We often think of insulating the walls or insulating roof spaces, but insulating the floor is also of paramount importance. The cold feeling you have when walking on the floor is certainly very real and a sign that this stage has been forgotten. To avoid repeating this kind of error or to remedy it, here are some tips that it is better to have consulted before and will avoid further setbacks in the course of insulating the floor.

Why Insulate the Floor?

Insulating a floor is therefore important, but before knowing how to do it, you need to know what you will gain from it. And it is also necessary to define what is your priority, thermal insulation or sound insulation?

From a thermal point of view, we know that the energy losses due to the ground are 10%, so it is easy to calculate the achievable savings and to know how long it will take to pay off your work.

For example, the insulation price for a typical house of 100 m², with 15 m² of glass surfaces and heating for more than 15 years is established at:

from 2,000 to 4,000 $ in case of insulation of a pavilion with basement;

from 3,000 to 5,000 $ if low floor insulation on the median or on crawl space not accessible.

It was also calculated that the annual energy saving was then $124 in the case of gas heating, $ 167 for electric heating and $ 183 in the case of oil heating.

If we consider an expenditure of $ 3,000 and aid of around 30%, we see that it takes 10 to 15 years to amortize this expenditure and that, over 20 years, for example, you have gained ‘money. But, above all, you will greatly benefit in terms of comfort.

How to Choose your Floor Insulation

The choice of insulation material is majorly based on its thermal properties: the coefficient R. It indicates the thermal resistance of the material. The higher the thermal resistance, the more efficient the insulation. To effectively insulate your floor, we recommend an insulation with a thermal resistance equal to or greater than 3 m².K / W (R ≥ 3 m².K / W).

The other element to take into account in the choice of insulation is its conductivity, that is to say its ability to transport heat. It is measured per m² in degrees Celsius and per Watt (m². ° C / W). This will result in the thickness necessary to obtain the desired performance.

Finally, when applying the coating directly to the insulation, check the compressive strength. It is this which determines the maximum crushing that the insulation can withstand.

After this threshold, the material settles and loses its insulation capacity. Compressive strength is calculated in kilopascals (kPa). These insulating materials are delivered in bulk or in the form of rolls but most often in sheets.

To make the right choice of insulation technique, you will also have to take into account the climate of your region and the characteristics of your floor.

Other elements will have to be taken into account in the choice of your insulation. The destination of the room is important. So, if you are installing a water room (bathroom, toilet, kitchen) you will need to provide moisture-resistant insulation, because in the event of an incident such as water leak, you will have to review all of your insulation and the finishes that go with it!

Also, the choice of coating can also influence that of the insulation. Indeed, some materials already have interesting thermal performances, such as carpets, plant fibers, parquet floors or certain vinyl coverings.

Other coatings require very meticulous floor preparation for a completely flat surface. Tiling, waxed concrete or laminate will therefore be reserved for more circulating rooms such as bedrooms or living room.

Floor insulation methods

To build a good quality insulated floor, you have to use the right method and choose the right insulation material. Here is an overview of the most common floor insulation method:

Layer 1 – Concrete slab: a reinforced concrete slab at least 10 centimeters thick is the essential basis for a good quality floor. This prevents moisture from entering the soil, strengthens its stability and prevents pests from eating away at the insulation layer.

Layer 2 – Protective cover and insulation: the protective cover is placed directly on the concrete. It provides additional protection against steam. Then put the insulation on the tarpaulin. To seal the edges of it, insulating strips are used.

Layer 3 – Pipes and screed: above the insulation layer, you can install the pipes for central heating or a heated floor. Once the pipes are installed, the assembly can be completed by applying a screed at least 8 cm thick.

Layer 4 – Finishing: put the floor covering of your choice on the screed.

How to go about insulating floors

The first step is to make the floor perfectly level by updating it. On a concrete surface, start by deburring the underside of your floor using a grinder and a new deburring disc. If the surface has holes, fill them with cement. Wait for complete drying before installing the insulation. If the surface is not completely flat, a leveling off the floor (2) with a plaster must be used.

floor insulation

On loose floor, such as clay, the ideal is to successively apply a layer of sand and / or gravel and then a thin waterproofing film before installing the insulation panels. Finally, before tackling the finish, it is advisable to fix a vapor barrier and possibly a reinforced concrete slab or a dry screed if the coating requires it.

Depending on the choice of floor covering, the insulation can be left bare or covered with a finish (plates or coating) depending on whether it is visible or not, or whether or not it requires protection against mechanical attack, for example.

Note: To limit thermal bridges, here are some tips:

• the insulating panels must be joined, placed continuously, and applied against the floor;

• also insulate corner walls and floor supports to treat thermal bridges.

• Take the time to study all the elements necessary for your choice before you buy materials: the local climate, the base of the floor, the insulation in place, the destination of the room, the type of coating, the type of heating.

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