Passivhaus at scale

Agar Grove Estate regeneration

The project has two ambitious elements to the brief – low energy Passivhaus design and a phasing plan that allows residents to watch their new home being built – and then move in.

Agar Grove is a collaborative masterplan, led by Hawkins\Brown, collaborating architect Mae, and landscape architect Grant Associates, which is doubling the original number of homes to just over 500, arranged in a series of streets and squares that stitch in with the wider neighbourhood. Hawkins\Brown has transferred across to contractor Hill to deliver the third phase, with Mae and Studio Multi retained as the Client’s Design Quality Monitoring Supervisors.

Some projects feel good for the soul, and demand long-term involvement. When it comes to sustainable estate regeneration, and if the project mission is to keep a community together, you can’t start with an empty site – you must work around and accommodate the people who want to stay.

The Agar Grove Estate was a 1960’s masterplan of linear paired blocks and a slab tower wedged into a corner site between two crossing railway lines, north of the St Pancras and King’s Cross rail yards. With two impermeable railway boundaries, the original estate layout – oriented on a strict north-south axis – ignored its edges, creating lots of unprogrammed space to the edges of the estate. Undercrofts and a ball-court in an unsupervised corner all led to antisocial behaviour.

Before this project started back in 2012, in stark contrast to the well-heeled regeneration on the opposite side of the tracks, the estate needed a deep re-work. Residents were living in undersized flats within poorly performing buildings that were damp and expensive to heat.

As part of its Community Investment Programme, Camden Council is transforming the estate to improve the quality of life for its residents. Part of this is paid for by rental income - and part is being cross-subsidised by the construction of new market sale homes. Our clients at Camden Council started with a simple project mission – that no-one should be made worse-off by the project and instead experience an improvement in their lives.

Part of this mission was that the residents could watch their new home being built – and then move in. Admittedly, you can’t double the density of an estate without some disruption and compromise. Bar the removal of four houses, with three leaseholds compensated and the renting family allocated a new apartment nearby, everyone else has been able to move only once – to their new home. This means granular phasing, to allow sequential infill of each corner of the site. This makes for extended timescales – but it does keep a community together.

The second element of our brief was that this should be a low energy Passivhaus project, with airtight construction, ventilation with heat recovery, minimal thermal bridging, super-insulation, and high specification triple glazing.

Camden Council declared a Climate and Ecological Emergency in November 2019 - however, Passivhaus was introduced to the project six years beforehand whilst we were developing the masterplan. This was forward thinking by Camden - to mitigate fuel poverty on behalf of their residents.

The first phase deploys generous full-width south-facing balconies that shield the large windows from the sun in summer and admit solar energy during the winter. The north side presents a more formal, closed façade to the street with more façade area given to the super-insulated walls.

Passivhaus projects at this scale were unusual in the UK when we started on site with contractor Hill and delivery architect Architype on the first phase. There was much to learn, particularly when dealing with airtightness in multiple adjoining homes, large balcony structures and high-level masonry construction.

The first phase was completed in 2018 and building services consultant and Passivhaus designer Max Fordham’s post-occupancy evaluation demonstrates that as well as saving energy – and fuel bills - homes built in this way are more comfortable, with good ventilation and stable temperatures. Due to the airtight triple glazing, the elevated railway line directly behind the building doesn’t disturb residents as it would in a conventional building.

The cost premium associated with Passivhaus construction has dropped in recent years as higher building performance is being prioritised and building regulations become stricter. Surely all homes should be built this way?