LADYBIRD FARM

Area: 286m2

Procurement: JCT Intermediate Contract (Negotiated Tender with QS)

As Built SAP: 95A Environmental Impact: 105A

Embodied & Operational Carbon: 361 KgCO2/m2 (Best Practice 2020 is <500 KgCO2/m2)

Construction Stage Air Pressure Test: 0.94 m3.h-1.m-2@50 Pa

LABC: Cornwall Council (Plan Check, Inspections)

This vernacular, passive house inspired dwelling replaces a former traditional cottage that had been unsympathetically extended and altered in 1960/70’s removing much of the original fabric and charm.  The remaining building was damp, tired, expensive to run and reached the end of its maintainable life.  Situated alongside our clients Grade II Listed property and curtilage Listed walled garden the new building needed to be sensitive, respectful and inspirational.

The original brief was to refurbish, alter and extend the existing building removing much of the unsympathetic 1960/70’s interventions to provide a sustainable family home.  The roof was to be replaced in its entirety, wall plates raised to provide a consistent eaves line in order to drain the roof with new rainwater goods, vault the ceiling and expose new oak trusses, remove blockwork walls, remove timber floors and concrete floors leaving only the original stone walls.  Having undertaken two detailed sketch schemes both were costed by a Chartered Quantity Surveyor and not deemed to be financially viable to proceed with.  Given the extensive refurbishment and what would have been left of the remaining fabric, the team’s decision was to consider a new uncompromised sustainable dwelling providing a similar level of accommodation, removing issues of damp, cold bridging and allowing the accommodation and rooms to better suit current living standards.

This would also enable passive house levels of insulation, ventilation, increased comfort levels and a greatly reduced requirement for energy and heating.

The proposed building is based upon a traditional vernacular form, traditional scale and mass similar in principle to the existing property, but with a modern twist.

Removal of the blockwork outbuildings provides significant visual enhancement and planning gain to the nearby setting of the Grade II Listed Tamsquite House.  In total 12 structures were removed.

The design carefully integrates the new building within its setting, using materials and forms that complement the existing structures. Vehicles are discreetly positioned behind a copper-covered walkway, ensuring they remain screened from view. This walkway also helps to create an enclosed walled garden, enhancing privacy and establishing a sense of arrival. The proposed slate roof rises subtly above the existing stone wall, echoing the character and proportions of the surrounding buildings.

The natural stone gable-end mirrors the traditional style of the farmstead, with parking thoughtfully set back and accessible via the covered copper walkway. An entrance gate, new stone wall, and the walkway together form a private, south-facing walled garden, while still allowing occasional vehicular access for maintenance. The rear elevation features a mix of natural stone and lime render, using sand-based pigments to create a soft, natural tone that blends with the landscape.

Externally, the landscaping includes a north-facing fern garden and stumpery, complemented by a herb garden alongside the boundary hedge and low retaining wall. Rear access and steps connect the balcony and roof terrace to the garden, reinforcing the link between indoor and outdoor spaces. The traditional natural slate roof incorporates a close mitred hip, terracotta ridge tiles, and clipped eaves, while the stone gables are finished with soft hydraulic lime pointing and slate verges, preserving a handcrafted aesthetic.

Functional elements are seamlessly integrated into the design. Gates allow for occasional vehicle access and maintenance such as treatment plant de-sludging. The tapered gable projection and balcony are designed to manage solar gain, with the balcony providing shade to the west-facing bedrooms below. Timber cladding to the end of the balcony further reduces heat from the southern and south-westerly aspects, while untreated natural timber introduces warmth and texture within the walled garden.

Inside, the bedrooms and bathroom are oriented towards the private south-facing garden. A copper brise-soleil provides additional summer shading to the south-facing windows, improving comfort and energy performance. The property incorporates a 4kW solar photovoltaic system with battery storage to generate renewable electricity, while first-floor windows are minimised to protect the privacy of the neighbouring walled garden at Tamsquite House.

The walls and ground floor were constructed using a newly developed Cornish ICF system known as R-Wall.  The insulation is waterproof being XPS insulation and provides extremely good U-Values.  Insulating underneath the slab ensured thermal bridge free construction and continuity of the concrete core not only providing strength but exceptional levels of airtightness.  The concrete was locally manufactured using secondary aggregate from the clay industry, helping to minimise the carbon content of the concrete.  The slab accommodated the underfloor heating pipes and provided the level sub floor which meant that a screed was not necessary, helping to save cost/materials and carbon.  A self-levelling compound was required underneath the final resin floor finish.  The roof consists of engineered I joists which use less timber, span further than solid timber and have minimal cold bridging.  Due to being predominantly a masonry fabric there is plenty of thermal mass to create a thermal fly wheel affect and smooth out temperature spikes. Acoustically the house provides calm amongst the storms, offering peace and tranquillity.

The basic principles employed during the design, specification and construction is to ensure that the building has low embodied CO₂ content.   Materials were selected that have not required a large amount of energy in their sourcing, processing or transportation.  The solutions include:

1. R-Wall ICF external walls and insulated ground floor: Ravatherm XPS high performance extruded homogeneous polystyrene closed cell insulation provides excellent thermal insulation, is waterproof with negligible moisture uptake with a high compressive strength.  The concrete core utilises secondary aggregates from the nearby clay industry which helps to minimise the carbon content.
2. Floor membrane: Visqueen Eco Membrane: Manufactured from 100% post-use polyethylene, diverting more waste from landfill.
3. I-Joists: Engineered timber joists made from small sections of timber and timber by products (see below). They offer many design and performance advantages over conventional structural products including a composition which resists shrinking and warping, an excellent strength to weight ratio straight and uniform dimensions. The joists also have FSC & PEFC Accreditation & Labelling, Life Cycle Assessment and ISO14001:2004 Environment Management System.
4. Timber for internal partitions & joists: recognised as one of the most sustainable building materials, all timber has been specified carefully ensuring that the chain of custody is clear.  This protects against irresponsible sourcing and irreversible damage to delicate ecosystems. Where possible, we advocate the use of European timber (FSC & PEFC) together with locally sourced green timber such as western red cedar which was used for cladding, fascias, barges and soffits.
5. Warmcel recycled newspaper insulation: Warmcel is a natureplus® certified product. This is a standard for products that meet the highest standards from raw material sourcing / extraction, to low emissions and clean production methods.  Warmcel is manufactured from recycled newspapers, these are collected from offices, schools, overruns from printing companies and kerbside collections. The manufacturing process uses very little energy, the combination of the cellulose fibre properties and its specific manufacturing process gives Warmcel an extremely low Global Warming Potential of -1.5 Kg Co₂/m².  The CO₂ sequestered within Warmcel is then locked into your building and is actually less than the CO₂ produced in the manufacturing process.  Unlike other insulations, Warmcel is an inert material with no off-gassing of Volatile Organic Compounds, making it the best insulation for a truly healthy home.
6. Timber by-products: such as the bitumen impregnated fibreboard to the roof (Bitroc), orientated strand board (OSB), and hardboard (air tightness layer) have also been incorporated in order to utilise further waste products.  Additionally, these products have lower chemical content in terms of adhesives and binders than composite materials such as chipboard and medium density fibreboard, both of which have reported harmful binders which can cause a health hazard when working with the materials.
7. Glulam Beams: Small sections of timber from sustainable sources glue laminated to provide a larger structural grade timber.  Used for ridge beam and stair trimmers.
8. Earthwool: insulation to acoustic walls and floors (where breathability is not required).  A+ Generic BRE Green Guide rating.  Made using recycled materials.  Made from rapidly renewable organic materials. No added formaldehyde binder.  No added dyes.  Up to 70% less embodied energy and recyclable.
9. Roof membranes: Designed as a breathing shell (vapour permeable) which is not susceptible to condensation build up and significantly reduces the risk of associated respiratory illness.  As it breathes the structural frame is less prone to decay and offers greater longevity
10. External Joinery: High specification triple glazed windows were specified to help reduce heat loss.  Velfac aluminium clad timber were chosen due to the high efficiency, sustainability, minimal sight lines and minimal maintenance due to being located close to the sea. All timber is FSC certified, have a lifespan of 40 years 2/3 of the aluminium is manufactured using renewable energy and approx. 40% come from recycled sources.  Each unit is designed to be disassembled and re-used at the end of its life cycle.
11. Rainwater goods: Zinc rainwater goods were selected because of their quality, durability, minimal maintenance, and recyclability.  We made the conscious decision to oversize all rainwater goods as a result of global warming, increased intensity of rainfall and flash flooding.
12. Natural Stone: Quarried locally supporting local economy and minimising transportation/CO₂.

A Phase 1 Ecology Survey was undertaken to establish if there was evidence of bats within the existing building and outbuildings.  Approximately 2000 droppings were found in the roof space.  2 emergence surveys were undertaken, a total of 9 bats consisting of brown long eared bats, common pipistrelle and soprano pipistrelle bats were found.  All species are common and widespread through the UK.  The existing building was carefully stripped with an ecologist present, no bats were found.

Mitigation was provided for common pipistrelle and soprano pipistrelle bats by the inclusion of four integral bat boxes, 2 located on the north elevation and 2 on the south elevation (pictured above).  The new building also incorporated a dedicated loft space for brown long eared bats which is located above the 1^st floor cloakroom near the east gable.

A sparrow terrace was located on the east elevation and a bee block on the south elevation.

The house exceeds the minimum Passive House U-Values whilst also having a very respectable SAP/EPC result and great air pressure test result, which just missed the stringent passive house standard of 0.6 by 0.34.  Given that this is the main contractors first low energy project using the R-Wall system we feel that this is an extremely good result. The house requires very minimal heating throughout the year and importantly does not overheat in the summer, eliminating any requirements for cooling.

Ladybird Farm operational carbon is 15kWh/m2 year compared to an average house of 140 kWh/m2 year.  Its embodied carbon is 361 kgCO2/m2, less than half of the baseline domestic of 800 kgCO2/m2.  Best practice 2020 is <500 KkgCO2/m2.  Ladybird Farm is only 61 kgCO2/m2 off the RIBA’s aspirational 2030 target.  Lifecycle embodied carbon totals 696kgCO2/m2 which becomes 414 KGCO2/m2 when sequestration is included, which meets RIBA 2025 targets.

This demonstrates that sustainability has been at the core of early design decision making and that we have continued to analyse carbon to ensure the As Built building is one in which we can all be proud of its sustainable and ethical credentials.  The whole-life carbon of Ladybird Farm is 819 kgCO2e/m2 over the lifecycle of the building (averaging a 60 year life span).   However, with the construction method utilised the expected building life span is in excess of 100 years which will greatly reduce this whole life carbon figure.  Operational carbon continues at a rate of approximately 383.5 kgCO2e/m2 per year.

U-Value Summary – Constructed

Walls – R-Wall                 0.11

Roof – Slate                       0.13

Roof – Terrace                 0.13

Ground Floor                    0.12

Roof windows                  1.0

Fixed Windows               0.79 – 1.15

Openable Windows        0.94 – 1.16

Sliding Doors                   1.3

Doors                               0.6

Passive House U-Value Requirements

Walls                                ≤ 0.15                               Roof                                   ≤ 0.15

Ground Floor                   ≤ 0.15                              Windows                         ≤ 0.80

The following provides a technical breakdown of the building services and performance of the building’s main components:

• MVHR system: 1 no. Vent Axia Sentinel Kinetic Plus B with integrated automatic summer bypass and humidity sensor boost control Built in Humidity Sensor and Wired Remote Controller. This system provides excellent indoor air quality (moisture, particulates, pollutants are filtered) and the rigid ducting is efficient and reduces noise levels.
• Air Source Heat Pump: 10kW Vaillant aroTHERM Energy A+++ COP up to 5.03 with R290 natural refrigerant delivering one of the lowest GWP of 3 with integrated smart monitoring
• UFH: GF (wet system at 150mm centres) within 65mm screed.  Continal Oneboard structural deck system to 1st floor.  All with Wireless smart programmable self-learning room thermostats operated wirelessly
• Towel rails: Electric towel rails to en-suites with built in programmable thermostats (not used for heating and not required for drying to MVHR maintaining a consistent 40-50% relative humidity in the house, installed as back-up).
• PV & Battery Storage:05kW + 9.2kWh battery storage
• Lighting: 100% dedicated low energy throughout inside and outside
• Cooking/White Goods: Minimum A rated appliances throughout
• Treatment Plant. High performance package treatment plant provides environmentally safe treated effluent with low running costs (10-14p per day).

As always in Cornwall the weather is a challenge, with unprecedented rainfall.  The 1^st floor sub deck was laid with a temporary waterproof layer.  Unfortunately, water had still managed to get in and swell the joints creating an uneven surface.  The main contractors were not content with levelling the surface as it would compromise the thickness of the sub deck.  They replaced the whole deck to ensure that there would be no future problems when laying the engineered oak flooring.

Other than this the build went to plan.  There were a few variations increasing the original contract sum by 9%.