Passivhaus | Q&A with Andrew - HPA

Passivhaus | Q&A with Andrew

Andrew Walters, our Associate Director became Passivhaus design certified last year after passing the Passivhaus examinations. As this is still a relatively new standard in the UK, we put some questions to him in order to take advantage of his understanding of the subject.

What makes a building a Passivhaus?

The Passivhaus standard is based around creating a comfortable indoor environment for occupants that is to be achieved using very little energy. The key things to consider are air-tightness and insulation combined with a mechanical ventilation systems with heat recovery.  To achieve Passivhaus Certification for a project the design has to be scrutinised by an assessor and work during the construction phase is inspected to ensure that the design is correctly implemented and the building energy performance in use is as designed.

What led you to decide to get Passivhaus accreditation?

I have been interested in Passivhaus for a long time and welcomed the opportunity to develop my knowledge.  Achieving the accreditation was a bonus.  The Passivhaus standard fits well with the RIBA Climate Challenge that HPA are committed to, to reduce energy demand by 60%, embodied carbon by 40% and potable water use by 40% by 2030.

How do you use your new Passivhaus knowledge on a day to day basis at work?

The principles of airtightness and insulation are applicable to all projects, and the requirements of the new building regulations are becoming more complex and closer to the Passivhaus standard.  The advantage of the Passivhaus is that the calculations are holistic and draw together heat loss through fabric and ventilation, solar gain and overheating in a single assessment.  The building regulations look at each part individually.

Are there any projects that you are working on at the moment that are Passivhaus standard?

We have a number of houses that we are working on where the client would like to build as a Passivhaus.  We have also designed some houses in the past using Passivhaus principles although they were not certified.

Can existing buildings be upgraded to Passivhaus standard?

There is a different standard for retrofit, called EnerPHit.  The principles are the same but the implementation is more difficult and construction detailing has to be tailored to the individual building.


Alongside his Passivhaus work, Andrew is part of the team assisting with the delivery of a number of large manufacturing projects, continuing to look at improving building performance and designing to be net zero. We look forward to sharing more on these projects with you in the coming months.

To meet the rest of the team at HPA, click here.

Latest News

Sign up to our newsletter to stay up to date