ᐅ Underfloor Heating in an Old House: Installation Starting from the Base Slab. Efficiency and Costs?

Hello everyone,
first of all, thank you for reading this.

We are in the process of buying a house built in the mid-1970s. According to the plans, the house (an end terraced house) is apparently built on a strip foundation. It is only partially basemented, with the basement extending about 4 meters (13 feet) into the house. From there, the floor drops half a level down to the basement and rises half a level up to the living area (slight slope).

Currently, there is an oil heating system installed that is about 20 years old, with radiators in all rooms. Unfortunately, I don’t know exactly how the structure above the ground slab is built, but according to a future neighbor, it probably consists of a thin layer of polystyrene insulation with 6-8 cm (2.5-3 inches) of screed on top.

The plan is to replace this with a gas condensing boiler (the tank will be placed in the garden) and underfloor heating. The quick and relatively affordable option would be to mill grooves in the screed for the pipes and then fill/level them with a thin layer of leveling compound.

I understand that this would waste quite a bit of energy through the floor slab... On the other hand, I don’t see the point in doing anything that would only pay off in 20 years or more, since I probably won’t recover the extra costs through heating savings within my lifetime. Or is the difference actually so significant that it would pay off within at most 10 years?

Thank you very much for your opinion.

Get an energy consultant who can calculate different options for you. Everything else is just guesswork. Underfloor heating does not automatically save energy.

Hello Nightdancer,
we have already considered that, as well as bringing in a specialist for the entire renovation. Who would be the right person for this, an architect or a building surveyor?
Later on, it will also be about the facade, for example brickwork, cladding, insulating a shed roof, etc.
Greetings from the Bergisches Land

Where is the property located? I provide real estate purchase consultations throughout North Rhine-Westphalia and Rhineland-Palatinate, occasionally also carrying out more advanced renovation planning and consulting, for example in Radevormwald/Gummersbach in 2013/2014. I am happy to send you information about my purchase consultation by email.

Considerations for energy-efficient renovation must always be planned as a comprehensive concept, including building services and heating systems. A floor heating system without adequate and especially energy regulation-compliant insulation under the slab makes little sense. The future insulation standard of the building is also crucial. A floor heating system, as a low-temperature heating method, requires a well-insulated building envelope. The sizing and design of the floor heating must, for example, be demonstrated in a heat load calculation. Before purchasing, the property should definitely be evaluated regarding its condition, any structural damages or moisture problems, and the extent of required renovation. Additionally, building, planning, and property ownership legal aspects must be reviewed so that you, as the new owner, can acquire the property free of encumbrances.

Of course, the house will be further insulated, but with moderation, as I see no point in spending over €100,000 on insulation. At that level, it would probably involve state-of-the-art insulation with a ventilation system and so on.

Next up are about 100m² (1,076 sq ft) of shed roof and two exterior walls (planned insulated brickwork), plus around 10 windows, which a friend who is a mason will install, along with guidance/help with the bricklaying and tiling. I will handle the electrical installation myself (I am trained), and a friend who is a plumber will take care of the plumbing.
All in all, we have €60,000 available for the renovation.
The house is empty, and all the walls are covered with old wallpaper/paint (no latex or anything hidden behind wood), so I can fairly easily see that there is no mold anywhere.

I will probably remove the old screed and rebuild from the base slab up. Since the budget is tight, it will likely be a dry screed, as this allows me to contribute most of the manual work and ensure the material is of good quality.

After all, the house is in a condition that it was lived in without any problems until recently (the owner has now moved into a nursing home).
We want it to last another 15-20 years, and then our heirs can renovate it energetically according to future standards... or in other words, tear it down ;-)

@wpic
Location is Radevormwald Dahlerau

I would seriously reconsider the underfloor heating... Removing and rebuilding the screed everywhere is a major undertaking.
Is underfloor heating really that important to you?
I’m also a bit skeptical about saving that much money with it in a well-insulated house, especially when you look at a 15-20 year timeframe.
Well, if it ultimately comes down to just having a warm floor, you could simply wear slippers as people used to do or lay down rugs, or just accept the floor as it is. After all, you’re not walking on an ice slab.

Before breaking up the screed, I would have the heating and plumbing systems checked and ask for a cost estimate.