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PHI - PassivHaus International


Claire Jamieson and Sara Darwin co-founded Passivhaus International in 2012.




Sara and Claire studied Architecture & Environmental Design together at Nottingham University.


Subsequently qualifying as British Architects, registered with the ARB, they had practised architecture in the UK for over 20 years when Passivhaus and energy saving methods of construction came onto their radar. Sharing an enthusiasm for modern residential design with sustainable solutions, Sara and Claire were among the very first in the UK to become Certified Passivhaus Designers through the Building Research Establishment in accordance with the Passivhaus Institute.


Claire is based at Phi Architecture Consultancy in Ripon, North Yorkshire and Sara is based at Phi Architects in Heaton Moor, Greater Manchester. Knowledge and developments are shared regularly to ensure we can offer the best advice and expertise through all associated disciplines of our work.

PHI maintains the principles of Passivhaus at the very core of everything it does. With the increasing awareness of the Climate Crisis, Extinction Rebellion, Carbon Zero, pollution and mounting issues of energy resources it was only a matter of time before architects would need to bring the science back into architecture. This is exactly what we do, utilising the design tools associated with Passivhaus PHPP, to attain the worlds highest standards of construction in our designs. This approach of both sustainable and environmentally responsible design is also supported by a strong emphasis on aesthetics and good proportion with the application of Phi Φ, the golden ratio. Design and architecture are not compromised by our approach and comfort through quality of living are dramatically improved.

Passivhaus International is committed to working with clients on an individual basis, to meet their aspirations, brief and budget, with cost efficient design and construction together with personal and inspirational solutions. We specialise in both renovation and new build work to Passivhaus principles


Claire's consultancy, Phi Architecture covers various areas of expertise, as well as providing her with a platform from which to continue to practice as an Architect and Certified Passivhaus Designer 

Phi Architecture provides a professional Passivhaus consultancy service in the Yorkshire regions and beyond, which integrates individual design with sustainable solutions. The service is strengthened by Claire’s knowledge and understanding of Passivhaus and EnerPhit. 

Claire has an extensive understanding of practical application in detailing and construction to attain airtightness and avoid cold bridging. She is proficient in the preparation of PHPP (Passivhaus Planning Package). This can be applied to any project to ascertain the best ways to improve energy efficiency, as well as it’s more conventional use for Passivhaus projects.

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