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Performance Data:-Blower Door Test

Updated: Aug 29, 2023

While we know our buildings out-perform ‘Minimum Code Standard’ houses, proof of concept can be verified by on-site testing and data capture that accurately measures a project’s as-built performance.


For residential properties, the World Health Organization recommends the air changes per hour should be between 4 and 5. This number is recommended for homes that do not use a ventilation system. Official data in NZ - points to on average, 6.5 air changes per hour for standard new buildings, and 8.5 air changes per hour for structures built between 1960 and 1980. That's a lot of air, heat and potentially vapour leakage!


Airtightness is an important factor in building thermal performance and comfort (in conjunction with insulation and other ‘fabric first’ considerations), and it is also a key indicator of construction quality.


A blower door is a machine used to measure the airtightness of buildings.


The machine comprises of an aluminium frame, canvas ‘door’ and an electrical fan. Air hoses are connected to the manometer (pressure gauge) fan to measure the differential pressure across the building envelope.


The pressure gauge measures the volume of air-flow through the fan at certain differential pressures (usually 10 pressure intervals between 10Pa and 75Pa) and this information is converted to air changes per hour (ach50, n50), or air permeability (QE50).


At Vitruvion we understand the importance, interaction and interdependence of breathability and airtightness. These relationships create airtight buildings with a healthy indoor environment that are efficient to run, while providing a robust and durable, ‘breathable’ thermal envelope.



See our Article about ventilation



Blower Door Text on site
A blower door test rig in action


Blower door testing provided on this project by: Enveloped NZ






The Passive House requirements for airtightness is less than 0.649 air changes per hour at 50 Pascal.


More about Passive House




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