WIS heating cables for concrete screed
WIS heating cables are classic, heat-storing electric underfloor heating embedded in a screed on thermal insulation. In an energy-efficient house they can be the only source of heat, and under the floor they work trouble-free for decades, covered by a lifetime manufacturer’s warranty.
How the WIS system works
The heating cable is laid on thermal insulation and then covered with a concrete screed. The screed stores heat and releases it evenly over the entire floor area. The output is matched to the building’s heat demand, and the cables are available in ready-made lengths from 9 m (180 W) to over 160 m.
- Cable rated at 20 W per linear metre, with double ETFE insulation resistant to 260°C.
- An earthed screen along the entire length of the cable, connected to the protective earth (PE) conductor: protection against electric shock, also in wet areas.
- One factory joint per room, made and tested with high voltage in the factory, not on site.
- Single-ended supply: the supply and return conductors are in one cable, so the electromagnetic fields cancel each other out.
Who it is for
The WIS system is chosen above all by people building a new house – energy-efficient, passive, masonry or prefabricated – with a screed laid on insulation. The solution has been proven in places such as cold Scandinavia, where it is successfully used as the only heat source.
If the screed has already been laid, or there is a foundation slab or a timber floor under the floor, SPM heating mats or DCM-PRO cables laid in the tile adhesive will be a better choice.
Any floor finish
On a screed with WIS cables you can lay ceramic and porcelain tiles, glued and floating vinyl panels, wooden boards, sintered stone, natural stone, microcement or resin. In the future the finish can be replaced without damaging the cables and without redoing the heating.
What the installation looks like
- You send an enquiry with the floor plan of the building. We select cables and thermostats for each room and prepare a quote in two options: with and without installation.
- Before installation, laying the EPS/XPS insulation and reflective foil and preparing the electrical installation are on your side (details below).
- Our team lays the heating cables, fits the floor temperature sensors, measures resistance before and after installation and documents the work with photos. Installation usually takes one day.
- The screed is poured by the building contractor. The thermostats are fitted in the prepared back boxes, and on request we carry out a free test run of each heating zone.
- The measurements are entered in the warranty certificate. You pay a 10% deposit when signing the contract and the rest only after installation.
Electrical requirements
Each heating zone has its own thermostat. Before installation, the electrician prepares:
- wall back boxes for the thermostats,
- a separate 230 V supply for each zone from the distribution board to the back boxes, with 3×2.5 mm² cable,
- 2 conduits of 20–22 mm diameter from each back box to the floor,
- separate protection for each zone in the distribution board (B16 and a common 30 mA RCD, type B).
Cost and bills
In the comparison with a heat pump we assume about PLN 160/m² incl. VAT with installation and thermostats. The exact amount for your house, including travel and thermostats, will be shown by the calculator once you enter your postcode.
The annual energy cost depends on the building’s heat demand: in a 70 m² house with a demand of 50 kWh/m²/year it is about PLN 3,500 at PLN 1.00/kWh incl. VAT. See also the 25-year comparison with a heat pump.
Frequently asked questions
Can WIS heating cables be the only source of heat?
Yes, in energy-efficient and passive houses. We match the output of the cables to the building’s heat demand given in the design.
What if a cable in the screed gets damaged?
After installation, every system undergoes resistance and insulation measurements. Unless it is damaged mechanically, e.g. by drilling into the floor, the cable should not fail on its own. If it is damaged, a minimally invasive repair is possible without breaking up the whole floor, and our company has specialist equipment for this.
What is the warranty on WIS cables?
A lifetime manufacturer’s warranty. The condition is registering the warranty after installation, with the measurements entered in the certificate.
Can the floor be changed later?
Yes. The floor finish can be replaced without damaging the heating cables and without redoing the heating.
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Want to know how much it would cost in your home?
Check the estimated cost in the calculator or send an enquiry – we will prepare a quote with and without installation.