It is always a consideration whether the further use of an older device does not require less energy or water than the production of a new, energy-efficient device. Therefore, the energy requirement along the entire product life cycle (from production to use to disposal) must be considered. Companies need the competence to weigh up the right time for a new purchase of devices, but also the determination to then purchase the most sustainable and not only cheapest devices.

LED 'light bulbs' are now available for really all lamps, even with pleasantly warm light colors. Also, think about the lights outside - are they LED as well?

We must use all suitable areas for photovoltaics (PV), as the alternatives on open spaces restrict nature and agriculture. One trend is PV on stilts, so that gardening or farming can still take place underneath. However, this requires building materials. Thanks to cheap panels from China, photovoltaics has become astonishingly inexpensive today. Unfortunately, there is hardly any money left for feeding into the electricity grid, currently around 8 pence per kWh. Therefore, PV should always be combined with its own electricity storage system (see below) so that as much electricity as possible is consumed by the owner. This saves around 35 pence per kWh, which we would otherwise have to pay to the electricity provider. In this way, your own PV system, adapted to your own electricity consumption, will pay for itself after just a few years. In the case of schools, the question is who is the sponsor. Banks are happy to grant loans for PV, and it is currently also subsidised. In addition, there are also providers who cover the costs and effectively rent the roof space and offer discounted electricity in return. Such providers then form so-called virtual power plants with other houses and their batteries. Citizens can also provide financing through community energy. An electric charging station for teachers or, in the afternoons, on weekends and during holidays, also for the public, could generate income for the operator. Administrative obstacles are there to be overcome."

First of all: private use of hydropower is possible, but absolutely the exception and must be well considered legally and in its effects on ecosystems. We can also only operate wind power plants with consideration for our neighbors (noise development). Some properties are actually sufficiently exposed to the wind. But many are later disappointed with how little yield they have then. Citizen energy really makes sense - if, for example, residents or also local compenies join together in a cooperative and usually operate larger wind turbines nearby. This promotes the acceptance of wind power in the area and the return does not end up with the large investor, but with the local people.

An electricity storage system primarily helps to maximize the yield of the PV system if the electricity is not fed into the grid for little money, but comes from the battery in the evening and then allows the full electricity price to be saved. Another advantage can be that some batteries function as an off-grid system in the event of a power failure. Even if the students may prefer to cancel classes in this case :-) The already mentioned virtual power plants then access your battery from the outside and make the electricity available in the neighborhood and compensate you for it. This stabilizes power grids and even with little wind and no sun, we can live on renewable energies. Note on lithium: Lithium, like many other raw materials, is often problematic during mining. However, the life cycle assessment must take into account that we can recycle lithium over hundreds of years. In the basement, older lithium batteries from the automotive industry could later be given a second life, or sodium batteries that require more space.

Motion detectors make sense in all rooms including outdoor areas, where we potentially let the light burn for too long, for example in the hallway, basement, garage, etc. Of course, it is important that the light does not stay on for too long.

Standby electricity consumption is often admonished and extrapolated. For example, if a TV consumes 5 watts in standby, that is 120 watt hours (Wh) per day, i.e. about one-eighth of a kilowatt hour, which costs about 35 cents. Schools can easily calculate for themselves what savings potential all their computers, copiers and interactive boards etc. have if they do without standby.

Modern lamps require little electricity, but all in all it is worthwhile not to let them burn unnecessarily, for example when we are not in the room for a long time. Corridors, toilet rooms, basements often have the lights on unnecessarily. In some areas, schools also have the lights on too long or too early.

The compensation of greenhouse gas emissions is very controversial. Someone flies, drives a car or organises a barbecue and donates an amount for the associated greenhouse gas emissions to a service provider who promises projects for greenhouse gas savings / binding (e.g. via forest reforestation). Unfortunately, many providers turn out to be flimsy because they do not achieve the promised effect at all. So only reputable providers should be supported. In addition, the compensation should not be misunderstood as a free pass. It is therefore important to avoid emissions as far as possible and only offset them for the rest (see also the point on donations). It is also conceivable that the school itself will plant a school forest or a meadow orchard. Municipalities usually have to create compensation areas for new development areas. The schools could then plant trees in great campaigns. It is important to note that offsets do not - as some people completely falsely claim - enable the continued use of fossil fuels. It's all about offsetting unavoidable emissions.

Apart from the fact that every appliance can have a high power consumption, a refrigerator is not defrosted regularly, the door seal is leaking, the washing machine is run at too high temperatures and spin speeds, etc.., there are still some unnecessary things that consume a lot of electricity: In schools, these can be exaggerated light installations, aquarium pumps, etc.

Thermal insulation is extremely important. Investing here means saving energy and costs. The argument that building will then become too expensive must be clearly put into perspective. One way, of course, is to have to insulate smaller living spaces. The other to become generally more efficient when building. Then ecological building materials will also become affordable. Old houses that can no longer be sensibly insulated are perhaps worth so much more as a new building that financing is not a problem. (Note: the figures are for Germany)

Heat pumps extract a large volume - air, soil, groundwater - small amounts of heat and add them to sufficient heat for the apartment and water heating. Similar to a refrigerator, only a refrigerant is pumped in a circle and the electrical energy is much lower than the heat energy obtained. Heat pumps in themselves are not necessarily expensive. But electricity is wrongly expensive compared to natural gas, which is why heat pumps are only worthwhile if less heat is needed overall in a well-insulated house. In cold Scandinavia of all places, heat pumps have long since prevailed, while a sham debate is being held in Germany. Wood heaters are at best one (1), as they are less bad than oil and gas. However, they emit ultrafine particles and we need wood for building materials. Windbreak can remain in the forest for biodiversity or be used for chipboard.

Appliances such as washing machines and dishwashers must state a value for water consumption when buying new. It is therefore worthwhile to compare water and energy consumption equally and also to research corresponding test reports, for example from Öko-Test or Stiftung Warentest. Schools usually also have one or the other water-using device.

We can use rainwater at least for garden irrigation in the case of unproblematic materials of the roof. With significantly more effort also for washing machine and toilet flushing. Even if it takes quite a long time economically before it's worth it, it's a good thing.

Ventilation systems have long been standard for passive and active houses. Not only do they help to ventilate properly - so not too late and not too long - but also to remove a large part of the heat from the warm, 'consumed' air. Rare, on the other hand, is wastewater heat recovery.

With old heaters with small radiators, the heating regularly generates over 60 degrees, so that the hot water with over 60 degrees can also be free of legionella. Modern heat pumps, many district heating networks and also the use of solar thermal energy on less sunny days can lead to temperatures of less than 50 degrees for heating. For the hot water, it must then always be reheated elaborately. On the other hand, if the temperature of the hot water can also be lowered, a lot of energy can be saved. However, this is only possible in compliance with the generally accepted rules of technology, otherwise legionella can occur. A help can be modern methods of ultrafiltration.

Most classrooms are too warm in winter - some walk around in T-shirts instead of wearing thick sweaters or a cardigan. The energy-saving potential is considerable.

Air conditioning systems are also gaining in importance in temperate latitudes. Intelligent construction and ventilation and the use of thermal protection roller blinds can avoid these power guzzlers. In warm regions, a corresponding education of the guests can take place. Often a fan is also useful.

Intelligent ventilation does not mean too late and not too long. It is too late when we get tired when we get tired with stale air, get headaches and the humidity becomes too high. It is too long if the air has already been exchanged and is cool, but we also ventilate the materials (walls, furniture) for even longer. Heat ultimately means that things or air vibrate. If the air is exchanged, but the objects and walls are still vibrating, the fresh air is quickly heated. If the walls also get cold, mold can form on them and we need expensive heating energy to get everything vibrating again. By the way, CO2 measuring devices help to ventilate in good time and not for too long. However, these should not be a useless gadget, but perhaps used for practice one after the other in the rooms and should also be lent out. A nice game is the competition to see how good the sense of the people in the room is to ventilate in time and not too long. Schools in particular have the potential to keep the doors in the entrance area not too wide and not too long.

Food from the region, from the weekly market and from the farm shop have not been transported far (there are of course also exceptions there) and strengthen the local economy. However, there are also inefficient short transport routes when vehicles with little load drive to the points of sale. E-mobility and cargo bikes can help here. Unfortunately, the regional is often also played out against the organic offer: regional, sprayed with pesticides food is not as good as regional organic food, and regional meat is not as good for the environment as the renunciation of meat.

Fortunately, tap water has long been a trend. Schools have drinking water dispensers and students have their drinking bottles with them, and managers also bring their drinking bottles to workshops. Many children are not even used to the unhealthy sugar drinks. Tap water is more strictly controlled than bottled beverages and saves a lot of energy and packaging. Schools can set up water dispensers - if necessary, also work with filters, for example to remove chlorine odors.

Food is wasted from the field to the factories and transport routes to the throw away by us, the restaurants and the supermarkets. This ultimately means that more areas are needed for cultivation and thus forests are cut down and biodiversity is endangered with sprays and fertilizers. We can shop more specifically, throw away goods not only because of the best before date, save food in the household (e.g. freeze bananas or make durable spreads and soups from leftover vegetables yourself), save specifically rescued food (e.g. too small or wrinkled goods) and also donate leftover food in many places, e.g. to the food banks. Canteens and kiosks and also events can query the demand in advance and thus prevent food from being thrown away. A dish can also be deliberately offered the next day, which advertises the utilization of the leftovers from the previous day.

No question - leaving the car behind and taking the bike is a proud feeling and healthy. If you don't want to exhaust yourself (for example on the way to work), you can consider an e-bike. If you have a lot to transport, a cargo bike. Often we can also share a cargo bike with others. And if you shy away from bad weather, you will find great cycling clothing today that completely invalidates the argument. Schools can support their teachers here.

Schools can offer sustainability days, flea markets, clothing bazaars, food festivals, repair cafes, etc. for citizens to come together.

This concerns, for example, any school T-shirts, caps or hoodies. Globally, conventional cotton is an environmental problem due to the use of pesticides and high water consumption. In addition, the textile factories poison entire rivers and exploit people during conventional dyeing. In addition to organic cotton, there are other natural fibres that sometimes cause much less damage to the environment. In the case of virgin wool, it is important to pay attention to the certification, which excludes animal suffering. By the way, there is now also outdoor clothing made of densely woven organic cotton as an alternative to plastic fibers. Plastic fibers also always allow microplastics to enter wastewater during washing and microplastics in the environment may lead to multi-resistant superbugs - a long story. In terms of points for clothing, if you don't buy conventional cotton, but choose recycled and organic cotton, you can give yourself a full 3 points for both. By the way, organic is also possible for curtains, tablecloths and bed linen!!

Many devices from vacuum cleaners to cordless screwdrivers to TVs are amazingly inexpensive today. Relying on valuable devices that last a long time, or even buying used devices, helps to save raw materials and energy. This means that the caretaker's office can also buy refurbished.

Unfortunately, many devices can no longer be repaired at all, for example if the control unit breaks down from the washing machine and costs more than a new washing machine. And yet there are workshops that also repair mobile phones, washing machines, lawn mowers, etc. - and even if it is as expensive as a new device, it is the good feeling of having done something for a better world again.

This does not mean the skate track or the artificial turf sports field, but motor sports, skiing on artificially snowed slopes, kiting in bird sanctuaries, sailing boats with biocides on the underwater hull, golfing with high water and pesticide use, quad bike rides in nature, parachuting, etc. Of course, these hobbies are fun, which is why it is rewarded if we actively choose the more environmentally friendly alternatives here and thus achieve a change in thinking among others.