Air permeability testing is mandatory for virtually all new-build and non-domestic construction in England and Wales. As a result, the test result feeds directly into the final SAP or SBEM calculation that demonstrates Part L compliance to Building Control. Our Hampshire projects range from single-unit self-builds in the New Forest to large commercial developments in Southampton city centre.
Air Tightness Testing Across Hampshire
Build Energy is based in Christchurch, placing us within easy reach of all major Hampshire locations. We regularly test projects in Southampton, Winchester, Basingstoke, Andover, Fareham, Gosport, Portsmouth, Eastleigh, Romsey and the New Forest district. In practice, most sites are accessible within 45–60 minutes, allowing us to accommodate short-notice bookings and combine testing with other compliance surveys where needed.
In addition, we cover both domestic and non-domestic buildings. Domestic tests include new-build houses and flats. Non-domestic projects include offices, schools, retail units and industrial buildings requiring compliance with Part L2 of the Building Regulations.
| Area | Typical Project Types | Approx. Drive Time |
|---|---|---|
| Southampton | City centre apartments, commercial | ~35 min |
| Winchester | New builds, conversions | ~40 min |
| Basingstoke | Commercial, new-build residential | ~60 min |
| Portsmouth / Fareham / Gosport | Residential, MOD-adjacent sites | ~45 min |
| New Forest | Rural self-builds, barn conversions | ~20–40 min |
| Andover / Romsey / Eastleigh | New-build estates, light commercial | ~40–55 min |
Why Choose Build Energy for Air Tightness Testing in Hampshire?
Build Energy is accredited for both domestic and non-domestic testing. Our engineers carry full calibration certificates and professional indemnity insurance, and we issue all test results the following day. We follow ATTMA TS1 and TS2 testing standards for domestic and non-domestic buildings respectively.
- Speedy certification – test results and documentation issued on the day, or following day of the visit
- Short-notice availability – most Hampshire sites booked within 3–5 working days
- Combined services – air tightness testing can be combined with SAP, SBEM or BREEAM assessments
- Direct Building Control liaison – we handle the paperwork so your project stays on programme
Do You Need an Air Tightness Test?
Part L of the Building Regulations requires an air tightness test for most new-build and conversion projects. Specifically, the table below sets out when a test is and is not required.
| Project Type | Test Required? | Standard |
|---|---|---|
| New dwellings (detached, semi, terrace, flat) | Yes – mandatory | Part L1 – max 5m³/(h·m²) |
| New non-domestic buildings | Yes – mandatory | Part L2 – max 10m³/(h·m²) |
| Conversion to dwelling (e.g. barn, commercial) | Not required | Part L1 |
| Extension to non-domestic building | Usually required | Part L2 |
| Refurbishment of existing dwelling | Not required | – |
If you are unsure whether your project requires a test, contact us with the project type and floor area and we will confirm within one working day.
How Air Tightness Testing Works
An air tightness test uses a calibrated fan unit – a blower door – temporarily sealed into a doorway of the building. In practice, the fan creates a pressure difference of 50 Pascals between inside and outside. Measuring the airflow required to maintain that pressure gives the air leakage rate in m³ per hour per m² of envelope area.
The process typically takes one to two hours for a standard domestic unit. Before the test, you will need to fully seal the building: close all permanent ventilation, tape letterboxes, and cover temporary works openings. We confirm all preparation requirements when booking.
We typically issue your results within 24 hours. If the building fails on the day, our engineer carries out a pressurisation walk-around to identify the main leakage paths. In that case, we can provide a re-test once remedial sealing is complete.
Recent Air Tightness Tests Across Hampshire
A selection of local projects where our engineers have carried out air tightness testing and consultancy:
- Canford School, Dorset – air tightness desktop review, on-site consultancy and final testing for a £2.5m library and hall refurbishment.
- The Grange, Stubbington, Hampshire – SAP, airtightness and Part E sound testing for a 16-home residential development.
- Adanac Park, Southampton – Part L energy modelling and airtightness testing across 10 industrial and warehouse units.
- Upton Country Park, Poole – thermal comfort analysis and air permeability testing for BCP Council’s new Welcome Centre.
- Veterans’ Bungalows, Bournemouth – air permeability testing, SAP assessments/EPCs and sound insulation testing for a new veterans’ housing scheme with Greendale Construction.
Frequently Asked Questions
What areas of Hampshire do you cover for air tightness testing?
We cover all of Hampshire from our Christchurch base. Regular testing locations include Southampton, Winchester, Basingstoke, Andover, Fareham, Gosport, Portsmouth, Eastleigh, Romsey, the New Forest district and surrounding villages. We also cover Isle of Wight projects on a case-by-case basis – contact us for travel costs and availability.
How long does an air tightness test take, and when do I get the certificate?
A standard domestic test takes around one to two hours on site. Non-domestic tests on larger buildings can take two to four hours depending on floor area and complexity. Your certificate and full report are issued within 24 hours of the test, suitable for direct submission to Building Control.
How quickly can you book an air tightness test in Hampshire?
Most Hampshire bookings are confirmed within three to five working days. For urgent completions – where Building Control sign-off is imminent – call us on 0330 055 34 05 and we will do our best to accommodate a faster appointment. Combined visits with SAP or SBEM surveys can often be arranged for the same day.
Call 0330 055 34 05 · email be@buildenergy.co.uk · or tell us about your project →