Build Comply
Air Tightness Testing
Air Tightness Testing
Retrofit, Domestic, Residential, Commercial, Plenums, Smoke Shafts.
Are you looking for Air Tightness Testing?
To comply with Approved Document Part L1 and L2 of the Building Regulations, ensuring your building is air tight is essential.
Likewise, this too is paramount in a retrofit project.
Air Tightness Testing, also known as air infiltration, air permeability, air pressure or air leakage testing is required.
Air Testing assesses the level of conditioned (heated or cooled) air leakage. Basically this is known as infiltration, evidently felt as uncontrolled ventilation. By ensuring that the building meets or exceeds the air permeability rating specified in a design stage SAP or SBEM Calculation, Air Testing guarantees energy efficiency and performance.
Our testing is routinely carried out using a blower door. Following the methodology to ATTMA standards in line with CIBSE TM23 or ISO 9972:2015.
Are you ready for your Air Tightness Test?
Click here to find our Air Permeability Site Status Checklist covering common leakage area preparation and recommended sealing
Air Testing Process
Our air tightness testing service is designed to be efficient, informative, and fully compliant with building regulations.
All our engineers are ATTMA accredited experts with over ten years real world on-site experience. We cover London, Southeast, East Anglia and the Home Counties with partners across the remainder of the UK mainland.
Here’s a step-by-step overview of what to expect:
1. Initial Enquiry and Fee Proposal
We begin by offering a price based on the size and location of your building. For a formal quote, we’ll request PDF drawings, and a copy of the design-stage SAP assessment.
Our prices for a single unit project start from £145+VAT which includes a 1-hour visit to site, 1 (no.) test and a short formal report/ ATTMA certificate.
At this stage, we can also discuss potential test dates to suit your programme. Our typical lead time is 5–10 working days on delivery, but we can often accommodate single tests at shorter notice.
We aim to issue formal fee proposals within 24-hours of receipt of all required information.
2. Booking and Preparation
Once a date is confirmed, our engineer will contact you ahead of the test to:
- Walk you through the preparation process including going over the Air Permeability Site Status Checklist.
- Confirm the air permeability target from your SAP (Standard Assessment Procedure) energy model.
- Agree on timings for the day.
This preparation is crucial, as the air test result directly impacts your building’s energy efficiency rating and is a key requirement for building control sign-off.
3. On the Day of Testing
For smaller homes and flats, we typically handle temporary sealing upon arrival. The testing process includes:
- Installing a calibrated fan system in an external doorway.
- Creating a pressure difference between the inside and outside of the building.
- Measuring the airflow required to maintain this pressure, which reveals how much air is escaping through the building fabric.
If the building doesn’t meet its target on the first attempt, we can use our equipment to identify leakage paths. If these can be addressed quickly, we’re often able to retest the same day.
Note: Achieving tighter air permeability targets may require design-stage consideration, including the use of membranes and tapes to maintain a continuous air barrier. See our FAQs for more guidance.
4. Results and Certification
We provide immediate feedback on the test outcome. If the building passes:
- We issue an ATTMA (Air Tightness Testing & Measurement Association) certificate within 24 hours — or the same day upon request.
- This certificate is accepted by building control and can be used for Part L compliance and energy performance documentation.
Note: Our standard terms on conditions state that cleared payment is required before the release of any final reporting and/ or certification. Read more here.
Have a project in mind? Let’s get to work.
What is a Air Tightness Test?
Air tightness testing (also known as air permeability, air leakage, infiltration or air pressure testing) is a method used to measure how much air escapes through gaps and cracks in a building’s envelope. In simple terms, it’s a check-up for your building’s energy efficiency.
Why does Air Testing matter?
A more airtight building means:
- Lower energy bills due to reduced heat loss.
- Improved comfort with fewer draughts and cold spots.
- Better compliance with building regulations and SAP assessments.
- Reduced carbon footprint and improved sustainability.
However, airtightness must be balanced with proper ventilation to maintain healthy indoor air quality — and that’s where testing helps strike the right balance.
How does the Air Test work?
At Building Compliance Testing, a single engineer carries out the test using a UKAS-calibrated blower door system. This system includes:
- A fan mounted within a canvas panel, installed in an external door or window.
- A fan speed controller to regulate airflow.
- A multi-channel manometer connected via tubes to measure pressure differences.
- Specialised software that calculates the air permeability based on the data collected.
The fan creates a pressure difference between the inside and outside of the building. The amount of air required to maintain this pressure reveals how much air is leaking through the building fabric.
Other approval methods of compliance testing include the use of Low Pressure Pulse Test (LLP).
What to Expect During the Test?
- The test usually takes 20 minutes to 2 hours, depending on the building’s size, layout, and weather conditions.
- Other trades can typically remain on-site during testing, as long as external doors and windows are closed and internal doors are left open.
- If the building doesn’t meet its target on the first attempt, we can often identify leakage paths and, if addressed quickly, retest the same day.
Building Regulation Requirements
Air tightness testing is a legal requirement for new dwellings under Approved Document Part L1 of the Building Regulations in England. This document sets out the standards for the conservation of fuel and power in new homes and is a key part of ensuring buildings are energy efficient and environmentally responsible.
- Under Approved Document L1, all new build dwellings must undergo air tightness testing (also referred to as pressure testing) to demonstrate compliance.
- The test must achieve a design air permeability of 8 m³/h/m² or less at a pressure differential of 50 pascals
- This requirement ensures that buildings meet minimum energy performance standards and contribute to the UK’s broader carbon reduction goals.
Air tightness testing must be carried out in accordance with:
- ATTMA Technical Standard L1, which outlines the procedures and quality assurance for domestic buildings.
- BS EN ISO 9972:2015, the internationally recognised standard for determining air leakage in buildings.
- More recently, testing may also need to comply with the revised CIBSE TM23 methodology, particularly for more complex or non-standard buildings.
Achieving the required air permeability is not just about ticking a regulatory box — it directly impacts:
- Energy efficiency and running costs.
- Comfort and indoor air quality.
- Compliance with SAP assessments and overall building control approval.
ATTMA Competent Person Scheme
As expected, the equipment used for Air Permeability Testing is highly specialised and demands frequent and rigorous calibration to ensure precision. As a result, equipment from Building Compliance Testing is calibrated by a UKAS approved laboratory to guarantee accuracy during on-site tests. Our sister company, Building Compliance Testing is registered with ATTMA, subject to regular audits to uphold high standards and accuracy. If you’re uncertain about whether your project necessitates an Air Testing, we can provide guidance. We also offer complimentary, no-obligation quotes at highly competitive rates for projects of all sizes.
ATTMA has four different levels of testing which have varying degrees of required competence and changes in the test standard.
- Level 1 – A single dwellings and small non-dwellings up to 4000m2
- Level 2 – Larger and more complex buildings exceeding 4000m2
- Level 3 – Large, complex, high-rise, phased and zonal handover buildings
- PH – Those members authorised to carry out testing of Passivhaus buildings
Building Regulation Testing Package
At Building Compliance Testing we understand the importance of ensuring that your building meets all necessary compliance standards. That’s why we offer a comprehensive Compliance Package, designed to streamline the process and provide you with peace of mind.
Our Building Compliance Package includes
- Part L – Conservation of fuel and power
- Part G – sanitation, hot water safety and water efficiency
- Part F – Ventilation
- Part E – Resistance to sound
The Compliance Package Benefits
✅ SAP including EPC, Air Permeability Testing, Water Efficiency Calculation, Sound Insulation and Ventilation Testing at a fixed price
✅ Reduce procurement costs, gain project efficiencies and achieve full compliance
✅ One site visit, one engineer, all the expertise
✅ Test results within 24-hours