To ensure guidelines are correct and uniform in every country, the Energy Performance Directive for Buildings (EPBD) has implemented a series of energy and indoor climate standards, including EN15251 – Criteria for the Indoor Environment including thermal, indoor air quality, light and noise.
Under this standard, the indoor climate is classified as 1, 2 or 3:
| 1 high level |
< 15% |
700 ppm |
| 2 average level |
< 20% |
850 ppm |
| 3 moderate level |
< 30% |
1150 ppm |
*) The CO2 level outside is typically 350 ppm and is factored into the table to give the absolute CO2 level in the room. The stated CO2 levels are lower than normal, because the building's degassing has been taken into account. Indoor climate class 2 conforms to the Danish Working Environment Authority requirement, once the building's degassing is taken into account.
The following applies for schools:
l/s
per m2 |
m3/h
per m2 |
l/s
per m2 |
m3/h
per m2 |
| Teaching |
1 |
2 |
6,0 |
21,6 |
7,0 |
25,2 |
| 2 |
2 |
4,2 |
15,1 |
4,9 |
17,6 |
| 3 |
2 |
2,4 |
8,6 |
2,8 |
10,1 |
| Auditorium |
1 |
0,75 |
16,0 |
57,6 |
17,0 |
61,2 |
| 2 |
0,75 |
11,2 |
40,3 |
11,9 |
42,8 |
| 3 |
0,75 |
6,4 |
23,0 |
6,8 |
24,5 |
*) The materials of a low contaminated building have been specially selected using indoor climate criteria, e.g. materials that are indoor climate certified.
Calculation example
- desired indoor climate class 2
- Low-pollutant building
- 28 pupils and 2 teachers
- Size of room 56 m2 |
30 persons x 7 l/s |
210 l/s |
| 56 m2 x 0.7 l/s |
39 l/s |
| Airflow per classroom |
249 l/s |
| CO2 level |
1032 ppm |