Underfloor heating
Material matters U
The very nature of underfloor heating means it is out of sight, but can it ever really be out of mind? To ensure installations are truly fit and forget, choosing the right pipes and fittings is vital, says Drew Clough from Rehau
nderfloor heating is an ideal choice for commercial customers looking for an affordable, environmentally friendly and
comfortable heating solution with flexible space planning options. However, to ensure the installation stands the test of time, careful consideration of the components fitted is essential. After all, with hundreds of metres of pipework in a single room, the last thing you want is a leak causing unscheduled downtime and even loss of income for a commercial client.
One way to avoid the issue of leaks is to ensure
careful specification of the pipework materials and fixtures. Polymer pipes are a suitable choice for heating installations as they are light, easy to install and offer excellent flow rates because of their smooth walls. Unlike metal pipes, polymer pipework won’t corrode or develop pinhole leaks, they remain limescale-free and can withstand surge pressures much better than copper, steel or CPVC alternatives to avoid water hammer. They also have a high burst strength. Currently, the most common polymer pipes used for underfloor heating in the UK are PE-X, PE- RT and PB.
PE-X
PE-Xa pipes are made from cross-linked polyethene manufactured with peroxide and have the highest flexibility of all PEX pipes. Kinks can sometimes happen onsite, but with PE-Xa pipes, these can be easily repaired using a heat gun to ensure any white lines or weak spots are repaired back to the original pipe strength, without the need for coupling. This is possible because PE-Xa has a memory effect, meaning it will always return to its original shape and strength when heat is applied.
Rehau pipework being pre-assembled at Byrne Bros for the TABs system
With a higher temperature, tension and expansion
tolerance than PE-RT and PB alternatives, and the highest degree of cross-linking for even, thick walled pipes, PE-Xa pipework also has a longer lifespan than other polymer pipes – more than 50 years in fact.
PE-RT
PE-RT pipes are made from polyethene of raised temperature resistance and are particularly popular because they can offer a cost saving when compared to PE-Xa, which is difficult to manufacture. PE-RT pipes are easily bent by hand, making installations quick. However, they are prone to kinking and need coupling to repair any kinks, which can become a potential weak spot in an underfloor heating system.
PB
Made from polybutylene, PB pipes are easy to install and bend well. Like PE-RT alternatives, they too cannot be repaired using a heat gun and require coupling to fix any kinks. In the US, the use of PB pipes is no longer advised due to the increased rate of failures in installations, but this is most commonly attributed to the high chlorine content of the water in the States which is not currently an issue in the UK. To keep costs down, many installers still choose
PE-RT or PB pipework, even though the risk of weak spots and leaks is increased, making this a false economy.
Fixtures
The saying goes that a chain is only as strong as its weakest link and the same can be said for underfloor heating pipework. Choosing a durable pipe will prevent leaks, but if the joints aren’t up to scratch, there is still a possibility of water escaping the system. REHAU recommends installers use a compression sleeve jointing technique, like the EVERLOC, for polymer pipework installations. A compression sleeve joint ensures a permanent seal without additional O-rings and uses the heating and shrinking of the pipe to seal it directly onto the connection. The pipe is not reduced in diameter, ensuring minimal impact on water flow through the system. In an underfloor heating installation, a compression sleeve joint can be used to run lengths of pipework consecutively. Compression sleeve jointing techniques have a
zero risk of leaking. To date, more than 850 million EVERLOC joints have been installed around the
May 2017 Rehau’s solution at Llandysul School in South Wales
world, and no leaks have ever been reported. REHAU underfloor heating was recently installed in the largest school ever built by Ceredigion Council in South Wales. The £30m Llandysul School was fitted with 11,000m2 9,200m2
of REHAU pipework, including system and 2,000m2
installed using the REHAU Tacker sheet fitted using its diffusion plate
system. The Tacker sheet system provides a fast and efficient way of fixing the underfloor heating pipework direct onto insulated sheets and has been used for all of the main parts of the building, while REHAU’s diffusion plates have been used for the sprung floor in the sports hall and dance studio. Both the tacker and diffusion plate systems use PE- Xa pipework and EVERLOC joints for maximum leak protection. The combination of PE-Xa pipework and
compression sleeve joints is so robust in fact, it's specified for chilled ceiling installations and also REHAU’s Thermal Activated Building Structures (TABS) system. TABS is a cooling and heating system which uses
the large thermal mass of concrete in a building’s structure to adjust the environment inside the building throughout the day. It does this by running heated, or chilled water through a network of PE-Xa pipes joined with EVERLOC sleeve joints, which are embedded inside concrete slabs within the building’s structure. TABS was used recently in the £260m extension to
the Tate Modern in London as a key element of the sustainable design of the building. In total 24,000m of REHAU PE-Xa pipework was embedded within the concrete floors of the building, to circulate cooled water and provide comfortable, cost-efficient cooling throughout the gallery areas. For installers, the issue of product selection often
comes down to price, previous experience and what they are most comfortable with fitting. But this may not always be the best option for customers and the most durable installations. By taking a closer look at the different materials on offer, installers may discover a new way of doing things which could mean more fit and forget installations and less costly call backs. • Drew Clough is the underfloor heating and plumbing product manager at Rehau
www.heatingandventilating.net
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
