How the crawl space in a home is made and how it works

Although it may lead us to a confusion of ideas, the name crawl space – in construction – does not identify the presence of a beehive or in general a wasp nest. Rather, the crawl space is a fundamental part of the building organism and is created to fulfill some important functions, which are not purely structural in nature, but rather thermal insulation and protection from rising humidity and harmful gases. Even though it is hidden in buildings already built, traces of it can be found by referring to particular points of communication that it has with the surrounding environment: let’s see them in this article, together with the typical construction techniques and its functioning.

What is a crawl space in construction

The crawl space is an element capable of creating a disconnection between the layers of structure a direct contact with the ground and those who will be a direct contact with our activitiestherefore the actual walking surface. Between one and the other you can easily reach thicknesses in the order of 50-80 cm. By realizing this disconnection, it becomes necessary to build acavity that he is capable of doing circular continuously air present inside it. We are therefore talking about a real layer of physical disconnection which performs these main functions:

• Guarantee insulation from the rise of water by capillarity from the groundwith consequent formation of humidity and progressive deterioration of the structures, both finishing and otherwise, which are affected by this aggressive environment.
• Guarantee insulation for thermal purposes from the energy transmission that arises between the foundation structures (in direct contact with the ground) and the finishing structures (in direct contact with the users).
• Guarantee protection from possible ascent towards the surface layers of radon gas naturally present in the ground, removing it externally and not allowing it to accumulate to the point of being harmful to human health.
• In some cases, and above all with the help of modern manufacturing technologies, the same it can also be used as a housing thickness for any system components of the building.

The functioning of the crawl space

The realization of these conditions occurs provided that avoid air stagnation inside the created cavity. For this reason, it will be necessary to create a path within which the air can move and circular, so as to create the conditions suitable for continuous exchange with the outside air. To guarantee the internal movement of the air it is therefore necessary to create some entry and exit points, to and from the external environment. In fact, the crawl space areas they are always found sunk compared to the ground leveli.e. the actual level of foot traffic outside the building. Therefore, it is necessary to connect these areas via special pipes.

However, how do you guarantee a flow of air that follows a certain direction and you don’t flooded inward? That is, it could happen that all the openings become an entry point for external air, until the available spaces are saturated. This condition is avoided thanks to a careful positioning of the inlet and outlet vents. A simple precaution, in this sense, is to keep some vents (which will be… entrance) at lower altitudes than others (which will be exit). In addition, the high vents are placed in southern area of the building, so as to benefit more from solar radiation. This creates a flow of air that can be exploited the chimney effect, that is, that condition in which hot air – which has a lower density than cold air – moves upwards naturally due to the pressure difference generated between the two fluids.

How a crawl space is made

The construction of the crawl space underwent several changes evolutions over time. Historically, the first examples of crawl spaces were created using the combination of medium-sized granular materialsuch as to create a good filling but also a cavity, necessary for the passage of air.

Nowadays, instead of these granular materials, the construction of a crawl space is carried out via prefabricated elementsusually of plasticcapable of guaranteeing the formation of a sort of internal tunnel with respect to the external layers, but which at the same time has good load-bearing capacity to locally support the loads that the floor above wants to promptly transfer to the foundation structures. Different heights are available on the market, which can be decided depending on the insulation needs or, as mentioned before, in the event that this cavity must also guarantee the accommodation of systems.

The connections with the outside are instead made using pipes, usually in PVC, equipped with end grilles to avoid unwanted entry of material. These also represent the points of control and maintenanceoperations necessary to guarantee the correct functioning of the ventilation system over time.