On what type of foundations to build a new house?
When you start the journey towards your dream house, the dilemma of how to execute the foundation slab often arises. If you are going to construct the reinforced concrete slab yourself, Marles can provide you with all the drawings, inventories, a rebar plan and all the necessary support in case of questions and dilemmas.
Many clients wonder why the foundation slab needs to be insulated at all. And which thermal insulation to choose.
The right solution or choice of thermal insulation is best found individually for each building. The actual thickness of insulation required is determined based on a PHPP calculation individually prepared by Marles for each building. Of course, all guidelines and legislation must also be considered in this process, as eventually only nearly zero-energy buildings will be allowed to be built.
Strip foundations have been replaced by a foundation pillow (floating slab)
By definition, a foundation is a structural element that transfers the load of a building to the ground. Foundations can be constructed in several ways, and which type of foundation is chosen depends largely on the load-bearing capacity of the ground itself. Until recently, strip and point foundations (small concrete walls in the ground that support the walls above) were still largely used. Today, to make low-energy, passive or nearly zero-energy construction more efficient, such strip foundations are being replaced by a foundation slab or a foundation pillow (a thick layer of concrete on which the complete overground part of the building is constructed). The foundation slab used nowadays in most buildings require, compared to strip foundations, less excavation, less formwork, allows for a faster construction and enables the thermal insulation envelope of the building to be built in the ground. This results in much better energy efficiency.
The foundations of a prefabricated house must allow for:
The foundation slab makes the thermal envelope of the building more efficient
The foundation slab, as the base of any building, therefore provides stability and load-bearing capacity, and protects the building from moisture and heat loss. The weight of the building in a new construction is distributed over the foundation slab, which has a much larger surface area and the pressures underneath are therefore lower or more distributed. For this reason, we recommend that a proven XPS thermal insulation is installed underneath the foundation slab, without the concern of it deforming.
The choice of foundation therefore also has a direct effect on the design of the thermal envelope of the building. When designing nearly zero-energy buildings, we should aim for an uninterrupted thermal envelope that will ensure a healthy and energy-efficient building. At Marles, we understand that a well-insulated house with a properly designed and precisely executed thermal envelope means significant energy savings not only in winter, when the house needs to be heated, but also in summer, when a properly designed and precisely executed thermal envelope can contribute to optimum living conditions and a pleasant indoor environment.
Why is the thermal envelope of a house so important?
The thermal protection of the foundation slab should be considered at the very beginning of the project, as without adequate thermal protection, the foundation slab, with its large concrete surface, will cause significant heat losses. In winter, uninsulated or poorly insulated floors and basement walls can cause as much as a third of the building's total heat loss. In addition, basement or ground-floor rooms are very uncomfortable and cold in such cases, causing living discomfort and, in some cases, even the appearance of mould.
Energy-efficient foundation pillow - what to look out for?
There are several types of foundation slab and the laying of thermal insulation, which vary depending on the type of building, the energy requirements of the building and, finally, the contractor. The frost zone has historically been addressed by building the foundation below the frost depth, depending on the location of the building and the soil type. However, when building low-energy, passive or near-zero-energy buildings without thermal bridges, this type of foundation on point or strip foundations is no longer an option. One of the innovative and widely used types of thermal insulation underneath the foundation slab is the SEISMIC foundation pillow or ANTIRADON foundation pillow by the company FIBRAN. Their SEISMIC foundation pillow solution, with an extended strip of thermal insulation beyond the floor plan of the foundation slab, is thus free of thermal bridges and at the same time protects the building from soil uplift due to freezing underneath the foundation slab. When constructing an energy-efficient foundation slab, it is essential that it is lined only with thermal insulation that has been tested for long-term load and exposure to damp conditions and does not change its properties. FIBRANxps thermal insulation is precisely such a thermal insulation, and does not dampen even when immersed in water for long periods of time, nor when moisture passes through the pores in the material.
The SEISMIC foundation pillow or the ANTIRADON foundation pillow
In addition to selecting the appropriate material, care must also be taken in the application underneath the foundation slab to ensure that the whole system is executed in a systematic and uniform manner. This is because in an earthquake, slipping of the individual elements under the foundation slab may also pose a problem. A special system to prevent such slips is therefore needed. The SEISMIC foundation pillow system solution ensures that the thermal insulation and waterproofing are bonded together in a composite with the foundation slab. Together they act as one strong and stable foundation pillow. In addition, the SEISMIC foundation pillow provides an uninterrupted thermal envelope that eliminates the impact of thermal bridges. In summary - the SEISMIC foundation pillow is a composite of a reinforced concrete foundation slab, thermal insulation and waterproofing, where all the layers are permanently bonded together. You can opt for a single or double layer of thermal insulation. For areas with potentially high radon concentrations indoors, there is the ANTIRADON foundation pillow, which is an upgraded version of the SEISMIC foundation pillow and provides additional protection against the passage of radon gas. For such demanding applications, the thermal insulation must be tested for use under long term loads and have a European Technical Assessment (ETA) for such applications.