Indoor climate classes

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.

The standard classifies indoor climates in A, B and C classes:

Indoor climate class Expected dissatisfaction
with indoor climate
Maximum CO2 level*)
A < 15% 700 ppm
B < 20% 850 ppm
C < 30% 1150 ppm

*) The CO2 level outside is typically 350 ppm and is factored into the table to get the absolute CO2 level in the room. The indicated CO2 levels are lower than normal, because the building's degassing has been taken into account. Indoor climate B thus does not conform to the Danish Working Environment Authority requirement, when the building's degassing is taken into account.

The following applies for offices

Room type Indoor climate
class
Floor area
(m2/person)
Total airflow,
low-pollutant building*
Total airflow,
non low-pollutant building
l/s
per m2
m3/h
per m2
l/s
per m2
m3/h
per m2
Single occupant office

A 10 2,0 7,2 3,0 10,8
B 10 1,4 5,0 2,1 7,6
C 10 0,8 2,9 1,2 4,3
Open-plan office

A 15 1,7 6,1 2,7 9,7
B 15 1,2 4,3 1,9 6,8
C 15 0,7 2,5 1,1 4,0
Conference room

A 2 6,0 21,6 7,0 25,2
B 2 4,2 15,1 4,9 17,6
C 2 2,4 8,6 2,8 10,1
Auditorium

A 0,75 16,0 57,6 17,0 61,2
B 0,75 11,2 40,3 11,9 42,8
C 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.

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