Glossary – HAT system

Abrasive mixture – Natural polishing agent used for cleaning heating pipes. This roughens the pipe surface to ensure maximum adhesion of the coating material. At the same time, the pipe is made 100% clean.

Added value: anyone who renovates their property with the HAT system adds significant value to the property. This proof is also essential for a subsequent home-owner in the event of a sale.

Administration – When renovating apartment blocks, we work in close consultation with the responsible facility management. However, we take over all of the planning and information responsibilities for the administration.

Aluminium composite pipes – High-quality, durable heating pipes with aluminium core; ensure even heat distribution. Since 1990, these pipes have replaced the simple plastic pipes, which become brittle.

Analysis – Detailed inspection of the heating water to determine the progression of the ageing process. This analysis determines the current status and whether renovation is necessary. At the same time, all parameters are recorded on site in order to put together a serious offer.

Analysis price – Current prices can always be found on our website.

Apartment blocks – We conduct renovations on a weekly basis and have extensive experience in this field. Beyond proper planning, our communication with the residents and the administration are also important factors. Meticulous organisation is important to us.

Brittle pipes – Sign of advanced ageing; due to the evaporation of stabilisers (also known as plasticisers). Continuous operation during the heating period accelerates this process. The warmer the heating water, the faster the vaporisation and therefore ageing of the pipes.

Brittleness – Material fatigue of plastic pipes due to ageing and temperature fluctuations. This is a major problem, especially with older, simple plastic underfloor heating systems, which were installed between 1970 and 1990.

Caloflex: Simple plastic pipe that was mainly used in the 1980s. Embrittlement is a risk here as well.

Carbon neutrality – All Naef GROUP renovation work is climate-neutral. This has been the case since 2015.

Ceiling radiant heating systems: These (iron) pipes were installed in the ceiling. Warm head – cold feet. One of the worst options from an energy perspective.

Coating (internal coating) – Plastic layer that seals the inside of old underfloor heating pipes and makes them diffusion-tight. This process does not insulate the pipe. Our coating is oxygen-tight in accordance with DIN 4726. Only such DIN certification confirms that the pipe is protected.

Condition analysis – Technical inspection of all underfloor heating components as a basis for deciding on the possible need for renovation. The water analysis is the most important test here.

Conductivity of heating water – The higher the conductivity, the more the water promotes corrosion.

Conventional flushing merely treats the symptoms and does not solve the problem of embrittlement of the plastic pipes. Impulse flushing also poses the risk that the pipes may become blocked.

Copper pipes – Do not age or become brittle and do not need to be renovated. Among the best options available.

Corrosion – Breakdown of metal elements due to excessive oxygen content in the closed heating system.

Customer satisfaction: this figure was around 98% between 2020 and 2025, as was our recommendation rate.

Customers: we do everything we can to ensure that they are not just satisfied, but delighted. Everything we do is dedicated to serving our clients.

Defective and leaking heating pipes can only be repaired on a non-warranty basis. You should never wait too long when symptoms appear (cold floor or spots) and should definitely have an analysis carried out.

Degassing devices are mainly installed in large heating systems. However, they do not solve the problem of ageing and embrittlement of the plastic pipes, but merely slow down the corrosion, which is itself a symptom of the ageing process in plastic pipes.

Diffusion-tight (DIN 4726) – Standard that ensures that no additional oxygen gets through the pipe into the heating water. Only our coating fulfils this requirement; no other provider can prove compliance.

DIN 4726 – Standard for the determination of oxygen diffusion in heating pipes. Standard that ensures that no additional oxygen gets through the pipe into the heating water. Only our coating fulfils this requirement; no other provider can prove compliance.

Duration of the renovation: The duration of a renovation depends on the number of heating circuits in a property. A detached house with approx. 12 heating circuits takes approx. three working days. However, an additional day of preparatory work and one day of finishing work is required. The renovation time may vary for properties with heavy deposits.

Energy efficiency – After the renovation, energy consumption is reduced thanks to improved heat transfer and the installation of new heating manifolds, which are fitted with flow meters. This leads to significant energy savings.

Flow rate meters – These are now standard with every new manifold in order to ensure precise control of the individual heating. Such flow meters are installed in every renovation with the HAT system.

Flushing – Simple water or pressurised flushing that is frequently offered. Unfortunately, this is never a sustainable solution for old underfloor heating systems. The risk of clogging or blockage in the pipe is very high, as the residues are deposits, usually in the middle of the underfloor heating system.

Gallotherm: Simple plastic pipe that was used in Switzerland in the 70s and 80s. Embrittlement is a risk here as well.

Haka pipe: this is a simple plastic pipe. It was frequently used in Switzerland in the 1980s. Embrittlement is a risk here as well.

Hastratherm: this is a simple plastic pipe. It was frequently used in Switzerland in the 1980s. Embrittlement is a major risk here as well. In many cases, these pipes can no longer be renovated as the embrittlement is very advanced.

HAT system – Original method for renovating old underfloor heating systems through cleaning and internal coating. This process was developed by Werner Näf in 1999. The original.

HAT system means: Heating renovation Alternative Technology.

Heating circuit – Individual heating circuit within an underfloor heating system. This always consists of a flow arm and a return arm. The warm water is fed into the flow arm and returns cooled via the return arm.

Heating circuit manifold – Connection point where all heating circuits converge and are connected. These are now made of chrome steel. In the past, they were made of iron or brass.

Heating costs: are reduced after a HAT system renovation. This is because the full pipe capacity is restored and the pipes are no longer clogged with sludge.

Heating water analysis – Testing the water for specific values to determine the ageing process as well as the general condition.

Incorrect storage – UV radiation or poor storage conditions damage plastic pipes even before they are installed. After installation, this is an unknown factor.

Individual heating cost billing: this is often installed in apartment blocks in the course of renovation.

Internal pipe renovation – Renovation of old pipes from the inside, without structural measures.

Iron manifolds – These are replaced by new chrome steel manifolds with flow meters as part of every renovation.

Iron oxide – This value is measured during each analysis and indicates the level of build-up in the pipe. This is misleadingly referred to as sludge, but is actually dissolved iron oxide that settles in underfloor heating systems. This results in rooms being heated unevenly or not at all.

Knickfinder (kink finder) – Another invention/development from the Naef GROUP. This device can locate kinks to within 5 cm. If desired, the kinks can be removed during the renovation and the pipes and connections professionally renovated.

Leakage – The ageing process of a plastic pipe can become so advanced that leaks occur. These are always in the bends and never in a straight section of the installed underfloor heating pipe. If hairline cracking occurs, the embrittlement is too far advanced and it is too late to renovate the pipe.

Long-term study – The HAT system has been in use since 1999. Hundreds of properties that were renovated more than 20 years ago were inspected. The measured values speak for themselves – even after 20 years, our coating is intact. After renovation, a service life of at least 30–40 years can be assumed.

Magnetic flow filter – Additional component that filters rust particles from the heating water and prevents corrosion. This filter also has an oxygen anode that reduces the residual oxygen in the system.

Manifold (underfloor heating manifold) – Centrepiece of the underfloor heating system for regulating the individual heating circuits or rooms.

Manifold labelling – Correct labelling of the heating circuits; this is checked during renovation. Often the original labelling is not correct.

Measuring the degree of embrittlement – This method is critical, as the degree of embrittlement can be different from one metre to the next. In addition, the samples would have to be taken in the heating circuit bends (not at the manifold). In other words, these points would have to be located structurally and the floor opened up locally. Even then, however, it is impossible to say how long the pipe will last, as various and many factors play a role in the ageing process.

Metal parts in the heating system rust due to oxygen ingress via diffusion, which increases over time due to the embrittlement of the plastic pipe.

Mild steel pipes: these were primarily used to connect radiators and do not need to be renovated.

Multibeton: this is a simple plastic pipe. It was frequently used in Switzerland in the 1980s.

Embrittlement is a major risk here as well.

Multilayer composite pipes – Heating pipes with an aluminium core. They ensure even heat distribution and are standard today in new buildings as they do not become brittle.

Naef GROUP – The inventors of internal pipe renovation. Werner Näf, the current President of Board of Directors, developed the HAT system. The original since 1985. Swiss market leader with 5 locations throughout Switzerland.

Oxygen diffusion – Oxygen ingress through the pipe wall, the main cause of build-up and a particular problem with underfloor heating pipes from the 1970s to 1990s.

Painting work – We also take care of this ourselves if we have to dig out flush-mounted distributors and there is damage to the masonry. We have our own painter/plasterer who takes care of it immediately.

Partial pressure – This phenomenon makes it possible for oxygen in the environment to diffuse through the plastic pipe, resulting in an increased oxygen content in the heating water. This is only possible if the plastic pipe is ageing and the stabilisers are no longer 100% present.

pH value of the heating water – This should be in the middle of the scale; otherwise it can favour corrosion in the system.

Pig cleaning – Simple cleaning method with compressed air, but without continuous diffusion-tight coating and often useless in the case of heavy build-up. It only treats the symptoms. The plastic pipe continues to age.

Pipe couplings – Used during installation to connect pipes. However, they reduce the correct flow rate as the couplings are smaller than the pipes. These couplings can be located and, if required, removed during a renovation.

Pipe kinks – Kinks created during installation that impede the flow of water are detected during renovation and can be removed if required.

Pipe lengths – The individual lengths of each heating circuit are determined by us during the renovation. This also allows us to optimise the system to suit your needs.

Plastic pipes – Early generations (1970–1990) are susceptible to embrittlement and diffusion. The ageing process can cause the pipe to become so brittle that hairline cracks appear. Leakage occurs. In this condition, it is often too late to renovate the inside of the pipe.

Preliminary work – This work is carried out by a heating specialist. The old manifolds are dismantled and the heating system is drained so that the renovation team can get to work.

Prices – The renovation price depends on how many heating circuits were installed in a property, as this influences the duration of the renovation. We assess all of this during the condition analysis and can calculate exactly what a renovation will cost without any surprises or additional costs for the client. We conduct renovations for an all-inclusive price.

Quotes – You will receive quotes no later than 2–24 hours after our visit or our analysis. This is only possible because we no longer have any administrative work thanks to the latest IT technology.

Recommissioning – The heating system is restarted after the coating has hardened.

References – We renovate well over 500 properties every year. Reference lists are available on request. However, our customers also regularly rate us on Google.

Renovation costs: A HAT system renovation is roughly 5 to 10 times cheaper than conventional underfloor heating replacement. Moreover, residents don’t have to move out.

Riser zone – This comprises metal pipes that run through the building to the corresponding heating manifolds. These do not need to be renovated and this is not recommended. The riser zones can be protected by installing a magnetic flow filter. We always install this; it prevents the residual oxygen in the closed system from attacking the metallic system parts or riser zones.

Room thermostats: these can be installed during a renovation. Today it is possible to regulate individual rooms electronically or via a mobile phone.

Sandblasting – Mechanical cleaning of the heating pipes with compressed air and an abrasive medium. The pipe must also be roughened so that the coating adheres.

Satisfaction – Is not enough for us – we want to exceed your expectations. This is what we strive for every day.

Sludge – Deposits in the pipe system that reduce the heat output. Due to embrittlement or the ageing process of the pipe, too much oxygen enters the closed circuit. This builds up on the metallic system components (riser zone, boiler, old iron manifolds) and forms rust, which settles in the horizontally laid underfloor heating pipes. It is not actually sludge, but rust that accumulates in the plastic pipe.

Start of renovation – Start of work: drying, cleaning, coating and recommissioning.

Stramax: Simple plastic pipe that was mainly used in the 1980s. Embrittlement is a risk here as well.

SWKI guidelines – The BT102-01 standard is consulted in a HAT system condition analysis. Their

standard values enable a clear assessment of the condition of underfloor heating systems.

Thyssen: Simple plastic pipe that was mainly used in the 1980s. Embrittlement is a risk here as well.

Total replacement – Replacement of all the underfloor heating pipes. This us usually avoidable today thanks to the HAT system if you don’t wait too long.

Tuflex – Was a Swiss plastic pipe manufacturer that produced pipes with insufficient stabilisers in the 1980s. In other words: underfloor heating pipes that were effectively already brittle were laid in new buildings. Damage occurred after a few years. We can no longer renovate this type of underfloor heating pipe, as the base material is missing or the pipe is actually crumbling in places.

Underfloor heating – Surface heating under the floor covering; provides pleasant radiant heat. The most popular choice in Switzerland.

Underfloor heating layout: during the renovation, it is possible to determine where and in which rooms the individual underfloor heating systems were installed. We do this automatically during each renovation; it can be detected acoustically during sandblasting.

Unitex: Simple plastic pipe that was mainly used in the 1980s. Embrittlement is a risk here as well.

Warranty – A HAT system renovation comes with a 20-year warranty on the coating. We can do this because we have the certainty that the coating will last significantly longer. Properties that were renovated 20 years ago or more are repeatedly inspected.

Water analysis – Testing of the heating water as the best indicator of ageing of the underfloor heating and to determine the general condition of the system. Cost-effective and informative.

Werner Näf – inventor of the HAT system (1999), pioneer of internal pipe renovation. Werner Näf developed the first internal pipe renovation process for the renovation of drinking water pipes back in 1985.

Winter time: we renovate all year round. In winter, we heat the house using a stove that is provided free of charge. (Blower)

Wirsbopex: Simple plastic pipe that was mainly used in the 1980s. Embrittlement is a risk here as well.

You live – we renovate: we always conduct renovations in occupied buildings and our employees know how to behave properly. Cleanliness, friendliness and communication with the resident are important to us.