When it comes to a retrofit project, a
client is wise to exercise malleable expectations from the outset. This was one of several ‘lessons learnt’
demonstrated by Cullinan Studio at their Green Sky Thinking event, where they
discussed the recent retrofit of their own new canal-side offices in Angel,
Islington. Prior to the conversion this three-storey post-industrial building,
historically a foundry, was one of the few that remained relatively untouched in
the area. At the event, the project’s director Johnny Winter spoke candidly
about the whole process from planning right through to post-occupancy data. It
is notable that the project still managed to achieve BREEAM Excellent, despite its
significant constraints.
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| Johnny Winter explains the structural strategies employed |
Having bought a large portion of Baldwin
Terrace in 1991, Cullinan Studio chose the central building in the terrace to
become its new home. The practice initially set out with high expectations of
their own time, budget and manpower. Johnny joked about their well-meant
positivity, which spurred them into hoping they could morph the building into suitable
offices during weekend DIY sessions over a three month period. However, as the
end of their lease in Camden drew near, they were forced to retreat next door, to
a more structurally sound and adaptable building they had earmarked for
redevelopment into flats. Here they were to remain “temporarily” for the next 20 years. In the meantime, the old
foundry building was rented out as artists’ workspace and an exhibition
gallery.
Whilst in retreat next door, the practice
spent time on an ambitious design to replace the old foundry building, only to
have the planning application rejected upon submission in 2004. As the practice
took stock and redesigned, a planning conservation officer revealed the significance
of the canal-side wall, which was deemed of special interest due to its
position on the edge of a conservation area. The retention of this wall, along
with the timber trusses spanning the roof, became a key planning condition, and
inevitably a driver for the whole redesign. The wall required serious structural
intervention, with its upper edge listing 180mm out toward the canal. After
quite a struggle, planning permission was finally achieved in 2008, although
unfortunate timing with the recession meant the project still stalled for
another three years before construction.
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| Building tour: the retained timber trusses |
The approved design kept the building
structure and listed wall intact but planned a ‘fabric first’ approach of super-insulating
the walls, floors and roof. The recycled newspaper insulation on the canal wall
ended up particularly thick; sprayed on up to 450mm deep in places due to the undulation
of the wall. Despite the structural constraints and the preservative approach
to the building’s fabric, the practice endeavoured to create a dynamic working
environment, by ensuring all three levels were visually and acoustically
connected in section. The Green Sky Thinking audience was curious as to whether
the practice had considered further negotiation with the conservation officer. Johnny
was almost certain that the issue was non-negotiable – had the practice gone to
appeal there was a risk that the whole building could have ended up listed,
upending the whole design process.
Yet in the end, dealing with the listing
wall proved to be a defining architectural feature of the project. The
engineers for the project, Price & Myers, had originally designed a temporary
retention structure to hold the listing canal wall, while the existing trusses
were taken away for cleaning and storage during the main building works. A
permanent steel retention structure would then be installed after. However, the
practice was keen to reduce the hassle and the waste of two separate
structures, and so redesigned the scheme with in-house structural expertise to
include a singular Vierendeel truss (amusingly mispronounced by the contractor as
a “venereal truss”). This truss could be installed as a permanent retention
structure at the same time as the footings. When construction finally began in
2011, the listing wall now 250mm out of plum, necessitating some temporary
bracing prior to installation of the Vierendeel. The building’s dynamically
connected levels were also simplified in both plan and section, retaining two
linked floors for the practice’s use and a separated top floor, meaning they
now had a lettable space.
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| Building tour: the mezzanine overlooking the Vierendeel |
The energy-saving practices implemented on
the project were subject to several recognisable issues. Four years after the
application the planned methods had become either unattainably expensive or
outdated; the canal inlet could not be used for water-based cooling due to
hefty British Waterways fees and a wind survey revealed the planned five
turbines would not produce a worthwhile output. In place of these other tenets
of sustainability had to be amped up, such as the aforementioned fabric
retention, the use of recycled newspaper and super insulation. Indeed the fabric
detailing has worked favourably with a pressure test of less than 5ac/h, an
encouraging measure for an existing building. The offices are naturally ventilated,
the pleasantness of which was confirmed on the day the Green Sky Thinking event
by the mild spring air percolating in from the Regent’s Canal.
Now that the building has been occupied for
a few months, Cullinan Studio have been able to take stock of its energy use. Johnny
noted that the Building Management System (BMS) has provided them with some
data, but has been frustrating due to it being almost too specialised. So they
have been able to identify when and how the building is malfunctioning but not
why! The existing lift overrun now houses an air source heat pump that serves
all the building’s heating needs, contrasting with the 22m2 of photovoltaic
panels, which have supplied a modest 600kW since October 2011. A question
cropped up here: why didn’t they design in a larger array? It was an obvious
cost issue, but there was a suggestion from the practice’s own Robin Nicholson that
the amount of VAT paid for the conversion could have been better spent on more
photovoltaics. Cost reductions have also meant insufficient absorptive acoustic
material on the canal-level floor, causing kitchen noise to reverberate up into
the mezzanine – an ongoing issue that will be rectified in due course.
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| Robin Nicholson on current planning attitudes |
Looking to the future, with a dwindling
postindustrial landscape left to be canabalised, the retrofit issue is quietly gathering
gravitas. When it comes to building conservation versus the imperatives of
energy-use reduction, the balance will have to shift. This was neatly summed up
by Robin, who used the example of planners’ reluctance to retrofit Georgian
sash windows with double-glazing to show that “planners need to wake up to retrofit”.
Meanwhile, in the case of Cullinan Studio’s
Foundry, the necessity of retrofit made for a more challenging and interesting
project. At the start of the project, retrofit was not the go-to option, rather
it was resultant from a circumstantial cocktail of economic climate and
planning conditions. Of course, the audience was keen to know if the practice
would still have chosen retrofit without the imposed planning controls.
Initially Johnny said he would have taken down the building and rebuilt,
hopefully using reclaimed bricks from the site. However it was the process of
engaging in retrofit that has actually swayed that original stance, and that “seeing an old building injected with a new
lease of life was inspiring.” It is hard not to agree, the resulting
building has become an object that is both pleasantly bespoke and inherently of
its place.
