Experience report: Heat pump in an old terraced house with radiators (indoor installation)

WOLFANG WAS SKEPTICAL AT FIRST...

“We wanted to move away from fossil fuels—but I didn't know if that was realistic in a terraced house.”
- Wolfang Andrä

I simply didn't want to use gas anymore—both for political and environmental reasons. My wife and I wanted to reduce our energy consumption and become more independent.

At the same time, however, I really didn't know whether a heat pump could work in a terraced house. We only have radiators, no underfloor heating, and the houses are incredibly close together. I was afraid that we would freeze afterwards or that the system would be too loud.

So I was all the more surprised at how well the solution worked in the end.

Definitely the space situation. In our residential area, there is a house entrance every five meters. There is simply no space for an outdoor unit. I thought long and hard about how an air source heat pump could be installed here—and most heating engineers immediately said, “It's not possible.”

Then there was the issue of the radiators. Many people believe that underfloor heating is essential.

I was afraid that the heat pump wouldn't be powerful enough in winter – or that the electricity costs would skyrocket. Looking back, that fear was unfounded, but of course I didn't know that at the time.

It was a lucky coincidence. My installer, Stefan Schellenberg, met alpha innotec at a trade fair and came away with the idea of using the Paros 4, an indoor air/water heat pump.

It doesn't need an outdoor unit because it draws in outside air through ducts and blows it out again.

For the first time, I had the feeling that this could really work.

THE HEAT PUMP USED:

Yes, and better than I had expected.

At first, we weren't sure whether the radiators would provide enough surface area. But Stefan Schellenberg set the heating curve correctly and we let the heat pump run continuously—without lowering the temperature at night.

Since then, we've had constant warmth and the system runs in long, quiet cycles.

This is important because heat pumps should ideally run evenly and not constantly switch on and off.

We didn't have to replace a single radiator. That was a huge relief.

The difference is enormous.

I used to need around 9,000 kWh of gas and an additional 3,000 kWh of electricity.

Today, I only need 1,800 kWh of electricity in total – for heating, hot water, and household use.

With the photovoltaic system that we installed at the same time, we cover a large part of our needs ourselves. I never would have thought that I would be able to reduce my energy consumption by more than 80%.

More on the topic of “Photovoltaics with heat pumps”

Very. I can hardly hear it at all.

And that's worth its weight in gold in a terraced housing estate.

An outdoor unit would always have been a risk here—too loud, too close to the neighbors.

The indoor installation is ideal for this. You hardly notice the heat pump in the basement.

The installation went smoothly. Two or three tradesmen were on site, and everything was done neatly and thoughtfully.

The biggest surprise actually came before that:

how many heating engineers simply said that it wouldn't work.

Without the experienced installer, I would probably have given up at some point.

I was particularly pleased that our neighbors—who live right next door—had the same system installed.

And they are just as enthusiastic.

Absolutely.

We now have a quiet, efficient heating system, hardly any running costs, and we are independent of gas.

And above all, I now have a solution that fits our terraced house perfectly—even though I thought it would be impossible at the beginning.

1. Don't let yourself be unsettled. There are many myths about heat pumps—especially that they don't work in existing buildings or with radiators. My project proves the opposite.
   
   
2. Find an installer who has experience with indoor installations. That was the decisive factor for me. Many companies refused, even though it was possible. Only the right specialist company showed me the right solution.
   
3. Pay attention to the heating curve setting. An optimized heating curve is essential. It determines efficiency, comfort, and power consumption. Since it has been optimally adjusted, the system runs quietly and continuously – exactly as it should.
   
4. Let the heat pump run constantly. No night-time reduction. Heat pumps work best when they run in long, steady cycles. This saves energy and extends their service life.
   
   
5. Check whether a photovoltaic system is possible. The combination of a heat pump and PV is unbeatable. I cover a large part of my consumption myself – this keeps operating costs extremely low.

Wolfgang demonstrates very impressively:

• Even terraced houses can be heated excellently with a heat pump.
• Radiators are not an obstacle.
• Indoor installation solves all noise and space problems.
• Energy consumption can be drastically reduced.

And: The system even works in the neighboring house right next door.

“We are incredibly grateful that we took this step.”
- Wolfang Andrä