ᐅ Mid-terrace house built in 2002, energy rating B, underfloor heating – heating system replacement

Hello everyone,

We are considering purchasing a mid-terrace house built in 2002
- 120m2 (1300 sq ft) living space over 3 floors
- 13cm (5 inches) EPS insulation on the exterior wall, double-glazed windows
- Energy consumption certificate rating B
- Gas boiler (condensing boiler Brötje Ecocondens BBS15) provides hot water and heating, 150l (40 gallons) tank
- Underfloor heating in all rooms, local thermostats on the walls (rotary controls similar to radiator valves in each room)

The gas boiler is about 20 years old, likely serviced regularly, no known repairs.

Given the current new regulations for heating, I have the following questions:
- What typical lifespan would one expect for a unit like this? Is it likely to fail soon? If I need to renovate anyway, should I replace it now?
- What costs would you estimate for replacing this with a new gas boiler in case of failure?
- Would it make more sense to switch to a heat pump heating system instead?
Since there is underfloor heating throughout, I believe operation with a heat pump should be possible, probably requiring a larger hot water tank (household of 4 people).

Space at the installation site is limited, but there are a few square meters free in the basement. The distance between the current location and the possible alternative site in the basement is about 15m (50 feet) piping; is it feasible to extend the pipes with insulation?

Is a split unit with an outdoor condenser subject to building permit / planning permission requirements or minimum distance rules? Could a neighbor block its installation?
If so, could a fully internal unit be a solution? That would only require fresh air and exhaust air ducts, with the rest inside the house, correct?

The shed roof has 45m2 (480 sq ft) available for solar panels, which combined with a battery storage system could further reduce energy demand.

These are my initial considerations. Am I missing anything fundamental?

For implementation including installation, I currently estimate:
- Replacement of gas boiler with heat pump + hot water storage: 15,000–20,000 EUR
- Solar system 8 kWp + 5 kWh battery storage: 20,000 EUR
Do you consider these figures realistic?
Does such a replacement make sense technically and financially?

I would appreciate any input, as I’m quite new to these considerations and probably can’t make further progress without expert advice.
Maybe someone has experience or expertise to evaluate these basic ideas.

First of all, what is the energy consumption of the house and what pipe spacing was used for the underfloor heating? Also, what supply temperature do you have in winter?

B351721 schrieb:

With the new framework conditions for heating, I have the following questions:
- What lifespan would you assume for such a unit? Is it likely to fail soon? If I have to renovate anyway, should I replace it now?

The question is like asking a 94-year-old grandmother how much longer she will live. The answer could be anything from "until tomorrow" to "at least another seven years."

B351721 schrieb:

- What costs would you estimate for replacing it with a new gas boiler due to a defect?
- Should I switch to a heat pump right away then?

Costs? A small single-digit thousand-dollar amount.
Switching to a heat pump? I would do it if it makes sense — see initial questions. It doesn’t make sense to replace €3,000 gas costs with €2,700 electricity costs.

B351721 schrieb:

The installation space is limited on site, but there are still a few square meters free in the basement. The distance between the current installation site and the possible alternative location in the basement is about 15m (50 ft) of piping—can this be extended with insulated pipes?

Is a split system with an outdoor unit subject to any permits or only realizable with minimum distances? Can the neighbor block it?
If so, could a fully indoor system be a possible solution? There would only be supply and exhaust air ducts, with the rest installed inside the house, right?

In Baden-Württemberg, there are no minimum distance requirements to property boundaries. Only certain noise levels must be observed. Pipe lengths do not play a significant role. By the way, there are also monoblock units that can simply be connected to the existing piping.

B351721 schrieb:

For implementation including installation, I currently estimate:
- Replacement of gas boiler with heat pump plus water storage: 15,000–20,000 EUR
- Solar system 8 kWp plus 5 kWh battery: 20,000 EUR
Do you consider this realistic?
Does such a replacement make sense technically and financially?

The heat pump plus installation mainly depends on what exactly is installed and how. This budget may be too low for well-known brands like Vaillant and others. I would go for a monoblock unit.
Photovoltaic systems should always be as large as possible to benefit from economies of scale. An 8 kWp system is too small for the battery and quite expensive in absolute terms compared to, for example, a 15 kWp system.

Thank you for the response!

I will try to find out more details about the current heating system in the next few days.
Regarding the solar output: I roughly estimated 8kW for my 45m2 (484ft²) roof area – is 15kW even feasible there?

Today we discussed whether a heat pump for domestic hot water would make sense to avoid using gas in the summer. Wouldn’t that mean installing an additional heat pump later, if the gas heating is to be removed or must be discontinued?

Ask the owner about the maintenance contract. Whoever has been responsible for the maintenance so far will be able to assist you. After 20 years, it is often difficult to obtain spare parts. The installers might still have removed units available to use as sources for spare parts.