On Monday 10th September 2018 local residents Sally and John will give an illustrated talk on the eco-renovation of their house in Combe Down.
The owners are unable to take part in our Green Open Doors event scheduled for some time in autumn 2018, so we invite you to come along to The Museum of Bath Stone to hear all about it. Below are some details about the thoughtful and inspiring work that they have undertaken on their home.
Type of house
It is was a house typical of its time, a 1958 detached house, built from reconstituted Bath stone blocks with cavity walls and with all windows facing east-west.
As is often the case, the house was draughty, with air bricks on all sides to the suspended timber ground floor, unfilled cavity walls, and a letter box flapping in the front door. An old gas boiler provided hot water for taps and for a single-pipe circuit of radiators. The gas fire in the sitting-room required an air supply and chimney. There was some insulation in the loft but not enough. As well as wanting to reduce energy demand, the owners also planned to rebuild at the side of the property to create new living areas, where a garage was poorly linked to the main house by an enclosed passageway.
In phase 1 of the refurbishment, the ground floor was stripped back to the foundations then built up again with deep insulation beneath a slate floor with underfloor heating pipework. A large capacity thermal store supplied by renewable heat from solar thermal tiles was installed, with an efficient gas boiler as back up whenever needed. Water and waste pipes were re-sited within the walls so that the outer skin of the house was no longer penetrated. Loft insulation was meticulously linked to the top of the walls and the eaves once the wall cavities had been insulated. Finally, a mechanical ventilation and heat-recovery system was fitted in the floor void at first-floor level.
In order to further reduce energy consumption it was then decided to go ahead with phase 2. This involved replacing the windows with triple-glazed units and adding external wall insulation to complete the ‘tea-cosy’ effect around the thermal mass of the house.
Energy efficiency measures
- solar thermal tiles
- gas condensing boiler
- thermal store for space heating and hot water
- sophisticated thermostatic controls
- underfloor heating
- slate flooring as part of the thermal mass
- Jablite and Celotex insulation to solid ground floors
- mineral fibre cavity-wall insulation
- phenolic foam external insulation and render
- triple-glazed timber windows
- extensive draught sealing
- mechanical ventilation with heat recovery
An airtightness test measured air permeability of the house as 3.8m3/h.m2, better than the Energy Saving Trust’s recommendation of 5m3/h.m2. An Energy Performance Certificate gave an energy efficiency rating of 84% and an environmental impact rating of 86%. The solar thermal roof slates provide virtually all the heat required during summer months, and usefully supplement the gas input at other times of year. Regular meter readings show that energy consumption has than halved thanks to the reduced heating needs.