical material, was compiled in an era when, apart from incandescent lamps and fluorescent devices, there were no other options. If we are guided only by these rules, then the most profitable and comfortable should be LED lamps with a maximum illumination temperature of 4-5 thousand K. In practice, such lamps turn out to be very irritating and blinding when used for a long time, so owners often deliberately use warmer lamps incandescent as more comfortable. The illumination calculation does not take this into account.
The falling cost of LED lamps and the significant increase in the price of electricity are making them more and more popular every day. Such lamps provide the opportunity not only to significantly reduce electricity costs, they make it possible to organize lighting in the premises that is quite close to daylight in the light spectrum. Therefore, calculating LED lamps by room area when planning to replace standard incandescent light bulbs is the most relevant today.
Everyone is used to the fact that in the toilet, for example, one incandescent light bulb with a power of 60 W is enough; in the living room, four similar light bulbs with a power of 100 W each need to be screwed into a suspended ceiling chandelier. For LED elements such parameters are unacceptable. When organizing a lighting system using LED sources, it is necessary to calculate the total light flux.
In this article:
Lighting standards for different rooms
As a rule, the illumination should be different depending on the purpose of the room. Bright light is necessary to perform any work, but it is not suitable for comfortable relaxation.
The degree of illumination of rooms in an apartment for different purposes according to SNiP standards:
- hallway - 100-200 Lx/m2;
- hall - 150 Lx/m2;
- children's room - 200 Lx/m2;
- bedroom - 200 Lx/m2;
- office - 300 Lux/m2;
- kitchen - 150-300 Lx/m2;
- bathroom - 50-200 Lx/m2.
Calculation of the payback of LED lamps primarily depends on the area of the room and ceiling height. You also need to take into account such a factor as the type of lighting: primary or additional, functional or decorative.
Important! If you plan to organize a functional lighting system, then the lighting devices require sufficient brightness of the luminous flux. If it is necessary to organize decorative lighting, it is worth using LED elements of lower brightness.
An example of calculating lighting with LED lamps
- X is a certain degree of illumination of a room depending on its purpose (Lx).
- Y - room area (m2).
- Z - coefficient (correction) for ceiling height. Its value is taken as one if the ceiling height of the room is 2.5-2.7 m; for 1.2 with a ceiling height of 2.7-3 m; for 1.5 at 3-3.5 m; for 2 at a height of more than 3.5 m.
The amount of luminous flux of LEDs depending on power:
| Power, W | Luminous flux, Lm |
| 3-4 | 250-300 |
| 4-6 | 300-450 |
| 6-8 | 450-600 |
| 8-10 | 600-900 |
| 10-12 | 900-1100 |
| 12-14 | 1100-1250 |
| 14-16 | 1250-1400 |
Calculation example
For example, let’s calculate LED lamps based on the area of the room for a hall with an area of 25 m2 and a ceiling height of 2.8 m.
- Substitute the values into the formula = X*Y*Z = 150Ln/m 2 x25m2x1.2 = 4500 Lm
Now from the table above we select LED light bulbs for a four-socket ceiling chandelier. In our case, these are lamps with a power of 12 W each with a luminous flux of 1100 lumens. Together they will provide the necessary illumination of the room.
You can also use an online calculator on the Internet to perform this calculation.
Important to remember! When organizing the main lighting of any room, it is quite important to achieve a uniform distribution of light flux over the entire area.
For example, if you need to create decorative lighting in a room using multiple LED ceiling lights best option- evenly place 8 recessed lighting devices on the ceiling with LED elements with a power of 5 W each.
- The calculations made used SNiP standards for the Russian state, which have been adopted for quite some time. In practice, the calculated number of lighting fixtures according to these standards may not be enough to effectively illuminate a room. Therefore, it is recommended to increase the obtained values by 1.5 times.
- When using multiple low-power lighting devices to organize a lighting system, it is recommended to install several switches so that not all lamps can be used at the same time. If brighter lighting is required, the second switch is turned on accordingly.
Calculation of LED lighting sources for a greenhouse in a suburban area plot of land or a greenhouse at the dacha is produced in a similar way. Calculation examples can be found freely on the Internet.
I will try to very briefly and simply outline the method of manually calculating indoor lighting, which I was taught in the “Calculation of Lighting” course at the LiDS lighting design school.
What should the illumination be?
When planning lighting, first of all you need to determine the target illumination that meets the standards and calculate the total luminous flux that the lamps in the room should produce.
It’s easy to decide on the standards - either we look for our type of premises in the tables SanPiN 2.21/2.1.1/1278-03 “Hygienic requirements for natural, artificial and combined lighting of residential and public buildings” and SP 52.13330.2011 “Natural and artificial lighting”, or We agree with the basic requirement for illumination of residential premises - 150 lux or office premises with computers - 400 lux.
Rough estimate of required luminous flux
By default, illumination calculation is done in the Dialux program. But the result needs to be known at least approximately in advance in order to compare the data with the estimate “by eye”.
As it is written even in Wikipedia, the average illumination of a surface is the ratio of the luminous flux incident on it to the area. But in a real room, part of the luminous flux of the lamp does not reach the working planes, disappearing on the walls. Illumination in a room is the ratio of the total luminous flux of lamps to the area of the room with the correction factor “η”. 
The proportion of light “η” that reaches the working surfaces can be estimated by eye. In the most general approximation, for a very average room with some kind of lamps, approximately half of the light reaches the working surfaces, which means that for a very rough estimate you can use the coefficient η = 0.5.
For example, in a room of 20 m 2 a lamp with a luminous flux of 700 lm (equivalent to a 60 W incandescent lamp) will create an illumination E = 0.5 × 700 lm / 20 m 2 = 18 lux. This means that to achieve the standard of 150 lux, you need F = 700 lm × (150 lux / 18 lux) = 5800 lm, or the equivalent of 8 incandescent light bulbs of 60 W each!
(Half a kilowatt of incandescent lamps for a small room! It is clear why lighting standards for residential premises are much lower than for institutions, and why no one has been lighting institutions with incandescent lamps for a long time.)
More accurate manual calculation method
But since rooms have different walls, different shapes, with high or low ceilings, the correction factor is not necessarily equal to 0.5 and is different for each case: in practice, from 0.1 to 0.9. Despite the fact that the difference between η = 0.3 and η = 0.6 already means a two-fold difference in the results.
The exact value of η must be taken from the luminous flux utilization coefficient tables developed back in the USSR. I provide the table in full with explanations in a separate document. Here we will use an excerpt from the tables for the most popular case. For a standard bright room with ceiling, wall and floor reflectances of 70%, 50%, 30%. And for ceiling-mounted lamps that shine towards themselves and slightly to the side (that is, they have a standard, so-called “cosine” luminous intensity curve).
Table 1 Luminous flux utilization factors for ceiling lamps with a cosine diagram in a room with ceiling, wall and floor reflectances of 70%, 50% and 30%, respectively.
The left column of the table shows the room index, which is calculated using the formula: 
, where S is the area of the room in m2, A and B are the length and width of the room, h is the distance between the lamp and the horizontal surface on which we calculate the illumination.
If we are interested in the average illumination of working surfaces (tables) in a room with an area of 20 m 2 with walls of 4 m and 5 m, and the height of the lamp hanging above the tables is 2 m, the room index will be equal to i = 20 m 2 / ((4 m + 5 m) × 2.0 m) = 1.1. Having made sure that the room and lamps correspond to those indicated in the caption to the table, we obtain a luminous flux utilization factor of 46%. The multiplier η = 0.46 is very close to the offhand guess of η = 0.5. The average illumination of working surfaces with a total luminous flux of 700 lm will be 16 lux, and to achieve the target 150 lux, F = 700 lm × (150 lux / 16 lux) = 6500 lm will be required.
But if the ceilings in the room were half a meter higher, and the room was not a “light”, but a “standard” room with reflectance coefficients of the ceiling, walls and floor of 50%, 30% and 10%, the luminous flux utilization factor η would be (cm . extended version of the table) η = 0.23, and the illumination would be exactly half as much!
Checking calculations in dialux
Let's build a 4 × 5 m room in dialux, 2.8 m high, with a working surface height of 0.8 m and the same reflection coefficients as with manual calculation. And we will hang 9 pieces of small lamps with a classic cosine diagram, 720 lm each (6480 lm per circle).
Rice. 1 Taken as an example, the Philips BWG201 lamp with a luminous flux of 720 lm, and its classic “cosine” light distribution
Will we get an average illumination of working surfaces of 150 lux, as we estimated manually? Yes, the result of the calculation in Dialux is 143 lux (see Fig. 2), and in an empty room without furniture and a human figure – 149 lux. In lighting engineering, values that differ by less than 10% are considered identical.
Rice. 2 The result of the calculation in dialux - the average illumination of the working surface (with a safety factor of 1.0) was 143 lux, which corresponds to the target value of 150 lux.
Rice. 3 Beautiful pictures that people believe in.
Conclusion:
A rough estimate using the primitive method according to the formula E = 0.5 × F / S will take 1 minute of time, to clarify the utilization coefficient using tables - another 3 minutes, for a project in Dialux after some training - about 20 minutes and another 20 minutes if you want to “adjust beauty." Dialux produces very beautiful pictures (see Fig. 3), which are worth the effort because people believe in them. But in terms of the ratio of efficiency and labor costs, hand-to-hand illumination assessment is unrivaled. Manual counting is simple, reliable and effective as a sapper's shovel, giving confidence and understanding.
Properly organized lighting of residential premises is one of the most important conditions for a comfortable environment in a house or apartment. Moreover, it directly affects the health of the people living in the apartment, their emotional state, and visual acuity, which is especially true for children. In a word, it would be a big mistake to let this problem take its course, focusing only on one’s own feelings (they may well be subjectively deceptive), and on issues of saving when purchasing lamps and lamps for them.
Prices for popular light bulbs
By the way, the desire to excessively “fill rooms with light” is also not welcome - this can introduce an irritating factor into the microclimate of the premises, and is not at all beneficial. When selecting fixtures and lamps, it is necessary to find that “golden mean” that would meet all the requirements. And for this it is best to make certain calculations. The algorithm itself is quite heavyweight, requiring the use of tabular data and the use of special formulas. But we hope that the user’s task will be simplified by the calculators for calculating room illumination, which are located below.
In order to correctly carry out the necessary calculations, you first need to understand the principle of their implementation. Therefore, the calculation will be preceded by some necessary explanations.
General concepts about carrying out illumination calculations
Many people, in the old-fashioned way, believe that the ability of lamps to produce the required amount of light is measured in watts. It is clear that this is a consequence of that ingrained habit developed during the period of uncontested dominance of incandescent lamps. Each owner roughly imagined in his mind, for example, that his living room needed two 100-watt light bulbs, and one sixty-watt light bulb was enough for the hallway.
However, a watt is a unit of energy measurement, and it only refers to the consumption of electricity per unit of time. A “logical bridge” just formed - the more watts, the brighter the light. But today, with a great variety of modern lamps, characterized by very low power consumption, but with high luminous efficiency, this approach is completely inapplicable.
In such matters, they operate with other quantities. Surface illumination is measured in lux (Lx), and the luminous flux created by a light source is measured in lumens (Lm). These characteristics are closely interrelated.
A light source with a luminous flux of 1 lumen, with a uniform distribution of this flux, provides an area of 1 square meter illumination at 1 lux.
Thus, it becomes clear that lux is a characteristic of the illumination of a room (what we want to achieve), and lumen characterizes the light source, that is, it is necessary to select lamps and lamps based on this criterion.
The standards for illumination of premises in an apartment are not taken “from the ceiling” - there are recommendations regulated by the current SNiP 05/23/95:
| Type of premises of a residential building | Norms of illumination of working surfaces in the premises of a residential building, Lux (according to the recommendations of SNiP 23-05-95) |
|---|---|
| Living rooms: living rooms, bedrooms, dining rooms | 150 |
| Children's | 200 |
| Offices or workshops where activities involving increased visual strain are expected: carrying out delicate technological operations, working with documents, books, etc. | 200 ÷ 250 |
| Kitchens | 150 |
| Corridors, hallways | 150 |
| Bathrooms, restrooms, combined bathrooms | 150 |
| Entrance lobbies | 30 |
| Flights of stairs and landings in entrances | 20 |
| Common corridors and areas on the floors of apartment buildings | 20 |
Working formula for calculations:
Fl = (En × Sp × k × q) / (Nc × n × η)
In the formula, the following quantities are indicated by letter symbols:
In the numerator:
Fl – required value: luminous flux indicator (Lumen) that each lamp installed in the luminaire must have.
Yong – standard illumination of working surfaces for a given room (Lux). These standards are shown in the table above.
Sp – the area of the room in which it is necessary to achieve the required level of illumination. If the goal is to create a special work area (for example, in a workshop or office in the area of a workbench or desktop) by installing a local lamp, then you can proceed from the area of this dedicated area.
k– correction factor called safety factor. Its value depends on the type of lamps installed (the possible loss of brightness by them over time is taken into account) and on the characteristics of the room - the degree of dust in the air or high concentration of vapors. For residential premises where cleaning is constantly carried out and large dust levels are not expected, the safety factor takes the following values:
— gas-discharge lamps – 1.2;
— halogen lamps and incandescent lamps – 1.1;
— LED bulbs – 1.0.
q– glow unevenness coefficient, taking into account the characteristics of the glow of different types of lamps.
— gas-discharge mercury lamps and incandescent lamps – 1.15;
— LED lamps and compact base lamps fluorescent lamps(which are often called energy-saving in everyday life) – 1.1.
In the denominator:
Nc– the total number of lamps that are supposed to be installed in the room in accordance with the interior design project.
n– the number of lamps installed in each of the selected luminaires
In a word, the work Nc ×n should show the total number of lamps used to illuminate the room. In this matter, sometimes you have to show a certain flexibility. For example, it is planned to install a whole ensemble in the room, which will include a three-arm chandelier in the center and four lamps on the periphery. This means that the total number of lamps is 7 pieces, and you can indicate in the calculator either one lamp with seven arms, or seven single-arm lamps.
η – this value is called the luminous flux utilization factor, and it makes significant adjustments to the calculation, taking into account the characteristics of the room, the type of lamps used and the location of their installation.
The utilization coefficient must be found separately, using first the calculation and then special tables.
Determination of luminous flux utilization factor
This is a calculated value entered into the tables for different types of luminaires. But in order to “enter” the table, you first need to find one more parameter - the so-called room coefficient i.
It is determined by the formula shown below:
i = Sp/ ((a + b) × h)
i– required room coefficient;
Sp– room area, m²;
a andb– linear dimensions (length and width) of the room, m;
h– the height of the lamp above the floor level. This should not be confused with the ceiling height - for example, if the lamp has a suspension length of 0.7 m and the ceiling height is 2.7 m, then h = 2.0
The proposed calculator will help you carry out the calculation.
Surely you already know that too dim or, conversely, too bright lighting in a room has a negative effect on the human body. In addition to eternal drowsiness, an insufficient amount of artificial and natural light entails more serious dangers - deterioration of vision and disruption of the psychological state. Solving the problem is quite simple - install more suitable lamps and properly organize the lighting in each room. However, before this, you need to find out what lighting standards exist for residential premises. This is exactly what we will talk about now.
What does SNiP say?
The main document that specifies existing standards is SNiP ( building codes and rules). So, according to this document, the following standards of illumination in lux (Lx) must be observed in an apartment and a private house:
- attic and basement passage – 20;
- toilet, shower, bath – 50;
- hall, corridor – 50;
- wardrobe – 75;
- bathhouse, swimming pool – 100;
- bedroom, kitchen – 150;
- children's - 200;
- personal office, library, utility room, room with billiards - 300.
Please note that in the bathroom you can optionally increase artificial illumination to 100 Lux, because... for applying makeup and shaving, the value specified in SNiP 05/23/2010 may not be enough.
So that you understand how to convert the provided numbers into more familiar values, remember - 1 Lux is 1 Lumen/1 square meter of room. Each light bulb must indicate such a characteristic as luminous flux (in lumens, Lm). All you need to do is first calculate the standard illumination of a living space, in your case one of the rooms, then convert the value to Lumens and select the appropriate light bulbs. Let's look at the calculation technology using an example.
We make calculations
Let's say you need to find out the standard of illumination in a bedroom whose area is 20 m2. First of all, we multiply the norm according to SNiP for this room by the area, namely 150 * 20, in total we get 3000 Lux. Accordingly, with this value, the total luminous flux of the lamps should be 3000 Lm. All you have to do is choose the appropriate light bulbs for your living space, for example, if you want, you can use 3 light bulbs of 12 W each, which in total will give no more than 3600 Lm according to the table:
This calculation is approximate, because Each has its own meanings, which you can find out upon purchase. This way, you can easily make the artificial light in the room the kind recommended by the lighting standards for residential premises according to SNiP.
By the way, this value can be measured using special device- a lux meter, which is quite simple to use, as proven by the video below.
Measuring work
That's all I wanted to tell you on this issue. We hope now you know what kind of illumination should be in a house and apartment and how to choose suitable lamps in watts and lumens.