“Oxford Retrofit Case Study – Achieving Exceptional Airtightness with Passive Purple”

View the printable PDF for #IMCasestudy4

Overview – Oxford Retrofit with Passive Purple

This Oxford retrofit project transformed an existing property into a highly energy-efficient, airtight home by utilising Passive Purple Internal applied to the warm side of the insulation. Once the airtight layer was completed, an exterior insulation system was installed, followed by a brand-new render system for a seamless finish.

The combination of liquid-applied airtightness technology and modern insulation ensures that this home benefits from lower heating bills, better indoor comfort, and enhanced building durability for decades to come.

Background – Preparing for Airtight Perfection

This retrofit presented no major structural issues, as the substrate was in excellent condition. To optimise adhesion for our liquid-applied membrane, a render primer was applied before installation began.

While the main surfaces were straightforward, retrofit projects often involve more detailed work due to existing gaps, junctions, and penetrations in the building fabric. Our team carefully applied Passive Purple Brush to these areas, ensuring that every joint, gap, and transition was fully sealed. The entire process took just two days, thanks to efficient preparation and precise application.

Solution – Creating a Continuous Airtight Barrier

For this project, Passive Purple played a central role in delivering airtightness and smoke-tight protection before the external wall insulation was fitted. Applying the membrane at this stage ensures:

• Air and smoke tightness across the full building envelope.

• Improved thermal performance by eliminating air leakage.

• Better indoor air quality through controlled ventilation.

• Enhanced fire safety compliance with Class B fire-rated technology.

By combining Passive Purple Brush for detailing and Passive Purple Internal Vapour Control for large areas, the installation achieved a robust, continuous airtight layer ready for the insulation and render system to be applied.

Results – Efficiency, Comfort, and Peace of Mind

This Oxford retrofit achieved outstanding airtightness performance while preserving the home’s character and structure. The new airtight envelope:

• Minimises heat loss for lower energy bills.

• Eliminates draughts for year-round comfort.

• Reduces condensation risk and prevents mould growth.

• Strengthens building longevity by protecting structural elements.

The client’s satisfaction speaks volumes—not only about the quality of the installation, but also about the value of airtightness in retrofit projects.

Results

The achievement of a 0.4 ACH score underlines the potential of modern retrofitting techniques to transform existing buildings into high-performance, energy-efficient structures. As we look to the future, retrofits will play a pivotal role in addressing energy consumption, reducing carbon emissions, and enhancing the quality and sustainability of our built environment.

Air Testing

Air testing- also known as air permeability testing, air leakage testing, and air pressure testing- measures the amount of air escaping through a building’s envelope.