Multizone ventilation systems in the tertiary sector

RITE requirements regarding ventilation in office buildings

Except for residential buildings, other types of buildings including office buildings must comply with the following requirements, as stated in the RITE (Regulations on Thermal Installations in Buildings).

_ Buildings must have a ventilation system to bring in a sufficient flow of external air that prevents the formation of high concentrations of pollutants in different rooms where human activity takes place.

_ Depending on the use of the building or premises, the category of indoor air (IDA) that must be achieved will be at least the following:

• IDA 1 (optimal air quality), in hospitals, clinics, laboratories, and daycare centers.
• IDA 2 (good air quality), in offices, nursing homes, student residences, reading rooms, museums, classrooms, and indoor swimming pools.
• IDA 3 (medium air quality), in commercial buildings, cinemas, theaters, auditoriums, hotel rooms, restaurants, cafes, banquet halls, and gyms.
• IDA 4 (low air quality)

_ The minimum flow rate of exterior ventilation air will be calculated using one of the five methods indicated below:

1. Indirect method of exterior air flow per person
2. Direct method by perceived air quality
3. Direct method by concentration of CO2
4. Direct method of air flow per unit area
5. Dilution method

_ In the case of using the method number 4, in an office building, the air inside will be of good quality (IDA 2). The occupation in this type of building can be considered as 10 m2/person. Following RITE requirements, when calculating the ventilation system, it must supply 12.5 dm3/s per person. Therefore, the supplied flow rate will be 1.25 dm3/s per m2 of usable area.

Demand controlled ventilation DCV. Multizone spaces

Maintaining the ventilation systems at their maximum flow rate constantly implies high energy consumption, both from the fans and the necessary energy to heat or cool the indoor air. Therefore, it is advisable for ventilation systems to adjust to the occupancy or the level of indoor pollutants (CO2, temperature, relative humidity, etc.), given that most office spaces, meeting rooms, shops, etc., do not exceed 60% occupancy throughout the day.

The demand controlled ventilation systems (DCV) are intelligent ventilation systems composed of low-energy consumption fans and electronic elements such as speed controllers, frequency converters, presence detectors, CO2 sensors, motorized dampers, and dual flow suction terminals. These elements ensure that only the necessary energy is used at all times to guarantee proper ventilation of the premises based on their pollution level.

The DCV can be applied in monozone or multizone spaces:

• Monozone: the space to be ventilated consists of a single open area, without partitions, that requires homogeneous ventilation treatment (open offices, shops, etc.).
• Multizone: the space to be ventilated consists of several compartmentalized areas, requiring individualized ventilation treatments (offices with individual offices, meeting rooms, etc.).