Certification Under Deadline Pressure: Failed Blower Door and Missing Commissioning
Three weeks before certification of an 8-unit passive-house project, the first blower-door test gives n50 = 0.85 h⁻¹. The contractor says the result is close enough and proposes to seal obvious gaps after the test without a retest. Ventilation has been installed but not balanced; the commissioning protocol is blank. Window installers used expanding PU foam at the frame-to-wall junction, and no airtight tapes or photos of the airtightness layer are available at the reveals. The PHPP still uses the design U-values and the planned ventilation efficiency; no as-built confirmation exists. The client wants the certificate for a green-loan deadline. The certifier has a site visit scheduled. The project is otherwise complete, and the design heating demand is 14.9 kWh/(m²a).
1. Can the certifier issue the certificate now? Explain which requirements are unmet and why the deadline does not change the answer.
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No. The airtightness criterion is n50 ≤ 0.6 h⁻¹, and 0.85 h⁻¹ fails it; close enough is not a certification category. The ventilation system is not balanced and the commissioning protocol is blank, so the certifier cannot verify the as-built ventilation performance. The PHPP still uses design values with no as-built confirmation of U-values, thermal bridges or ventilation efficiency, and the window junctions have PU foam with no airtight tape or photographic evidence. The design heating demand of 14.9 kWh/(m²a) leaves almost no margin for as-built deterioration, so the as-built model could easily exceed 15. A green-loan deadline is a commercial pressure, not a technical criterion. Issuing a certificate on this evidence would misrepresent the building and expose the certifier to justified challenge. The correct path is remediation, retest and a revised as-built PHPP before certification.
2. Set out a remediation and verification sequence that could still achieve certification.
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First, carry out a proper leak survey under depressurization, using smoke or thermal imaging, and seal the identified paths: window and door junctions, service penetrations, sole plates, party-wall joints and ceiling penetrations. Replace or supplement the PU foam at window junctions with a compatible airtight tape or membrane that is continuous with the wall airtight layer, and photograph each critical junction before closure. Retest the blower door after sealing; if the result is still above 0.6 h⁻¹, repeat the leak survey and retest rather than accepting the first value. In parallel, balance the ventilation system, complete the commissioning protocol, and record airflows, fan power, temperature ratio and bypass operation. Update the PHPP with as-built U-values, thermal bridges, window data and ventilation efficiency, and check all criteria including summer. The certifier should then review the new evidence and site inspection before issuing the certificate.
3. Which items in the evidence package are critical and which are secondary? Justify the priority.
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Critical items are the valid blower-door report at or below 0.6 h⁻¹, the completed ventilation commissioning record, and an as-built PHPP that demonstrates compliance with heating demand, heating load, PER, airtightness and summer criteria. Photographic evidence of the airtight layer at window and service penetrations is also critical because it verifies work that will be hidden. Manufacturer certificates and installation confirmations for windows, the heat-recovery unit and the thermal-bridge products support the PHPP entries. Secondary items include decorative finishes, landscaping and general snagging, which do not determine certification. The priority follows risk: airtightness and ventilation are performance-critical and currently undocumented, while cosmetic issues do not change the energy balance. If time is short, the team should fix and retest airtightness and commission ventilation first, then complete the as-built PHPP; paperwork for secondary items can follow without blocking the certificate.