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Purpose of the work
As a consultant and operator of Blower Door testing, one often wonders about the durability of materials over a building's lifetime. It is not uncommon to see products where tapes and sealing materials fail after a very short period. This raises the question of whether airtightness can truly be considered a quality parameter in low-energy construction.
Method of approach
Revisit Passive House after 16 years and conduct a Blower Door test with the same setup to see if there has been a change in the building's tightness after 16 years.
Content of the contribution
Back in 2008, I was fortunate to be part of a project where the contractor had a strong focus on details and the quality of materials. The final test showed an n50 value of 0.09 h ¹, which at the time set the record for the world's tightest Passive House.
In December 2024, I was lucky to revisit this house and conduct a new Blower Door test. The initial test in 2024 measured an n50 value of 0.12 h ¹. We inspected all windows and doors, adjusted them to ensure they closed properly, and were then able to achieve the same value as in 2008.
It is gratifying to see that when robust and high-quality materials are used, the achieved airtightness is maintained over many years.
For me, it was also interesting to hear about the excellent indoor climate achieved with a very tight building envelope and controlled ventilation. Passive Houses are not very widespread in Denmark, and in the NZEB buildings we do have, we often see challenges with overheating during the summer period. Overheating was not an issue in this house, and I attribute much of the credit to the Passive House concept, where the design is strongly guided by the standard.
Conducting Blower Door tests on very airtight buildings is a challenge.
I do not fully understand the reason behind this challenge, but I have observed that our standard software struggles to stabilize at a measurement point. It continuously fluctuates, overshooting and then undershooting, which can go on indefinitely.
The solution I used was to completely disable the software's automatic control, preventing the fan from self-regulating. Instead, I manually adjusted the fan speed and waited for the pressure to stabilize. Once fluctuations became minimal, I manually triggered the measurement.
I recommend increasing the number of measurements per point to a minimum of 500 samples, preferably 1000 (in Retrotec, the measurement time is extended).
By following this process, the test can be completed without issues and takes only slightly longer than an automatic measurement conducted on a more standard house.
Results and assessment of their significance
It was possible to measure the same result after adjusting doors and opening windows.
Conclusions
It must be concluded that if you use high-quality, solid materials, the building's tightness will also be maintained.
For further information please contact Lars Due at: lars@isolink.dk