After World War II there were basically only two widely practiced ways of heating dwellings, either by a stove in each room or by central heating with steam or hot water passing through radiators. In some regions they also used night-storage electric heaters taking advantage of the cheaper rates for power at night.
By the early-1970s, however, underfloor heating (ufh) with hot water started spreading from Switzerland, Austria and Germany whereas electrical systems (foils in Spain, cables elsewhere) never got far beyond a dismal 5 percent market share.
Only after the breakthrough made by plastic pipes did ufh become one of the most widely used systems. In Germany copper pipes can occasionally be found in ufh, but their share is negligible and so is hot air and electric radiators. In Germany hydronic ufh with plastic pipe has reached 70 percent in houses and around 30 percent in apartments. In southern Europe ufh's breathtaking rise is fed by those countries' habit of tiled floors.
Plastic pipes started off with diameters of 20 mm and more (still 25 mm for outdoor use in ramps etc). A combination of energy-saving legislation and improved insulation has brought a steady reduction in diameters to the present average of 14 mm with 12 and even 10 mm already showing on the horizon.
The original PP has been mostly displaced by PEX as the material of choice while PB (remember Shell/Celanese?) remains marginal. It has become quite common to mix ufh with radiator systems in the same building (example: ufh on the ground floor/living area and rads in bedrooms upstairs) but baseboard has not succeeded.
Plastic pipes in hydronic heating are plagued by a common and recurring scourge -- they are not oxygen-proof. This has led pipes to be coated with an oxygen diffusion barrier. Oxygen can be absorbed into the water stream through the pipe wall and cause havoc in the boiler if a tiny metal particle has been left in the system by a careless plumber. Pinhole perforation is the undesirable consequence.
The recently improved welding of ever thinner aluminum foils for multilayer pipe, which is oxygen-proof by nature, helps ordinary PEX to be displaced in ufh, too, as it makes the multilayer pipe more pliable and Uponor's position as European market leader more unassailable.
European Differences
Different to North America, radiator heating and ufh are independent of the heat source and the energy used. Boiler manufacturers do not normally recommend the use of any particular heating system or pipe and neither would they have any in their product range. Heating in Europe is routinely supplied by "systems companies" who pick the components for their heating systems from the market and assemble ready-to-install packages, complete with guarantees and instructions. They train the plumbers and supply the specifiers with the software to provide the plumbers with individually designed and calculated projects, complete with materials list, drawings etc.In Germany, large systems companies such as Polytherm, Roth and Velta, have expanded their reach throughout Europe, and in France the major pipe manufacturers (e.g. Acome, Alphacan) have become systems companies themselves.
Hydronic heating systems are the most widely used by far in Europe and on the rise in the British Isles and Scandinavia. Therefore, in marketing it is never much of a question whether to promote hydronic systems in new buildings, but rather a question of which of the umpteen well-established hydronic systems to promote. Regional usage may influence the prevalence of radiators over ufh, or vice versa, much more than that of hydronic over electrical heating.
As a result, suppliers of ufh and other forms of hydronic heating have teamed up into trade associations (similar to your Radiant Panel Association) with the aim of promoting the benefits of their particular systems over others.
An increasing cost burden has prompted manufacturers to align more closely with systems companies, witness Velta belonging to Wirsbo, Polytherm to Hewing, and both Wirsbo and Hewing being part of the Uponor Group, which, in turn, is poised to become one of the world's biggest pipe manufacturer. Similar examples from other European markets abound.
