Rose Walk Close

Description of the works:

Deeper Green were asked to extend and make more energy efficient a draughty late-1960s-built chalet bungalow on an exposed site high above the town of Newhaven. The project was complete in the autumn of 2026. The house now requires around 40% less energy to heat it, makes about 107% of its own annualised energy needs and has the ability to accommodate multi-generational family living.

Assessing the existing context

Due to its exposed and high location close to the English Channel, the house suffered from high levels of thermal discomfort in the winter particularly when windy. A previous owner had had the cavity walls filled with formaldehyde insulation which had cracked, shrunk and, in various places, dropped to a point where significant pockets of cold air were forming on the warm side of the injected material. U-PVC double-glazed windows had been fitted without due regard for airtightness and the suspended timber ground floor cumulatively added to the draughty nature of the interiors.

The proposals

Our clients were realistic about the budget and we set about scoping the most sensible eco-retrofit strategy of the existing building as well as doing a spatial study for a new extension and a complete rearrangement of the ground floor. Deeper Green’s Eco-Retrofit Scoping Study consolidated on a suit of upgrades that would result in a reduction of heating demand from around 6.1kW peak to around 3.5kW, even with the increased volume of the new extension. This was a 42% reduction. This paved the way for the replacement of the existing gas-fired boiler with an all-eelectric form of heating, chiefly supplied by an air source heat pump. The new extension was to take the place of an existing double-garage. This increased the habitable area of the building from 100m2 to 142m2 – a floor area increase of around 30%.

Additionally, the clients wanted a new entrance porch and a sauna and a shower room on the ground floor. Some of the 142m2 of habitable area of the building was in fact completed as a ‘Garden Room’. As the space was mainly intended for storage, it was not to be heated. However, the room is fully insulated and has dormant underfloor heating fitted into the screed. Thus, the space is future-proofed for an easy Regulations-compliant conversion to habitable space if needed.

Another design feature of the project included, locally grown and manufactured coppiced sweet chestnut cladding which was used to clad the new porch external walls. This is a durable and dimensionally stable material which helps the Wealden woodland industry. Best of all, the coppice growing technique is the fasted way of growing hardwoods and all the material is of course locked carbon removed from the atmosphere through photosynthesis.

The final contract sum was around £343.5K + VAT with some elements delivered under the Government’s 0% VAT boiler replacement scheme.