Panorama programme

Working within the Code for Sustainable Homes isn’t exactly easy when you’re dealing with a typical four-bed semi. When the development is a rather grander construction – something more befitting a Bond villain or Russian oligarch – those challenges are greatly multiplied.

This was the experience of Silcock Dawson & Partners when designing a large private dwelling, Swinhay House, which is nearing completion in Gloucestershire. The 2800m2 home, spread over 11 levels, incorporates

several self-contained apartments, a 25m swimming pool, a bowling alley, squash courts and an eight-bay garage as well as the main living accommodation.

The central spine of the main building extends through to a panorama room with 360° views and a 15m-high tower. Dominating the building is a winter garden beneath a free-span glazed roof. “The original concept was for an open-plan house with the main living spaces opening directly onto the winter garden,” says Gordon Hodges, regional director of Silcock Dawson.

The heat loss through these heavily glazed elements presented one of the biggest challenges for the design team. The building was designed under the 2002 Part L requirements and the large expanse of glazing was traded off against the substantial, well-insulated walls.

The glazing units for the 500m2 winter garden were developed with the Scandinavian supplier and provide U-values of less than 0.6W/m2K, while the front elevation incorporates motorised blinds within triple- glazed panels.

The panorama room and viewing tower have up to 75% of their elevations glazed. Here again, triple-glazed, low-energy glass units with motorised integral blinds were used to help to cut heat loss and solar gains.

The other issue was how to heat this substantial building. There is no mains gas supply within a mile of the site and the client rejected bulk storage of oil, LPG or biomass fuel, so Silcock Dawson opted for ground source heat pumps. Two coils were laid, one in the 2m-deep artificial lake and another buried in the surrounding grounds.

Three 90kW units meet the bulk of the heating and cooling demands. The unit for the main building supplies an underfloor system and provides fresh air tempering via the air handling unit supplying ventilation air.

Several pumped circuits provide zonal control and flexibility, and the unit can also provide cooling via the underfloor coils and air handling unit.

The swimming pool water and air heating demands are met by another 90kW ground source heat pump, operating at a higher flow temperature to meet the needs of the space.

An additional feature is the ability to reclaim stored heat from the swimming pool water to heat the house during times of low thermal load, without the need to operate the GSHP. A secondary plate heat exchanger is provided, with automated valves, to divert the source of the heating system from the GSHP to the heat exchanger, using the existing system pump sets and distribution pipework.

The temperatures required in the winter garden will depend on the final planting scheme but will generally be allowed to drift, within a band of 20-25°C, estimates Hodges. The ventilation system is based around a dedicated air handling unit. The fresh air inlet is via an 80m subterranean duct, designed to provide a tempering effect on the fresh air, cooling in summer and preheating in winter.

The system has the facility for recirculation of air in the winter plus a full fresh air mode during the summer for internal temperature control, using automated opening at high level within the structure.

In total, Swinhay House has taken almost four years to design and build. “It’s a unique building and was very much a design co-operation with the client, who was closely involved with the decision-making throughout,” says Hodges. “Projects like this don’t come along very often, and when they do you jump at them.”