ᐅ Older apartment with gas boiler heating – underfloor heating now, heat pump later

Hello dear community,

I have a quick question. We will soon be moving into our 80m2 (860 sq ft) condominium and are planning some renovations. The building has an energy rating of D, was built in 1890, but the apartment itself dates from the 1990s (top floor).

Currently, the apartment has a 26 kW gas boiler for heating and hot water. Since we want to replace the flooring, we are considering whether now is the right time to install underfloor heating. We haven’t really budgeted for it, but I figure it’s now or never with the new floor. We were also planning to install an air conditioning system in the medium term, basically a light heat pump.

Question: Would underfloor heating also reduce the gas boiler’s consumption without any other changes? I’m wondering if, in a worst-case scenario, you could just switch on the air conditioning as backup. And if we do install underfloor heating, should we remove the existing radiators or leave them in place?

Does a “proper” heat pump make sense here? For example, on the roof? Or would a combination of the gas boiler, underfloor heating, and air conditioning as backup create an energy mix that doesn’t encourage Putin to invade more countries and doesn’t demand five-figure costs for an unplanned heat pump installation (not to mention getting approval from the homeowners association)?

Basically, if I spend a lot of money installing underfloor heating now, is that just future-proofing, or can it also directly reduce gas consumption?

Thanks in advance for your feedback.

Your idea is commendable but will not work that easily.

First of all, the gas boiler will not be designed for low flow temperatures, so extensive mixing will be necessary. The entire hydraulic system must be adapted (if possible), as underfloor heating circulates very large volumes of water.
Also, billing for the heat consumption could be problematic, and I cannot assess whether any actual savings would result.

If the apartment is even suitable for underfloor heating! The 1990s construction date does not guarantee good insulation. Suddenly having a floor temperature of 45°C (113°F) just to make it warm is also not effective.

The bigger issue, however, is that the homeowners’ association must approve your plan. You simply cannot break up the screed and install underfloor heating on your own, as the screed is not your property. Whether the air conditioning system will work without permission cannot be judged from a distance either.
The same applies to installing your own heat pump—you are not allowed to do this alone.

Benutzer200 schrieb:

First of all, the gas boiler is likely not designed for low flow temperatures, so extensive mixing will be necessary. The entire hydraulic system would need to be adjusted (if possible), since underfloor heating circulates very large volumes of water. Also, billing for the heat consumption could become problematic; I can’t say for sure if it would actually lead to savings.

Sorry, correction: I have a gas condensing boiler, not a conventional boiler, which is supposedly more compatible with underfloor heating. Are there not also underfloor heating systems installed directly in the screed? For the air conditioning, I have approval from the homeowners’ association. However, from what I have seen, a heat pump is significantly louder, so that is definitely an issue, even on the roof.

selterdurst schrieb:

Are there not also underfloor heating systems that are installed on top of the screed?

Only electric ones...

selterdurst schrieb:

But a heat pump is probably significantly louder, as far as I have seen, so that is definitely something to consider, even on the roof.

"Loud" is relative. Compared to an air conditioner, there's not much difference.

How do you get your hot water? Does your boiler work like an instantaneous water heater? With a heat pump, you need a hot water storage tank or you would have to switch to electric instantaneous water heaters.

Benutzer200 schrieb:

Only electric...

If there is enough space or ceiling height, couldn't you add another layer on top, at least using a dry screed system? Or maybe milling?

Is it really not allowed without involving the homeowners' association?

I would say it might depend on the declaration of division. Especially with a later attic conversion, it could be considered a separate sub-community that can act more independently, as it is clearly separable and would actually need to be maintained differently.