Air Tightness Test Scotland: What Do You Need To Know?

Building regulations across the UK can be a tricky subject to follow especially if you’re not on top of them all the time. It is not so simple as one size fits all when building a home, and this comes down to many factors, from the climate of an area, the techniques used to build and even materials. Below we will look at the building regulations and how they affect air tightness tests in Scotland.

How are Scotland’s building regulations different?

It is a good rule of thumb to assume that Scottish building regulations are more stringent than the UK standard building regulations used in England and Wales, but this isn’t to make a builder’s life more difficult, but easier. Read our ‘What is air tightness?’ article for more information on general air tightness.

Scotland’s building regulations are used differently from the England and Wales building regulations. Scotland drives the standard of their homes with the building regulations, giving strict guidelines on the minimum standards for building a new house in the most energy-efficient way. In England and Wales, the EPC is used to drive energy efficiency, not the building regulations.

If you build or project manage a house in England or Wales to the minimum, rather than the nominal standard set by the building regs, you will fail your EPC, and the building might not be signed off by building control. In Scotland, the new building regulations are being used to drive all homes to be more energy efficient and pass an EPC. This gives builders and homeowners a clearer understanding of what is needed when building, buying or selling a property.

Building to Passivhaus standards

Scotland is driving forward with improving the energy efficiency of their homes. It is easy to see why; over 72% of respondents agreed that properties should meet the legally-binding energy standard, which makes it hard for the government to pay attention to

In a recent consultation, there was overwhelming support to improve the energy efficiency of Scottish buildings by 2040. As a result, the Scottish Government have committed to new “Passivhaus-equivalent” regulations by the end of 2024, with updates following this year. New Scotland Regulations mean that new homes must be designed a home to Passivhaus standards, which means it has some important differences from the rest of the UK. 

What are Passivhaus standards? 

Passivhaus standards set a series of more rigorous standards than traditional housing. These standards are designed to greatly reduce the building’s ecological footprint and make it an ultra-low-cost building that requires little energy for both heating and cooling.

Passivhaus and Air Tightness

To achieve Passivhaus status, a building must have an air tightness of 0.6 Air Changes per hour @50Pa, as referenced on the Passivhaus site. This is much stricter than the current limits of 8 m3/hr m2 @50Pa used in England and Wales and 7 m3/hr m2 @50Pa currently used in Scotland.

To achieve such a low air tightness score, great care must be taken during building construction from start to finish. This means that all gaps must be sealed and all windows and doors must be of high quality and fitted correctly. As this is often a labour-intensive and expensive process, building regulations allow a looser tolerance for fitting items, contributing to the significant performance gap between the design and construction of buildings.

Passivhaus and Air Flow

The key to building a Passivhaus can be boiled down into the phrase, “Build Tight, Ventilate Right”. The air tightness required for an energy-efficient home must be balanced with the fresh air needed to create a healthy indoor environment, particularly in homes with many bedrooms. This is where controlled airflow comes into play. Passivhaus’ design requires a mechanical ventilation system with heat recovery (MVHR) to provide fresh air to each room without losing energy to heat or cool the space, much like a kitchen or bathroom fan to remove unwanted steam or fumes from each room

Controlled airflow is also the norm for traditional buildings – by the end of 2023, it is expected that over half of all new builds will have a System 3 or 4 (i.e. Mechanical Ventilation) system installed. This is because existing building regulations already promote draught-free homes, just not to the extent of Passivhaus: Scotland, England and Wales all recommend an air tightness of at least 5, below which controlled airflow is a design requirement in Scotland. This means that all housing designed to be built in Scotland should have mechanical ventilation as a minimum requirement. We discuss more about mechanical ventilation in our article Part F Building Regulations

What does this mean for the rest of the UK? 

Even though Scotland is using different regulations to the rest of the UK, it will slowly start to make its way south of the border. One key reason is efficiency – as many larger-scale house builders operate North and South of the border, designing to the stricter specifications and applying these to every build rather than constantly adapting designs and requirements for different regions is often more cost-efficient. 

How can AeroBarrier help you reach and exceed Scottish building regulations? 

AeroBarrier helps you reach your lowest air tightness result possible, helping you adhere to any building regulations regardless of country. Our test and treatment provide a simple solution and can help fill gaps in the building envelope up to 12mm wide. This simple and easy solution can help stop the need for expensive rebuilds and repair works. Speak to our team today and get a free quote.