Energy Conservation in Households

Ann Vikkelso, Copenhagen Environment and Energy Office

The energy crisis in 1973 brought the domestic energy consumption into focus in Denmark. As an immediate initiative energy saving campaigns were carried out to influence people's user habits. In longer term the requirements on energy consumption in new buildings have been intensified, more energy efficient devices have been developed, and work on designing low energy buildings has been done.

The individual consumer has great influence on the size of energy consumption in the house, partly by virtue to our consumer behaviour, partly as a result of the devices we choose to use.

When working on increasing domestic energy consumption, it is important to look at the total energy consumption of the house, related to different initiatives. For example installation of mechanical ventilation with heat recovery causes a fall in heat consumption, but at the same time extra consumption of electricity is introduced, and it is produced at lower efficiency than the heat (unless there is electric heating). Likewise replacement with more efficient electrical devices will cause a fall in free heat supplement. Some people use this as an argument against increasing electricity efficiency, but often the reality is that the heat cannot be used, and electricity is an inefficient heat source (at coal-fired power plants the efficiency is only 30-40%).

Low Energy Building

The house functions as a climate shelter, which we use to maintain a comfortable climate for ourselves, regardless of the surrounding nature's behaviour. Sometimes it is too hot, other times it is too cold. The natural conditions that have an influence on energy consumption related to heating or cooling are temperature, humidity, wind speed, and solar irradiation. In our northern climate it is mainly a problem to maintain a convenient temperature during the winter.

2/3 of a buildings heat loss is a transmission loss and l/3 is a ventilation loss. The transmission loss depends on surface area of the building, insulation standard, temperature difference between outside and inside, and forced cooling because of wind.

An important principle of low energy building is adaption to the surrounding nature. This means to close to climatic liabilities and open to the assets. For example wind is an asset on hot summer days, but a liability during winter. As the climate differs on different localities, it is important to make clear which criteria must be given a high priority, in design. Often we can get inspired by traditional local building, which has evolved through many years experience with the actual climate.

To be characterized as a low energy building in Denmark, it is pure technically required that the buildings heat consumption does not exceed 50% of the consumption of a building complying with the building code. Danish Institute of Technology sets up 10 very concrete instructions to be followed for low energy building 11/:

1. Choose simple solutions.

2. Place only windows, where positive heat balance can be achieved.

3. See to efficient insulation without thermal bridges.

4. Consider tightness and fresh air supply.

5. Build glass rooms that decrease surface area of the building.

6. Locate living rooms at the sunny side.

7. See to efficient regulation of central heating installations.

8. Use solar heaters and solar walls as solar heat contribution.

9. Minimize electricity consumption by choosing high efficient electric devices.

10. Use materials with low energy consumption for manufacturing and transport.

Utilization of active and passive solar heating is treated in the chapter on solar energy.

Building Shape

Homes should be built compact and well-insulated. The energy consumption is very dependent on the surface area and shape of the building. For example a roof with high pitch deflects the wind, and reduce the effect of the cold winter winds.

Multi-family homes have a lower energy consumption per mì than single-family homes. Figure 7.2 shows the effect of better insulation and compact building.

An interesting development is organic shaped houses, which fit into the surrounding nature, and at the same time take advantage of the ground shape for shelter, etc.

Location of the Building

The building should be oriented so that it makes the best possible use of the sun. During winter the sun can provide a significant supplement heating of the home through large south facing windows. To have full benefit of passive solar heating, building materials with big thermal mass are used, e.g. concrete, masonry, and stone. In that way the daytime sunshine can be utilized in the evening (day-to-night storage). At the same time a big thermal mass reduces diurnal temperature shifts, as well as problems with overheating during summer will be less.

Windows should be vertical, because they are self-regulating that way, as the sun stands higher above the horizon during summer than during winter.

Overheating during summer can also be met by for example overhangs or window shades. Likewise. shading plants can minimize summer heat gain. For this purpose deciduous trees should be chosen, so they shade as little as possible during the winter season.

The building should be sheltered from cold winds especially during winter. In Denmark the predominant wind directions are north and west. If the ground is south sloping, the house can be built into the slope. Soil is a good insulator, and the hill functions as a windbreak. There can also be build banks of earth at the northern side of the house. Another option is to establish wind breaking banks close to the house, or plant evergreen trees as wind mantle. Also a fence, garages, and sheds function as windbreaks.

Interior Design

The home should be organized with primary living rooms (sitting room, kitchen-dining room) to the south, where the sun provides light and heat. This way they are also placed farthest away from the cold winter winds. In the centre or to the north are located the secondary living rooms (bedrooms), that are only heated occasionally. Non-living rooms like scullery, workshop and garage are located to the north. This way they are insulating the heated part of the house.

Chimneys from heating installations should be located in the centre of the house, to utilize heat from the smoke as good as possible. A chimney along the outer wall is to heat for the birds.

There should be a windbreak or weather porch at the entrance to reduce heat loss. The entrance can profitably be placed lower than living rooms, as the cold air stays down.

The Dome

The dome is one example of ecological and energy conscious building. The dome is an almost ball-shaped house made of triangular elements.

The advantage of the dome is that it is simple. And it only takes a small consumption of materials to build a stable and strong envelope without pillars and interior walls. The ball-shape implies that the total surface is smaller compared to an ordinary house of equal size. The round shape of the dome also implies that it is less sensitive to wind, which furthermore improves the energy economy. The dome is more difficult to furnish than ordinary houses, but creative persons will probably rather find it an exciting challenge than a drawback.

Villa VISION

Villa VISION is an idea of the future home, where the architects behind have "tried to reach a new balance between nature, house, and residents" !1/. Until now the house has been shown as full-scale model at an indoor exhibition, but in the 90'ties it will be built at a site close to Copenhagen.

The idea is, that the house itself will produce the energy demand, so it is independent of fossil fuels. At the same time the ideal is, that the residents are in balance with the rhythm of the day. The house's floor plan is round, with an eastern room oriented in the direction where the sun rises at midsummer, and the western room in the direction where it goes down. Towards south is located a room with front and roof covered by photovoltaics for electricity production. These rooms are the family's bedrooms. The areas towards south-east and south-west, between the three rooms, are glazed-in patios that help lowering heat consumption, as they reduce the outer surface of the house. The living room is located in the centre. The roof of the living room slopes towards south, and solar collectors for hot water production are placed on it. To the north are the kitchen and a hall. The northern outer walls are covered with soil up to the windows.

The house will be extremely well-insulated with 40 cm mineral wool, and the newest and most energy efficient technologies in all fields are utilized. The patios will have charcoal-gray floors, walls, and pillars, to absorb as much heat as possible, and give it off again during the evening. The glass cover will be made of vacuum glass with silica-aerogel, which is 5 times more efficient than sealed glass units. Water saving devices will be installed everywhere in the house, the kitchen will be equipped with a waste separation system, and it is planned to clean and recycle the waste water locally.

The intention is, to equip the house with as much automatic control of energy consumption as possible, to eliminate bad user behaviour. Control systems for heating, light, ventilation, opening of windows, etc., will be utilized.

Villa VISION is a very hi-tech idea of tomorrow's home. There are many other possibilities for reducing energy consumption at home, where we still control our everyday life - and we consider our actions ourselves. But anyway, I think, Villa VISION gives some interesting ideas for alternative building organization and design.

Insulation

Huge savings can be obtained by insulating old houses, and it must be a matter of course to construct new houses with efficient insulation.

It is however not only insulation depth that counts. Also hot water consumption, ventilation loss, regulation, and user behaviour influence the total heat consumption. For each degree the temperature is lowered about 6% of the energy consumption is saved. 20›C is sufficient in living rooms, and unused rooms should not be heated.

All radiators should be thermostatically controlled, to ensure a comfortable, but not too high temperature. At the same time can perhaps be installed clock-timers that turn off the circulation pump at night, or automaticalIy lowering of night temperature. However, the latter is unnecessary, if one remembers to turn off the heat.

Blocks of flats and other homes with collective heat supply ought to have individual metering of the heat consumption, as it encourage energy savings.

Insulation of Existing Buildings

The heat consumption is often large in older buildings that are poorly insulated and uptight. Afterinsulation will under most circumstances give a higher comfort in addition to lower energy consumption. Problems with draught are rectified, partly because the building often gets tighter, partly because the inner walls get warmer. When draught is avoided, it is possible to lower the room temperature, and at the same time keep up the comfort level, in this way extra energy is saved.

It is substantial that the insulation is made carefully. All edges must be cut precisely. A damp course is placed at the warm side of the insulation, to hinder damp in passing through the building layers and condense at the cold side with the risk of causing damp damage. It is also important to ensure that all water pipes are at the warm side of the envelope, also after insulation. Otherwise the loss from hot-water pipes will be unnecessarily large, as well as there is a risk of bursting a water pipe that can freeze.

Walls

Cavity walls can be insulated by blowing insulation material into the cavity between the outer and the inner wall. This is done from the outside. Today the following materials are used for cavity wall insulation in Denmark: granulated mineral wool, granulated paper, polystyrene balls and granulate, expanded volcanic stone material, plus PUR-foam and FU-foam.

Solid walls can be insulated either at the inside or at the outside. The two methods have different benefits and disadvantages. Outside insulation covers the total wall surface including horizontal divisions, by which thermal bridges are avoided. On the other hand is the front is totally changed.

Outside insulation is often more expensive than inside, but it is profitable if the front is going to be renovated anyway. It is easier to insulate at the inside, and it can be done as going along. On the other hand, it is a disadvantage in small flats that the already small living space gets even smaller, when insulating at the inside.

Ceiling and Loft

The insulation thickness at lofts should at least be 200 mm, and all parts of the construction with surface to the open air must be insulated. It will often be smart to insulate flat roofs at the outside. At the same time it is possible to establish a sloping roof. A

Floor

Floors over crawl space or unheated cellars are often easiest to insulate from below, by putting up insulation plates between beams. The simplest way to insulate floors directly on the ground (terrain floor) in houses without cellar, is vertical insulation of the plinth and foundations. Terrain floors can also be insulated with SO mm of mineral wool at the top of an existing concrete floor.

Windows

A great share of the house's heat loss is through the windows. The heat loss can be reduced by replacing the old windows with sealed units, or even better heat mirror windows. Heat mirror windows insulate nearly twice as good as ordinary sealed units with air-filling.

The improved insulation is achieved by coating the glass with a special coating that lets most of the light and solar radiation pass through, but holds back the heat radiation from inside the house. New types of windows with even higher heat resistance are being developed, as already mentioned.

Heat loss through windows can also be reduced by setting up interior windows when having single layer windows or sealed units. A single layer window in combination with an interior window insulates just as well as an ordinary sealed unit, and it is cheaper. Further improvement can be achieved by establishing shutters that are closed at night. There exist various types, also some that can be handled from the inside. Likewise, use of heavy curtains during winter, or tight-fitting roller blinds that causes stationary air, can reduce the heat loss.

Water Conservation

Around one fourth of domestic energy consumption is spent on water heating. The energy consumption can be lowered by

• reduction of hot-water consumption

• regulation of temperature

• economical water heating during summer

• lagging of tubes and tanks

• stop of hot-water circulation

• maintenance of the installation

Water savings can be achieved by changing behaviour, by using various water saving devices, and of course by taking care that the water installations in the house are tight. If a household saves 50 litres of hot water a day, it matches an annual energy saving of 100 litres of oil.

Many water installations have an unnecessary high water consumption. Old water taps and showers often have a maximum flow of 15-20 litres per minute. Low-flow fittings, that ensure a maximum water flow of 6 or 8 litres per minute, can be mounted at all taps and showers, and will often be payed back in a few months /81.

When the maximum water flow is reduced, there should at the same time be mounted aerators at the tapping places. These yield an airy jet of water, and therewith a bigger rinsing effect, also when the water flow is low. Likewise exist showers especially developed to function well at low water flow.

In connection to showers can also be installed a shower-stop that shuts off 90% of the water. As the water is not shut totally off the water temperature is kept. So if the shower-stop is closed during soaping, one avoids wasting hot water to regulate the temperature, when the water is turned on again.

If new taps are installed, it is a good idea to choose single-handle taps, and preferably thermostatically controlled for the shower. A thermostatically controlled mixer tap functions as the shower-stop. Single-handle taps are easier and faster to regulate than two-handle taps, so less water is wasted.

Good user behaviours:

* Take short showers instead of tubs.

A tub consumes 100-150 litres of hot water, while a low-flow shower only uses 8 1/min.

* Shut off the water, while soaping and shampooing.

* Take cold showers, it is healthy and refreshing.

* Don't let the tap run unnecessarily.

* Don't wash dishes under running water, use a bowl instead.

* Use cold water to rinse dirty service.

Electricity Conservation

From 1972 to 1987 the total gross energy consumption has not changed in Denmark, while the electricity consumption has increased. Efficiency of the individual electric device has improved during the same period, so the increased consumption is due to more electrical appliances than before.

The large electricity consumers in the household are lighting, laundry, cooling, and cooking. Higher consumption is introduced, because we get more and more electrical appliances. Nearly all Danish households have a refrigerator, a freezer, a washing machine, and a TV-set. But also tumbler driers, computers, dishwashers, etc., get more and more common.

The total electricity consumption is a product of electrical device efficiency, number of appliances, and the time they are used.

There are large technical possibilities for rational use of electricity. New efficient devices on the market consume considerably less electricity than older models. By utilizing the technical potential of savings, it is possible to save 2/3 of the electricity consumption in Denmark /6/. When replacing old appliances, the electricity consumption ought to be examined carefully, as the most energy consuming appliances consume up to 3 times as much electricity as the most efficient on the market, figure 7.20.

It is important to work on regular labelling of electrical appliances, so the consumers have a chance to compare the different products when shopping. In Denmark it is fixed by law that all ovens shall be labelled with energy consumption. Unfortunately it is not all manufactures who respect this. On the other hand one can get help from the Consumers Agency that tests white goods. The test evaluates both consumption and quality. Likewise the power utilities have established a database with information on electricity consumption for a wide range of refrigerators, freezers, washing machines, and dishwashers. Part of the information is published in free brochures /11/, and one can phone the local power utility to get information on specific devices.

There are further savings to be achieved by correct use of the electrical appliances, as well as it is necessary to consider, if we need all these electrical devices at all. The energy service dry clothes can easily be obtained without using a tumbler, thus without consuming electricity.

Lighting

The most common source of light in homes is the incandescent lamp, and in some places the more efficient fluorescent tubes. But during the last years low energy light bulbs (CFL, Compact Fluorescent Lamps) have been developed. In principle CELs work the same way as fluorescent tubes, but they fit in an ordinary holder. In contradiction to fluorescent tubes, electronic low energy light bulbs can stand being turned on and off again and again, without reducing the life span.

An 11 W low energy light bulb delivers just as much light as a 60 W incandescent lamp, and it lasts for 8000 hours, whereas the durability of an incandescent lamp is only 1000 hours. The low energy light bulb is more expensive than ordinary light bulbs. It costs appr. 130 DKK, compared with 8 DKK for an incandescent lamp. In Denmark this is amply compensated by saved electricity. As the electricity price is 1 DKK/kWh the profit will be:

(60-11) £ 0.00lkW £ 8000h £ 1DKK/kWh + 10 £ 8DKK + 130DKK = 340 DKK

Especially at places lightened many hours every day, the lamps should be replaced with low energy light bulbs. This provides both the largest energy saving and the shortest pay-back period.

10 pieces of good advice on lighting

1. Use energy saving light bulbs, where it is possible (be aware of the reproduction of colours).

2. Use high efficient holders, when possible (needed screening shall be met).

3. Choose lamps that do not get dirty quickly, and are easy to clean.

4. Choose electric components that meet the standards.

5. Use individual light from work lamps, where it is possible, instead of large general lighting. The light quality has to be satisfactory.

6. Divide the lighting system into sections, which can be operated individually. Plan the lighting in details to ensure flexibility.

7. Turn off unnecessary light either manually or automatically, e.g. by a timer.

8. Utilize natural daylight (take care of heat and blinding problems).

9. Choose light colours for the room surfaces, hereby as much light as possible is reflected.

10. Introduce systematic maintenance of lighting.

Refrigeration

More than 10% of the Danish electricity consumption is spent on storage of food in refrigerators and freezers. By utilizing the most efficient refrigerators and freezers on the market, this consumption can be reduced to 25% of the consumption related to old models.

LER200 is a 200 litres low energy refrigerator developed at Physical Laboratory 3, Technical University of Denmark, which consumes less than half of the energy other refrigerators of the same size consume. The saving is obtained by doubling the insulation thickness, and increasing efficiency of the cooling system. If an old refrigerator is replaced by a LER200 more than 300 kWh electricity is saved per year.

Proper placing, maintenance, and use of refrigerator and freezer:

* Place refrigerator/freezer so there are space around condenser and ventilation grating. If the refrigerator is build in, there must be 10-15 cm space over me fridge and a small crack at the bottom.

* Place possibly the refrigerator in a colder room (larder, scullery). Place the freezer cold (cellar, outhouse).

* Do not place the refrigerator close to a radiator, cooker, or other heat source.

* Keep condenser clean. Dust insulates and increases the electricity consumption.

* Examine the tightening strip. It must be whole, and the door must close tight. It can be controlled that the door closes tight, by trying if a paper strip is stuck all way round the door.

* Keep a temperature of 5›C in the refrigerator and +18›C in the freezer, it is cold enough. Control the temperature with a thermometer.

* Defrost the fridge frequently, if it hasn't automatic defrosting. The frost layer must not exceed 1/2cm

* Thaw out frozen food in the refrigerator. The cold from 1 kg frozen meat corresponds to at least one hour's electricity consumption.

* Cool down warm food before it is put in the refrigerator/freezer.

* Do not open the refrigerator or freezer more often than needed, and don't keep it open for a longer period.

Cooking

Electricity is a poor energy source for cooking actually many cooks prefer gas. Gas is also better from an energy point of view. The efficiency of an electrical cooker and a gas cooker is more or less the same, namely about 50%. But as electricity mainly is produced at coal-fired power plants with an efficiency under 40%, the real efficiency of an electrical cooker is only 20%.

The electricity consumption, and at the same time primary energy consumption can therefore be lowered by shifting to gas. And at least replacement of gas with electricity, should be stopped in areas where gas is supplied. Another possibility is to boil water in an electrical kettle, where the heating element is built-in, this way the heat loss decreases significantly. Likewise there are great potentials for electricity saving, by utilizing electrical pots with a heating element built-in at the bottom, good heat distribution, and efficient insulation of the pot. But this is a field, where the development has only just begun.

The microwave oven has been proclaimed as a great energy saver by many, especially when cooking small portions, and when "boiling" vegetables. But a mini oven doesn't consume more energy than a microwave oven, and- neither do vegetables steamed in small amounts of water, in a pot with a tight lid. On the contrary a microwave oven often introduces bad user habits, where food is taken directly from the freezer, and thawed/cooked in the microwave oven.

Energy conscious cooking:

* Use even pots. A pot with an uneven bottom consumes up to 50% more electricity.

* Use pots that fit the size of the hotplate. The pot must cover the whole plate.

* Regulate the hotplate properly. Step-regulated plates are set at the highest level until the food is boiling, then it is fumed down as much as possible.

* Remember always to put a tight lid on the pot.

* Cook with little water. A few decilitres of water is enough to cook potatoes and vegetables. It saves up to 30% electricity, and the vegetables keeps taste and nutrients better. Egg can be boiled with only a few teaspoons of water, and the plate can be turned of, as soon as the water is boiling.

* Do not cook frozen food (it ought to be thawed out in the refrigerator)

* Utilize the afterheat. Turn of hot-plates and the oven 5-10 minutes before the food is ready.

* Put the food in a cold oven.

* Fill the oven, different meals can easily be prepared at the same time.

* Poor the coffee into a vacuum jug, instead of keeping it warm at the coffee brewer.

* Don't let the cooker hood run on higher level than needed.

* Keep the cooker hood clean. Rinse the filter once a month.

Laundry

Considerable amounts of energy for laundry can be saved. In average one fifth of the electricity consumption in households is used for washing clothes. Technical improvements of washing machines have been achieved, so the most efficient washing machines at the market today consume only 50-60% of the electricity amount consumed by older models.

There are also great saving potentials related to good user behaviour:

* Fill the washing machine every time. Invest in a few extra socks and underwear, so it is unnecessary to wash with a half-full machine.

* Skip the prewash, when it isn't needed. It saves 20% electricity.

* Do not wash at higher temperature than needed, wash at 60›C instead of 90›C saves 30% electricity, and it also wears the clothes less.

* Use of tumbler drier is needless. The tumbler is a significant energy consumer, and wears the clothes.

* Do only wash dirty clothes. There is no need for changing a l-shirt several times a day.

The heating installation

A good part of electricity used for running the heating installation can be saved. In central heating systems the circulation pump can be turned off, when there is no heat consumption. This can be done manually, or by mounting a thermostat or a clock timer at the pump. If there is an electrical water heater, this can also be regulated by a clock timer.

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