UNDERFLOOR HEATING INSULATION

Underfloor heating insulation is an essential, required part of complex underfloor heating (UFH) systems designed to prevent downward heat loss. It means, insulation boards do not let the heat pass through from the heater to the subfloor. Therefore the heat gets pushed upwards, onto the floor surface where you want the heat to go. Generally speaking, underfloor heating insulation reduces the amount of time the room takes to warm up and cool down, the room can spend longer at its cooler set-back temperature, reducing heat loss and conserving energy. In fact, underfloor insulation creates a solid barrier for the heat produced, thanks to which the heat is transferred upwards, which means that the system uses less energy, much less than traditional radiators. Underfloor heating insulation boards are placed underneath your flooring, whilst also ensuring that the optimum heat levels are retained. On other hand the installation itself is more expensive, but the operation costs much less. While the working temperature of the underfloor heating is usually 40°C, traditional radiator heating need a temperature of 60°C. Thanks to the lower temperature used, the boiler consumes less gas and thus our bills are lower by 35%. Therefore it is very important to use high quality insulation for underfloor heating. The heated floor must be well protected against heat loss, so usually PIR rigid or EPS100 polystyrene insulation boards are placed on the leveled substrate. In order to facilitate the work, special PIR insulation boards glued to the foil are often used. A mesh is printed on such a foil, which facilitates precise arrangement and fastening of pipes. The thickness of the insulation should be selected so that the heat transfer coefficient of the floor is less than 1.0W/m2K for floors on ceilings above heated rooms, 0.25W/m2K over unheated basements and 0.3W/m2K for floors on the ground. The best insulation material used for underfloor heating turns out to be PIR insulation, because it has foil faced on both sides which makes the heat reflected upwards, thus warming our feet. It is also resistant to moisture from any dripping pipes or leaks. The term underfloor heating insulation refers to the large pre-formed sheets of insulation which can be bought in 2400mm x 1200mm (8’ x 4’) size.

UNDERFLOOR HEATING - SYSTEM TYPES

When considering underfloor heating, you have a choice between two distinct systems:

 Electric Underfloor Heating:
This system utilizes either electric heating cables or mats, which are installed directly within the concrete screed layer, positioned between the thermal insulation and the tiles. The selection of the underfloor heating system depends on various factors concerning the space. When confronted with constraints regarding floor thickness, the preferred option often becomes the heating mat. These mats are characterized by their slim profile, typically less than 7mm, facilitating swift installation beneath floor tiles. However, they come with certain drawbacks: they tend to consume a significant amount of electricity, exhibit a sluggish response to temperature fluctuations, and necessitate continuous operation. Consequently, they are usually deployed as emergency solutions when floor thickness is restricted. 

 Wet Underfloor Heating:
Alternatively, water heating pipes constitute another viable option. These pipes are laid directly within the concrete screed layer beneath the floor, situated between the thermal insulation and the tiles. The water-based underfloor heating system proves to be notably more cost-effective compared to its electric counterpart. Here, water serves as the primary energy carrier, coursing through the pipes positioned beneath the floor. Given the human body's optimal temperature of 36.6°C, excessively high temperatures are unnecessary for maintaining warmth. Typically, the set temperature for water pipe systems ranges between 30-35°C, adequately heating the entirety of the home's surface. Operating as a low-temperature underfloor heating system, it boasts efficient energy utilization, minimizing both electricity and gas consumption for water circulation.

The water temperature within the pipes while the system is inactive hovers around 15°C, requiring minimal energy to elevate it to 30 degrees Celsius. To heat the water within the underfloor heating system, mixers connected to a gas boiler are employed.

PEX pipes with a diameter of 16mm are commonly utilized for water underfloor heating. These pipes are laid at 15cm intervals to form closed loops, ensuring that the water within each loop returns to the mixer. While the maximum permissible length for each loop stands at 50 meters, the most optimal length ranges between 30-40 meters, guaranteeing uniform heat distribution.

It's imperative to refrain from extending loops beyond 50 meters, as water at the end may have already cooled, resulting in cold patches on the floor. Water underfloor heating should be avoided in areas expected to be permanently inaccessible, such as locations earmarked for kitchen furniture placement.

A notable drawback of this water-based underfloor heating system lies in its thermal expansion, potentially causing the floor to rise by up to 2mm. This factor should be taken into account during skirting board installation.

UNDERFLOOR HEATING U-VALUE

For underfloor heating, a U-value of between 0.13 and 0.25 is typically required to meet current building regulations. To achieve 0.13 U-value performance with a typical PIR rigid foam insulation, it would require approx. 125mm thickness. In terms of EPS70 or EPS100 polystyrene, a minimum of 200mm is required to achive the same U-value figure. On the other hand, an XPS polystyrene board would need a thickness of 100mm. Extruded polystyrene boards called XPS are dedicated to be used on concrete floors as they offer much higher than standard EPS (Expanded Polystyrene) resistance to pressure which is 300kPa where standard polystyrene is 70kPa.

UNDERFLOOR HEATING THICKNESSES | THINNEST INSULATION

Insulation boards always improve the efficiency of your underfloor heating system by allowing a quicker heat up time, when no heat is getting wasted by going downwards away from the floor surface. Wet underfloor heating can only reach high levels of energy efficiency, if it is properly insulated. This will reduce additional heating costs and provide the interior space with comfortable background heat. In order to install the best insulation for your wet underfloor heating system you can use a 15mm insulation board, although its thickness could be up to 50mm. Normally, better insulation is required for earth-filled bases to avoid any unnecessary heat losses. The insulation boards are available in a range of thicknesses, from 15mm to 200mm suiting any individual project requirement. The boards should withstand a load of 10-30 tonnes per metre square. It is recommended to use a minimum layer of 50mm Polyurethane insulation. If there is not enough space for 50mm insulation, 30mm can be used.

UNDERFLOOR HEATING INSULATION MANUFACTURERS | PRODUCTS

When we talk about underfloor insulation either Celotex, Xtartherm or Kingspan are the products of choice. While Celotex offers a 12mm TB4000 foil faced insulation board, Unilin offers 15mm Thin-R range. Both brands are qualified to be the thinnest insulation boards for underfloor heating. On other hand Kingspan and its K103 floorboard offers fibre-free rigid thermoset phenolic core with thermal conductivity of just 0.018 W/mK across all thicknesses. In fact, K103 is a premium product for underfloor insulation, followed by Unilin Safe-R SR/UF phenolic core insulant product. Among widely available insulation materials, extruded polystyrene (XPS) insulation offers one of the broadest range of compressive strengths and is one of the few products where manufacturers invest the time to test and declare compressive creep on underfloor heating systems. It is significantly denser than other types of underfloor insulation, which gives it a greater compressive strength. Its closed cell structure also resists both moisture and water vapour ingress. Due to its compressive strength, XPS is regularly used in underfloor system applications. Either STS or Soprema SL boards are a great option.

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