Say you were the third generation of a farming family in the southwest of Scotland, and you intended to build a new farmhouse that made a statement about resource consumption. Building an environmentally conscious house in this climate requires insulation up to the ears. Now let's say this was a sheep farm you were running … well, you would, wouldn't you?
And so did Mary and Neil Gourlay, who turned to Mark Waghorn Architects for help in designing Three Glens, a five-bedroom house on their working farm near Moniaive. All of the house's external walls have been insulated with help from the livestock. "The wool has come from sheep on the farm, but has been treated in a similar way to sheepswool insulation products on the market," Mark Waghorn told Gizmag. The U-value for these wool-insulated walls is calculated at 0.18 W/sq m (a squeak outside of the rigorous requirements of Passivhaus).
But man cannot insulate with wool alone, and so Three Glens is triple-glazed, with the windows achieving a Passivhaus-besting U-vale of 0.7 W/sq m. The design is so airtight that mechanical ventilation, complete with heat-recovery system, has had to be added in in order to circulate air sufficiently. (Trickle vents in the windows were avoided on grounds of thermal inefficiency.)
Much of the stone used in the building fabric was taken from the surrounding fields, exposed through ploughing over the course of many years. The building is clad with oak grown on the farm.
The house is warmed with underfloor heating fed by a ground-source heat pump, and supplemented by a wood-burning kachelofen set into a stone wall. This is a much more efficient means of deriving heat from wood than an ordinary metal stove due to its improved insulation and ability to burn wood at higher temperatures. The stone wall which acts a thermal mass which helps to regulate temperature in the living areas.
Three Glens draws upon a renewable source of energy abundant in this part of the UK: wind. A 100-kW turbine nearby generates enough power for 25 homes, and most of the energy produced is put into the grid. All the house's water needs are met by a borehole, with a solar thermal system contributing to water heating.
As well as being a working farmhouse, Three Glens will double as a guesthouse with meals made from ingredients either grown on the farm or others nearby.