PASSIVHAUS | MAX FORDHAM Max Fordham has been designing Passivhaus projects for nine years, including two very different housing projects that won the residential CIBSE Building Performance Award in consecutive years. Gwilym Still chronicles the development of Passivhaus at the practice, and explains why it is integral to Max Fordhams net zero strategy PERFECTING PASSIVHAUS P assivhaus provides a way of designing and delivering high thermal comfort, low operational energy buildings, with rigorous quality control baked in. It has been tried, tested and proved over 30 years and, in the past few years, we have seen a dramatic growth in interest in the method of building. With COP26 focusing our minds on the climate emergency, this is a good time to reflect on our experience of using Passivhaus and the drivers behind its growth. Agar Grove Estate Max Fordhams first Passivhaus project was the multi-residential London Agar Grove Estate redevelopment, which started in 2013. The initial brief wasnt for Passivhaus but, as a client, Camden was keen on the quality aspect of Passivhaus and on using it as a way to address fuel poverty. Phase 1a was completed in 2018, Phase 1b in 2021, and 1c is on site now. The post-completion monitoring of 1a has shown Passivhaus delivering occupant comfort and enjoyment, and has been recognised in a range of awards including Residential Project of the Year at the 2020 CIBSE Building Performance Awards bit.ly/CJDec21PH As a phased development, it is interesting to see which aspects of the scheme have changed from one phase to another, and which have remained the same. The general primary structure and airtightness approach have been consistent between phases, and weve worked to avoid very thick wall build-ups, which with a masonry weather skin led to expensive brick hangers providing vertical support to brickwork and significant thermal bridging from them. The energy system has shifted from a gas-fired, low-temperature heat network scheme with heat interface units on 1a and 1b, to an allelectric ambient loop system for 1c, with water source heat pumps in each apartment. Max Fordhams house The large-scale Agar Grove was followed by a project on the opposite end of the size spectrum: our founder Max Fordhams house, also in Camden,1 which won the same CIBSE award, but in 2021 (Windows of opportunity, CIBSE Journal, September 2019, bit.ly/CJDec21HP2). Max had worked on very low-energy housing before, and wanted to deliver an all-electric building with very low or no heating demand. The building features insulated shutters to reduce heat loss at night, and domestic hot water produced by an air source heat pump, with the air intake in a sun trap so the local microclimate raises the air temperature and helps improve performance. It had a good summer comfort stress test in the summer of 2019, with peak external temperatures rising to 36C, and the internal temperature not going above 27C. It has the same radial microbore pipework arrangement for domestic hot water seen on many Passivhaus schemes. 20 December 2021 www.cibsejournal.com Bad files.indb 20 26/11/2021 15:16