A blower door test is a diagnostic procedure used to measure the airtightness of a building envelope. It is a critical tool in assessing energy efficiency, identifying air leakage paths, and ensuring compliance with UK Building Regulations (particularly Part L: Conservation of Fuel and Power). The test is commonly used in new builds, retrofits, and residential extensions to validate ventilation strategies and thermal performance.
A blower door test involves mounting a calibrated fan in an exterior doorway, which depressurises or pressurises the building to measure air leakage. The results are quantified as air changes per hour (ACH) at a reference pressure (typically 50 Pascals, written as ACH₅₀). Lower ACH₅₀ values indicate better airtightness.
Explanation: #
- Purpose:
- Identifies uncontrolled air leakage, which impacts energy efficiency, indoor air quality, and thermal comfort.
- Validates compliance with Part L1B (Existing Dwellings) and Part L1A (New Dwellings) of the Building Regulations.
- Supports Passivhaus certification, where airtightness thresholds are stricter (≤ 0.6 ACH₅₀).
- Procedure:
- A fan is sealed into an external door frame.
- The building is depressurised to 50 Pa while airflow rates are measured.
- Infrared thermography or smoke pencils may be used to locate leaks.
- Real-World Applications:
- Retrofits: Detects gaps around windows, loft hatches, or service penetrations.
- New Builds: Ensures compliance with Approved Document L (2021 edition).
- Ventilation Design: Informs Mechanical Ventilation with Heat Recovery (MVHR) system sizing.
Synonyms: #
- Airtightness Test (commonly used interchangeably in UK construction).
- Air Permeability Test (though technically distinct, often conflated in practice).
Related Terms: #
- Air Permeability – Measured in m³/(h·m²) @ 50 Pa, the air leakage per square metre of building envelope.
- ACH₅₀ – Air Changes per Hour at 50 Pascals, the standard metric for airtightness.
- Part L (Building Regulations) – Governs energy efficiency requirements in England and Wales.
- MVHR (Mechanical Ventilation with Heat Recovery) – A system often required in airtight homes to maintain air quality.
- Thermal Bypass – Heat loss caused by air leakage, addressed via blower door testing.
- Infiltration Rate – Uncontrolled air leakage into a building.
- Passivhaus Standard – A rigorous energy efficiency standard requiring exceptional airtightness.