Blower Door Test: How we guarantee airtightness in a Passivhaus villa

On the Costa Blanca, wind and humidity are a constant. In traditional construction, these elements seep through multiple crevices and roller blind boxes, sending climate control costs soaring. For this reason, in a Passivhaus home, energy efficiency does not depend solely on thermal insulation. The airtightness of the building envelope is another fundamental aspect to achieve a high-performance building.

To verify that this seal is perfect, we do not rely on estimates: we use precision technology. To objectively measure the air infiltrations of a home and verify if it meets the required levels, the Blower Door test is performed.

What does the Blower Door Test consist of?

The test is as visual as it is effective. A watertight frame with a powerful fan is installed in one of the home's exterior openings (usually the main door). This equipment generates a pressure difference between the interior and exterior, typically 50 Pascals.

While this pressure is maintained, the sensors measure the airflow required to compensate for the infiltrations occurring through the envelope. Furthermore, during the test, millimeter-sized leaks can be located in key areas such as window perimeters, utility penetrations, or junctions between the facade and the roof, allowing them to be sealed immediately.

The n50 value: Passivhaus vs. traditional homes

One of the main results of the test is the n50 value, which indicates how many times per hour the air volume of the home is renewed due to infiltrations when there is a pressure difference of 50 Pa.

In the case of the Passivhaus standard, the home must achieve a result of n50 ≤ 0.6 air changes per hour. To put it into perspective, a traditional newly built home in Spain usually ranges between 5 and 7 air changes per hour. In other words, the demands of this standard compel us to build houses up to 10 times more airtight than conventional ones, guaranteeing total control over the indoor temperature and blocking exterior humidity.

The Ca La Mer case: A challenge overcome at Bersife

At Bersife, airtightness is not theory; it's real data. In our Ca La Mer project (a certified Passivhaus villa in Xàbia), we carried out exhaustive monitoring that demonstrates our level of execution.

• First test (2023): During the construction phase, with the structure and main seals completed, the home achieved a spectacular 0.38 h⁻¹. A result that positively shatters the official limit of 0.6.
• Second test (October 2024): With the house completely finished, we carried out a final measurement with a massive challenge: a fireplace had been built. In bioclimatic architecture, a fireplace is the greatest enemy of airtightness, as it is literally an escape route for air to the outside. Despite this handicap, Ca La Mer achieved a result of 1.30 h⁻¹.

Managing to keep the house at a highly energy-efficient level (the "Very Good" range is between 0.6 and 1.5 h⁻¹) while having an integrated fireplace is a true technical achievement. It proves that, with flawless execution, it is possible to combine maximum traditional comfort with the efficiency standards of the future.

‍

Frequently Asked Questions (FAQ)

1. Why is airtightness so important in a Passivhaus home?

‍Good airtightness allows for the control of unwanted air infiltrations and helps the thermal envelope function as a continuous system. This reduces energy losses and facilitates the operation of the mechanical ventilation system with heat recovery.

2. What happens if the Blower Door Test detects leaks?

‍The great advantage of this test is that it allows us to pinpoint exactly where infiltrations occur (such as in joints, windows, or doors). Once located, these areas can be sealed and corrected, followed by a new test to verify the improvement achieved.

3. Can a fireplace be installed in a high-efficiency home?

‍Yes, but it requires extreme construction precision. Fireplaces facilitate air leakage, which penalizes airtightness. However, as we demonstrated in our Ca La Mer villa, with good design and meticulous insulation, outstanding airtightness results can be achieved even with a fireplace.