🌀 Blower Door Airtightness Test
In short
Measurement of building air permeability by fan pressurization method (Blower Door). The test is performed according to PN-EN ISO 9972:2015; Measurement range Δp: 10–60 Pa (min. 5 steps). The procedure comprises 7 steps (about 1 h 55 min–2 h 25 min in total); it is used for: Energy certification of new buildings, Quality control of building execution (envelope airtightness), Passive House standard — requirement n₅₀ ≤ 0.6 h⁻¹.
At a glance
- Standard: PN-EN ISO 9972:2015
- Category: Construction
- Procedure steps: 7
- Total time of stages: 1 h 55 min–2 h 25 min
- Test pressure: 50 Pa (standard)
- Measurement range Δp: 10–60 Pa (min. 5 steps)
- Requirement (mech. vent.): n₅₀ ≤ 3.0 h⁻¹
Overview
Blower Door test is standard method for assessing building air tightness. Involves mounting fan in door opening and creating underpressure/overpressure of 50 Pa — airflow required to maintain this pressure difference is measured.
Result: n₅₀ [h⁻¹] — air change rate at 50 Pa. Allowable values: traditional construction n₅₀ ≤ 3.0 h⁻¹ (with mechanical ventilation) or ≤ 1.5 h⁻¹ (passive buildings), ≤ 0.6 h⁻¹ (Passive House standard).
Testing is required: for buildings with NFOŚiGW subsidy (Clean Air), energy certification, NF15/NF40 standards, Passive House, BGK subsidies. Air leaks generate heat loss (even 30–50% in old buildings) and moisture problems (condensation).
Method principle
Calibrated fan (Blower Door) is mounted in door opening using adjustable frame and airtight membrane. Fan creates underpressure (or overpressure) in building.
Measurement performed in 10 pressure steps (10–60 Pa) during depressurization and pressurization. Airflow Q [m³/h] and pressure difference Δp [Pa] are recorded. Data approximated by curve Q = Cₙ × Δpⁿ. At 50 Pa, Q₅₀ is read.
n₅₀ = Q₅₀ / V [h⁻¹]
where V — heated zone volume [m³].
Applications
- Energy certification of new buildings
- Quality control of building execution (envelope airtightness)
- Passive House standard — requirement n₅₀ ≤ 0.6 h⁻¹
- NFOŚiGW "Clean Air" subsidies — required test
- Heat loss diagnostics in existing buildings
- Air leak localization (combined with thermography or smoke)
- Acceptance of residential and public buildings
Key parameters
| Parameter | Value |
|---|---|
| Test pressure | 50 Pa (standard) |
| Measurement range Δp | 10–60 Pa (min. 5 steps) |
| Requirement (mech. vent.) | n₅₀ ≤ 3.0 h⁻¹ |
| Requirement (passive building) | n₅₀ ≤ 0.6 h⁻¹ |
| Measurement uncertainty | ±5–10% |
| Method per standard | A (in use) / B (building envelope) |
Standard
- Standard number
- PN-EN ISO 9972:2015
- Title (PL)
- Cieplne właściwości użytkowe budynków — Określanie przepuszczalności powietrznej budynków — Metoda pomiaru ciśnieniowego z użyciem wentylatora
- Title (EN)
- Thermal performance of buildings — Determination of air permeability of buildings — Fan pressurization method
Step-by-step procedure
-
Building preparation
Close external windows and doors. Open internal doors. Seal mechanical ventilation ducts (method B) or leave natural (method A). Turn off heating devices with chimneys.
-
Fan mounting
Mount frame in external door opening. Stretch membrane. Install fan. Connect manometer — internal and external tube (through membrane).
-
Zero measurement (baseline)
Measure natural building pressure (wind, chimney). Record Δp₀ — should be <5 Pa. If >5 Pa — weather conditions unsuitable.
-
Depressurization test
Start fan. Create underpressure from 60 Pa to 10 Pa in 10 steps. At each step: 10 s stabilization + 10 s measurement. Software records automatically.
-
Pressurization test
Reverse fan (or rotation). Repeat sequence 10–60 Pa at overpressure. Record Q and Δp.
-
Result analysis
Software calculates: Q₅₀, n₅₀, C, n (from regression). Check R² ≥ 0.98. Calculate average from depressurization and pressurization.
-
Air leak localization (option)
At maintained underpressure 50 Pa use smoke generator or thermal camera to locate air leaks (windows, installation penetrations, connections).
Required equipment and apparatus
| Equipment | Example | Indicative price |
|---|---|---|
| Blower Door set | Minneapolis Blower Door Model 4, Retrotec 6100 | 15,000–35,000 PLN |
| Differential manometer | DG-1000, APT Energy Guardian, accuracy ±1 Pa | 3,000–8,000 PLN |
| Adjustable frame + membrane | Fits door openings 600–1200 mm | included in set |
| Laptop with software | TECTITE Express, FanTestic, automatic measurement sequences | 2,000–5,000 PLN (license) |
| Smoke generator (option) | Smoke pencil, Regin S220 — air leak localization | 200–2,000 PLN |
Health and safety (OHS)
- Operating fan — do not insert hands in propeller
- Underpressure in building — doors may slam violently
- Smoke generator — do not inhale, ventilate after testing
- Work in heating season — operator thermal comfort
Frequently asked questions
Which standard describes this test?
The test is performed according to PN-EN ISO 9972:2015 — “Thermal performance of buildings — Determination of air permeability of buildings — Fan pressurization method”.
How does this method work?
Calibrated fan (Blower Door) is mounted in door opening using adjustable frame and airtight membrane. Fan creates underpressure (or overpressure) in building.
What is the measuring range and accuracy?
Test pressure: 50 Pa (standard); Measurement range Δp: 10–60 Pa (min. 5 steps); Requirement (mech. vent.): n₅₀ ≤ 3.0 h⁻¹; Requirement (passive building): n₅₀ ≤ 0.6 h⁻¹.
How long does the test take?
The times given for the individual stages add up to approximately 1 h 55 min–2 h 25 min. The procedure comprises 7 steps.
What equipment is required?
Blower Door set, Differential manometer, Adjustable frame + membrane, Laptop with software, Smoke generator (option). Indicative cost of the core instrument (Blower Door set): 15,000–35,000 PLN.
Where is this test used?
Energy certification of new buildings; Quality control of building execution (envelope airtightness); Passive House standard — requirement n₅₀ ≤ 0.6 h⁻¹; NFOŚiGW "Clean Air" subsidies — required test; Heat loss diagnostics in existing buildings; Air leak localization (combined with thermography or smoke); Acceptance of residential and public buildings.
What safety precautions apply?
Operating fan — do not insert hands in propeller; Underpressure in building — doors may slam violently; Smoke generator — do not inhale, ventilate after testing; Work in heating season — operator thermal comfort.
Which laboratory can perform this test?
The test is performed by laboratories accredited to ISO/IEC 17025. On LabCoda you can find them by the standard number PN-EN ISO 9972.