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West Cork Passive Farmhouse

On a picturesque Island in West Cork stands a tall, grey detached farmhouse and stone-clad studio.  Even though the farmhouse looks like a traditional building, both house and studio were built to passive house standards.  The Architect James Murphy O’Connor explains: “By using traditional techniques but being more rigorous about how they are applied, any project can achieve passive standards. They don’t necessarily need to be contemporary buildings”.  With careful planning with regard to minimising thermal bridging and maintaining airtightness, the team achieved a very efficient building in a traditional building form.

The Kingspan foundation system which isolates the building from the ground was a major contributor towards making sure that the house had no thermal breaks. The walls are made with single leaf blocks that were rendered before the external insulation was put on. The roof is of traditional construction but with airtight membranes.

A similar foundation system was used for constructing the studio building, but the studio’s walls are of wide cavity wall construction with full-fill pumped bead insulation, so that they can support the stone cladding exterior. In both buildings, the windows are set into the insulation layer to prevent thermal bridging. Holes for services were planned and kept to a minimum. Airtight tapes were used at the window and floor junctions.  All these measures ensured that the house met the exacting airtightness target of the passive house standard.

In addition to a wood burning stove, the house is heated by a Nilan Compact P system. The unit combines an exhaust air-to-water heat pump with heat recovery ventilation to supply underfloor heating to the house and the studio. The unit also provides the domestic hot water.

The noteworthy thing about this A2, passive standard building is that the cost was similar to a conventional build. “The cost of this build is no more than if we used basic construction techniques and achieved a BER A2 rating,” said Murphy O’Connor.

A large part of this was due to the quality work of the contractor, David Evans, with whom Murphy O’Connor has worked with on various projects over the last 15 years. This was the first Passive House build for both Murphy O’Connor and Evans. So the challenge of the build was as much to do with the design as with the fact that it was a new experience for both of them, particularly in the need to focus on the small details that are so crucial with passive house builds. Evans recalls “without that prior experience, you don’t know how critical they are. So we probably over-focused on certain elements of it, particularly in relation to the airtightness.”

The key to achieving this standard is planning ahead, “it helped that Evans is such a conscientious builder”, said Murphy O’Connor.  The contractor was willing to learn, get the right advice, ask the right questions about airtightness and even to invite reps from the various companies to visit the site if necessary to demonstrate how to use products such as the airtightness tapes. The result was that the building achieved a successful airtightness pressure test of 0.5 air changes per hour at 50 Pascals at the first attempt. Both were in agreement that although achieving a rigorous low energy building standard is more onerous on the designer and the contractor, it results in a better building.

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