Is this the greenest house in the area?

PROFESSOR John Twidell and wife Mary answered the Mail's carbon footprint challenge.

The couple sent an email to the Mail last week outlining the green features in their home, the Amset Centre, Bridgford House, Horninghold near Hallaton

Prof Twidell is also a member of the Transition Town Harborough group.

Below is a copy of Prof Twidell's email:

"100 per cent carbon-neutral living and 50 per cent zero-miles food.

The village

Reconstructed between about 1890-1910 by estate owners the Hardcastle family. The houses renovated and built by Thomas Hardcastle between 1900-1910 were built to make the village a 'garden village'.

This was a 'green' architectural movement at the turn of the century for 'sustainable living' e.g. each house had a vegetable garden and trees were planted. The village is now listed as a Conservation Area for planning policy. There is also a Tree Preservation Order.

The buildings and garden

Bridgford House (so-called about 1945) was originally built in 1906 as stables for the estate horses and vehicles. It was slowly changed into domestic use from about 1945 to 1985.

The original walls are solid brick, without a cavity. The structural floors are concrete on soil without insulation beneath.

The whole plot is about one acre, with about 20 mature trees plus about 20 fruit trees, many shrubs, flower and vegetable plots, poultry enclosures, play and games facilities.

Sustainable strategy


Monitor and quantify. Move to 100 per cent renewable energy, heating and electricity for house; increase energy efficiency of lighting, heating, appliances etc; increase vegetable and poultry production to at least self-sufficiency.

Longer term

Increase on-site microgeneration; improve structure; produce transport fuel on site; improve biomass heaters, increase use of well-water, rainwater and grey-water.

Fossil-carbon abatement

Renewables substitution for household and office energy, substitution of food-miles by on-site food production, biodiesel manufacture on site for own vehicles, export and trade of on-site renewables to compensate of necessary air travel.

Building thermal insulation

This is a major and prime challenge for any old building, especially barn conversions.

To date:

Loft insulation throughout. Fibrous insulation between joists.

Cavity-wall insulation where there are cavities (front only, otherwise solid walls).

Under-tile foam insulation: (i) above water-tank area in the roof, (ii) under roofs of attic rooms.

Insulating under-carpet covering: in snug and study. Surprisingly effective for comfort.

25 mm expanded polystyrene insulation under kitchen wood-board floor, above original concrete.

Future aims: external insulation on north, west and east sides, conservatory on south side, increased loft insulation and under-tile proofing.

Green electricty

The utility grid-electricity supplier is Good Energy. This company only supplies electricity from renewable energy generation, principally from wind turbines and landfill gas engines.

Large hydro is not included in the generation. There is (i) a 'ixed price tariff, and (ii) a day/night tariff whereby the price of the electricity is cheaper at night (midnight to 8am summer and winter) to compete with standard large suppliers. However, both day and night rates are about 10 to 20 per cent higher than standard from nuclear and fossil fuels. We have the fixed tariff, since we offset midday import with our own PV microgeneration.

Heating and cooking

The central heating system (with domestic hot water heating) has several features:

A wood/straw-bale fired boiler from Denmark is the main source for central heating and potable-water heating in winter (about November to late April).

The burning chamber is cylindrical (length 1.5m, diameter 0.8 m) and so can take large logs, sections of timber and waste biomass.

All the biomass fuel should be completely dry (e.g. stored undercover in an open shed for at least one summer). Once burning, there is little smoke from dry biomass.

A condensing oil boiler that is 95 per cent efficient. This is used as back-up in case the wood fired system fails (e.g. lack of cut wood!). This boiler has sophisticated microprocessor timing and temperature-setting controls.

Much improved controls and safety for the main wood-fired boiler.

Installation of a wood fired 'range and oven'. This is the Stanley Range/Oven in the kitchen.

As well as cooking, this range heats the domestic water and central heating (in practice about two or three radiators can be heated).

Norwegian Jotul wood-burning stove in the main sitting room.

In 2005 we fitted a modern pellet-burning heater (Extraflame, Italian) in a family room (snug). It was purchased from and fitted by a local farmer who has diversified into wood fuel provision (Rural Energy, Owston, Leicestershire). Pellets bought off the internet; delivery shared with a neighbour.

A solar water-heater is fitted on the south side of the main roof. The heat goes to a compatible (tall) water cylinder with two heating coils. This tank stores the hot water and is well insulated. The lower coil is heated from the solar water heater, the higher coil by the wood-fired boiler and Stanley Range.

Thus the solar heat is the first used when cold water enters the tank from the bottom. The tank is in a clothes airing cupboard in a central area to use the lost heat.

The water cylinder has a short electrical heater at the top, with a thermostat near the top. We seldom activate this. However, if activated, a time clock enables this heater at about 4am, but the electric heating only comes on if the temperature is below 45C. Thus electricity is 'called' as a last resort. In practice this is very seldom and relates mostly to the occupancy of the house in summer when we have visitors staying over. The electricity supplier is a green company.

The three heating systems for the central heating are in parallel. Normally the oil boiler is not used. The solar water heater effectively provides pre-heating during the months October to May, and majority domestic water heating May/June to Sept/October. The domestic hot water load to be 50 per cent solar heated on average through the whole year. The main effect has been to dramatically reduce electrical heating in the summer, and to improve the water heating in the spring and autumn from the Stanley Range.

In winter, the main wood-fired boiler is kept fuelled continuously for central heating and domestic hot water. The Stanley is used for cooking, baking and provides socially comfortable heat in the kitchen, plus some extra heat for the house.

Between winter and summer, the main boiler is not used, with the Stanley Range providing cooking and domestic hot water, plus some heat for the house as needed.

The use of wood for heating and cooking

The vital aspect of using wood for fuel is that the wood must be dry. In practice this means keeping it under cover in an otherwise open enclosure for 12 months (certainly it should be 'summer dried' in preparation for the winter). The water dries from the internal wood structure within months, but takes up to a year to dry from inside the cells of the wood itself. Most wood sold as 'dry''is not really dry.

A large Wood Store (about 4mx 5mx5m) is used. This should be at least 80 per cent full for the next winter ahead.

In practice there is much wood available. The limitation is the hard work in cutting, transporting and storing it. A Land Rover, large trailer, chain saws, safety clothing, climbing ropes etc are needed. Plus much hard work and muscle power. HEATING WITH WOOD IS NOT A TRIVIAL TASK - be warned.

Energy conservation

Thermostatic valves were installed with each radiator to give individual room control (e.g. turn off unoccupied rooms).

Heat reflecting and insulating panels were fitted behind each radiator to lessen wall loss.

Low energy, compact fluorescent lights, mostly ~ 11 W

Some 12 volt and 240 V halogen spot-lights (~ 60W).

LED lights (~ 1.5 W per halogen replacement) replacing mains halogen (~ 60 W) for 'spot reading or working'

Solar washing line in garden.

Clothes airer above range in kitchen.

Airing cupboard, contains insulated hot-water storage tank, so uses waste heat from solar collector and boilers.

Condensing clothes-drier in winter, recovered heat in kitchen (uses Green Electricity*)


In September 1974, 40 BP Solar photovoltaic panels (crystalline Si) of 3 kW total nominal capacity were fitted to the south-facing garage roof. Some shading occurs from trees safeguarded by the Tree Preservation Order. A 50% grant was received form the UK programme for such grid-linked microgeneration. The inverter/controller interface is Sunny Boy. Generation has average 1750 kWh/y, for which Good Energy pays a ROCS payment of 4 p/kWh and electricity priced at 10 p/kWh is offset. We are now lobbying to be able to sell the ~ 850 kWh/y of exported power, but no buyer can be found since the meter-reading charge is 50/y (a significant barrier). We try to match our use of electricity to the solar supply, but a good-match is not possible in practice.


5 x 30 W solar photovoltaic panels charge a 12 volts battery through a controller. Some lights are 12 volts with internal inverter. There is a 500 W, 12 V / 220 V, 50 Hz inverter for main supply.

A 50 W wind turbine also charges the battery in parallel (but the site is obviously not windy because of the trees).

A demonstration solar water heater.


All the houses in Horninghold had wells installed around 1900 as part of the 'Garden Village' construction. There was also a pumping house for cattle watering to a distance of more than a kilometre. Only some of these beautifully constructed brick wells remain, as at Bridgford House.

A mains-electricity water pump has been installed at the foot of the 10 m deep well. This is used in sunny summer-days for vegetable-garden irrigation (porous tubing along rows, all with taps to allow parallel feeds). Thus, the pumping coincides with otherwise excess generation from the 3 kW photovoltaic array.

Water pipes have been installed to bring pumped well-water to the house. At present a metered supply comes from Seven Trent, and the sewage goes to Anglian Water (having a metered supply saves about 500 per year!). Water use averages at 0.3 m3 per day.


There are 4 rain-water tanks*, with a combined volume of about 2,500 litres. Most water is used in the polytunnel and garden for plants, but is also available for general outside cleaning (e.g. car).

The 1000 litre tank beside the polytunnel fills from the roof of the garden shed and can drip-irrigate plants in the polytunnel.


This provides sufficient vegetables for the whole year. The cultivated area for soft fruit and vegetables is about 45m x 40 m = 1200 m2

Fruit trees: 10 apple, 2 cherry, 2 plum-cherry, 2 mulberry, 1 quince, 4 pear, 4 plum.

Polytunnel - .lettuce throughout the winter, tomatoes in summer, early and late strawberries, seed trays and seed planting. Drip watering from a tank filled by runoff from a garden shed.

Irrigation is from the well and the connected water tanks through permeable rubber tubes alongside the crops.


6 hens and 3 ducks provide apple supply of eggs, apart from mid winter, late Dec to mid January. Surplus crops, waste food, weeds and grass cuttings augment wheat feed from a neighbouring farm.


Closhmerle. Separate containers are used for :

• compostables (waste vegetables, some newspaper and cardboard etc, light clippings from plants)

• glass (green, brown, clear are separated)

• cans and tins

• plastic drinking containers

• dead batteries

• scrap metal (that really has no further possible use!

• ultimate rubbish (mostly non-drinking plastic and the most horrible weeds) goes to the Council collection.

• paper and cardboard is either added to the kitchen compost, or bundled for burning in the closed boiler.

Composting and 'branch stacks'

• Around the garden are various 'convenient' heaps, e.g. for composting leaves and turfs, and various 'stacks' left in place for small mammals and wildlife. The compost heaps are dug out after about 2 years and used on the garden. All growth < 1 year old is composted. All older trimmings and cuttings are dried for burning, or added to the stacks.

• After ~ 10 years, the partially composted stacks are cleared for excellent compost at ground level and the remnant for fuel.

• Chicken droppings and bedding is collected for concentrated manure and for making liquid manure.

• Horse and sheep manure (about 4 large trailer-loads per year) is imported from nearby stables, from which there are abundant supplies. The limit is the hard work and effort, rather than the supply.


All around the garden, there are various 'eco-patches'. These are to encourage wild flowers, insects, birds life, etc. No pesticides or artificial chemicals are used (apart from reluctant slug-killer and occasional lawn-weed killer for peer-group village pressure).


• large front conservatory

• rear and side wall external insulation

• house water from well

LOCAL FOOD ('zero miles')

• Our own vegetables and eggs provide ~30% of our metabolic input.

• Lamb and beef from farms in the village, and our poultry provide ~75% of meat.

• Poultry feed is 80% our own crops and village-farm wheat, 20% commercial feed


• We have tested biodiesel fuel in my car and will use this in future when a supply is found costing no more than ~110% of fossil fuel.

• A tank is being installed for ~1,000 litre biodiesel deliveries.


Our house is now 90% fossil-carbon-free for heating; 100% fossil-carbon-free for electricity (our PV and Green Electricity); we export ~850 kWh/y of fossil-carbon-free electricity. This abates net about 1 tonne/y of fossil-carbon of our heat and about 1 tonne/y of fossil-electricity.

Growing and providing about 50% of our own food 'calories', and buying local meat (neighbouring farm lamb and beef, local turkey at Christmas), saves about 1 tonne/y fossil-carbon of supermarket 'food miles'.

Total abatement about 3 tonne/y for 2 people (1.5 tonne/(person y)

APPENDIX. Product details

Condensing boiler Oil-fired, used as back-up for central and potable-water heating. CSB Boiler, HCC heating. Manufactured and installed (1997) by Barnatt-Millns Group, The Old Coach House, Coach Roadf, Hougham, Grantham NG32 2JF (tel 01400 250293).

Cooker Range: 'Stanley Cooker/range, type 'Donald' – solid fuel' (includes dry wood and peat). Manufactured by Waterford Foundry Ltd. (see Stanley Cookers (importers and distributors), Gledrid Industrial Park, Chirk, Clwyd, LL14 5DG |(tel 01691 772922). Installed (1994) by Barnatt-Millns Group, The Old Coach House, Coach Roadf, Hougham, Grantham NG32 2JF (tel 01400 250293).

Green Electricity Supplier 'Good Energy' (100% new renewables)., Tel: 0845 456 1640 Fax: 01249 766091, Email:

Good Energy, Monkton Reach, Monkton Hill,Chippenham, Wiltshire SN15 1EE


Energy Meter (energy plug for measuring power and energy of devices) <>

Pellet-stove Extraflame I.C. Mini (Via del'Artigianato 10, 36030 Montecchio PrecaLCINO, Vicenza, Italy; tel +39 044 586 4488;, Supplied and installed by Rural Energy, Green Lane, Owston, (near Oakham), Rutland LE15 8DX (tel 01664 454989,,

Solar Water heater Solar collector (3 m2) manufactured by AES (Lea Rd., Fores, Scotland; Double heating coil storage cylinder 238 litres. System installed Feb 2000 by Sustain (address then: 45 Rowley Fields Av., Leicester LE3 2ES, mansger Mark von Kanel): 2,690 inc VAT, no grant then. Similar installers are listed on the Energy Saving Trust web site.

Under-carpet insulation: Axfelt, manufactured by Axminster (Carpet Company); purchased from Uppingham Carpets, High St. West, Uppingham.

Rainwater tanks/butts

(a) Rexam Harcostar Ltd, Windover Rd., Huntingdon, Cambridgeshire PE18 7EE. Tel (0) 1480 52323 Fax (0) 1480 413203.

(b) Recycled orange-juice tanks, LBS, Standroyd Mill, Cottontree, Colne, Lancashire BB8 7BW; ph 01282 873 333.

Wood stove: Jtul (Norwegian). Installed (1994) by Falcon Fires, 33 Fleckney Road, Kibworth Beauchamp, Leics. LE8 0HF (0533 796079)