Air Tightness Testing: A Key Step for Building or Retrofitting Your Home or Commercial Building in Ireland

If you’re building a new home or carrying out major renovations to it, or building a new commercial building, you’ve likely heard about air tightness testing — but what exactly is it, why does it matter, and when should you get it done?

Air tightness testing is now a crucial step in modern construction, especially in Ireland, where the climate demands a well-insulated, energy-efficient building. This article explains everything builders and homeowners need to know about air leakage testing: how it works, why it’s required, and how Q50 can help you ensure your property meets the latest standards and avoids long-term energy loss.

What is Air Tightness Testing?

Air tightness testing measures the amount of uncontrolled air leakage in a building. This is the air that escapes or enters your property through gaps and cracks in the building envelope — such as around windows, doors, pipe penetrations, attic hatches, and joist ends. These air leaks can significantly impact heating costs and comfort levels.

In Ireland, air tightness is measured using a blower door test in accordance with European Standard IS EN ISO 9972:22015. During the test, a fan is mounted into a doorway to pressurise or depressurise the building. This allows a trained technician to measure the rate at which air is escaping.

The result is given in air changes per hour (ACH) at 50 Pascals of pressure. In simple terms, this tells you how many times the air in your building is replaced by outside air in one hour under test conditions. The lower the number, the better.

Why is Air Tightness Important?

A poorly sealed building means higher energy bills and a colder house. But beyond that, air leakage also affects your compliance with Irish Building Regulations, particularly Part L, which sets out energy performance standards for new builds and major retrofits.

Here are a few key reasons air tightness testing matters:

●     Energy Efficiency: Air leaks lead to heat loss, making your heating system work harder.

●     Cost Savings: Tighter buildings use less energy — that means lower bills year after year.

●     Comfort: Reducing draughts means fewer cold spots and more stable indoor temperatures.

●     Regulation Compliance: All new builds must achieve a certain standard to meet NZEB (Nearly Zero Energy Building) regulations.

●     BER Rating: Air tightness results are a key input for your Building Energy Rating, which affects property value and grant eligibility.

When Should You Carry Out the Test?

Timing is important. The best time for an air tightness test is before your build is completed but after the envelope is sealed (i.e. after ‘first-fix)— when windows, doors, roofing, and basic sealing are in place, but before finishes like plastering or painting are done.

Testing at this stage allows you to locate and fix leaks before they become hidden behind finished surfaces. If you're unsure when your project is at the right stage, Q50 will advise you based on your build schedule. However, under Irish Building Regulations, a ‘final’ test must be carried out when the building is completed. The result of the ‘final’ air pressure test is the relevant result to achieve compliance under Part L.

Common Air Leakage Points

Most people are surprised by how many places air can leak from in a building. These include:

●     Service penetrations for pipes and cables

●     Joist ends and wall/floor junctions

●     Loft hatches and attic access points

●     Around recessed light fittings and extractor fans

●     Window and door frames not properly sealed

●     Chimney openings or unused flues

Finding these issues after you’ve moved in is a costly headache. Identifying them early helps you avoid future regrets.

How Q50 Can Help

At Q50, we offer a full suite of air leakage testing and diagnostic services. We don’t just give you a number — we help you understand what that number means and how to improve it.

Our team uses professional blower door equipment and a range of specialist equipment including thermal imaging cameras, smoke machines, smoke pens and hot-wire-thermal-anemometers to locate leaks and advise on sealing strategies. We’ve worked with homeowners, architects, and builders across Ireland, ensuring new builds and retrofits meet compliance standards while also achieving real energy savings.

If your first test doesn’t meet the required standard, we’ll provide a clear report and action plan, so you know exactly what needs to be improved. Once remedial works are complete, we can retest and issue certification.

Air Tightness and the Building Regulations

Since 2017, all new buildings in Ireland are required to demonstrate an air permeability rate of no more than 5 m³/hr/m² or better at 50pa. This means that the leakage rate should not exceed 5 cubic meters of air through one square meter of the envelope area in one hour (at an induced pressure difference between the inside and the outside of the building of 50 Pascals). The same applies to commercial buildings since 2017. However, most energy-conscious builds aim for much lower results, typically below 3 m³/hr/m².

Achieving this standard doesn’t happen by accident. It takes planning, proper detailing, and onsite follow-through. That’s why we recommend involving Q50 early in the project — so we can support you from first fix to final test.

Don’t Let Air Leaks Ruin Your Investment

An energy-efficient home is more than just insulation and a heat pump. Air tightness is the hidden factor that makes those systems truly work. If you’re building or retrofitting, don’t leave this to chance.

Call Q50 today to schedule your test or chat with us for some friendly, no-pressure advice (excuse the pun!). We’re here to help you make sure your home is comfortable, compliant, and built to last.

Contact Chris Moore on 086 313 0970 or email chris@q50.ie