Not only is water a precious resource in its own right, there is also an energy component in storing and transporting it and making it drinkable. On average, a person in the UK uses 135 litres (30 gallons) of water per day. Of this total about half is used flushing toilets and for personal hygiene. A really thorough home ecological improvement strategy should have three components:
• Reduce consumption;
• Harvest rainwater;
• Recycle grey water.
Reducing consumption
Flushing toilets use about 30 per cent of total household consumption. This can be reduced by changing to a low flush toilet (2-4 litres) or a dual flush cistern. Aerating (spray) taps on basins, sinks and on shower heads make a big impact on consumption. All appliances should have isolating stop cocks so that the whole system does not have to be drained off if one item has a problem. Washing machines and dish washers vary in the amount of water they consume. This is one of the factors which should influence the choice of white goods which will be considered later in this topic.
On average, about 200 litres of rainwater fall on the roof of a 100-m2 house each day in the UK. In many homes this is collected in water butts and used to irrigate the garden. However, it has wider uses. There are several proprietary systems for collecting and treating rainwater so that it can be used to flush WCs and for clothes washing machines. An example is the Vortex water harvesting system which serves roof areas up to 200 m2 and 500 m2, respectively. Recycled rainwater must only be sourced from roofs. Storage tanks are either concrete or glass-reinforced plastic (GRP). There are controls to ensure that mains water can make good any deficiencies in rainfall. If filtered rainwater is to be used for other domestic
Typical domestic rainwater installation with storage tank in the ground and a pressure pump in the tank
1 Vortex fine filter
2 Inflow smoothing filter
3 Tank
4 Floating fine suction filter
5 Suction hose
6 Multigo pressure pump
7 Pressure hose
8 Automatic switch and ballvalve
9 Overflow trap
10 Installation controls
11 Magnetic valve
12 Open inflow for drinking water feed
13 Backpressure flaps
Figure 11.1
Rainwater storage system layout. Courtesy of Construction Resources.
Typical domestic rainwater installation with storage tank in the ground and a pressure pump in the tank purposes, other than drinking, it must be subject to further purification, usually by ultra-violet light. Best use of the filtered rainwater will be made if associated with dual flush WCs. Figure 11.1 shows a typical configuration for rainwater storage.
1 Vortex fine filter
2 Inflow smoothing filter
3 Tank
4 Floating fine suction filter
5 Suction hose
6 Multigo pressure pump
7 Pressure hose
8 Automatic switch and ballvalve
9 Overflow trap
10 Installation controls
11 Magnetic valve
12 Open inflow for drinking water feed
13 Backpressure flaps
It is possible to go a stage further and use rainwater for drinking, but this requires even more rigorous filtration, as employed for example in the Southwell zero energy house designed by Robert and Brenda Vale and the Hockerton Project. In the former case the water from the roof passes through a sand filter in a conservatory. From here it is pumped to storage tanks in the loft and from there through a ceramic/carbon filter to the taps. As an act of faith in the English weather, there is no mains backup facility.
A variation on the water recycling strategy is to re-use grey water from wash basins, showers and baths. If waste water from a washing machine is included, then virtually all the waste water can be used to meet the needs of flushing toilets. Again there are systems on the market which serve this function, including water storage.
The Hockerton Housing Project has all these facilities and more because it uses rainwater collected from its conservatory roofs for drinking purposes. The water is stored in 25 000 litre underground tanks where particles have time to settle to the bottom. The water is treated first by passing it through a 5-micron filter to remove the remaining particles. Then it is sent through a carbon filter to remove dissolved chemicals. Lastly it is subjected to ultra-violet light to kill bacteria and viruses. The author can vouch for its purity! For the average home this may well be a step too far, but those who feel inspired by this possibility should contact the Hockerton Housing Project at www.hockerton.demon.co.uk
Rainwater recycling systems can be found at Construction Resources (Tel: 020 7450 2211; www.constructionresources.com).
For the really dedicated there is the composting toilet which eliminates the need for water and drainage. In Europe a popular version is the Clivus Multrum from Sweden. It is a two-storey appliance in that there has to be a composting chamber usually on the floor below the toilet basin. A fan-assisted ducted air ensures an odourless aerobic decomposition process. The by-product from the composting chamber is a rich fertilizer. A UK distributor is Kingsley Clivus Environmental Products Ltd, Winkleigh, Devon (Tel: 01837 83154; www.kingsleyplastics.co.uk).
For a comprehensive list of related products see: World of Composting Toilets (www.compostingtoilet.org).
Domestic appliances
As the building fabric of a home becomes more energy-efficient, the impact of appliances, such as white goods and TVs becomes a much more significant element of the energy bill. Refrigerators and freezers are particular culprits. In 1999 the European Commission decreed that all white goods, refrigerators, freezers, washing machines, dishwashers, etc., should be given an energy efficiency rating from A to G. This has certainly been effective in sending E, F and Gs to the bottom of the best buys. However, whilst A is the top of the scale, there is variation within this category and it is well worth investigating fridges and freezers which perform better than the threshold level for A rating.
Here are examples current at the time of writing. An example of an ultra-low energy chest freezer is the ‘Norfrost 2000′ which claims to be the ‘world’s most efficient freezer’. It has exceptionally low running costs at 20 p per week (at a unit rate of 7 p/kWh) which is a 65 per cent improvement over standard models. Over its lifetime it is reckoned to represent a cumulative saving of 75 per cent as against the norm. It is manufactured in Scotland (www.norfrost.co.uk).
There is also the Bosch ‘Classic’ range of refrigerators in the A category which use 212 kWh per year for an average household. This results in an approximate annual running cost of £14.84 (www.bosch-da.co.uk).
An organization which specializes in promoting super-energy efficient cold appliances is Energy+. The criterion for being included on its lists is that a product consumes no more than 42 per cent of the energy used by the average European cold appliance. It runs competitions and in 2001 the best two-door Energy+ fridge-freezer was the Electrolux ER8100B with an energy efficiency rating of 33 per cent against the norm.
The best one-door Energy+ fridge freezer was the Whirlpool ART 599/H with an energy efficiency index of 35 per cent (www.energy-plus.org).
Another manufacturer which is up with the brand leaders is Liebherr with its range of Class A fridges and freezers (www.lhg.liebherr.de).
The sitting of a fridge-freezer can be important. For example, it should not be in the path of direct sunlight or near the cooker. It is important to ensure that door seals are fully functioning; inadequate sealing can result in a significant loss of efficiency. Also the temperature settings should be checked: 3 to 5°C for the fridge and -15 to -18°C for the freezer are the recommended temperatures. Fridge and freezer thermometers will prove a good investment.
Washing machines
The energy profile of washing machines has two aspects: the motor and the water heater. Most machines heat water internally by electricity and this may account for up to 90 per cent of the energy demand. If the domestic hot water system is heated by gas it would make sense to opt for a machine which draws its hot water externally. The ultimate energy efficiency is attained if it is supplied by solar thermal hot water. From an ethical standpoint The Good Shopping Guide (Ethical Marketing Group, London, 2002) recommends Candy, Hoover, LG and Miele.
Points to consider
• Front-loading machines are more economical in their use of water than top loaders.
• Machines which allow temperature and water level to be adjusted to the particular load are to be preferred.
• Most loads can be washed in warm or even cool water.
• Machines are most efficient when dealing with full loads.
Dishwashers
• As with washing machines, an appliance which uses water from a gas heated or solar thermal domestic cylinder is the most efficient.
• Where possible operate on short cycles.
• Ensure that the machine is loaded to capacity.
Finally, with all white goods it is vital to ensure that they are rated A on the EU energy efficiency scale. Where possible check the manufacturers’ estimated annual energy consumption.
Stand-by consumption
A surprising amount of electricity demand is due to stand-by electrical consumption. Some appliances, such as televisions and personal computers, have optional standby modes which, nevertheless are left on power because the consumption involved is regarded as insignificant. Others, like fax machines and cordless telephones need to be permanently on standby. Even appliances with electronic clocks consume power. It has been estimated that a typical household could consume 600 kWh per year on standby alone. For the EU it has been calculated that standby power accounts for 100 billion kWh/year, about one-fifth the consumption of a state the size of Germany.
Main points
• Collect rainwater in water butts for irrigating the garden.
• Consider replacing fittings and appliances with water-saving features, e.g. spray taps and low flush or dual flush toilets.
• Rainwater collected from roofs can be collected and treated to be used to flush toilets and supply washing machines.
• More extensive treatment is required if roof rainwater is to be used for personal hygiene and even more for drinking.
• Composting toilets avoid the use of water and provide a useful source of fertilizer.
• When replacing white goods, only select appliances with an EU ‘A’ rating. Where possible select an appliance with an energy performance rating better than ‘A’.
• If DHW is heated by gas, choose a washing machine which draws water from the DHW system rather than heating it internally by electricity.
• Avoid leaving TVs, PCs, etc., on standby. Standby mode wastes a considerable amount of electricity over time.
• When choosing a gas-fired central heating boiler, select a unit with electric ignition, rather than a pilot light.
• A useful source of information is The Good Shopping Guide which lays emphasis on the ethical aspect of choice (Ethical Marketing Group, London, 2002).
