Find out which heat pump is suitable for your old building
The heat pump is one of the most widespread heating systems in new buildings, but the question of whether and which heat pump is suitable for your old building often remains unanswered. If you look at the reality in Europe's building structure, however, it is precisely this question that needs to be clarified. The majority of these are older buildings with poor insulation standards. However, it is precisely these inefficient building envelopes with fossil-fuel heating systems that cause particularly high emissions and result in high heating costs for the owners. So there is great potential for savings, because a heat pump can also work well in an old building. The prerequisite is a careful selection and examination of the available alternatives, as well as coordination with the circumstances on site. Here you can find out how to do this.
How do you find out what to look for?
The starting point for the heating system replacement should be a heating load calculation, sometimes also called heat demand calculation. This clarifies the requirements for the new system. This is best done with a qualified specialist, such as an energy consultant. There is often even government funding for this. As part of the consultation, it is typically clarified:
- How much energy does the heater need: This depends on the area to be heated, insulation, as well as
- How much energy is needed for hot water: this depends on the number of people in the house and their showering and bathing habits
- What are medium-term plans for the building: such as plans to improve the building envelope
- Possible heat sources for a heat pump: is a borehole feasible or is only an air-to-water heat pump an option?
- In some cases, space and installation options are also roughly clarified in advance
If the possibility of an energy consultation does not exist, you can also get a simplified idea of what your requirements are for a heat pump in your old building. A good indication of this is your heating consumption in recent years. As long as you have not carried out any major renovation projects in the meantime or radically changed your heating behavior, this is a very good indication.
Based on the gas and oil consumption, the past heating requirement can be calculated very quickly. It is important to know that these heating systems were often oversized in the past. Especially if they were installed at times when energy was much cheaper. Especially if you are planning to improve the building envelope soon anyway, you should not make this mistake again.
What role does the location play in the selection of a heat pump for the old building?
However, if you want to find out which heat pump is really suitable for your old building, you must also consider the climatic conditions at your location. Indeed, climatic conditions significantly affect the operating efficiency of heat pumps. Air-to-water heat pumps, which extract heat from the outside air, can be less efficient in very cold temperatures because you have to turn very low sub-zero temperatures into high flow temperatures. So in areas with cold winters, it is important to make sure that the output at temperatures below 0°C is still sufficient to warm the building. For high-quality machines, you can usually find these values in the data sheet. But not only the pure power is relevant, but also the efficiency in providing the power. You can read this efficiency from the so-called COP. The COP value indicates how much thermal energy is obtained from one unit of electricity. Only if this is above 2 does the operation of a heat pump really make sense. However, it is better to achieve a value significantly above 3 over the course of the year. Learn more about this here (link to COP article).
What is the best benchmark for the efficiency of a heat pump in an old building?
Heat pumps are very complex, technical machines that can be assessed with a correspondingly large number of values. Especially when it comes to efficiency, this can make you almost dizzy. If you want to assess efficiency at a glance, the easiest way is to use the COP or, even better, the SCOP.
The SCOP includes all COPs for a certain supply temperature level. So if the COP measures how efficiently a heat pump measures at a certain temperature, then the SCOP is the average across all temperatures, so to speak. This was developed precisely to compare different machines. The idea behind it, the SCOP represents a typical year in Central Europe and shows how efficient the machine is under those specific conditions. If your house is located in a warmer area than the standard, the machine will perform better and vice versa. By the way, for the evaluation of a heat pump specifically in old buildings use the SCOP 55°C and not the SCOP 35°C - this takes into account the slightly higher required supply temperatures.
A calculation specific to your environment could then give the annual performance factor, but is a bit more demanding and so not available from every manufacturer. However, the German Heat Pump Association (link: https://www.waermepumpe.de/jazrechner/ ) provides one based on your zip code.
Why do we always hear about problems with heat pumps in old buildings?
About 10-20 years ago, when the heat pump technology was less advanced and the components were not yet so sophisticated, it was often difficult to connect a heat pump in an old building. The reason for this is the relatively high flow temperature required. Designed for fossil heating, older buildings often have few radiators with little surface area. This makes it difficult to transfer heat to the room, so the heating water has to circulate at a very high temperature. This can be anywhere between 40-70°C. For fossil fuel heaters, which are combustion-based, this was not a problem. But especially early versions of heat pumps, which had to proceed from cold ambient air just by playing with pressure and refrigerant, this was a significant obstacle.
Nowadays, heat pumps are much further along in this field thanks to advances in components, architecture or innovations such as propane heat pump. For example, there are now a large number of machines that can also reach 70°C flow temperature. At the same time, even older buildings often only require 50°C or 55°C in the flow.
So how do you find the best heat pump for your old building?
Before the search, start with your requirements. Ideally, you will call in an expert to help you analyze the heating requirements of your building. This forms the basis for selecting the best machine - so you know in which performance class to look. By the way, fully modulating inverter heat pumps are flexible in terms of output downwards and are often an ideal solution for this purpose. Especially if you plan to improve the insulation.
After you know what power is needed, you can start to compare suitable machines. It is important to pay attention to the performance at lower outdoor temperatures - if you have chosen an air-water heat pump. Another excellent measure for comparison is the SCOP at 55°C. Alternatively, you can also use the AWC calculator from BWP. With this, you are well on your way to finding a suitable efficient heat pump for your heating replacement in an old building.
