ᐅ Which type of heat pump is suitable for an existing building?

Hello everyone,

I am currently renovating my end-terrace house (133 sqm (1,433 sq ft), 3 floors, no basement) and need to decide which heat pump is suitable. Here are the key details of the renovation:

• New windows and front door
• New water pipes and bathrooms/guest WC
• Existing insulation in the roof and on the ceiling of the lower floor (will remain unchanged)

At the moment, there is an electric underfloor heating system installed, which I will keep for cost reasons and not remove. However, I plan to mill the screed and install new underfloor heating pipes.

I have already received several offers from heating companies, but they contradict each other:

• One company offered me a Vaillant VWL 75/6A with a 300-liter (79-gallon) hot water tank.
• Another company says this is too small and recommends a Vaillant VWL 105/6 Plus system.

My energy consultant carried out a heat loss calculation, which indicates a standard heating load of 8,303 W.

Now I’m a bit uncertain which heat pump is the right one. Is the smaller unit sufficient, or should I opt for the larger one? Has anyone had experience with similar projects or can offer some advice?

Thank you very much for your help!

Without details about the wall construction, previous consumption, or the underfloor heating design, no one will be able to estimate what you need.

The exterior walls are made of 36.5 cm (14 inches) hollow bricks and are finished with a high-quality textured plaster.

I recently purchased the house and have not yet lived in it, so I cannot provide my own consumption data at this time. (There are 2 adults and one baby in our household).

Before moving in, I am planning a renovation. The previous energy consumption was quite high, which is likely due to the former use by a large family and the electric underfloor heating that consumes a lot of power.

I have attached the previous energy consumption data.

asaid10 schrieb:

My energy consultant performed a heating load calculation, showing a standard heating load of 8,303 W.

With that, I would install a 7 kW monoblock system from Pana (though I am a fan of it).

asaid10 schrieb:

Existing insulation in the roof and on the floor ceiling below (will not be changed)

Renovation and you won’t change anything there? What kind of insulation is installed? With good insulation, I would have guessed even a 5 kW monoblock.

nordanney schrieb:

I would install a 7kW monoblock system from Pana (I’m a fan of that too).


Renovation and you’re not doing anything with it? What is installed currently?
With good insulation, I would have guessed a 5kW monoblock would be enough.

From the heat load calculation, I understand that at least an 8.3 kW heat pump is needed, right?
I’m still unsure which one is the right choice, since the heating contractors give different advice.

The ceiling of the upper floor is insulated, but it’s also quite old. It dates back to 1990, so 34 years old. I would leave it as is for now and not do anything, since my budget doesn’t cover everything.

I wouldn’t install a photovoltaic system for cost reasons at the moment either (maybe in 2-3 years, but I’ll already lay empty conduits for it).

asaid10 schrieb:

I would leave it as it is for now and not do anything because my budget doesn’t cover everything.

Installing insulation in the top floor ceiling yourself to reach new build standards takes about an afternoon’s work and costs less than 1,000€ (around $1,100).
This is one of the most effective measures you can take.

So, the conclusion is: an old building with practically no insulation will not be energy-efficiently renovated if only the windows are replaced.