HELLESVEOR FARM

Our refurbishment of the historic Hellesveor Farmhouse near St Ives transforms a damp, neglected building into a low-energy, healthy home at the heart of a sustainable family business. Located within an Area of Outstanding Natural Beauty, the farmhouse now meets Passive House retrofit principles, with airtight construction, cellulose insulation, MVHR, and solar energy systems.

A new timber-framed extension wraps the north side, super-insulating the masonry and resolving damp issues. The internal layout reorients living spaces to the sunny south garden, with generous glazing and rooflights enhancing daylight. The original granite walls now act as thermal mass, while the roof structure has been retained and upgraded to a cold-bridge-free warm roof.

Natural, low-impact materials dominate, including timber, stone, and breathable finishes. The retrofit drastically reduces energy demand (peak heat load cut from 21.7kW to 4.3kW) and supports ecological goals with reclaimed landscaping and wildlife-friendly barns – an exemplar of sustainable rural regeneration.

Andrew and Mel Rogers took over the family farm in 2014 and employed ARCO2 to help consolidate planning consents and evaluate options for the infrastructure and buildings on the farm.   Three intensive years of design and construction have followed with a clear mandate to create a highly sustainable family business with an eye to the future.

Until 2015 the farmhouse was severely neglected and in very poor condition, suffering from rising and penetrating damp with the roof, chimneys and some windows leaking.  The prospect of wholesale refurbishment and replacement of the sub-standard north extension provided the opportunity to thoroughly address these issues whilst simultaneously working to current Carbonlite Retrofit best practice guidance to drastically improve energy efficiency and building fabric/occupant health (ARCO2 are Passive House designers and AECB Carbonlite Retrofit qualified).

The Farmhouse has good solar orientation and aspect. The principal elevation (which now faces the garden) points south and has generous window openings set within high quality ashlar granite. The remaining elevations are of relatively poor quality cement washed/ part rendered stone and brickwork and it is likely that all of these walls would have been covered in a white wash or full render finish earlier in the building’s life.  It was an easy decision to super insulate north east and west walls by externally wrapping them in a thick timber framed insulating “blanket”.  The new extension on the north side forms part of this blanket wrap.

The existing massive granite walls – formerly the source of damp, heat loss and discomfort – are now the “thermal battery” of a very energy efficient comfortable home.

The altered internal layout carefully considers solar orientation and its relationship with the rest of the farm (and holiday business).  The entrance and service spaces (kitchen, utility, bathrooms, office) are positioned on the north side of the plan and have new triple glazed rooflights to greatly improve daylight levels.  Living spaces and bedrooms face south and open onto a private sunny garden.  The south elevation has only a modest amount of insulation in the form of a lightweight internal plaster but retains the high quality formal granite elevation.  Perhaps the bravest intervention has been the removal of a section of masonry between window and door on the south elevation – providing a spectacular and characterful glazed opening to the living space which opens onto the verandah and garden.

The previously dark staircase has now become a centre piece to the house with its generous rooflight allowing daylight deep into the plan.

The original principal roof structure of trusses and purlins has been retained but insulation now conceals their depth within a new spaced rafter warm roof construction (350mm thick cold bridge free).  This is sealed and taped on the underside and wind tight on the outer face to prevent air movement within the insulation layer.  Thermally the loft is now part of the house making it an ideal space for the building services (MVHR, hot water tank, solar pumps, boiler) without heat loss – an “engine room”.  It also provides ample warm dry space for storage.

Accessibility: the Farmhouse now has level access into and through the entire ground floor with an adaptable floor plan (wet room shower and office annex on the ground floor).

A fabric first approach to environmental design; highly insulated with cellulose based insulants, exterior timber frame and sheathings; air tight construction; Mechanical ventilation with heat recovery (MVHR) for moisture control with purpose made lead roof outlets.  Energy efficiency and excellent indoor air quality and comfort; Natural daylight; Healthy to build, use and deconstruct; Significantly lower running costs and CO2 emissions. Solar thermal and photovoltaic panels have been added to the south roof slope meeting a large proportion of the energy needs of the house.

Low energy design: Passive house design principles, minimised cold bridge detailing, solar gain (without overheating), energy efficient heating systems, thermal mass, renewable energy generation.  Peak heat load reduced from 21.7kw to 4.3kw.  (see calculation in “Drawings” below).

Air tightness and insulation: designed, built and sealed to achieve very low air leakage (yet to be tested but a result of 1m3/m2/hr@50p or less is anticipated).  Wind tight externally, vapour permeable.  Tapes by Siga and Pro-Clima, timber sheathings.  Cellulose fibre blown insulation (Warmcel)

Windows: triple glazed timber by Livingwood, average whole window U-Value 0.9W/m2K

Timber frame: The extension is a twin-stud wall, site stick-built, minimising cold bridging.  Sole plates only treated.  Timber sheathings, air tight breathing construction.  External insulation to the existing masonry walls is carefully detailed at the plinth to minimise cold bridging and deal with rising damp.

Low impact materials: The building uses low environmental impact materials with priority given to inert natural materials (timber, stone etc) with as little processing as possible.  Timber and it’s derivatives are used extensively (eg. cellulose fibre insulation), this locks up carbon for the life of the building.  These materials are safe to work with and can also be safely de-constructed and re-used/ re-processed in the future. Graphite enriched expanded polystyrene (EPS) is used beneath the flooring as the “greenest” foam insulant, all other insulation is cellulose based.  Where highly processed or high embodied energy materials are necessary (eg. plumbing fittings) high value materials have been chosen in order to ensure that these are separated and recycled when the building is demolished (eg. use metal instead of composite plastics).

Finishes: Vapour permeable, water based.  Externally, stains are used instead of paint, this maintains breathability and makes re-coating more strait forward as the stain finish gradually weathers away (rather than peeling or flaking).

Lighting and power: daylight design with controlled solar gain.  Rooflights introduced on the north slope to greatly improve natural light levels in the centre of the house.  LED Low energy lighting.

Water systems: Foul drainage for the whole site is now managed by a purpose designed treatment plant leading to an in-field soakaway. All surface and roof water also drains to soakaways on site.

Heating and ventilation system: High efficiency whole house mechanical ventilation with heat recovery (MVHR) for energy efficiency and excellent indoor air quality.  Designed with compact duct layout of large diameter and sound damping.  High efficiency direct air supply wood stove.  Heating controls time and temperature control to best practice.  LPG condensing boiler supplying low temperature underfloor heating downstairs and radiators upstairs.

Energy generation systems: 6sq.m solar thermal evacuated tubes supplying hot water, 4kWp photo-voltaics

Waste and recycling: the campsite business has a centralised recycling area provided for all onsite users.

Community: The farm and holiday business are a prominent part of the small Hamlet of Hellesveor.  There are number of public footpaths and tracks that pass through it enroute to the coast path and West Penwith landscape all of which are retained and visually enhanced by the restoration of the historic buildings.  Hellesveor’s visual impact within the AONB was considered within the planning applications for the site.

The building uses low environmental impact materials with priority given to inert natural materials (timber, stone etc) with as little processing as possible.  Timber and it’s derivatives are used extensively (eg. cellulose fibre insulation), this locks up carbon for the life of the building.  These materials are safe to work with and can also be safely de-constructed and re-used/ re-processed in the future. Graphite enriched expanded polystyrene (EPS) is used beneath the flooring as the “greenest” foam insulant, all other insulation is cellulose based.  Where highly processed or high embodied energy materials are necessary (eg. plumbing fittings) high value materials have been chosen in order to ensure that these are separated and recycled when the building is demolished (eg. use metal instead of composite plastics).

Finishes: Vapour permeable, water based.  Externally, stains are used instead of paint, this maintains breathability and makes recoating more strait forward as the stain finish gradually weathers away (rather than peeling or flaking).

Earth and stone Cornish hedges using site field stones and demolition stone.  Natural stone walls with slate copings (all reclaimed from within the property).  Reclaimed cobble setts.  Natural planting.  Many of the unheated storage buildings/barns on the site remain accessible for nesting birds and bats.

Low energy design: Passive house design principles, minimised cold bridge detailing, solar gain (without overheating), energy efficient heating systems, thermal mass, renewable energy generation.  Peak heat load reduced from 21.7kw to 4.3kw.

U-values: A target of less than 0.13W/m2K.  Some existing walls have received only a thin layer of lightweight plaster (U-value of approx. 1.5W/m2K), other elements of new construction (eg. extension walls and all roofs) are between 0.11 and 0.13  which is the target range for a Passive House.

Air tightness and insulation: designed, built and sealed to achieve very low air leakage (yet to be tested but a result of 1m3/m2/hr@50p or less is anticipated).  Wind tight externally, vapour permeable.  Tapes by Siga and Pro-Clima, timber sheathings.  Cellulose fibre blown insulation (Warmcel)

Windows: triple glazed timber by Livingwood, average whole window U-Value 0.9W/m2K

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ARCO2 designs contemporary sustainable homes across Cornwall, including North Cornwall, South Cornwall and coastal locations such as Polzeath, Rock, Padstow, Mawgan Porth, Falmouth and beyond. Our work combines contemporary architecture with low energy design principles, carefully responding to landscape, climate and long-term building performance.

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