
Renovate underfloor heating using the original


Head of Department HAT-System during status analysis
Our analysis will give you clarity
Reliable water analysis
Our experts determine a total of six values based on a water analysis and assess them in accordance with the applicable SWKI guidelines. If there are substantial deviations from the defined reference values for one or more parameters, we will develop solutions for your system. We will give you a detailed analysis protocol together with a catalogue of measures that gives you complete transparency and a sound decision-making basis. Thermography images from a thermal imaging camera supplement the analysis and identify defects in heat distribution if necessary.
Embrittlement measurement
From time to time, we are asked about brittleness measurement. The ageing of pipes is examined by physical tests. In order to achieve a reliable result, samples must be taken from different areas of the underfloor heating, which requires extensive floor openings. In many cases, samples are only taken from the distributors, which is not sufficient since the embrittlement of a floor heating pipe can vary greatly over its entire length. The embrittlement in the bends is often greater due to the constant tension. Therefore, we advise against such tests, especially if samples are only taken in the visible locations.
We are celebrating 40 years of pipe interior renovations
The problem with underfloor heating




The oxygen input, which increases with embrittlement, causes further corrosion processes on the metal components, while the sludge progresses. Higher flow temperatures usually compensate for the heating’s decreasing efficiency. It is a vicious circle, as this further accelerates the embrittlement process of the plastic. The heating circuits are even more stressed by the excessive operating temperature. Leaks and water damage then crop up, and it becomes inevitable that the entire underfloor heating will need to be replaced at some point. Therefore, you should have a professional condition analysis carried out if you see the following signs.
Sustainable renovation of underfloor heating using the HAT system
Is renovation necessary and feasible according to the status analysis? Then we can offer you the original HAT system for interior underfloor heating renovations. We have been renovating old floor heating pipes since 1999, making them diffusion-tight in accordance with DIN 4726. And all without the need for a construction site.
The first step in a renovation is to completely dry the pipes with specially prepared compressed air. This is followed by internal cleaning with a gentle, chemical-free, delicate finish inside the pipes, to remove mud residues and incrustations. Each pipe is then evenly coated from the inside using a specially developed coating material. Once it has been left to dry for 48 hours, this coating will have created a new pipe within the old one, which can then connect to the existing plastic pipe. The coating provides long-term protection for the old underfloor heating and makes it waterproof against any diffusion in accordance with the DIN 4726 standard. We are the only company that can provide this level of work. We renovate underfloor heating within a very short period of time and with a minimum of noise and dirt emissions. A pipe renovation is around 10 times faster and much cheaper than a total replacement. You can still use your rooms during the renovation work. With our HAT system, we can demonstrably extend the functionality and durability of your underfloor heating by at least 20 years, as evidenced by a twenty-year guarantee.
The problem with underfloor heating
Analysis of underfloor heating
Renovation using the HAT-System
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Let us inspire you – our testimonials
We renovate around 1,000 properties every year. For us, having satisfied customers is not enough. We want to inspire you. We strive to receive the very best customer ratings, and work hard to achieve this goal – which makes the positive feedback we regularly receive even more satisfying. Thank you very much for your trust in us and our services.
Total pipe interior renovation completed to the highest standard. The timing in January was perfect, as the impressive oil-saving effect was immediately apparent. I would highly recommend the Naef GROUP and its competent team.

Erwin Bänteli
The pipe renovation in our entire building was carried out cleanly, efficiently and neatly. We are very satisfied with the information provided and the work performed.

Martin C. Huber
After hearing the positive experiences of two colleagues, we had our 39-year-old underfloor heating renovated by the Naef GROUP – and we were not disappointed. All employees of the Naef GROUP were very professional, competent and friendly, from the preliminary assessment to the follow-up work stage. The job was completed very neatly and precisely, and finished exactly on schedule.

Ruedi Grunder
The most frequently asked questions about underfloor heating renovation
The HAT system is the original internal pipe renovation method for plastic underfloor heating pipes. Existing heating pipes are cleaned from the inside and then given a high-quality internal coating – without opening up floors or walls.
In the first step, the existing pipes are gently cleaned and completely dried. This is followed by coating the pipes with a specially developed internal sealant. This permanently protects the pipes from further ageing processes and makes the pipe permanently oxygen-tight in accordance with DIN 4726.
This process creates a new “pipe within a pipe”, which considerably extends the service life of the existing underfloor heating system.
The HAT system was developed by the Naef GROUP in 1999 and has been continuously developed ever since. As the developer and pioneer of this technology, we have many years of experience and countless successfully renovated reference properties.
Yes, renovation with the HAT system can be carried out without any problems at any time of year.
It is important to us that you feel comfortable in your home at all times, even during the work. That’s why we also ensure a pleasant living environment during the renovation phase.
If required, we can provide you with modern mobile heating units free of charge to keep your rooms at a pleasant temperature during the work. This means that work can also be carried out comfortably during the winter months.
No, there is no need to move out.
Our motto is: “You live – we renovate.”
The work is organised in such a way that your rooms remain habitable throughout the renovation. As neither floors nor walls need to be opened on a large scale, dust and noise emissions are kept to a minimum. Only the compressor causes a bit of noise.
So the impact on your everyday life is minimal.
A HAT system renovation includes more than just the underfloor heating pipes.
Important components of the heating system are modernised at the same time, such as new chrome steel heating manifolds, magnetic flow filters and – if desired – individual room controls.
These services are included in our all-inclusive offer. For you, this means full cost transparency without force-account work or unexpected additional costs.
No, we take care of that completely.
If heating manifolds are flush-mounted, we carry out the necessary milling and chiselling work ourselves to create space for the new manifolds. This work is included in the renovation price.
We install dust protection systems with powerful extraction systems to ensure that the work is as clean as possible.
If – depending on the condition of the wall – minor damage should nevertheless occur, we can also carry out this work for you. Our in-house painters and plasterers professionally restore the affected areas.
For you, this means: everything from a single source.
Pipe kinks or couplings usually occur during the installation of underfloor heating in new buildings. Such spots can result in individual rooms not getting properly warm.
Our specially developed Knickfinder (kink finder) – a proprietary development of the Naef GROUP – such problematic spots can be pinpointed to within 5 cm.
The use of this system is free of charge as part of a HAT system renovation and enables targeted analysis of the affected area.
The duration of a renovation mainly depends on the number of heating circuits in the building.
A typical detached house with around 12 heating circuits usually requires one day of preparatory work, around three days for the actual renovation and a further day for follow–up work.
In total, a renovation therefore takes around five working days.
If there are heavy deposits in the pipes, the duration may be slightly longer. However, we will detect this in our prior technical analysis.
The HAT system has been used successfully since 1999.
We have since reinspected many of the systems that were renovated over 20 years ago. The measured values show that the coating is completely intact even after decades.
In our experience, a service life of around 30 to 40 years can be assumed after renovation.
For this reason, the Naef GROUP offers a 20-year guarantee on the coating and finish.
A consultation that makes all the difference
Ein Beratungsgespräch, das den Unterschied macht





























