Indoor environment of your building: indicators for evaluation

In this article we will analyze the requirements of the UNE standards regarding the parameters of the indoor environment that must be considered before designing a ventilation system and how to evaluate the indoor environment of buildings (indoor air quality).

The UNE standard responsible for detailing which indoor environmental criteria influence the energy efficiency of buildings is the UNE-EN 15251. This standard also details the methodology that must be followed to assess, in the long term, the indoor environment, as well as the criteria for taking measurements.

Which types of buildings does the standard affect?

The UNE standard applies to non-industrial buildings where the guidelines for the indoor environment are stipulated based on occupancy, that is, residential buildings, offices, hospitals, hotels and restaurants, gyms and sports centers, and shops and shopping centers.

How to evaluate the indoor environment?

Since the loads of buildings can change depending on the space and time, the designed system may not be able to meet the target for which it was initially designed (in all areas of the building and at all times), which makes it essential to calculate the long-term activity of the indoor environment. This evaluation is essential to highlight the climatic factors (indoor environment) in the energy efficiency certificate.

But what are the indicators to calculate the activity? The evaluation of the indoor environment of a building can be based on four indicators: design-based, calculation-based, measurement-based, or through subjective evaluations such as questionnaires.

Design-based indicators

To assess the category of the indoor environment of a building, the following indoor environmental factors are taken into account:

• Thermal criteria for the winter season
• Thermal criteria for the summer season
• Air quality
• Ventilation
• Humidity
• Lighting
• Noise

Indicators based on indoor environment calculations

To evaluate the category of the indoor environment of a building, a method based on computer simulation for thermal evaluation is used, according to the prEN 15265 and prEN 15255 standards, using computer programs that allow the calculation of various indoor environment indicators for different objectives.

Indicators based on measurements

The estimation of indoor air quality and the ventilation of the building is carried out through a representative sample taken in the different units in which the air is treated and in different areas of the building. There are two different methods to carry out this evaluation: through the ventilation method and through the air quality method.

The first takes into account the air flows measured within the ducts. The second evaluates the air quality in those buildings where the main source of air pollution comes from people. To do this, it measures the concentration of carbon dioxide, both when the building is fully occupied and by taking representative samples of the air from a room or through measurements of the concentration of carbon dioxide present in the air expelled through the extraction vents.

Questionnaires

The subjective reaction of the people inhabiting the buildings can likewise be used to carry out an evaluation of the indoor environment. In these questionnaires (conducted with more or less frequency), questions related to the general acceptance of the indoor environment, the thermal sensation of the occupants, and the air quality perceived by each of them should be asked.