We are currently working on a large, energy efficient extension to an existing Grade II listed 18th century farmhouse. The farmhouse has an interesting history architecturally with previous extensions added to it in the 1990s after being listed in 1966. Our brief was to provide a contemporary side extension to replace the dilapidating utility and to make the farmhouse more energy efficient as a whole, as the client found their home to be really cold, especially in winter. One of our key strategies for doing this was to relocate the kitchen into the thermal envelope of the new extension as the kitchen is the house’s most demanding energy area.

The new extension is based on Passivhaus principles, which means we aimed for a super energy efficient design. As certified Passivhaus designers, we were able to gather existing information on the energy use of the farmhouse and use this to model ways to improve its efficiency. We used this information to help the client choose options most appropriate for them in terms of budget, savings on bills and comfort. A variety of products and technologies were chosen such as, Natural Building Technologies wall systems and air tightness measures and a Mechanical Ventilation and Heat Recovery (MVHR) system. We also added some more discrete energy saving measures to retrofit the listed farmhouse such as insulation below the floorboards and on the backs of doors. The idea was to reduce the number of thermal bridges as possible as this is where the heat tends to leak out of a building.

Timber slatted ceiling

We worked closely with the client to develop a design that would meet their needs whilst being sensitive to the historic nature and listing of the building. From the outside the extension is rendered white and looks completely different to the style of the farmhouse to avoid being pastiche. Inside, the materials are very honest to what they are with exposed recycled brick floor, a polished concrete floor and timber slatted ceilings. Our client was just as excited as us about being sustainable and eco-friendly which was really great!

As well as being the architects, we were also the Contract Administrators so have been coordinating the build while it is on site. The project is due to be completed this month and as the family have been living in the farmhouse while works have been going on, they are really looking forward to enjoying their more thermally efficient home and cooking in their new kitchen.

View of contemporary extension next to existing Grade II listed farmhouse