A Troubling Transition For Passivhaus?

October, 2023 |

At the annual UK Passivhaus conference this year, it was encouraging to see signs of the scaling up process and of broader industry engagement in the PH standard. There were also aspects of Passivhaus adoption that were troubling. Addressing these is important to move forward positively and reduce the inherent risks of operating within a transition period. The first was observing the disconnect between Passivhaus and embodied carbon. Secondly, continuing to see Passivhaus projects overly complex in their design and construction solutions.

EMBODIED CARBON AGNOSTIC?

There are two sides of the coin when delivering truly sustainable low carbon housing. Both sides of the coin are important and integral. The one side is answered by the Passivhaus standard which enables energy efficiency while living comfortably. The other side is building materials and their impacts on health and well-being – the making, handling, living within, reusing, recycling, and disposing at end of life. Transition requires a new economic paradigm for both performance and ‘stuff’.

Our tendency to disconnect these two matters reflects a troubling lack of holistic thinking. Passivhaus, while rooted in addressing Climate Change, remains agnostic around embodied carbon. There is little time, if any, to ignore this significant part of the transition story and we must now consider carbon use seriously, in all its various manifestations. Our success or failure in this endeavour carries with it serious impacts for the entire biosphere.

High embodied carbon materials, including oil-based products, are being used as core Passivhaus solutions, especially for large scale projects, at the scale where big business thrives. The Passivhaus community continues to promote high embodied carbon solutions, while the wider building industry continues to resist low embodied carbon solutions. Beyond a general resistance there are active blocking behaviours from big business, some of which have links into the oil industry. The Grenfell tower fire has led to even more negativity towards materials that were not present in the tower at all – the primary insulation material in the tower was PIR (polyisocyanurate). PIR and similar insulations are frequently used in Passivhaus projects within all elements – floors, walls, and roofs. Yet we continue to avoid the use of alternate products, especially wood fibres, hemp, and cellulose – low carbon options that offer co-benefits that PIR or similar insulations can never deliver. PIR gives off multiple toxic substances when burning. Imagine if wood fibre did similar and how quickly production would be decimated by the arising bad press. Low embodied carbon materials are continually dismissed by referencing perceived fire risks, without in-depth exploration. The benefits for human health and well-being are widely ignored.

For those introducing low carbon materials and systems into the market there is clearly more work to be done. This requires investments in time and money – especially to provide detailed and high-quality evidence around fire, particularly for wall and roof build ups. Companies need to work together to support each other in this endeavour. The ASBP, founded in 2011, provides one avenue to do that. Strong push backs are needed on the misconceptions – more education on performance benefits, especially moisture control and decremental delay, and a stronger message around the health and well-being benefits.

There remains a need for exemplars to showcase low embodied carbon Passivhaus projects, at both the small and larger scales. Passivhaus has rapidly increased industry understanding around units of energy (kWhs) and what a poor energy use statistic looks like, against a good or exceptional one. Equally, we need to understand embodied carbon measurements, what does poor and excessive use of embodied carbon look like (kgCO₂e/m²) versus good or exceptional uses. We must commit to measure embodied carbon, minimally the core thermal/structural shells of our new buildings. The add-on to PHPP, PH Ribbon, is one helpful tool to enable early interrogation of specification choices.

If a higher embodied carbon solution is needed for a project, this should be treated like retrofit exemptions (the building is Grade I or II listed for example), and the designer should provide a written justification as part of the sustainability process. There will always be justifiable exemption arguments.

If you agree there are two sides to the carbon ‘coin’, consider ways you might support this vital area of much needed growth. Within the current economic system, it is extremely challenging to grow markets for counter cultural solutions and products. Specification and design choices support one type of market or another. We have power in our hands to support or resist essential change, more than we properly appreciate. Supplying low carbon solutions means an uphill struggle to build knowledge, to provide technical and testing data, to address affordability without volume, and to build a market share that would be able to compete on a level playing field.

How we value and select ‘stuff’, what costs we consider (beyond the immediate price tag), and the level of quality that we accept as essential, these are core sustainable matters. We need to repurpose more in the future, but how will this be possible if we specify low quality and non-recyclable elements at the start of a building’s life? Built-in redundancy has become so embedded in our culture that we are not yet being sufficiently challenged to think, design, specify and procure differently and place more emphasis on what occurs before construction, in the making process, and what happens beyond, after practical completion.

OVERLY COMPLEX PASSIVHAUS

Inefficient construction or spatial solutions have huge impacts on construction costs, especially in Passivhaus projects where the performance of the fabric is in focus. The cost uplift from adopting Passivhaus should be small (0-10%), but this uplift can quickly become frighteningly high. Exceptional uplifts cannot be directly attributable to Passivhaus adoption, and it is misleading to relate these to the ‘learning curve’ of the contractor. High levels of cost uplift will be intrinsically linked to inefficient and complex design forms, material choices, and construction detailing solutions. Poor spatial design alone can have a large impact on cost, predominantly through unnecessary increases in the envelope area. For new housing, optimising the overall ‘Passivhaus’ floor area, in relation to the numbers of delivered units, is key to affordability. Construction solutions that involve multiplicity of layers, including excessive cutting/fitting of insulation, will elevate labour time significantly and add an additional burden managing quality on site. Unnecessary complexity in the sequencing of works will prove expensive for the client. Simplicity in construction is essential to address the cost burden, especially those who are not delivering one-off exceptional projects (an art gallery) but are looking to deliver good essential buildings (affordable housing).

How these aspects of a project are addressed within the Passivhaus context is unclear. The ongoing reputation of Passivhaus deserves a review process beyond the PHPP energy performance alone, to include design efficiency and the construction solution adopted. Excessively expensive and possibly troubling construction solutions will not assist the wider adoption process and possibly introduce risks around longer-term moisture management, fire, and degradation of thermal performance over time. Inexperienced Passivhaus designers and Architects should be made aware of risks from creating unique solutions, especially as they move away from known construction solutions. Transition periods involve a time of elevated risk. The most important transition challenges of moisture management and fire occur within both high and low embodied carbon routes. Finding robust solutions that follow best practice in all aspects is key. Should there be a Passivhaus ‘Grenfell’ moment, there will be a powerful industry at hand keen to slay the Passivhaus dragon. The overlooking of errors afforded to big business is unlikely to be afforded to Passivhaus.

CONCLUSION

There is much to celebrate in the Passivhaus arena. Large scale building projects are happening, and more and more people are adopting the necessary ‘fabric first’ approach. We may see Scotland adopt a Passivhaus or Passivhaus equivalent standard over the next two years, the first country in the world to do so. We are all working hard to see this transition period move rapidly towards standard practice. But we remain firmly in transition, and in this period of rapid change we must all be aware of the risks and manage these thoughtfully and intelligently. We cannot overlook key aspects that drive best and safe practice, while also addressing all our climate change obligations. We are firmly on the road, but not yet at the destination.