Retro-Fit Revolution: Elevating Buildings with Passivhaus Principles

16 January 2024

In the realm of sustainable architecture, retrofitting has emerged as a potent tool to transform existing homes into energy-efficient havens. Drawing wisdom from two seminars featuring Alan Budden of Eco Design Consultants and Dave Judd of Ecological Building Systems, this article explores the integration of Passivhaus principles into retrofit projects, paving the way for improved energy efficiency, comfort, and environmental impact.

Alan Budden, an advocate for eco-friendly design, delved into the key elements and practical examples of retrofitting during the seminar. He emphasised the distinction between deep and shallow retrofit, advocating for a phased approach if necessary to achieve the deep objective. In the context of retrofits, the term 'Enerphit' was introduced, representing the retrofit version of the stringent Passivhaus standards.

The Passivhaus criteria, including maintaining a surface temperature above 17°C (resulting in no condensation or mould), achieving very low heating demand, and ensuring excellent air quality, were highlighted as benchmarks for retrofit success. Shallow retrofit, with a 30% reduction in carbon emissions, was contrasted with deep retrofit, boasting a remarkable 75% reduction in carbon emissions. The advantages of deep retrofit extended beyond carbon reduction to include lower energy demands, reduced peak loads, decreased grid storage requirements, significantly lower energy bills, and improved health and comfort.

The foundation of successful retrofitting lies in detailed design, improving aspects such as air tightness, insulation, thermal bridges, adding triple glazing, and efficiencies in building shape. During construction, adherence to the designed plans, meticulous documentation through photography, and scheduling air tightness checks are important.

Good workmanship is key to achieving standards: using soft insulation for better fitting, consideration of cladding and fixing methods, scrutiny of the Lambda value of insulation, and the correct placement of insulation. External insulation, in particular, was recommended due to its ability to push the dew point further outside the building, reducing the risk of interstitial condensation and thermal bypass. A cautious approach to window placement should be taken, moving windows forward in the elevation whilst externally insulating to prevent cold bridging, and thinking carefully about the use of large areas of unshaded glazing as these contribute to overheating.

Dave Judd, representing Ecological Building Systems, presented an innovative retrofit solution called Retro EcoWall. This concept, grounded in tried and tested Passivhaus principles, centres around the use of natural insulation products to ensure buildings are able to breathe, a key principle preventing condensation, damp, and mould.  Products such as Gutex, a rigid wood fibre insulation board, are moisture vapour diffusion open, windtight, and offer benefits such as reduced thermal bridging through timber framing, good sound insulation, and carbon sequestration.

Retro EcoWall, as an internal insulation system for traditional solid or masonry walls, optimises thermal performance while managing moisture effectively. The system incorporates insulating cork, lime, and wood fibre insulation, each contributing unique properties to enhance comfort and sustainability. The key benefits of Retro EcoWall include low U values, rapid application, protection against condensation, mould, and building deterioration, retention of breathability in traditional walls, and a low embodied carbon footprint.

In conclusion, retrofitting, when coupled with Passivhaus principles, becomes a transformative force for existing homes. The insights into deep retrofitting shed light on the multifaceted advantages, while Retro EcoWall exemplifies an innovative application of natural insulation. As we move towards a sustainable future, retrofitting becomes not only a necessity but a creative opportunity to blend the old with the new, enhancing the efficiency, comfort, and environmental friendliness of our homes.