The document summarizes a unique building in Cornwall that combines headquarters and helicopter hangar facilities for the Cornwall Air Ambulance Trust (CAAT) in an eco-friendly design. Completed in 2012, the building uses materials like hemcrete walls and achieves an "Excellent" BREEAM rating. It provides efficient operating facilities for CAAT's air ambulance services while minimizing environmental impact through designs like compact footprint, passive solar features, and natural ventilation.

1. 20
Eco-friendly materials in a
unique helicopter air base and
office facility.
Combining headquarters for the Cornwall Air Ambulance Trust (CAAT)
and the operating base for its helicopter ambulance, this unique building
includes a modern air hangar and office space for the charity’s fundraising
staff. Completed in 2012, the building has many environmental features,
including hemcrete walls.
Introduction
Truro
Exeter
Newquay
Cornwall Air Ambulance Trust
Key dates
June 2010 : Project Manager,
architect and engineer
commissioned
June-Dec 2010 : £1M secured
from ERDF Convergence
Funding, planning application
April 2011 : Work commenced
on site
February 2012 : Cornwall Air
Ambulance Trust moves into
its new base.
Entrance - Photo © Graham Gaunt Photowork

2. www.libnam.eu 2
Context
With its scattered rural population,
air ambulance cover is vital to
the Cornish community - the
Cornwall Air Ambulance Trust gives
lifesaving service across the Duchy
funded entirely by donations and
fundraising. The Trust is one of the
most active and prominent charities
in Cornwall and its new building is
the focus of this activity, making it a
hub of community activity as well as
an operational air base.
In 2010, the charity had outgrown
its office facilities, and needed to
update its helicopter base. A project
was launched to build a combined
facility on a well-connected site
adjacent to Newquay airport. The
project progressed swiftly, with
construction commencing in April
2011 and the Trust moving into its
new base in February 2012.
The design brief specified a building
which minimised its environmental
impact whilst providing efficient
operating facilities and comfortable
office accommodation. Features
which contributed to this include;
a compact building footprint which
minimises external walls, building
orientation which takes advantage
of passive solar gain and shields
workspaces from the noisy helipad
and airport runway, design and
Plan © Chapman Workhouse Architects
N

3. French-British collective Libnam3
layout which maximises the use of
natural ventilation and daylight. The
building achieved a BREEAM rating
of «Excellent».
Building overview
Set on a high and exposed site
near the north coast of Cornwall,
the CAAT building covers an area
of 835 m², which includes a 590 m²
hangar and 245 m² of office space.
It is unusual in combining two very
different functions, and this has led
to the use of a range of materials
and construction techniques. The
hangar uses steelwork to achieve
the necessary large clear span, with
highly insulated walls clad in locally
sourced corrugated fibre cement
panels. The foundations, ground
floor slab and helipad comprise 30%
recycled aggregates in the concrete
mix, sourced from the China Clay
works near St Austell. The hangar
is roofed with a highly insulated
standing seam aluminium.
The use of natural materials is
focussed on the smaller, more
intimate office area. Here, the
external walls are built from
hemcrete, a carbon negative
material composed from shiv (the
woody core of the hemp plant) and
a lime-based binder. The interior
walls are timber studwork. The office
area has a green roof insulated with
250 mm Cellotex. The building is
heated by air source heat pumps,
with hot water from a solar thermal
panel.
The site is not connected to mains
water, and due to long distances,
connecting to the mains was
prohibitively expensive; therefore
standalone water and drainage
services were required. A new
borehole was sunk and the site
provided with a bio-digester for
foul drainage and a management
system for water runoff. A 45000
litre grey-water tank provides
recycled water for the fire service. A
sustainable drainage system takes
surface water from the car park
and helipad; this includes a petro-
chemical interceptor to prevent
pollution from any oil spills. To
conserve water, all toilets are fitted
with dual flush cisterns and the taps
and showers have flow restrictors
to minimise consumption. This has
resulted in net water consumption
of 4.18 m3/person/year.
Ecology and biodiversity were
considered throughout the design
and build. An ecologist was
employed to review the plans and
monitor the construction process.
New wildlife habitats were created
by the green roof and the series
of traditional Cornish hedges
constructed to form the site
boundary.

4. www.libnam.eu 4
Technical focus :
Hemcrete and lime
render on an exposed
site
Hemcretewasselectedbytheproject
architect for its low environmental
impact, self-insulating and acoustic
properties. The CAAT’s helicopter
lands and takes off very near the
office part of the building, and
noise protection was thus an
important issue. The architect and
project manager visited a new build
hemcrete house in north Cornwall
as part of their research and were
particularly impressed to find that it
was heated only by solar gain and
had excellent heat retention.
The product used for the CAAT
buildingwasTradicalhemp,supplied
and installed by «Back To Earth Ltd»
from Devon. The hemcrete was
supplied as a dry mix of hemp with
a lime binder and mixed with water
on site. Shuttering was used on both
sides of the building to hold the
hemcrete in place whilst it dried. The
external plastic shuttering boards
were removed once the hemp had
become solid. Internally, 9mm Multi
Pro XS racking board was retained
and treated with lime plaster to
create the interior finish. Marine
grade plywood was used to create
studwork around window and door
openings. The CAAT team found
the hemcrete installation easy and
straightforward. The work coincided
with good weather during summer
2011 and the hemcrete dried out
quickly.
A self-coloured lime render was
Inside the hangar - Photo © Graham Gaunt Photowork

5. French-British collective Libnam5
applied to create the external finish.
To minimise any potential damp
problems, the hemp/lime walls
are protected by an upstand at
the foot of the wall. The building
is also surrounded by a gravel
border which prevents rainwater
from splashing up onto the walls.
Since completion in 2012, the lime
render has weathered extremely
well despite the building’s exposed
position.
Barriers and solutions
Maintenance in an exposed site
The building’s hardwood windows
were originally treated with a natural
oiled finish, which in most situations
would last for at least five years
without maintenance. However the
finish has proved inadequate in the
exposed, coastal setting and a more
durable product has been applied.
The building’s green roof has been
a success, but has also been subject
to some trial and error in terms of
maintenance. Within the first nine
months, several saplings had self-
seeded and grown to 3-4 feet tall.
The self-seeded plants had out-
competed the roof sedum and their
roots had disturbed the substrate. A
regime of six-monthly weeding has
now solved this problem.
On-site training
On site standards were maintained
Meeting room - Photo © Graham Gaunt Photowork

6. www.libnam.eu 6
throughout the build through a
site induction process delivered by
the main contractor, and toolbox
talks covering topics including the
building’s environmental aims,
waste management and ecology.
Several visits to site were made by
local schools and students from
Cornwall College.
A comprehensive
approach to
construction
management and
building lifecycle
A strength of the Air Ambulance
project is that care was taken
throughout the planning, design
and construction to ensure the
environmental impact of the
building was minimised.
During the design phase, a Low and
Zero Carbon Feasibility Study was
undertaken to determine the most
Office space - Photo © Graham Gaunt Photowork
Hemcrete and lime render - Photo © études ET
chantiers

7. French-British collective Libnam7
efficient systems for the building;
this resulted in the selection of air
source heat pumps for heating
and solar thermal hot water
which deliver 26% savings in CO2
emissions over traditional heating
systems. The building is designed
to maximise daylight and solar
gain, avoid heat loss and prevent
the need for air conditioning. In
all areas of the building, materials
were selected with consideration
to embodied energy, durability and
ease of maintenance, demolition
and recycling.
The principal contractor set targets
for energy and water consumption
use during construction which were
benchmarked to the most efficient
industry standards. These were
followed up by strict monitoring to
ensure the targets were achieved.
Water saving measures were
encouraged by the contractor which
resulted in total consumption of
159 m3 which equates to less than
10 m3/ £100K, putting the project
amongst the most efficient in the
construction industry.
During construction the contractors
implemented a rigorous Site Waste
Management Plan, which minimised
the amount of material sent to
landfill and encouraged the re-use
and recycling of site waste. The
principal contractor participated
in the Considerate Constructors
scheme, achieving recognition for
‘Performance beyond compliance.’
Building in operation - Photo © Graham Gaunt Photowork

8. 8
Stakeholders
Client : Cornwall Air Ambulance Trust
Project Manager : Stephen Murdoch, Wagg
Constultants
Architect : Chapman Workhouse, Truro
Engineer : URS/Scott Wilson
Prime contractor : Morgan Sindall Ltd
Mechanical and electrical services : EIC Ltd,
Redruth
Windows and doors : Camel Glass,
Wadebridge
Hemp and lime : Back to Earth Ltd, Devon
The highly insulated walls, roof and floor have limited heat loss throughout
the building to <0.2 w/m²K. The test result for air leakage in the occupied
part of the building achieved 4.6 m3/hr/m²@50Pa.
The project contributed to the local economy through its construction, with
65% of the value of the contract being placed with Cornish subcontractors.
There is also a significant ongoing contribution; the new facility has enabled
the Trust to employ seven new members of staff, representing an increase
in Gross Value Add (GVA) to the local economy of over £860,000 by 2015.
The Trust, as a very active local charity, is focussed on engaging with
and supporting the local community. Many aspects of the building were
designed with this in mind and the new building facilitates flexible use for a
wide range of meetings and community events. The hangar has even been
used to host up to 200 people.
Performance
Section © Chapman Workhouse Architects
Contact
Cornwall Sustainable Building Trust
http://csbt.org.uk/