Passivhaus Affiliate

Passivhaus retrofits provide long term benefits

Retrofitting the existing housing stock will play a lead role in meeting UK Government 80% reductions in greenhouse gas emissions by 2050. Encouragingly, a range of low energy retrofit projects were discussed on 3rd December 2013 at the Passivhaus Trust’s Residential Retrofit Seminar. Recent exemplar projects designed to EnerPHit standard included large scale social housing Wilmcote House by ECD architects and a detached residential home Thornhill Road by Eco Design Consultants.

Left to Right: Andrew Simmonds, Nick Newman, Loreana Padron, Kate Ball and Alan Budden. Photo Credit: Kirsten Priebe

Key issues that arose during the afternoon:

Affordable Retrofitting:

Andy Simmonds CEO of the AECB, says ‘we can no longer avoid fuel poverty, and short sighted lower cost/lower energy saving retrofitting is not the solution.’ Although they usually contain a higher capital investment,  Passivhaus retrofits can provide holistic solutions by upgrading internal comfort, and significantly reducing energy use which will result in economic savings. Not to mention the value added to the upgraded house.

Long term savings were addressed By Nick and Loreana of ECD architects who discussed Wilmcote House, a large scale social housing retrofit in Portsmouth to EnerPHit standard. They fought hard to maintain the original specification, with building services/products vying for sales and undercutting prices with less efficient energy measures. They said that although initial costs may be slightly higher, once the long term energy saving and cost benefits were explained to clients, it was an easy decision. More Government funding schemes would be beneficial. Eco funding barely covered 10% of the Wilmcote House development, with Portsmouth Council picking up the bulk of the bill.

Artist's impression of Wilmcote House, Portsmouth: ECD Architects

Retrofit verses new build: Questions were raised as to whether it may be more cost effective to knock down an existing home and build new to Passivhaus standard. ECD Architects noted that this cost exercise hasn’t yet been carried out but  Wilmcote House will be gathering data soon that may be able to provide some answers early next year. However ECD architects did state that other costs not associated with the building fabric such as decanting all residents if starting from scratch were saved by retrofitting with residents in place. Clear comparative costs for common building types would be useful.

Interestingly, Marion Baeli who has examined 20 case studies added that there are retrofits that did not reach Passivhaus standard, but spent much more than certified projects.

Incentivising Passivhaus retrofits would aid market growth. Some suggestions included removing VAT on retrofit projects so that it remained cheaper than new build.


Alleviating the performance gap:

Although there were significant energy savings in most of the low energy retrofit projects, striving for Passivhaus standard significantly alleviates the performance gap. The standard quantifys all the energy flows through the fabric to an acceptable level of accuracy.  Stringent quality assurance measures on site then ensure the building is built as close to the proposed model, with final certification providing evidence of performance.


Industry Training & Education:

On site quality assurance and mainstream industry training is still needs improving. This was exampled by Kate Ball, owner of Thornhill Road, a 1950’s residential home. Kate had to educate contractors regarding insulation details, how to use new airtightness products, and ensuring the airtight layer was installed in the right place at the right time. It is usually eagled-eyed Passivhaus enthusiasts who help (be that client/architect/ consultant) ensure good workmanship of contractors still adjusting to the required level of detail.

Window insulation detail, Thornhill Road: Eco Design Consultants

Adopting the correct terminology would help champion Passivhaus retrofit; Airtightness is a scary word! Many people respond better to draught and damp free, and comfortable indoor environments. 


Materials & markets

Moisture issues with internal insulation altering existing breathable building fabric must be addressed, and there was some discussion regarding Passivhaus materiality being dominated by petrochemical corporate companies. If one company adopted, or began to promote breathable, lower embodied natural materials in Passivhaus design, it may be the catalyst for opening up a competitive market.


It was great to hear such developed debates surrounding the subject. All seminar presentations can be found here:

  • Achieving Enerphit at scale: case study of Wilmcote House tower block refurbishment:(available soon)

    • Loreana Padron & Nick Newman, ECD Architects

The event was concluded by a book launch of ‘Residential Retrofitting:20 case studies’ with speeches from Paul Davis of PD + Partners, Hattie Hartman, Sustainability Editor of The Architect’s Journal, and the author herself, Marion Baeli.

Left to Right: Paul Davis, Marion Baeli, and Hattie Hartman

Left to Right: Paul Davis, Marion Baeli, and Hattie Hartman at Residential Retrofit: 20 Case Studies book launch. 

4th December 2013

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