“Goodbye gas. Hello sustainable energy!” An ordinary seventies house is given an energy upgrade.

Enschede, Netherlands

Our future-proof and comfortable home thanks to a heat pump from Vaillant

“We were pleasantly surprised that our seventies semi could benefit from a future-proof heating and hot water system. With our new air-source heat pump and integrated solar boiler, we have a comfortable home without using fossil fuels.”

General house and system information


The facts

The energy concept



Our new heating solution

Learn how a 70s house can be upgraded with a heat pump.

The facts

The facts

  • Modernisation project: 1974 semi-detached property
  • Three floors, including loft conversion
  • Well-insulated attic with double glazing throughout
  • Spacious garage and driveway

The energy concept

The energy concept

  • Outdoor installed aroTHERM monobloc air-source heat pump
  • Modern heating system with integrated cooling function
  • 300 litre hot water tank
  • Additional solar powered hot water tank
  • Roof mounted solar panels
  • Underfloor heating
  • Digital heating controls, including app



This air-source heat pump system is installed in the Netherlands, in Enschede.

The initial scenario

The Koobs family’s home had an existing gas boiler. But they wanted to have a sustainable, environmentally friendly heating and hot water system that would remain energy efficient long into the future. Conditions for a switch from fossil fuels were favourable, as the previous owner had insulated the loft and installed underfloor heating - which works particularly well with an air-source heat pump system. The house also had cavity wall insulation and double glazing.

The solution

The basic idea was clear: to switch from gas to renewable energy. The old gas boiler was replaced with an energy-efficient aroTHERM monobloc air-source heat pump with a combined 300 litre hot water storage tank. Consuming the bare minimum of electrical energy, this pump extracts its heat from the air at temperatures as low as -20 degrees Celsius and supplies the house with both heating and hot water. It was installed outside in the driveway to save space and is so quiet that nobody notices it. On top of generating heat, the pump's integrated cooling function ensures pleasant, comfortable atmosphere, even in summer. Temperatures can be regulated by a thermostat in the individual rooms or via an app. The 300 litre hot water tank in the garage provides plenty of hot water for the family of three.

The heat pump system would itself have been adequate for energy production but, with a view to sustainability and even greater hot water capability, a solar hot water tank was added. In fact, solar now provides a large proportion of the home’s hot water. Excess energy is fed into the power grid and the family can get money back via a balancing system. "But what convinced us the most was how sustainable this closed energy cycle is," says Floortje Koobs.

For the rare occasions when temperatures fall extremely low, there is a back-up electric heater.

Lower energy bills and more comfort

Thanks to the switch to an air-source heat pump system, combined with a generous solar hot water storage tank, energy bills are much lower than they were with the original gas boiler system. With the additional benefit that this sustainable concept provides a constantly balanced, comfortable room temperature, all year round.

Why choosing Vaillant is a good decision

The Koobs family consulted experts before the energy optimisation. They were convinced that the investment in a heat pump and a solar hot water tank would pay off. Due to the significantly lower energy costs, this investment will pay for itself in about seven to ten years. Added to this is, the Koobs qualify for a state subsidy because they are using sustainable energy. Of course, they also feel good about reducing their CO2 footprint.

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