Shape Architecture was commissioned to undertake the redesign of a Country House near St Albans. The brief was to make it a more energy efficient contemporary building that opened up onto the gardens that surround it.
We have upgraded the thermal performance of the building fabric through the addition of thermal insulation board to the inner face of all external walls. A new roof and roof structure has been incorporated that again is extremely well insulated.
For the windows we obtained planning permission to revise the existing sash windows with a newer more energy efficient product by George Barnsdale. Replicating the aesthetic of the existing, the windows were double glazed and opened with a turn and tilt function. This change from sash was favourable in allowing a more dexterous window which also was in-keeping with the original look. The detailing of window frame to wall opening has been carefully handled to minimise any air leakage.
Larger format glazed doors by skyframe onto the gardens have been introduced alongside new rooflights to ensure adequate daylight is brought into the interior space which itself has been simplified and ‘opened up’
A ground source heat pump has also been provided linked to underfloor heating and in this we worked alongside the energy specialists Better Planet.
Tomas Larsson of Better Planet describes their work below.
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Ground Source Heat Pump
Given that this property will be brought up to more or less new built standard in terms of insulation, a ground source heat pump was identified as the best renewable option for space heating and domestic hot water.
As sizing of the heat pump and the ground loops is crucial, the first step was to do a room by room heat loss calculation. As a result, a 30 kW heat pump from the leading European manufacturer NIBE was specified. This unit has an impressive COP (Coefficient of Performance) of 4.36 indicating that it can produce 4.36 kW of heating for each kW of electricity supplied, in space heating mode.
The heat pump is supported by 1.2 km of ground loops placed 1m below ground level and connected to the plant room via a ground manifold and flow and return pipework.
The domestic hot water is prepared in two heat pump cylinders with a combined capacity of 800 litres.
An underfloor heating system was designed for operation at low flow temperatures which is crucial in the context of heat pumps. On ground level it is a standard system in screed. On the first and second floor the underfloor pipes are placed in pre-grooved gypsum boards.
The system is controlled by digital thermostats connected to internet allowing remote monitoring and control.
The heat pump installation will be eligible for government support through the Domestic Renewable Heat Incentive. Under this scheme, the client will receive quarterly tariff payments over 7 years. With this in place, a significant amount of the cost for the heat pump installation will be recovered.