Regulations regarding ventilation requirements: RITE 2007 and C.T.E.- HS3

Regulations regarding ventilation: RITE and C.T.E. - HS3

The requirements for air quality differ depending on whether the application is the Technical Building Code or the RITE 2007 in a specific project. In the former, the requirement focuses on the renewal of air in indoor spaces, specifically the air flow (liters) that must be renewed every second. The RITE, on the other hand, performs a prior classification to define air quality as optimal (IDA 1), good (IDA 2), average (IDA 3), or low (IDA 4). This is because the RITE is applicable to multiple types of buildings, each employing a type of air classified based on its quality requirement:

• Clinics, hospitals, laboratories, and nurseries (IDA 1)
• Offices, residences, reading rooms, museums, classrooms, and swimming pools (IDA 2)
• Commercial buildings, cinemas, theaters, auditoriums, hotels, restaurants, cafes, gyms, and sports facilities (IDA 3)

Conversely, the Technical Building Code, in its Basic Document HS-3. "Indoor Air Quality", directly addresses the volume of air to be renewed in each type of space, as its application is limited to residential and parking buildings:

• Bedrooms: 5 l/s per occupant
• Living rooms and dining rooms: 3 l/s per occupant
• Bathrooms and washrooms: 15 l/s per local
• Kitchens: 2 l/s per m2 of usable area
• Storage rooms and common areas: 0.7 l/s per m2 of usable area
• Parking lots and garages: 120 l/s per parking space
• Waste storage rooms: 10 l/s per m2 of usable area

European Regulation: EN 15242 Standard

Regarding the European regulation governing ventilation systems, the EN 15242 standard was approved by Aenor in 2007 (UNE EN 15242:2007). This standard proposes methods for quantifying air flows for energy calculations and for assessing indoor air quality and summer comfort. In section 6.3, the methodology for calculating passive and hybrid ventilation is described. It thus provides proven tools to quantify the efficiency of "non-mechanical" ventilation, as passive ventilation consists of ducts and their components, without using electric fans. Hybrid ventilation combines mechanical ventilation with natural ventilation.

Using the formulas included in the EN 15242 standard, ventilation flows can be calculated based on meteorological values and window measurements. These formulas allow for the calculation of both the effect of cross natural ventilation and non-cross ventilation. Their equations are the same as those used to justify passive ventilation strategies in Passivhaus design (nearly zero-energy homes).

In section 7.4. "Summer Comfort", ventilation is recommended as a strategy to achieve a good level of comfort in summer. The disadvantage of mechanical ventilation is noted, as the positive effect of nighttime ventilation cooling can be neutralized by the excessive electrical consumption of fans. For natural ventilation, the importance of considering user habits and acoustic pollution is emphasized.

When defining a natural ventilation strategy in this standard, there is a focus on evaluating environmental factors of the rooms, both external and internal, such as:

• Emissions from construction materials, such as volatile organic compounds from cladding and construction materials.
• Microclimatic conditions: the climate of the area and the microclimate of the location influence both the behavior of a natural ventilation system and the performance of a mechanical ventilation system. When designing any of these systems, consideration must be given to the location of adjacent buildings, which may alter the wind action on our building. Regarding the location, factors such as acoustic pollution, which varies significantly from a rural to an urban environment, are especially important. An inadequate system, despite being properly sized, can result in poor indoor air quality if it does not adequately match its use in a specific location. The temperature differences between day and night should also be studied when designing the ventilation system.

Influence of construction materials on indoor air quality

The air tightness of buildings results in energy savings. However, it can be counterproductive for people's health by decreasing the indoor air quality. When passive measures are implemented in the building envelope, it is often not taken into account that these measures can worsen the air quality if the user does not ventilate frequently. Surface condensation can also appear if thermal bridges are not properly addressed. Generally, indoor air quality can be influenced by construction materials through two types of pollutants: chemical pollutants and biological pollutants.

Volatile organic compounds (VOCs) are chemical pollutants belonging to different families such as alcohols, aldehydes, glycol ethers, etc. They all share a common chemical base of carbon and the peculiarity of volatilizing into the air in gaseous state at room temperature at varying speeds. The health effects of prolonged exposure to VOCs are not yet fully understood. It is known, however, that 80% of these compounds found inside a building are irritating to mucous membranes and the eyes, and approximately 25% are suspected of being carcinogenic.

Biological pollutants may originate from air conditioning, ventilation, and cooling systems, as well as from a lack of maintenance of the installations. The proliferation of biological pollutants in the air we breathe depends on environmental conditions such as temperature, relative humidity, light, and air renewal. Low temperatures in a humid environment may favor the growth of microorganisms such as mold. Conversely, elevated temperatures favor the development of other types of microorganisms such as legionella, which is common in cooling systems that operate with water.