Class Q Atcost Barn Conversion

Posted 23rd November 2018

Class Q Barn Conversion

We at Conker have designed and overseen various portal frame barn conversion projects since the inception of “Class Q” consent in 2014. Class Q allows for the conversion of these structures via a simplified “prior consent” application, as opposed to the full planning permission process. In turn, Class Q enables alternative, potentially more efficient uses of land in rural settings where a new dwelling would not normally be permitted.

This large “Atcost” concrete frame barn was purchased by the client with prior consent already granted. However, the design as approved was uninspired. The layout also failed to capitalise on the broad views over the countryside. In addition, the client was ambitious and wanted to aim towards Passivhaus levels of thermal efficiency for the conversion.

In this particular instance, inaccuracies in the portal frame’s geometry and the need for additional external wall insulation meant that the outline and footprint of the building would technically need to increase. Therefore the opportunity was taken to redesign the scheme completely into one that worked technically and architecturally and submit for full planning permission, which was granted on first application with positive feedback from the local parish council.

Agricultural buildings have much greater headroom than is normal for residential buildings, therefore the internal heated volume is larger than necessary. Passivhaus assessments relate useful floor area with external surface area, this is known as the ‘form factor’. Form factor for barns is unusually poor, requiring higher than normal Passivhaus levels of thermal insulation. There are also challenging thermal bridges to overcome.

Based on these difficulties it was decided to aim for EnerPhit standard, a standard set by the Passivhaus Institute specifically geared for low-energy retrofits of existing buildings.

We recently completed the technical design and Building Regulations submission and the project is currently awaiting tenders.