Water Underfloor Heating with Screed

Wunda’s Screed System

The Wunda screed system is ideal for those who enjoy ambient heat. The thermal mass of all screeds hold heat, but make It difficult to quickly adjust temperatures. Screed systems use close pipe centres and set back thermostats for optimum control. Maintaining low input temperatures that make floor heating environmentally friendly and energy efficient suitable for new properties.

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Not sure which UFH system is right for your upcoming project? Compare the differences below

	Screed	Rapid Response®	Joist
Extensions
New builds
Renovations
No need to dig up floors	–		–
Fast heat up time	–		–

When using screed, floor heating pipes are fixed on top of insulation. the screed is then poured encasing the pipes. Once it has set, heat can be applied to the screed. The heat passes through the floor finish and gently dissipates into the room. Given that optimal pipe centres are used, floor heating can be very economical using input temperatures between 30-50°C

Screed Floor Fixings

Wunda’s pressurised leak proof pipe can be secured to the insulation using a variety of fixing methods, some installers prefer to staple over the pipe into the insulation (left), others find the self-adhering clip tracks most efficient (centre), and others prefer to fit the pipe into castellated pipe tray. Once fitted the difference between this fixture methods is negligible, so it really comes down to installer preference.

Pipe staples

Clip tracks

Castellated panels

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Wunda supply two popular tried and tested pipes

Screed is a levelling compound typically comprised of sand and cement or anhydrite chemicals. Once set and dried, heat can be introduced to the system gently. These systems work fastest when used with a setback thermostat preventing the thermal mass from going cold.

HDPE/AL/PEX Pipe

Designed to work at high temperatures, it was developed for above ground general plumbing and radiator heating. This pipe is more suitable for plumbers. and regular installers who like to use one type of pipe for all work and are prepared for the extra work to fit this stiffer pipe in SCREED systems using Lightbulb ends, It is very difficult for anyone other than the professional to use this pipe in modern floor heating, especially in older homes and dry fix systems.

Pert/AL/Pert Pipe

Designed to work with pliability and strength at low floor heating temperatures it has become the most popular and widely used floor heating pipe in the world. The aluminium core makes the pipe very efficient transferring heat, increasing output by as much as 8%.

Sand and Cement and Chemical Screed

Chemical Screed

The thermal mass of all screeds make it difficult to quickly adjust temperatures with some taking hours to cool down. Chemical Screeds can use a shallow amount of screed of around 51mm allowing it to set quicker reducing install time, and enabling it to heat quicker than traditional sand & cement screed

Sand & Cement Screed

The minimum sand and cement screed that can be used is around 70mm. This will take longer to set than a chemical screed

Your Screed System Questions

Screed systems are traditionally used in new build projects. Screed systems require the floor heating pipes to be fixed to the sub floor insulation layer prior to being encased in a layer of concrete or chemical screed. The warm water in the pipes heat up the concrete (screed) which acts as a thermal store and radiates it into the living space. This process can take a few hours to both heat up and cool down and is less controllable than overfloor systems.

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