Carbon-Neutral Agricultural Renovation in Cornwall

Specifying Eco Building Materials

Throughout the build, Perry and Sally challenged their builders to be as green as possible. “We would ask, ‘is there a more environmentally friendly solution?’ and Dan and his team really got into the spirit of it,” says Sally. The couple’s central consideration was that every product and material used in the building was either reclaimed (such as the ridge tiles on the roof and the slate flagstones on the hearth, porch and hallway) or as sustainable as possible. Inside the timber frame, Sally and Perry chose to insulate with Rockwool.

Sally was lucky to find their solid oak flooring on an online auction website and bought it at a discount of several thousand pounds against retail prices. They were resolute about not using standard gypsum plasterboard, but with few alternatives available, they agreed on wood wool board, finished with lime plaster. “It’s very expensive, and not great to work with, either – it looks like Weetabix,” says Sally. “But everyone’s attitude was very open and positive.”

See More: Eco Homes: 30 Sustainable Self Builds to Inspire Your Eco House

Green window and door frames add colour to the exterior, and look great amidst the timber and stone exterior

Unable to avoid MDF entirely, the couple chose a formaldehyde-free brand for use in some of the cupboard doors. The area of a home where MDF is most often found is in kitchen design. But, working closely with the couple, Norsk Carpentry made a bespoke design using birch ply and tulipwood.

Cabinets in the utility room and upstairs yoga room have been handmade, but it is the downstairs bathroom that attracts the most attention. Here, Perry and Sally have installed a composting toilet, built from spare oak and sweet chestnut “We want to be as ecologically sensitive as possible and reduce water use,” says Sally. “We cover the waste in the composting toilet with sawdust, mixed with coir in a 50:50 ratio. When we empty it, we compost the material and eventually use it to fertilise our trees. It is a labour of love.”

In the yoga room the built-in bookshelves, wall bed and pull-down desk are made from solid ash, by joiner Simon Hayward, which adds to the serenity of this multi-functional space

Deciding on Power & Heating

Renewable energy was a key consideration for Perry and Sally and they approached it in a characteristically innovative manner. On the roof is a 9.4kW array of solar panels, hooked up to battery storage, which means they can be self-sufficient for power for a minimum of six months of the year. This includes the energy needed to charge their electric car, tools and bicycles. Any surplus is sold back to the grid. During the winter, they produce less electricity and draw more from the mains, using a renewable supplier.

Less conventional was the couple’s choice of a masonry heater, which is a highly efficient form of radiant heater, popular in northern Europe. Perry and Sally’s stove is a woodburning Ecco model with a contra-flow chimney built within silicon carbide casing, which can stay warm for up to 12 hours after the fire has gone out. This is fuelled by windfalls from their land and garden pruning, all of which are carefully seasoned. Perry is also careful to secure their future supply through significant planting.

Read More: Should Landscaping be a Priority for Self Builders?

CLOSER LOOK Efficient stove… Perry and Sally’s Ecco Stove is fuelled by logs from the garden and produces radiant warmth, staying warm for around 12 hours after just one to two hours of firing. The advantage for masonry heaters comes from the construction of the flue passage. These flues are designed to extract as much thermal energy as possible, with some clever features. The stove is DEFRA-exempt and is fitted with a hotbox, which provides some heat to the domestic hot water storage cylinder Sally and Perry’s stove has contraflow flue gas channels which maximise heat absorption and distribution properties by evenly distributing heat through the silicon carbide stove body, while reducing waste heat to the atmosphere. The chimney is lined with pumice, which is a natural insulator, and it allows the flue gases to quickly reach their optimum temperature, whilst also keeping the chimney warmer longer.

Sally sourced a second-hand programmable electric Aga, which she had stripped and rebuilt. The house is so well insulated that either the Aga or the masonry heater is sufficient to warm it, even in the coldest months. “Last Christmas our children came to stay and everyone was complaining about the heat and wearing t-shirts because it was so warm!” says Sally. All the windows in the new home are triple glazed. This, plus all their other measures, means it’s not surprising Perry and Sally’s project achieved a coveted A rating for energy efficiency.

The couple also added a mechanical heat recovery and ventilation system to the mix. This expels damp, stale air, transferring the warmth to a fresh supply. “We were worried about damp,” says Perry, who also installed a French drain around the property. “Granite can act as a sponge and the original spine wall here is very old and doesn’t have a damp course.”

Read More: MVHR – Mechanical Ventilation & Heat Recovery FAQ

Award-Winning Result

The project has created an extraordinary two-bedroom home finished in stone and timber, which sits quietly in the rural West Cornwall landscape. Perry and Sally considered every detail of both the construction and the finish, eliminating undesirable materials such as plastic or formaldehyde-based MDF.

This approach has garnered plaudits, and their home is the well-deserved winner of the prestigious Cornish Building Group Awards (2022). “The judges commented on the attention to detail, the environmental credentials and the lovely energy in the house,” says Perry. “We think that energy comes from all the natural materials.”

The house is the well-deserved winner of the prestigious Cornish Building Group Awards 2022

With a fair amount of earlier experience under their belts from renovations and extensions, they weren’t novices, although this has been their biggest project by far. That experience meant they were confident to create a home to their exact specification.

Despite their thorough planning, however, this carefully specified build has taken longer, and cost more, than Perry and Sally initially expected. This was partly due to the added complications of the pandemic restrictions. “It has cost twice what we thought it would,” adds Perry. “The project has also been an intense two years, living in the chalet bungalow with Sally’s mum (who still lives there), and juggling the build with full time work.”

Rooflights filter natural illumination into the upstairs rooms. These spaces feature ample wooden details, from the ceilings through to flooring and joinery

However, the couple feel that the satisfaction of achieving their ambitious standards was well worth the wait and the cost. Plus, they have found the process extremely rewarding. “I love Matt’s original sketch so much I kept it as my phone background as a source of motivation during the build,” says Perry. “Now it has been replaced by a photograph of the real thing.”

“It’s great to finally have our own space and our possessions back,” says Sally. “We have designed the house to fit how we live.” Sally and Perry both enjoy how good it feels being in their bespoke home. “Seeing the pleasure of everyone when they come here, including the award judges, is wonderful. People often comment on the house having a lovely energy,” says Sally.

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