The Sustainable Building Spectrum When Passivhaus Doesn’t Quite Fit the Bill

By Magdalena Arent, Building Performance Consultant at Holmes Miller

Passivhaus certification has become known as the industry's gold standard for energy efficient new buildings, especially in the context of the UK’s goal to achieve net zero by 2050. Architects and contractors alike are zeroing in on this rigorous standard as the blueprint for creating low-carbon structures that are built to last, performing as intended, therefore cheaper to run and more pleasant to be in.

With the climate crisis intensifying, it's promising to see more clients taking ownership of reducing their building’s energy consumption, both at the construction phase and in its operation. Many are now recognising the importance of exploring new ways to create more sustainable buildings and are looking for the right advice on how best to minimise their environmental impact.

Passivhaus isn’t just a benchmark—it’s the target for sustainable design we should all be striving towards. It sets absolute targets for heating and electrical use, allowing for flexible design without neglecting non-regulated energy limits, which can significantly bring down energy costs. For large commercial buildings such as leisure centres with swimming pools, and supermarkets, the reduction in final energy bills can provide substantial savings. The calculations are also climate specific, making the Passivhaus methodology suitable for any location worldwide.

But when clients come to us looking to design green buildings, achieving full Passivhaus certification isn’t always realistic. Its stringent requirements for airtightness, ventilation, and triple-glazed windows, for example, are often seen as expensive at a time when client budgets are tight. And this isn’t the only challenge. Achieving full Passivhaus standard also requires a level of time and commitment which some may feel is too high for something that isn’t a mandatory requirement.

Governments are now recognising this though, and things look set to change in the coming years. Scotland has committed to developing a Passivhaus equivalent standard with detailed benchmarks, yet to be established, due to be mandatory by 2028. In Wales, the current Passivhaus label is deemed to comply with their building regulations.  

There are also other ways to create sustainable buildings without having to face these challenges. And for those who can’t quite justify the added investment needed to achieve Passivhaus status, or for buildings where it simply doesn’t suit, that doesn’t mean settling for mediocrity. Aiming for a slightly less stringent certification that still far exceeds building standards is a no-brainer.

We recently designed a sustainable strategy for the reuse and retrofit of Penicuik High School – a 1930s energy-hungry school building in Midlothian, south of Edinburgh. The project will transform the school into an inclusive, energy-efficient learning environment for over 900 pupils, with a new three-storey extension to enhance capacity and double the support space for students with additional support needs (ASN).

The client’s key aspiration is to create a school designed in line with Scottish Futures Trust’s Learning Estate Investment Programme (LEIP), with an operational energy target of 67 kWh/m2 /annum for ‘core areas’ and ‘core hours’. Key retrofit measures include a combination of Crittall triple glazed windows and Passivhaus certified windows, enhanced insulation, Mechanical Ventilation Heat Recovery (MVHR) units and the most efficient solution for domestic hot water provision.

Overall, our approach is expected to reduce energy usage by at least 60%, regardless of fuel source.

Adapting historic buildings like this one to meet modern sustainability standards can be challenging, but LEIP recognises this by setting its energy target on a sliding scale. Its approach of focusing on total energy demand promotes an efficient design first, before applying other cost effective and carbon saving solutions such as heat pumps and PV panels.

Tackling existing stock plays a crucial role in safeguarding the future of our communities and the planet. Rather than stray away from these challenges, architects must embrace and find creative ways to navigate them to put the right methods in place.

Our approach to Penicuik High School demonstrates how combining thoughtful energy-efficient design and retrofitting can deliver meaningful impact. While not every project can incorporate all of these approaches, even small steps can contribute to creating more sustainable spaces. There are a range of credible, affordable and achievable alternative standards that still deliver substantial energy efficiency improvements. The key lies in assessing each project individually to find the right one.

Take the Passivhaus Institute (PHI) Low Energy Building Standard, for instance. It mirrors the core requirements of Passivhaus, and offers the same quality assurance, but offers more leeway on energy usage. This makes it a practical alternative that doesn’t mean sacrificing the benefits of high-performance design, such as a healthy, comfortable building with excellent air quality.

Similarly, realising the challenges posed by Passivhaus, the Association for Environment Conscious Building (AECB) has introduced the CarbonLite standard, which bridges the gap between Passivhaus and current building regulations. This standard still uses the same Passivhaus Institute assessment tool (known as PHPP), the same calculation methods, and still has rigorous quality assurance, but has less onerous demands in terms of heating and primary energy and airtightness.

CarbonLite provides a robust framework for sustainable construction, enabling clients to contribute to the net zero mission without the heavier burden of Passivhaus certification. The model works particularly well for retrofit projects, as it allows a staged approach. This might begin with upgrading to a clean heating system, with more costly adaptations such as improved insulation planned in for a later date.

At the beginning of every project, we’ll present these various options to our clients to help align targets with their aspiration, but the beauty is they don’t need to decide at the outset. We can work with them throughout the design process to help them choose what works best.

The choice between Passivhaus, AECB, or another certification isn’t just about ticking boxes; it’s about making real strides toward energy-efficient design. As designers, that’s something we should all be aspiring to.

Holmes Miller recently launched a revised sustainability charter, and as part of this we’ve adapted our approach to embed low carbon design into the bedrock of every project, whether it’s aiming for Passivhaus certification or not. Passivhaus principles guide our design process from the ground up, with aspects such as compact form, optimised glazing and shading, and low energy equipment placed at the top of our priority list to ensure we’re driving better efficiency across all our buildings.

Passivhaus may be considered the jewel in the crown of sustainable design, but if we really want to improve the way we build, educating clients on the spectrum of options available to them is crucial. It’s always better to do something than nothing, and sustainable design doesn’t have to be an all-or-nothing approach. It’s about taking realistic, incremental steps to make every building better - and in the fight for a greener, happier and healthier future, every step counts.