ᐅ Underfloor Heating in an Old House: Installation Starting from the Base Slab. Efficiency and Costs?
Created on: 18 Aug 2016 12:39
G
Gummikuh
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.
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.
B
Bauexperte19 Aug 2016 11:25Hello,
as @wpic already pointed out correctly, you should definitely not carry out the renovation on your own! Even if you are a professional in a specific area, there are many things to consider that you have probably never heard of.
You wrote further down that you have budgeted EUR 60,000 for the renovation; in my opinion, this will not be enough. Especially with an older building, there are always new surprises; I know this very well because we are currently renovating two houses.
Have you looked into funding from KfW? If not, you should do so soon, definitely _before_ getting into action mode.
In any case, you should hire a professional to accompany you. Among other things, they will advise you about the windows, which you want to have installed by a mason. If some of them are floor-to-ceiling, the roofer will certainly have a say as well.
As an additional bonus—if you apply for funding for the renovation and hire an energy consultant for this, the consultant’s fees are also subsidized.
Best regards,
Bauexperte
as @wpic already pointed out correctly, you should definitely not carry out the renovation on your own! Even if you are a professional in a specific area, there are many things to consider that you have probably never heard of.
Gummikuh schrieb:Are there already detailed calculations on whether underfloor heating would be worthwhile at all and, if so, how closely the installation would need to be spaced?
Now the whole thing is to be replaced by a gas condensing boiler (the tank will be placed in the garden) and underfloor heating.
You wrote further down that you have budgeted EUR 60,000 for the renovation; in my opinion, this will not be enough. Especially with an older building, there are always new surprises; I know this very well because we are currently renovating two houses.
Have you looked into funding from KfW? If not, you should do so soon, definitely _before_ getting into action mode.
In any case, you should hire a professional to accompany you. Among other things, they will advise you about the windows, which you want to have installed by a mason. If some of them are floor-to-ceiling, the roofer will certainly have a say as well.
As an additional bonus—if you apply for funding for the renovation and hire an energy consultant for this, the consultant’s fees are also subsidized.
Best regards,
Bauexperte
Removing the screed and properly insulating the floor plus installing a dry screed system is a good idea. We did the same in our house, which is also built on strip foundations on a slope. Whether you have underfloor heating or not (we do!), insulating the floor makes sense and is not really expensive. We received a quote of about 2000 euros for breaking out the screed in the lower level area (split-level) of around 60 m² (645 sq ft), but we decided to do it ourselves instead. With two people, it can be completed in one to two days using a chisel and a sledgehammer. When insulating, you should make sure to meet the U-value requirements specified in the energy savings regulations, as you don't want to have to redo it later. For us, this was 2 cm (0.8 inches) of 0.035 W/(m·K) insulation plus 6 cm (2.4 inches) of 0.022 W/(m·K), along with 25 mm (1 inch) of 0.035 W/(m·K) insulation from the underfloor heating system board (dry system). Altogether, this adds up to about 13 cm (5.1 inches) of build-up. It’s best to choose an energy consultant from the DENA list (google).
Similar topics