40% House

George Marshall and Annie Levy have reduced the energy consumption of their mid terrace house by nearly 60% through the thorough application of simple and readily affordable measures. The house shows how conventional, low tech measures, when combined with careful and aware behaviour, can achieve significant emissions reductions.

About the house
The house is a 1936 mid terrace ex-council house. When George and Annie moved into the house in 2000 it was in a poor condition after years of low cost letting and botched DIY renovation.

Why did they want to do it?
George and Annie wanted a house that functioned well for a new and growing family without compromising their environmental principles. George saw the project as a chance to take a sabbatical from his work as an environmental campaigner and develop new skills and knowledge that could give a fresh perspective his work.

About the renovation
The starting point for the renovation was the family needs – moving the bathroom upstairs, converting the loft into a mezzanine workspace for Annie overlooking the bedroom, and building an extension at the rear. The environmental aspects of the design came second.

Insulation
The external walls were constructed of concrete blocks laid in a ‘rat trap bond’ in which every other block crosses the cavity, creating powerful cold bridges that undermine the effectiveness of cavity insulation. External insulation was therefore the best option- especially given the need to render the wall to cover the ugly marks left after the ‘Cotswold style stone cladding’ fell off in the night! The insulation was 75-100 mm of standard expanded insulating foam (Celotex or similar), bolted to the wall and finished with lathe and render.

The insulation of the loft conversion and the extension were conventional in both materials and application- expanded foam between and over the rafters in the roofs, rockwool in the cavity of the extension. Both were over specified to achieve 2-3 times the level of insulation required by building regulations. The roof of the extension was also turfed under a system installed by Index, a specialist roofing company. “The more green the better” says George.

Heating
The house is heated by an 8Kw condensing gas boiler and radiators. To achieve maximum efficiency George and Annie installed 25% more radiator capacity and a boiler that was substantially smaller than would conventionally be fitted. “At first the plumber refused to install it because he said it was too small” says George. A roof-mounted evacuated tube solar panel, manufactured by Thermomax, provides additional water heating.

Large skylights in the south facing roof bring light flooding into the bedroom. On sunny days in spring and autumn the double height room becomes a ‘solar generator’ and a thermostatically controlled fan pulls the warm air from the top of the mezzanine down a duct to the rear extension.

The overall system achieves high levels of performance because George has been systematically ‘tweaking’ the boiler output, flow rates, thermostatic radiator valves and timers to achieve optimal performance. “Most people never realize the theoretical savings of the new technologies because they don’t put in the time to fully set the controls” says George. The main living room is kept at 17-18 degrees, and the bedrooms around 16-17 degrees, several degrees lower than conventional houses.

Water conservation
All toilets are fitted with dual flush devices. Waste water from the bath and shower is held in a tank (the old copper hot water tank) in the new utility room underneath and used to flush the downstairs toilet. In addition to saving a lot of water (overall the house uses 60% less water than an average family home) the heat in the water keeps the utility room warm for clothes drying. ‘The water can sometimes be a little smelly’ warns George and says that next time he will fit a proper water filter.

Fittings, materials and appliances
All appliances are A rated. The washing machine and dish washer are filled directly from the hot water tank to minimize electricity use. All lights are low energy bulbs and are about to be replaced by the new generation LEDs. All electrical switches are accessible- either as switches of wall mounted strips- and the children have been trained to switch everything off at the point when not in use.

Re-use and salvage
During the renovation there was a strong emphasis on the reuse of materials. Demolition waste was sorted and, where possible, reused for new construction or as hardcore. Timber from local salvage yards was used for the new stairs to the loft and the sarking of the extension roof. The sinks, one toilet and all the kitchen fittings were also salvaged.

Ventilation
Much thought was given to encouraging air to flow through the house. Pre-warmed air enters the house through a glazed sun porch at the rear. Vents at the top of the extension roof and in the casing surrounding under the bath enable air to rise up through the house and through trickle vents at the apex of the roof.

What were the main obstacles they encountered?
The approach of the building inspector was highly critical and sometimes obstructive. He overruled the structural engineer, demanded extra steel reinforcement in the roof, and held up the installation of the turf roof for several weeks. The local planning department also brought work to a standstill through a challenge that was unfounded and subsequently withdrawn.

Where did they find the information?
Most information came from general reading and from the builder. There weren’t any really good references at the time, though now George would strongly recommend “The Whole House Book”.

Top Tips
1. Exceeding building regulations on insulation is cheap and easy.
George says that builders see it as a point of pride that they go absolutely no further than minimum building regulations on insulation. However, as he found, there is a very low cost for a builder in doubling or tripling insulation levels.
2. Plan re-use into the renovation process.
Plan ahead to re-use as much demolition waste as possible in a renovation. In addition to  environmental benefits there are major cost savings in material costs and skip hire.
3. Size your boiler right
4. Few condensing boilers operate at full efficiency because they are too large for the house. As a simple rule of thumb, boiler output of a new boiler should not be greater than the maximum combined heat output of the radiators.

Energy Savings
Gas consumption fell from an average of 56 kWh/day (97-2000) to 26 kWh/day (2001-2003). Electricity during the same period fell from an average of 8.5kwh/day to 4.2 Kwh/day. The total energy related emissions fell from 5.5 tonnes to 2.6 tonnes per year, a reduction of 53%. A subsequent switch to Unit E renewable energy pushed the reduction to 65%. Given that the renovations increased the floor area within the heated part of the house by 30%, energy savings per square metre had fallen by 73%.

Contact
There is a website on the house and the theory of eco-renovation, with a good links and contacts directory at www.theyellowhouse.org.uk

George and Annie can be contacted at george@coinet.org.uk

The house is not usually open for visitors, though special cases can sometimes be made.