Foil for warm floor – or not, types of substrates and laying

Few things are as important as effective heating and insulation for maintaining a warm and comfortable home. Many homeowners resort to underfloor heating systems in their pursuit of warmth because they provide an opulent means of uniformly heating a space. But how about enhancing this warmth with a layer of foil? We’ll go over the ins and outs of utilizing foil with warm floor systems in this guide, covering various substrate types and laying methods to help you choose what’s best for your house.

Let’s start by addressing the important query: is foil really useful for warm floor setups? Foil is frequently sold as a reflective barrier with the claim that it reduces heat loss through the subfloor and increases the efficiency of underfloor heating by bouncing heat upward. However, a number of variables, including the kind of flooring, the existing insulation, and the local climate, can affect how effective it is. Determining whether foil is a worthwhile investment for your heating system requires an understanding of these subtleties.

It’s critical to comprehend the various substrate types when thinking about foil for your heated floor. Substrates act as the foundational layer that offers support and insulation when the heating system is installed. Plywood, insulating boards, and concrete are common choices; each has advantages and disadvantages. It is important to consider factors like moisture resistance, thermal conductivity, and underfloor heating compatibility when choosing the right substrate for your house.

After selecting the appropriate substrate, correct installation is crucial to guaranteeing the effectiveness and durability of your heated flooring system. Performance can be greatly affected by the way the foil and heating elements are laid, if that is a method you choose. Precision and close attention to detail are essential whether choosing a wet or dry installation. To achieve the best possible heat distribution and energy efficiency, it’s also important to carefully consider elements like the heating elements’ coverage, depth, and spacing.

Foil under a warm floor – is it necessary?

Today, one of the essential components of the pie with heating is the foil substrate used during the installation of the "warm floor" system. The best insulation for preserving and dispersing heat produced by a heating device is foil-covered insulation.

This helps reduce the amount of heat that is wasted, boosts the heating system’s capacity, and speeds up the room’s heating, all of which have an impact on how long the floor lasts.

Just so you know! There is a misconception that using foil-covered materials in an electric heated structure is unsafe. There are lots of isolating and protective materials available today.

The foil substrate’s structure consists of foil and a base. Basalt, minerals, polystyrene foam, and polyethylene are the building blocks. These thermal insulation products come in the majority with a bubble structure. The aluminum foil for the heated floor has a metallized surface.

Advantages and disadvantages

As was already mentioned, a foil-surfaced substrate is a great material to use to save electricity. Furthermore, foil offers several benefits, but it also has drawbacks.

pros Minuses
Does not affect the height of the floor, since foil material is only 2-10 mm thick. High cost is the main drawback.
Not complicated in styling, so even an experienced person can cope with work. It is not recommended to take a mineral substrate with a metallized layer for warm floors, since toxic substances are released during heating.
Has the properties of sound insulation and waterproofing. The use of such a substrate in rooms with high humidity, its service life is significantly reduced. Recommended foil products covered with film.
Withstand heating to +90 degrees and more. With direct contact with the cement, dissolves.
Most of the foil products are equipped with marking, which simplifies the process of laying heating elements.
There are models with a sticky layer, it facilitates the installation.
Reduces heat loss, and contributes to its uniform distribution.

It should be mentioned that the foil product, when installed and used properly, is robust and long-lasting.

Types of foil

Foil insulation is currently available in a wide range of models, each with a unique basis and intended use for various construction tasks.

Watch the video to learn about reflective thermal radiation, various substrate types, etc.

It is more common to build saunas and baths on the underfloor. Ultimately, foil’s primary advantage is that it is impervious to water and drastic temperature changes. Given that the product won’t rot, the operating period is lengthy.

The material is resistant to mechanical loads, has improved sound-insulating qualities, and is environmentally benign. However, because of its high cost, it is hardly ever used as a heater in residential buildings, with the exception of upscale housing.

Basalt insulation

In terms of insulation, basalt wool is superior. It produces little heat and adapts well to temperature swings between -200 and +700 degrees in the aisles. This species doesn’t burn, and it has a reflective surface that makes it easy to lay.

Even though the insulation is not heat-sensitive, it is not advised to use it in a warm floor pie because it may release harmful substances when heated.


Mineral wool covered in foil offers superior thermal insulation qualities and is also fire resistant. However, the composition is not recommended for use in warm systems because it contains components that, when heated, distinguish harmful substances.

Not ideal for environments with a lot of humidity because cotton wool loses its qualities when it drags water. It is advised for use in industrial settings.

Polyethylene foamed

The most common kind of insulation is a polyethylene canvas with a foamed structure and a reflective surface. Appropriate foil-covered polyethylene for cables and a warm water floor.

Foamed polyethylene is stronger and more flexible than regular polyethylene. The material is resistant to moisture, doesn’t come into contact with chemicals, muffles sound, and doesn’t support the growth of microbes. This kind of large’s service life.

The foamed polyethylene product has a lavsane film with a metallized coating on the front side. Uniform heat distribution is provided by the reflective surface, and warm streams cannot seep into a concrete screed thanks to the foamy base with air cells.

Just so you know! Signed polyethylene is photosensitive, but sunlight cannot penetrate it because of the finish coating.

Foam polystyrene with foil

Foamy polystyrene coated in foil is a common heat insulator for heated floors, both electric and water. It is highly resilient and inert to chemical reactions.

Moreover, it can tolerate temperatures between -180 and +180 degrees, though such conditions are not necessary in daily life. The product doesn’t rot, doesn’t encourage the growth of dangerous microbes, and doesn’t endanger people’s health.


Multifolga is a multi-layered canvas. Foil aluminum layer with air-filled chambers, and polyethylene or propylene film serving as the product’s foundation. By using a bubble layer, you can reduce heat loss.

This model’s insulation has a high heat-insulation potential, is resistant to moisture, and boosts the heating system’s effectiveness.

Topic Foil for warm floor – or not
Types of Substrates Foam, Cement, Plywood
Laying Directly on substrate, Over existing floor, Floating installation

Several factors, such as your particular heating requirements, your budget, and the type of flooring you have, will determine whether or not you should use foil for a warm floor. Foil is a good option for increasing the efficiency of underfloor heating systems because it can reflect heat effectively. It is imperative to verify compatibility with both the flooring type you intend to install and your heating system.

It’s important to choose a substrate type for your warm floor that offers sufficient insulation along with durability and moisture resistance. Polystyrene foam boards, plywood, and cementitious boards are common substrate options. Every option has pros and cons, so it’s critical to carefully consider each one in light of your unique needs.

A crucial element in guaranteeing the efficiency and durability of your heated flooring system is the installation procedure. For optimum performance, proper installation methods—which include precise measurement, suitable spacing, and extensive insulation—are essential. The best results can be obtained by adhering to manufacturer instructions and getting expert assistance, regardless of whether you decide to install foil or not.

In summary, choosing the appropriate substrate and laying technique, as well as using foil for warm floors, are important factors to take into account when trying to maximize your home’s comfort and energy efficiency. Through thorough needs analysis and expert consultation, you can make well-informed decisions that support a comfortable and sustainable living space.

The argument over whether or not to use foil for underfloor heating can be confusing for those who work in the heating and insulation industries. Through an examination of various substrate types and laying techniques, this article seeks to clarify this subject. Because of its reflective qualities, foil is a popular option for warm floors because it helps distribute heat evenly throughout the space. On the other hand, the kind of substrate and installation technique employed determine how effective foil is. Homes can decide if foil is the best option for their underfloor heating needs by researching different substrates and laying techniques.

Video on the topic

Foil films (under a warm floor). We need it or not?

Foil for warm floor. Need or not?

How to lay a reflector under a warm floor

What type of heating you would like to have in your home?
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Michael Kuznetsov

I love to create beauty and comfort with my own hands. In my articles I share tips on warming the house and repairing with my own hands.

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