| The Apple Barn
The extensive renovation and retrofit of a 16th-century barn in Devon, to become a modern, light-filled and highly efficient family home.
The design aims to respect the form of the existing barn and the agricultural context that surrounds it. Maintaining a central double height space retains the legibility to its former use, with two storage wings accessed by larger machinery through the large central doors. A central bridge now connects two separate bedroom wings, while cosy living spaces sit beneath. The kitchen and dining spaces really are the centre of the home, filled with natural light, contemporary and warm in character. The variety of space creates a wonderful modern home. The insertion of new exposed timber structure, to sit alongside the existing, provides a warm character, but also allows the building to be read as an agricultural barn with a working history.
The retrofit strategy involves a highly insulated, breathable and thermal bridge free construction, using natural materials that help to prolong the life of the existing building and provide a healthy internal environment. We used the Passivhaus Planning Package to evaluate and reduce the homes running costs.The project had its complexities: working within the constraints of Permitted Development and negotiating a sensitive flood risk strategy, whilst designing to high-efficiency standards.
We are delighted that the project is complete, ourselves and our clients are thrilled with the results, and we love seeing the building in use.
The design aims to respect the form of the existing barn and the agricultural context that surrounds it. Maintaining a central double height space retains the legibility to its former use, with two storage wings accessed by larger machinery through the large central doors. A central bridge now connects two separate bedroom wings, while cosy living spaces sit beneath. The kitchen and dining spaces really are the centre of the home, filled with natural light, contemporary and warm in character. The variety of space creates a wonderful modern home. The insertion of new exposed timber structure, to sit alongside the existing, provides a warm character, but also allows the building to be read as an agricultural barn with a working history.
The retrofit strategy involves a highly insulated, breathable and thermal bridge free construction, using natural materials that help to prolong the life of the existing building and provide a healthy internal environment. We used the Passivhaus Planning Package to evaluate and reduce the homes running costs.The project had its complexities: working within the constraints of Permitted Development and negotiating a sensitive flood risk strategy, whilst designing to high-efficiency standards.
We are delighted that the project is complete, ourselves and our clients are thrilled with the results, and we love seeing the building in use.
Project Factfile:
Project Stage: Complete 2020
Location: Devon
Architecture: Croft Design Collective LLP
Main Contractor: Woofenden Construction
Structural Engineer: Simon Bastone Associates
Ecologist: Simon Geary Ecology
Annual Heat Demand: 26 kWh/m2a (Design Stage)
Air Tightness: 1.7 Ach @50pa
MVHR: Nuaire
Insulation: Cellulose, Glapor
Windows: Velfac, Harmony
Air Tightness Products: Pro Clima
Location: Devon
Architecture: Croft Design Collective LLP
Main Contractor: Woofenden Construction
Structural Engineer: Simon Bastone Associates
Ecologist: Simon Geary Ecology
Annual Heat Demand: 26 kWh/m2a (Design Stage)
Air Tightness: 1.7 Ach @50pa
MVHR: Nuaire
Insulation: Cellulose, Glapor
Windows: Velfac, Harmony
Air Tightness Products: Pro Clima
Sustainable Design
Achieving high levels of insulation and airtightness in an existing building is not easy, retrofit is a technically challenging and often mis-understood art. The Apple Barn achieves excellent levels of fabric efficiency, and in the right way. We have done this using an entirely breathable construction. For example Glapor and Limecrete in the floor construction allows moisture in the ground to be properly managed. The cellulose insulation, lime plaster and timber structure in the walls and roof, allow water vapour to breathe through the construction rather than getting trapped. The drained and ventilated cavity behind the existing walls moves the condensation point to a place where moisture can be properly managed. The careful detailing of junctions to ensure a thermal bridge free construction eliminates cold spots, or concentrated areas of heat loss, that could lead to condensation risk. The use of breathable materials often results in more natural materials which also reduces the embodied carbon of the construction.
The project was assessed in the Passivhaus Planning Package and daylight analysis tools to minimise the homes energy demand and ensure great levels of natural light throughout. All of these measures create a highly comfortable home, with very low running costs, and low impact on the wider environment.
The project was assessed in the Passivhaus Planning Package and daylight analysis tools to minimise the homes energy demand and ensure great levels of natural light throughout. All of these measures create a highly comfortable home, with very low running costs, and low impact on the wider environment.
Technical Considerations
Creating a highly insulated, breathable construction, whilst managing the flood risk of the site is a tricky challenge. We had to work with a condition that meant the first 600mm in height had to be a flood resilient construction. In discussions with the environment agency, and suppliers, we established that the Glapor and limecrete floor, could be considered flood resilient. The normal strategy is to use closed cell barriers to stop water entering the ground floor construction. In contrast, as the Glapor’s performance and structural integrity would not be affected by the temporary presence of water it was allowable. In a similar way, the insulation for the first 600mm of wall construction is Cork Granules, rather than cellulose, as this is an insulation material that would not be affected by the temporary presence of water.
It was identified during surveys that one wall of the barn was leaning out and needed to be tied into the new internal structure to ensure that there would be no further movement. This is usually done with metal straps, however this would cause too much of a condensation risk in the highly insulated fabric. We therefore designed a solution, using a glass-reinforced plastic re-bar (usually used in concrete construction). The plastic rebar had the same tensile strength as the steel strap, and a significantly lower thermal conductivity. We worked with the engineers to design connection details at the end of the rebar to tie into the timber frame and external wall.
It was identified during surveys that one wall of the barn was leaning out and needed to be tied into the new internal structure to ensure that there would be no further movement. This is usually done with metal straps, however this would cause too much of a condensation risk in the highly insulated fabric. We therefore designed a solution, using a glass-reinforced plastic re-bar (usually used in concrete construction). The plastic rebar had the same tensile strength as the steel strap, and a significantly lower thermal conductivity. We worked with the engineers to design connection details at the end of the rebar to tie into the timber frame and external wall.
