The Long Game: Mark Siddall

September 3, 2020

Mark Siddall is principal of Low Energy Architectural Practice (LEAP). His practice and consultancy has been operating for nine years and helps people create buildings that support their forever home lifestyle


My interest in sustainable architecture began in 1991 when I first visited the Centre for Alternative Technology (CAT) in Wales. Two houses impressed me – the Wates House and the Segal House.

Some 14 years later, while researching passive solar architecture, I discovered the Passivhaus Standard. Back then there were no Passivhaus buildings in the UK and most of the information about Passivhaus was in German, so I began the process of translating documents and learning physics to evaluate whether it was suitable for the British climate.

What struck me at the time about the Passivhaus Standard was its simplicity. At its core, there is a deep, genuine concern for the health, wellbeing and comfort of the people living in and using buildings. This was then overlaid with a nuanced appreciation of the climate emergency and how it could be tackled.

These criteria, harnessed with a refined appreciation of building physics and robust levels of quality assurance, meant the Passivhaus Standard was an obvious choice for creating sustainable low energy buildings in the UK.


Since there is so much greenwash out there in the construction industry, creating truly sustainable buildings can still be a challenge. To be honest, it must be difficult for good, honest people to know who they can trust. All too aware of these problems by 2011 I faced a major dilemma – leave the construction industry for ethical reasons or do something different. I decided to establish LEAP.

Today, LEAP helps people create sustainable low energy homes. To do this, the practice provides architectural services, Passivhaus consultancy and, as a part of the CarbonLite programme, training for architects, engineers and trades.

Documentaries about some of the projects the practice has worked on can be found at


Faced with the climate emergency and the ensuing breakdown in biodiversity, sustainable buildings are an essential part of our future.

If we are to tackle these problems we must do so together. We must ask profound questions about our way of life. We cannot shirk responsibility. We must act together, and we must act now. We can’t wait for the Government – no matter what the flavour.  If we act quickly, we will be able leave a legacy our children and grandchildren can be proud of.

We must refurbish the homes where we live, and we must demand better standards of design and construction for every new building that is to be built.

My plan, and the plan for LEAP, is to keep on supporting change and to help those that want to make a difference.