Wall material layers: what are they and how are they calculated?
Wall material layers are a set of materials that form the structure of an opaque vertical casing. Let’s see which ones are mostly used, how they are created and how they are calculated.
Defining a wall’s material layer composition is an essential step to limit thermal losses and ensure optimized usage of energy resources.
In this article we’ll take a closer look at what a material layer composition for a wall section is, how they are calculated and how the use of a BIM software for building design can bring various advantages.
What is wall material layer?
A Wall material layer refers to the set of materials (or layers) that make up the envelope of a building.
In the design phase, defining a wall materia layer means identifying the materials to be used and define their exact position and their thickness, based on specific regulatory and design criteria (climatic area in which the building is located, exposure, intended use of the building, sustainability, durability, etc.).
Once the design wall material layer has been defined, it is always advisable to carry out some regulatory checks to verify whether its composition complies with the provisions of the relevant legislation currently in force.
For example, the wall material layer must meet predetermined values and characteristics such as: fire resistance, thermal insulation, sound insulation, etc.
External wall material layer compositions
A correct design of the outer opaque wall material layers is also essential to obtain optimal behavior of the entire building, meet the increasing need of saving resources and obtain thermal comfort that ensures well-being for its users.
Here are some examples of material layers for external walls:
- insulated externally;
- insulated internally;
- cavity walls;
- dry or prefabricated;
- ventilated facades.
In addition, it is also possible to have stratigraphies that derive from a combination of types, such as, for example, externally insulated cavity walls.
In other cases, on the other hand, the walls can be subject to subsequent modifications such as in the case of single-layer walls on which the insulation is applied on the external side (coat) or empty box walls enhanced with blowing systems or with the addition of prefabricated elements for ventilated facades.
Wall material layer calculations
Calculating the wall material layers means identifying the envelope thermal transmittance values, the Glaser diagram and thermal bridges, etc.
The thermal transmittance of a wall represents its ability to disperse heat, evaluated in one square meter of surface of the enclosure and with a temperature difference between outside and inside of 1K.
In practice, it is the inverse of the thermal conductivity, generally specified by the letter U and is measured in W/(m²*K), (watt/square meters*kelvin).
The thermal transmittance value is calculated by dividing the thickness of the layer (in meters) by the thermal conductivity value of the material.
This calculation is important because:
- its value makes allows us to understand how the chosen material is actually capable of insulating the building;
- it also achieves significant energy savings;
- it limits unwanted heat dissipation;
- it also allows you to optimize energy resources.
This obviouslymeans that the calculation of a material composition is no longer carried out manually but there with specific software that can help us to perform certification, diagnosis and energy modeling, together with thermal bridges calculation, interstitial condensation checks (Glaser diagram), etc., and of course the pssibility the produce all relevant documentation required for presenting the project.
If you are looking for an easy and free way to perform these checks, I recommend a software for calculating the thermal transmittance and Glaser diagram.
With this method, you can easily build up the wall and slab material layers, in fact, these software tools usually provide a wide variety of material types with pre-loaded conductivity charateristics to analyse the building’s thermal behavour. Simply describe how the different materials are combined and specify the desired thicknesses of each layer.
The software calculates the thermal transmittance of the envelope in real time and allows you to view the temperature diagram checking compliance terms with the thermal transmittance limit values.
How to build up a material layer composition
If you are approaching the world of BIM or already using BIM software, you already know that the 3D/BIM model of the project building contains all the useful information for its entire life cycle.
Among all the essential information, there is never a lack of the characteristics and energy data of the casings, the technical data sheets of the materials (bricks, insulators, plasters, etc.), the value of the thermal transmittance, etc. It is therefore fundamental to assign each casing a specific stratigraphy that you can create from scratch or choose from the catalogue that the software offers you.
Let’s see how to create a material layer composition with a BIM software.
To create custom material layers, you can edit existing ones from the catalog or maybe add new ones.
With the new Edificius usBIM for example, you can proceed in the following ways:
- search among the many types of material layers currently present in the libraries;
- modify an existing material layer by moving them to other positions within the composition.
- modify an existing material layer composition by adding the other necessary layers, selecting them from the Edificius library;
- modify an existing material layer by deleting layers or replacing them with new materials.
- create a new material layer by adding layers from Edificius libraries.
To learn more, I recommend watching this useful collection of video tutorials that illustrates all the necessary steps to create and work with material layers using Edificius.
Once the material layer has been created and assigned to the building’s envelope casings, you can then focus on managing the other modelling details to produce a realistic looking building.
For example, you can control the intersections of the various materials in the intersections between multiple shells and make sure that there is continuity of the same layer. You can prioritize different layers by creating a hierarchy between the different layers. This allows you to obtain the correct intersections between the various materials that make up and the different material layers.
Higher priority layers are assigned in order to penetrate through other intersecting layers until they join up with other materials with the same priority. The objective is to represent the true physical condition of the building.
To do this, simply activate the “core” checkbox and select the “layer type”.
For example, materials that have the “core” check box set to on, have a higher priority and when they intersect other materials with a lower priority, they are crossed until they come into contact with other materials with the same priority value.
The priority value is increasing and can be selected them from a drop-down menu starting from the “finishing” layer up to the “structural” layers. To know whether each individual layers has been assigned correctly, you can view the property sheet under the “Priority” item (the higher the value, the higher the priority).
A further priority definition can be made thanks to the “+” and “-” symbols, present in “type of layer” section. Changing the priority levels assigns an increase or decrease of the so-called “score” visible in the properties box.
This methodology allows you to correctly represent the intersections between the different layers of materials for the various elements.
Now you can view the Material Layers in the 3D view or directly on the construction documents.