What is Airtightness Testing and Why Do We Need It?
Airtightness testing checks how much air leaks uncontrolled through gaps, cracks or holes in a building’s structure. If you’re wondering why that’s important, think about it like this: when you try to heat or cool your home, any drafts or leaks will let all that effort (and money) float away. The test helps find where unwanted air is getting in or out so those spots can be sealed, making buildings warmer in winter and cooler in summer.
In the UK, airtightness testing is required by law for newly built homes and commercial buildings. It’s part of the Building Regulations (Part L) that aim to make buildings use less energy. The less air that escapes, the less heating or cooling you need, and that means lower energy bills and fewer carbon emissions.
At Ratio Seven, we specialise in airtightness testing for both domestic and commercial buildings. We work across the UK to help projects meet regulations, save energy and create more comfortable spaces.
When Does a Building Need Airtightness Testing?
Most newly built homes and business properties must pass an air leakage test before they can be signed off. The test proves that your building has been built with care and attention to air sealing. For homes, it’s usually tested once construction is nearly complete but before final finishes go in, around the same time as the final plastering. For commercial spaces, it depends on the building size, design and usage, details we cover in our Commercial Air Testing service.
Conversions and extensions might also need testing if they include large new sections.
For developers, self-builders and architects, testing should be considered early on in planning. Why? Because knowing where problem points are before it’s too late can save a lot of trouble, delays and expense later.
How Does Airtightness Testing Work?
Our team uses a blower door test, which is the most common way to check airtightness. Here’s how it works:
- We fit a temporary fan in an external doorway.
- All other external doors and windows are shut.
- The fan pulls air out, creating lower pressure inside.
- Air from outside rushes in through any gaps or cracks.
- Our equipment measures how much air is leaking and at what pressure.
We then produce a report showing whether the result meets the required standard. If not, we point out the problem areas, so they can be fixed quickly. The standard you’re aiming for depends on your building type and the target laid out in your SAP (Standard Assessment Procedure) or SBEM (Simplified Building Energy Model) assessment.
A pass means your building meets the airtightness section of Part L of the Building Regulations.
How Airtightness Affects Your Energy Bills
Air leakage is like leaving the heating on and opening windows at the same time. While it might only seem like a bit of extra draught, even small leaks can add up to big losses over time.
When we test a building for the first time, it’s not unusual to find that lots of heat is being lost without anyone realising. Insulation alone can’t solve the problem. Insulation slows down heat transfer, but airtightness stops draughts. Together, they make a home or workspace perform properly.
By sealing gaps and fixing weak spots, the result can be a warmer, quieter and more eco-friendly home. Our clients are often surprised by how much more comfortable and quiet their building becomes after they resolve air leakage issues.
To learn more about how this fits into your building plans, our Air Testing FAQs provide clear answers.
What Happens If Your Building Fails the Test?
Don’t panic. Failing a test isn’t the end of the world. We’ll guide you through fixing the issues. Some minor air leaks can be resolved on the same day of testing. For more serious leaks, we help identify the causes and suggest the best solutions.
Examples of common problem areas include:
- Gaps around pipes or cables coming through walls
- Poorly sealed windows or doors
- Gaps in the roof structure
- Loose floorboards
- Plasterboard edges not sealed properly
Once the issues are sorted, we’ll retest the building. At Ratio Seven, we aim to make the process as smooth as possible, helping your site stay on schedule.
When Should You Book Your Airtightness Test?
We always recommend booking testing as early as possible in your project timeline. That way, we can advise you during the early construction stages and help avoid common mistakes.
The ideal time to carry out an airtightness test is after the building is sealed but before final fix items like skirting boards or floor finishes are installed. This is when the building envelope (walls, roof, floors, windows, doors) is complete.
Try to make sure the building is as close to complete as possible before testing, but still accessible in case small fixes are needed.
To see how we support both construction teams and homeowners throughout the UK, visit our airtightness testing UK services page.
Domestic vs Commercial Air Tightness Testing
While the basic method for testing homes or commercial spaces is similar, there are some key differences.
In domestic settings, we test individual homes or pairs of houses (semi-detached). The pass mark is usually five cubic metres of air leakage per square metre at 50 Pascals of pressure (m³/h/m²@50Pa), depending on the design target.
For commercial air-tightness testing, the buildings are often more complex with large open areas, multiple floors and lots of mechanical systems. The targets relate to energy use, layout and purpose. For full details, our team manages Commercial Air Testing with specialist knowledge.
Either way, we bring years of hands-on experience to make sure you hit your airtightness goals.
Air Tightness Testing FAQs
We know some phrases like “blower door test” or “part L compliance” can sound confusing, especially to homeowners new to the process. That’s why our Air Testing FAQs break everything down into simple terms.
You’ll find answers to:
- What do I need to prepare before the test?
- Do I need to be on-site?
- How long does it take?
- What happens if I fail?
- What documents do I get with a pass?
Whether you’re a first-time self-builder or working on multiple housing projects, you’ll find the answers useful.
Let’s Make Your Building Airtight
Working with buildings is about getting lots of details right. Airtightness is one of those big details that might not be visible when it’s working well, but makes a huge difference if it’s not.
At Ratio Seven, we help builders, contractors, developers and homeowners meet compliance with accurate testing, friendly advice and quick results. Whether you’re building a new home, converting an old one or designing a commercial space, ensuring airtightness will lead to better comfort, lower energy bills and easier approvals.
Visit our air tightness testing page to book a test or contact us directly. Let’s make sure your building is ready to perform at its best.
