ECOFLOOR systems (heating cables or heating mats) can be used as the main heating system, or simply to provide comfortable underfloor heating – most commonly in the bathroom. In the latter case, where the room is heated by another heat source (e.g. a hot-water radiator) and the electric heating mat serves as a comfort underfloor heating system, the time required to warm up the tiled floor is a key factor. The system is operated for relatively short periods (around 1–2 hours in the morning and evening) and is required to heat the floor tiles as quickly as possible. Conversely, heat accumulation and prolonged cooling of the floor are unnecessary and undesirable in this context. The rate of heat-up can, of course, be influenced by the type of system, and only direct-heating systems should be used for supplementary heating.
However, even the use of a direct-heating system does not guarantee that the floor will heat up quickly enough. The behaviour of the floor depends on its overall composition, and if no thermal insulation is incorporated into the structure, the floor may take up to several hours to heat up. This problem is particularly noticeable in renovation projects, as older buildings usually have no insulation, and retrofitting 6 cm of polystyrene is difficult and considerably expensive. This means either removing approximately 10 cm of the floor to create space for insulation and a new floor, or raising the floor by these 10 cm. And this is often technically impossible. Nevertheless, there is a solution that is both technically feasible and affordable – installing additional F-Board insulation directly beneath the ECOFLOOR heating mat. The insulation increases the thermal resistance of the structure beneath the heating mat and ensures that the heat is directed primarily into the floor tiles rather than into the underlying structure. The insulation is available in thicknesses of 6 and 10 mm. When using 6 mm F-Board, the thickness of the entire new structure is just 2.5 cm, including the heating mats and the new floor tiles.
The importance of this insulation is demonstrated by three specific applications in which measurements of the floor temperature rise were carried out. In all three cases, heating mats with an output of 160 W/m² were installed directly in the adhesive under the floor tiles.
Bathroom in a block of flats
The flat, which includes a bathroom, is situated on the second floor of a block of flats in Jeseník. The building was constructed in 1908; it is a solid structure, built of solid fired bricks, with external walls 80 cm thick. Like the external walls, the ceiling and floor structures are also solid. The beamed ceiling is covered with wooden boards, on top of which lies a 4 cm thick brick floor, supplemented in the bathroom by a 4 cm thick concrete floor. The house is characterised by very good thermal storage properties and an ideal humidity microclimate. The flat is heated by a hot-water system; in the bathroom, a heating mat was installed in the adhesive under the tiles to provide comfortable underfloor heating. There is no additional insulation between the heating mat and the floor structure. The flat below the bathroom is occupied by another tenant
As can be seen in the graph shown, the floor took 3.5 hours to heat up from 20°C to 28°C, and a full 5 hours to reach 29°C. After 5 hours of operation, the heating mat was switched off, followed by a very gradual cooling of the floor. The system clearly behaves as a storage heating system – this is due to the 8 cm layer of construction (4 cm of concrete + 4 cm of brick screed) beneath the heating mat.
Given that this was intended to be merely supplementary comfort heating, the entire system can, unfortunately, essentially be described as non-functional. This problem could have been very easily prevented by installing additional insulation, as will be seen in the following application.
Bathroom in a detached house
During the renovation of a bathroom in a detached house, the homeowner requested the installation of an electric heating mat. Here too, it serves only as supplementary comfort heating; the bathroom is heated by a hot-water radiator. The bathroom is located on the ground floor, with a cold, unheated cellar beneath it. As this is an older property, there is no (!) thermal insulation in the floor. The floor consists of an 8 cm thick concrete slab (2 x 4 cm) with waterproofing. CLIMAPOR-POLYPLAN 2 mm thermal insulation, the heating mat and new floor tiles were laid on the prepared floor.
As can be seen from the graph shown, although there is no thermal insulation in the floor structure apart from the 2 mm POLYPLAN, and there is an unheated room beneath the bathroom with an average temperature of 5–8 °C, the system works very well and the floor warmed up in just 26 minutes. The temperature fluctuations in the upper part of the graph (28–29°C) are caused by the thermostat, which switched the heating mat on and off alternately once the desired floor temperature was reached. The floor also cools down considerably faster than in the first case, as the CLIMAPOR-POLYPLAN insulation prevented unnecessary heat build-up in the concrete floor.
Test specimen with F-Board insulation
As the FENIX Group has been marketing F-Board floor insulation as a new product since April 2007, tests were carried out, amongst other things, to measure the floor’s temperature rise. A test floor sample was created in the test room, the design of which corresponds to a renovation scenario where a new floor is laid over the original tiles. On top of the existing ceramic tiles (laid on a concrete subfloor without thermal insulation, the concrete being laid on natural ground), 6 mm F-Board insulation, a 160 W/m² heating mat and tiles were fixed using adhesive mastic. In the graph below, it is worth noting that, unlike in the bathrooms in the two cases mentioned above, the temperature in the test room was only ~20°C.
If we compare the temperature rise graph in the test room with that of the floor in the bathroom of a detached house where CLIMAPOR-POLYPLAN insulation has been installed, the floor temperature rose from 22°C to 28°C in 24 minutes – that is, ‘only’ two minutes sooner. However, this warming occurred at a significantly lower room temperature, which has a major impact on the cooling of the floor and thus on the rate at which it heats up. Thanks to the greater thickness of the F-Board insulation, better system dynamics are achieved.
This insulation has further advantages over CLIMAPOR-POLYPLAN – it is manufactured in panels and is very easy to install. CLIMAPOR-POLYPLAN comes in rolls, and during installation the material’s so-called ‘shape memory’ comes into play – POLYPLAN tends to form ‘bridges’ on the floor. Furthermore, F-Board is coated on both sides with a layer of sealant reinforced with glass fibre. This ensures excellent adhesion between the individual layers and, at the same time, greater mechanical load-bearing capacity of the floor. When the recommended sealants are used and the installation procedure is followed, F-Board also acts as a waterproofing layer, which is a huge advantage, for example, in renovation projects or timber-framed buildings.
Conclusion
To facilitate comparison, all three applications have been combined into a single graph so that the rise rate can be compared directly over a 2-hour period. The curves for each application are shown in the same colour; floor temperature curves are in bold, whilst room temperature curves are in light type.
In conclusion, it can be said that additional insulation in systems designed to provide occasional comfort heating for tiled floors is certainly worthwhile, and this initial investment will pay for itself many times over in the form of flexible and energy-efficient operation.
