Zirkoninpolku 2

KLA Talotekniikka Oy commissioned an inspection of the airtightness of ventilation ducts in the Kivistö Residential Block new construction project. The airtightness of the ducts had to comply with the Finnish Building Code, Section D2/2012, regulations, and guidelines.

Test procedure and airtightness requirements

• Encased supply and exhaust units were pressure tested at 500 Pa, with a maximum allowable leakage of 1.8 l/s·m² (Class A).

• Class B ducts were pressure tested at 400 Pa, with a maximum allowable leakage of 0.45 l/s·m² (Class B).

• Class C ducts were pressure tested at 500 Pa, with a maximum allowable leakage of 0.18 l/s·m² (Class C).

The inspection followed SFS 4699 standards and D2 section 3.7.1 guidelines. According to regulations, a ventilation system is considered sufficiently airtight when it meets at least airtightness Class B.

Airtightness classifications:

Class A:

✔ Ducts visible in ventilated rooms

✔ Pressure difference to the room < 150 Pa

Class B:

✔ Ducts outside ventilated spaces

✔ Covered ducts inside ventilated spaces

✔ Ducts in ventilated spaces where the pressure difference > 150 Pa

Class C:

✔ Used based on case-specific considerations depending on:

• Ventilation system functionality

• Building pressure conditions

• Indoor air purity

• Noise levels

Class D:

✔ Exhaust ducts from contamination Classes 1 and 2 may be overpressurized within the building, provided that the ductwork meets Class C requirements. This is typically achieved with Class D airtightness.

Class K:

✔ Ventilation machines

✔ Chambers

✔ Machine rooms

Inspection scope and methodology

Normally, the entire duct system is tested for airtightness. However, in this project, the duct system was built from type-approved components, allowing for spot-check testing as per regulations.

According to regulations:

• If the component airtightness matches the required duct airtightness, 20% of the system must be tested.

• If the component airtightness exceeds the required duct airtightness, 10% of the system must be tested.

For this project, the inspection covered 20% of the surface area of main ducts located outside ventilated spaces, starting from the ventilation unit.