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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 : 2011Construction : 2012Open 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

Contextoffer 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 overviewConstruction and layoutThe 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 tightnessA 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 energyAll 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 buildingThe 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 the build 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-valuesFloor 0.1 W/m2KWalls 0.1 W/m2KWindows (average) 0.9 W/m2KSloping roof 0.14 W/m2K

Terrace- Photo © The Emerald

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Barriers and solutionsUsing 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 pricesOther 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 communityThroughout the build, Tim Kemp worked to make sure the local community was involved and informed. The Emerald continues to support its local community; 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 elements in the Building Regulations. 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.

StakeholdersClient : Tim KempProject Manager : Bill RossArchitect : Tony Smith, re:form Studio, TruroTimber frame supplier : Tru Homes, DevonRoofing : Marnick Roofing, FalmouthGreen roof : Blackdown Greenroofs, SomersetRenewable heating : Nu-Heat, HonitonElectrician : LPA Electrical, CornwallPlumber : Steve Gray & Sons Ltd, TruroSanitary ware : Roca LtdWindows & sliding doors : NordanPlastering & wall insulation : Evolution Interiors, RedruthFurnishings : 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

ContactCornwall Sustainable Building Trusthttp://csbt.org.uk/