Ventilation ducts: regulations and characteristics

Below, we provide an overview of the current regulations related to the ducts of your ventilation system. According to the CTE DB HS 3, Indoor air quality, the section must be uniform and not present obstacles. Air-tight, they must have a finish that protects against dirt and be accessible for registering and cleaning at their ends. To prevent the appearance of condensations, they will be thermally insulated.

For both hybrid ventilation and mechanical ventilation, if the duct passes through fire sector separating elements, the provisions established in section SI1 of the CTE DB SI, Fire Safety must be considered: “The fire resistance required for the fire compartmentalization elements must be maintained at the points where these elements are crossed by facility elements, such as cables, pipes, ducts, ventilation ducts, etc., excluding penetrations whose passage section does not exceed 50 cm².”

In the case of hybrid ventilation, the extraction ducts must have a hybrid fan at their upper end, for the extraction of air. Collective ducts can serve, at most, six floors. Furthermore, those on the last two floors must be individual.

If we have a mechanical ventilation, each of the extraction ducts must have a mechanical extractor at its end (except for the kitchen ventilation duct). Multiple ducts are allowed to share the same extractor (except for parking ducts).

Types of ducts and technical characteristics

There are several types of ducts available in the market:

• Insulating material (expanded polyethylene)
• Metal (galvanized steel)
• Thermoplastics

The expanded polyethylene ducts and accessories are used for air distribution systems in ventilation when it is necessary to reduce heat losses or prevent condensation in the ducts. Ducts and accessories that are easy to install and maintain should be chosen.

Manufactured in EPE (Expanded Polyethylene), it should be ensured that those with the following technical characteristics are installed:

• A surface transmission coefficient of 0.041 W/m.k (EN 12667)
• A thermal resistance (R) of 0.56 m2 k/w
• A minimum temperature range of -30°C and maximum of + 60°C
• Fire classification Class B1 (DIN 4102)
• Air tightness Class C (EN 12237:2003).

The galvanized steel ducts and accessories are made from durable galvanized steel. It should be ensured that those with the following technical characteristics are installed:

• That guarantee a Class D tightness according to EN 12237.
• That are easy and quick to install. There are patented systems on the market with fixing grooves without joints or putty. Thanks to the Click system, they are assembled without tools.
• That guarantee maximum energy efficiency of the ventilation systems.
• The galvanized sheet must have a fire resistance of two hours at a temperature of 400°C.
• A working pressure that ranges from -5000 Pa to + 3000 Pa.

The thermoplastic ducts, capable of eliminating up to 99% of the bacteria present in the ventilation network (thus providing permanent protection against external contaminants). It should be ensured that those complying with the following technical characteristics are installed:

• Fire resistance according to UNE EN 13501-1:2002: Self-extinguishing B-S3, d0
• Maximum supported temperature: + 80°C
• Thermal conductivity: 0.0544 - 0.0662 W/m.k
• Tightness according to UNE EN 12273: Class D
• Duct properties: Antistatic and Antibacterial

All types, subjected to testing, must withstand the test of time and guarantee a lifespan of more than 20 years.