- 6 min read
Calculation of the energy index
The energy index serves as a measure of the energy consumption, which results from the interaction of the properties of the building shell, the selected eating system, other building services installations, the local climate, the mode of operation and the user behaviour. In order to be able to calculate the energy index, the reference value for energy reference area must be determined. The energy reference area is the sum of all areas, for which the use of heating is necessary. This usually includes all common rooms (living, dining, kitchen, sleeping, wet rooms and hobby rooms), but also stairwells and corridors. Unheated rooms such as laundry rooms, heating and technical rooms, garages and cellars are not included in the energy reference area.
Calculation of the energy index
Heating including hot water = total heat
All heated surfaces = energy reference area
Total heat (kWh) / energy reference area (m²) = energy index Ew (kWh/m²)
If the energy requirement for hot water is included in the heating output, this must be deducted from the calculation.
E-key figure heating (kWh/m2a)
The average is 140 kWh/m2a - the optimum would be 80 kWh/m2a.
The average is 120 kWh/m2a - the optimum would be 70 kWh/m2a.
The average is 100 kWh/m2a - the optimum would be 60 kWh/m2a.
Assessment
If your calculated energy index is above the optimal value, you can assume that there is potential for savings. The optimal value can usually be achieved with a comprehensive energy renovation. The average value applies to existing buildings that do not have extensive thermal insulation.
An overview of the heating systems
Air heat pumps use the free environmental energy from the outside air. The constructional and financial expenditure is relatively low because no drilling is necessary. It is therefore free primary energy (heat from the ambient air), which is emission-free and is associated with low energy consumption. The acquisition costs are moderate and the operating costs are also relatively low.
Water heat pumps use the heat from spring, sea or ground water as an energy source. As with the air source heat pump, the construction effort is comparatively low. The water quality is decisive for how high the costs for operation and maintenance will be. This water quality can only be assessed after the system has been built and can also change over time. As a rule, the water heat pump is more suitable for larger objects. The approval process is complex and not possible to be done with every renovation.
The geothermal heat pumps use the heat from deep in the ground as an energy source for heating and hot water preparation. They require drilling by specialised companies. This is also a free primary energy (heat from the ground), which can be used emission-free and has a low energy consumption. The acquisition costs are somewhat higher comparatively, but the operating costs are minimal. This variant is not possible with every renovation.
Wood is a domestic energy source that can be used comfortably in modern wood systems. Wood heating can be combined with other heat generators. It is also emissions-neutral, resulting in slightly higher acquisition costs, but as a domestic fuel it has low operating costs. However, it requires a little more space in the basement than other systems and the maintenance of the system is more complex.
A heating network refers to the idea of supplying several properties with heat for room heating and domestic hot water using a central heat generation system. Instead of operating their own heating system in each building, a heating centre can be created at a suitable location, which supplies the required heat for all connected buildings. The heat is generated by burning wood chips and pellets, for example.
Waste heat from an industrial plant (e.g. waste incinerator) can also be used. Or a large heat pump system based on the use of sea water generates the heat. This is then routed to the individual properties via the district heating network (pipeline network). The heat in the built-in heat exchanger is transferred to your heating system by means of the district heating transfer station in your own house. Heating networks are by far the most convenient way of heating. District heating is also environmentally friendly because the heat is generated in a CO2-neutral manner using a regionally produced fuel.
A solar thermal system or a domestic hot water heat pump with a photovoltaic system can also be considered as a recommended supplement to heating systems.
1. Solar thermal system
Solar systems supply hot water and can also support the heating. It is a free primary energy (sun), which can be used as an optimal addition to the common heating systems (including oil and gas heating). Heating support is possible, but depends on the dimensions and location. Energy consumption is low and investment costs are moderate. The solar thermal system leads to a reduction in operating costs. However, it cannot be used on every roof.
2. Photovoltaic system
In these systems, electrical energy is produced on the roof and used to operate the heat pump and for other electrical consumers. The investment costs are moderate, but lead to a noticeable reduction in operating costs. Photovoltaic systems can also not be used on every roof. Often a large proportion of self-produced electricity has to be fed into the public grid. The return tariffs for the electricity not used by the owner differ.
Heating refurbishment options
If the cantonal energy regulations are not yet in force in a canton, the remaining time can be used for less expensive conversions, i.e. the conversion can be done with any heating system (no legal restrictions). This also applies to cantons where the energy regulations have already been put into force, but the building energy certificate is Category D or higher.
If the cantonal energy regulations have already entered into force in a canton and the building energy performance certificate is Category E or lower, renovation is possible with a standard solution only.
The 11 standard solutions according to the Energy Act
The 10% renewable energy is achieved with a solar thermal system for water heating.
Wood burning is emission-neutral and is therefore considered renewable energy.
Air-to-water or brine-to-water heat pumps generate heat for heating and the preparation of hot water all year round.
The gas heat pump combines the advantages of condensing technology with renewable energies. Natural gas/biogas serves as the primary drive energy.
The heat comes from waste incineration, wastewater treatment or renewable energies.
For example, fuel cell technology produces heat and electricity in the house at the same time.
The electricity generated in the photovoltaic system operates the heat pump for producing hot water.
The old windows are replaced by new ones with high thermal insulation.
The facade and/or roof are equipped with thermal insulation.
A combined heating system that covers the base load with renewable and peak loads with fossil energies.
An apartment ventilation system with heat recovery is installed.
Economy and cost of heating systems
What does a heating system actually cost, taking into account investments every 20 years, annual service/maintenance, and daily energy purchases? Enclosed you will find a comparison table. (In the example, the current amount of energy is 4,600 litles of heating oil/year.)
Conclusions
In the long term, the geothermal heat pump is certainly the most effective solution, provided that drilling at the relevant location is possible and the space available on the property and on the property allows it, even if the investment costs for the conversion are the highest.
You may also be interested in
Contact
Contact your personal advisor
Engel & Völkers Switzerland
Poststrasse 26
6300 Zug | Switzerland
Tel: +41 41 500 06 06