Indoor space quality

The legislative and regulatory framework concerning building design has evolved significantly since the early 2000s.

The European Union has drawn attention to the fact that buildings are responsible for 40% of final energy consumption - and 75% of them are still energy inefficient - requiring member states to make a major efficiency recovery through mandatory enforcement directives. On the other hand, this action must not be to the disadvantage of the comfort and well-being of building occupants, also in view of the high proportion of time spent indoors.

IEQ - Indoor Environmental Quality

In recent years, the concept of "indoor environmental quality" (or IEQ) has become established, a global approach with four dimensions:

  • thermo-hygrometric comfort;
  • air quality
  • visual comfort;
  • acoustic comfort.

Several scientific studies have shown that indoor environmental quality has a direct effect on the comfort, health, well-being and productivity of a building's users.

Productivity impact of building-related elements (source: BPIE)
Element Impact on productivity Context
Lighting 7% to 26% improvement in the learning process in environments with high levels of daylight compared to those with low levels of daylight Schools
Improvement of the learning process by approx. 20% with additional access to daylight (via skylight) compared to rooms without daylight
30% increase in reading speed thanks to activating cold light
30% increase in concentration thanks to biologically optimized light
Reduction of the average length of stay (hospitalization) between 16% and 41% in rooms with a high daylight level Hospitals
Air quality and lighting
Significant progress in cognitive functioning with improved air quality and lighting conditions
Visual comfort

To allow people to carry out visual tasks safely, efficiently and accurately the lighting function must be correctly designed.

The basic requirements are:

  • adequate lighting to ensure safety and movement;
  • conditions to facilitate visual performance and color perception;
  • acceptable visual comfort for those using the space.

The criteria to be adopted will of course vary according to the activities to be carried out in a certain environment, but must in any case ensure comfortable visual conditions.

By "visual comfort" we mean a condition of subjective visual well-being induced by the lighting environment, as indicated by the UNI EN 12665 standard.

In providing the condition of visual comfort, the design of the lighting environment must consider two factors:

  • visual performance;
  • environmental pleasantness.

Visual performance is defined by the speed and accuracy with which the task is carried out, which is why the illuminance and brightness in the environment and on the reference level are crucial, but other factors such as the size of the visual task and the distance from the eyes also come into play. However, there is also a subjective element, represented by the visual capabilities of the individual person. The pleasantness of the environment reflects the general sensation perceived in an environment and is therefore influenced by various factors such as the spatial and functional characteristics of the environment, the person's preferences, attitudes and psychological aspects and the different contributions made by natural and artificial light.

High-quality environments, lower costs

The largest cost in today's organizations is generally the staff and consists of salaries, health care contributions and induced social costs: surprisingly it can be up to ten times higher than the cost of workstations.

Poor quality environments lead to more frequent absences, which cause a cost increase under the heading 'staff'. In minor cases, these are temporary illnesses and indispositions, but if neglected, they can lead to more serious consequences. Sick Building Syndrome (SBS) is not uncommon. In this case, specific illnesses cannot be identified, but people do suffer from conditions that appear to be related to their time in the building and which tend to disappear when they leave.

Investment value

A building with a high quality interior not only has a positive effect on the people who spend time in it, but can also be a good investment.

According to recent research, there are at least three benefits:

  • an excellent indoor environment translates into a value up to 8% higher than a standard building and the 'price premium' that the market is willing to recognize will increase in the coming years;
  • a higher rental income for the whole or parts of the building of 5-10% more;
  • a higher occupancy rate (around 10%) of the working environment.

(source: REHVA Journal)