The emerald-en

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Low carbon holiday
accommodation.
The Emerald provides self-catering holiday accommodation on the site of
a former farm in quiet countryside near Truro. The Emerald was the first
UK holiday accommodation to achieve Level 6 of the Code for Sustainable
Homes. Level 6 is the highest standard under the Code and is awarded only
to zero carbon homes.
Introduction
The Emerald
Truro
Exeter
Carnon Downs
South facade - Photo © The Emerald
Key Dates
Design and planning :
2011
Construction : 2012
Open for business : 2013

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Following a successful career in
industry, Tim Kemp realised his long
held dream of creating a holiday
resort in Cornwall under the guiding
principles of sustainability and
accessibility. The Emerald is a small
resort, with four new build self-
catering cottages built to Level 6
of the Code for Sustainable Homes,
and a further cottage occupying
the old lodge house. The site was
formerly a farm ; Tim and his family
live in the farm house and two of
the holiday cottages occupy the
site of an old barn. Surrounding the
accommodation are gardens, leisure
facilities and a 35 kW solar park.
The Emerald was a very personal
project for Tim and his wife Brigitte.
They wanted to achieve the highest
environmental standards and
Context
offer high quality accommodation
to families who, like them, have
children with special needs. They
see these aims both as ethical
choices and important in attracting
their target market to the Emerald.
The decision to aim for Code level
6 was determined by Cornwall
Council stipulating that, in order to
gain planning permission as a «rural
exception» site, The Emerald must
demonstrate exceptional design
and environmental standards. Tim
took this on and, relishing the
challenge, he became committed
to achieving the highest possible
standard and worked closely with
his architect and project manager
to achieve it.
Plan © Lavigne Lonsdale
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Building overview
Construction and layout
The Emerald holiday cottages have
timber frames resting on concrete
strip foundations. The external walls
are clad in cedar and contain two
separate layers of insulation board
totalling 275 mm in depth. Ground
floors are of beam and block
construction with insulating blocks
augmented by 200mm of insulation.
There are four cottages in two semi-
detached pairs. One pair is single
storey and especially adapted for
wheelchair users. These cottages
have green roofs planted with
sedum and insulated with 180 mm
insulating board. The other pair of
cottages is on the site of the farm’s
old barn, these have slate covered
pitched roofs which contain a total
of 275 mm insulation.
Importance of air tightness
A key part of the design and build
was to maintain airtightness and
success in this area was central
to achieving Code Level 6. The
architect and timber frame supplier
paid great attention to detail to
ensure that joints throughout the
building were airtight.
Renewable energy
All the cottages are heated by
air source heat pumps serving
underfloor heating. Electricity is
supplied by The Emerald’s own
35 kW solar farm. Water heating is
by the air source heat pumps and
solar thermal panels.
Grey water from sinks and showers
is harvested in underground
retention tanks that feed the toilet
cisterns and washing machines.
Surface water is collected in water
butts and used for watering plants.
Foul drainage goes to bio-digesters
and soakaways that form part of the
Sustainable Urban Drainage System.
All of the sanitation facilities are
restricted by flow limiters, and all
white goods have A+ status to meet
the very low target of 80 litres per
person per day required by Code
Level 6.
Sunshade - Photo © The Emerald

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Technical focus :
Achieving excellent
U-values in a timber
framed building
The Emerald demonstrates the
airtightness and U-values that
can be achieved in a timber frame
building with careful design and a
very high quality build. The U-values
are as follows:
Architect Tony Smith specified a
timber frame as this was the most
effective approach to achieving
the U-values required to achieve
Code Level 6. The decision to build
semi-detached units, rather than
detached, was also dictated by the
need to achieve high U-values.
Two key elements came together
to ensure the designed standard
was delivered on site; the quality
of detailing specified by the timber
frame sub-contractor (Tru Homes)
and close supervision and on-site
training by the Project Manager, Bill
Ross.
Bill conducted a series of
‘Toolbox Talks’ on site to make
sure contractors had all the right
information and understood what
thebuild was trying to achieve. There
was a specific talk on air tightness,
The design team included an
ecologist and an arborist, who
created a landscape setting
featuring native species which
maximise biodiversity on the site.
The Emerald - certified U-values
Floor 0.1 W/m2K
Walls 0.1 W/m2K
Windows (average) 0.9 W/m2K
Sloping roof 0.14 W/m2K
Terrace- Photo © The Emerald

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Barriers and solutions
Using the BRE «Green Guide»
One of the stipulations of Level 6
this was especially relevant to the
mechanical & electrical trades
whose work carries a high risk of
breaching the all-important airtight
membranes. Bill found that many
workers had experienced a lax
attitude to airtightness on other
sites. He found they responded well
to the talks, were interested in the
issues raised and carried out the
instructions. Bill encouraged the
idea that he would much prefer to
be told about a breach in the airtight
membrane than for mistakes to be
covered up.
Inside - Photo © The Emerald
of the Code for Sustainable Homes
is that all materials must either be
certified in the Building Research
Establishment (BRE) «Green Guide»,
or independently certified, a process
incurring additional cost and delay.
This was restrictive as some locally
sourced materials might be highly
suitable, but it would be impractical
to get them certified, and they
therefore could not be used.
Procurement – looking out for
inflated claims, and inflated
prices
Other problems with procurement
centred on the tendency of
suppliers to inflate their prices
when they heard the words «Code
for Sustainable Homes». Project
Manager Bill Ross found that
when he mentioned the Code,

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promoting themselves as specialists.
The specification, which was not
used, turned out to be inadequate
and biased towards the company’s
own products.
From his experience of The Emerald,
Bill Ross believes that competent,
qualified plumbers and electricians
have the skills required to build to
Code Level 6 – those claiming to be
especially skilled in green building
and heating systems can be making
false claims. The team found that
on-site training was successful
in attaining the high standards
required for the build. Air-tightness
skills acquired during The Emerald
build have been transferred by Bill
to his subsequent projects, and are
thus benefitting the tradesmen he
worked with contributing to better
skills within the Cornish building
industry. Construction students
suppliers would come back with
an inflated price. An example was
the oak door linings, skirtings and
architrave; the joiner’s quote went
from £3,000 to £5,500 on being told
the timber had to be sustainable
with a proven supply chain. Bill
believes that timber sales are open
to malpractice as suppliers can have
documentation showing they have
purchased from a given source, but
unless each piece of wood is marked
individually, you cannot tell if it came
from the certified delivery. (National
chains will stamp each individual
piece of wood.) The problem of
over-charging would be avoided if
Code-compliance information was
provided up front by suppliers.
The Emerald team also found that
some suppliers overstated their
green credentials. An example
was in a specification for the air
source heat pump (ASHP) and
underfloor heating system, which
was commissioned from a company
Garden - Photo © The Emerald

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Focus : The Code for
Sustainable Homes
At the time of writing (spring 2014)
the UK Government had recently
announced the scrapping of the
from Cornwall College attended the
site on a number of occasions to
learn about sustainable building.
Being part of the local community
Throughout the build, Tim Kemp
worked to make sure the local
community was involved and
informed. The Emerald continues to
supportitslocalcommunity;offering
exclusive use of the swimming pool
to children with special needs every
Wednesday and sponsoring the
local children’s football team.
Cut plane © re:Form Architectural Studio
Code for Sustainable Homes, in
favour of additional sustainability
elementsintheBuildingRegulations.
How Cornwall and other councils
will certify higher standards for
rural exception sites in the future
is uncertain, but lessons from the
Code remain valuable and will be
relevant to future schemes. The
Code scores buildings against nine
elements:
• Energy and CO2 emissions
• Water
• Materials
• Surface Water Run-off
• Waste
• Pollution
• Health and Wellbeing
• Management
• Ecology.
If one element of a building has a
low score, this must be balanced
by higher scores elsewhere. The
Emerald team raised some questions

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about the weighting of different
elements, for example planting
for biodiversity in the landscaping
scheme could be used to offset
certain ‘second best’ choices in
building materials. For cost reasons,
The Emerald used Brazilian slate
to roof two of the cottages, the
team were aware that this was a
compromise, but by getting the
highest scores for other parts of
the building, they were still able to
achieve Level 6. The team found
that project management had to
adapt to the Code’s mechanism; low
scores for procurement decisions
made early in the project would
limit the choices available later on,
if the overall high score was to be
attained.
Stakeholders
Client : Tim Kemp
Project Manager : Bill Ross
Architect : Tony Smith, re:form Studio, Truro
Timber frame supplier : Tru Homes, Devon
Roofing : Marnick Roofing, Falmouth
Green roof : Blackdown Greenroofs,
Somerset
Renewable heating : Nu-Heat, Honiton
Electrician : LPA Electrical, Cornwall
Plumber : Steve Gray & Sons Ltd, Truro
Sanitary ware : Roca Ltd
Windows & sliding doors : Nordan
Plastering & wall insulation : Evolution
Interiors, Redruth
Furnishings : Julian Foye, Truro
In its first two years of operation, The
Emerald’s solar park has generated
55,000 kW of electricity. There has
been a significant surplus over the
consumption of the holiday units.
Performance
Solar park - Photos © Celia Robbins - CSBT
Contact
Cornwall Sustainable Building Trust
http://csbt.org.uk/