Underfloor heating in old buildings, subsequent installation

Hello,

since we are still looking for an apartment or a house, I would like to generally inform myself about the retroactive installation of underfloor heating.

1. Is a retroactive underfloor heating even sensible if an existing gas heating system with radiators is present? If a garden is available, does it make sense to install an air heat pump, especially for older buildings that are generally not very well insulated? Is gas heating suitable for an air heat pump?

2. Since older buildings usually have a low room height, I am concerned whether the insulation on the floor + underfloor heating will take up too much space and then cause problems with the door height. What options are there for the doors, do they simply have to be smaller?

3. Can the distribution for the underfloor heating take place in the basement or will there be too long distances for the underfloor heating in the house?

4. Since this is a retrofit, how complicated is it to build a vertical shaft for the underfloor heating, for example for three floors (ground floor, 1st floor, and 2nd floor)? Is it allowed to use the chimney for this?

Thank you!

1. it depends
2. shortening doors... suitable for Appenzeller and others who have come up short
3. Yes, can be installed in the boiler room.
4. it depends

1: Yes. Possibly supplemented by ceiling heating and wall heating where it makes sense. If so, then properly, since underfloor heating is only subsidized in conjunction with heat pump conversion. If it is not high mountain terrain, an air-to-water heat pump is quite reasonable. Refrigerant R290. Additional insulation would also be advisable. Definitely roof and basement. Exterior walls and windows depend heavily on the existing structure and how important that is. Engineering firms or (good) energy consultants calculate this. And yes, retrofitting underfloor heating is worthwhile: In an uninsulated old building (on average from the 70s), I have achieved very heat pump-friendly 36° supply temperature at NAT -10° because of this.

2: There are systems with lower installation heights – but they do cost a bit more. I installed one just last year for exactly that reason (more details gladly via PM). Sometimes it can also be structurally sensible to have 5 instead of 8 cm screed. Depending on the case, you may not need insulation underneath. You can also insulate the basement from below. Between the ground floor and upper floor it doesn’t matter anyway, as the heat at worst goes downward. And yes, doors can be shortened.

3: Usually, one goes directly from the heating room all the way to the top and branches off a heating circuit distributor for each floor. The distribution to the individual rooms then takes place in the screed, parallel to the heating loops. Often a hallway is also used through which everything runs. It might then not even need its own circuit, which is usually too small anyway.

4: Replace old riser pipes (radiators were also routed from bottom to top), maybe the old chimney as well. By the way, the lines from the photovoltaic system also run well through there. And the pipes of the ventilation system. ;-). The old niches for radiators under the window sills sometimes also offer flexibility. Either for riser pipes or for the heating circuit distributors.

Good luck!

since we are still looking for an apartment or a house, I would like to generally inform myself about the retrofitting of underfloor heating.

You are really putting the cart before the horse here. Apart from the fact that you can only discuss how to best do something with concrete properties: do you seriously want to choose the property based on how well underfloor heating can be retrofitted there?

especially with old buildings, which are generally not very well insulated

... this will be relativized precisely by legal retrofit obligations.

a vertical shaft [...] Is the chimney allowed to be used for this?

Your ideas are at a level of naivety that advises against your own interference in technical planning processes.

Oh come on , I was also more naive and dumber before the new build and renovation. You have to start somewhere. And the fact that you even consider the thoughts of the OP shows foresight. And yes, actually I would definitely choose a house based on whether it has underfloor heating or if it can be retrofitted. In the long term, every house will be heated with a heat pump, and then the factor "area" is extremely relevant for follow-up costs. Also, it is a comfort gain that, in my opinion, cannot be outweighed by gold.

Oh come on @11ant, I was also more naive and dumber before the renovation and remodeling. You have to start somewhere. And the fact that someone even thinks about the OP's concerns shows foresight.

Foresight is better than stupidity, I agree with that, but then it stops: countless threads here show people who, driven to the brink of madness by stories about how comprehensively informed one must be as a builder, lost their minds. I know plenty of people with houses that, fifty years ago, were considered unbelievably low-tech by today's standards, who are approaching eighty healthy and well without ever having compared boiler data sheets.

And yes, indeed, I would definitely choose a house based on whether it has underfloor heating or whether it can be retrofitted.

Based on experience, used properties can be at risk of compromise in more than seven and a half aspects—yet making precisely this detail the "master question" would probably have been commented on by Thööölke as a "risk" ;-)