As the demand for energy-efficient, sustainable buildings continues to grow, PassivHaus certification has emerged as the gold standard for energy performance. One of the critical components of achieving this certification is PassivHaus air testing, which ensures that the building envelope is airtight, minimising heat loss and maximising energy savings.

At Melin, we specialise in PassivHaus air testing of all building types, whether you’re constructing a new build dwelling or retrofitting an existing property, a large social housing development or a new school or warehouse, we are here to support you through the strict airtightness requirements needed for certification. Whatever your exciting project may be, our experienced engineers can guide you through the testing process and help you achieve the highest levels of building performance.

What is PassivHaus?

PassivHaus is a rigorous energy standard developed in Germany that focuses on reducing the need for energy-intensive heating and cooling systems by ensuring that buildings are highly insulated and airtight. The PassivHaus standard is widely recognised for creating buildings that are both energy-efficient and comfortable, reducing energy consumption by up to 90% compared to traditional buildings.

To achieve this, PassivHaus buildings must meet strict requirements, including a maximum air change rate of 0.6 air changes per hour (ACH) at 50 Pascals of pressure (ACH50). This standard ensures that very little air escapes through the building’s fabric, significantly reducing energy loss.

What is PassivHaus Air Testing?

PassivHaus air testing, also known as a blower door test, measures the amount of air leakage in a building's envelope. This testing is critical for ensuring that the building meets the airtightness criteria of the PassivHaus standard.

During the test, a fully calibrated, appropriately sized fan is used to pressurise and depressurise the building, allowing our technicians to measure the rate of air leakage. The result is expressed in terms of air changes per hour (ACH), with the aim to keep this number as low as possible.

Achieving the PassivHaus standard of 0.6 ACH50 and below is a very stringent requirement, and our highly skilled engineers are here to help you reach it with our customary exquisite site manner and efficiency.

PassivHaus Air Testing – The Stages

Conducting airtightness tests at two key stages helps ensure that issues are detected and resolved early, improving the likelihood that the building will pass the final test. It also helps avoid delays in achieving certification, which can be costly for both developers and clients.  It is not uncommon for developers to insist on up to 4 air tests due to the importance and significance of the air test in achieving overall building PassivHaus certification.

Preliminary or Mid-Construction Airtightness Test (First Fix)

This test is conducted during the construction phase, before all the internal finishes are complete. It is typically done after the building's main structural elements have been installed, but before plastering or interior finishes are applied.  Usually carried out once timber frame is erected, openings sealed, and air tightness barrier installed. This is often referred to as the "first fix" stage, where services like electrical wiring and plumbing have been fitted, but finishing details have not yet been added.

Why it’s done:

• To identify any significant air leaks that can be addressed before the build is finalized.
• Allows for corrections to be made early, preventing costly rework later.
• Provides feedback to ensure that the construction is on track to meet the PassivHaus standard of 0.6 ACH50 or below.

What happens during this test:

• The building is sealed as much as possible.
• A blower door test is conducted to assess the airtightness level.
• Smoke diagnosis or thermal imaging may be used to detect any leaks or problematic areas that need sealing.

2. Final Airtightness Test (Completion Stage)

The final airtightness test is conducted after the construction has been completed, but before the building is fully occupied. This is the critical test used for PassivHaus certification and is sometimes referred to as the "handover" or "completion" test.

Why it’s done:

• To verify that the building meets the stringent airtightness requirement of the PassivHaus standard (≤ 0.6 air changes per hour at 50 Pascals).
• It confirms that all remedial measures have been successful, and the building is ready for certification.
• It ensures that the building will perform as designed in terms of energy efficiency, comfort, and sustainability.

What happens during this test:

• The building is fully sealed and pressurized using the blower door test.
• The air leakage rate is measured to confirm it meets PassivHaus criteria.
• A detailed report is generated, which is submitted as part of the PassivHaus certification documentation.

Optional Retesting (If Required)

In some cases, after either the preliminary or final test, if the building does not meet the required airtightness level, remedial work can be done, and a retest can be performed. At Melin, we offer same-day retesting to ensure any issues can be addressed without causing significant delays to your project timeline.

Why is Airtightness Crucial for PassivHaus?

Airtightness is one of the cornerstones of the PassivHaus standard because it directly affects the building's ability to retain heat, prevent drafts, and maintain comfortable indoor temperatures year-round. The benefits of airtightness in a PassivHaus building include:

1. Reduced Energy Demand: By minimizing air leakage, the building requires significantly less energy for heating and cooling, leading to major savings on energy bills.
2. Improved Comfort: Airtight buildings are free from drafts and cold spots, providing a consistently comfortable indoor environment.
3. Enhanced Indoor Air Quality: Airtightness, combined with proper ventilation systems, ensures that air is filtered, reducing pollutants, allergens, and moisture-related issues such as mold.
4. Sustainability: PassivHaus buildings contribute to a lower carbon footprint by dramatically reducing the energy required for day-to-day operations.

Our PassivHaus Air Testing Process

At Melin, we follow a thorough, step-by-step approach to ensure that your building meets the stringent airtightness standards set by PassivHaus:

1. Pre-Test Consultation: We start by reviewing your building design and construction plans to identify any potential areas that might pose airtightness challenges. Our experts provide advice on how to improve airtightness before the testing phase.
2. Blower Door Test: Our team conducts the blower door test using state-of-the-art, fully calibrated equipment. This test pressurizes and depressurizes the building to measure the exact rate of air leakage. 
3. Leak Detection (if needed): If the building does not meet the required air change rate, we can perform additional diagnostic tests such as smoke diagnosis or thermal imaging to locate specific air leaks. This allows the construction team to address any issues swiftly and precisely.
4. Same-Day Retesting: Once remedial measures are implemented, we offer same-day retesting to ensure that the building meets PassivHaus airtightness standards without delaying your project timeline.
5. Certification: After a successful test, we provide a detailed report and specific  PassivHaus Air test Certificate, including the air change rate and all necessary documentation to support your PassivHaus certification application.

Why Choose Us for PassivHaus Air Testing?

At Melin, we bring expertise, reliability, and cutting-edge technology to every PassivHaus air test we conduct. Here’s why clients trust us:

• Nationwide Coverage: We offer our PassivHaus air testing services across the UK, no matter where your project is located.
• ATTMA-Accredited Engineers: Our fully accredited ATTMA Level 1, Level 2, and PassivHaus test engineers have extensive experience in airtightness testing for a wide range of buildings.
• Advanced Equipment: We use the latest calibrated blower door testing equipment and diagnostic tools, ensuring accurate, reliable results every time.
• Flexible Scheduling: We understand that construction timelines are tight, so we offer flexible scheduling, quick turnaround times, and out-of-hours testing if required.
• Competitive Pricing: Our pricing is competitive, and we offer additional discounts for multi-unit developments and when PassivHaus testing is combined with our other services such as Part F Vent testing, SAP and Sound testing etc.

Additional Services for PassivHaus Projects

In addition to airtightness testing, Melin provides a range of complementary services designed to support PassivHaus projects, including:

• Thermal Imaging: Detect thermal bridges or areas of heat loss, ensuring your building’s thermal envelope is performing at the highest level.
• SAP Calculations: Our SAP assessments ensure that your building meets energy and carbon compliance requirements.
• Ventilation Testing (Part F): We offer ventilation testing to ensure that mechanical ventilation systems are operating effectively, which is essential for maintaining indoor air quality in airtight buildings.

Get in Touch……………

If you’re working on a PassivHaus project and need a professional team with market leading knowledge and expertise, look no further than Melin. Our team is dedicated to helping you achieve the airtightness levels required for PassivHaus certification, ensuring your building is both energy-efficient and comfortable.

Contact us today to schedule your PassivHaus air test or learn more about how we can support your project!