Composition of the Stratigraphy and Solutions for the Building Envelope

Managing the stratigraphy of opaque building envelopes is crucial to ensure that each layer meets specific performance criteria, such as fire resistance, thermal and acoustic insulation, and more.

In this article, I’ll walk you through how to efficiently manage the stratigraphy of your project, streamlining the process for ease and speed.

Using 3D/BIM building design software, we’ll explore how to define the stratigraphy of all building envelopes—walls, floors, roofs, and more—while setting key characteristics and parameters for each layer from the design phase onward. This includes tasks like establishing layer hierarchy, creating Glaser diagrams, and more.

Let’s dive into how to leverage the full potential of this tool for your project.

Interface

What is the building envelope and how does it integrate with BIM modeling

The building envelope is not simply the “skin” of a building; it is a complex and dynamic system that acts as the primary filter between the internal and external environment. In an era where energy efficiency and living comfort are regulatory and moral imperatives, the envelope assumes a crucial role: it must ensure thermal insulation, protection from weather agents, moisture control, and acoustic insulation, all while maintaining aesthetic coherence with the architectural design.

The integration of this system with BIM modeling represents a fundamental leap in quality compared to traditional CAD design. In BIM, the envelope ceases to be a simple line or hatch on a 2D plan to become a “smart object” rich in data.

When we model an envelope in a BIM environment, we are not only defining the geometry (thickness, height, position), but we are associating a series of vital parametric information to that element: thermal transmittance, surface mass, vapor resistance, and structural behavior. This integration allows us to anticipate issues during the design phase, simulate the energy behavior of the building even before the first stone is laid, and ensure that information flows correctly to the open format IFC, essential for interoperability between different disciplines (structural, mechanical, architectural).

Key components of a building envelope in architectural design

To understand how to correctly manage the editing of an IFC file or native modeling, it is essential to break down the envelope into its fundamental components. In BIM language, these are not just “layers,” but entities with distinct physical and functional properties that must be properly mapped to avoid export errors or data loss.

The key components that define the quality and functionality of the envelope include:

• structural layer (Core Layer): it is the load-bearing core of the wall or roof (e.g., reinforced concrete, load-bearing masonry, XLAM panels). In BIM, this layer is often defined as “Core” and serves as a reference for aligning joints between walls and floors;
• thermal insulation: essential for the energy balance. Its correct definition in the model (thickness, conductivity, etc.) is critical for subsequent energy analyses. A common mistake is not correctly specifying the continuity of this layer, creating virtual thermal bridges in the model;
• vapor barriers and retarders: often overlooked in geometric modeling because they are “thin,” they are instead decisive in hygrometric calculations (such as the Glaser diagram). They must be present as informative data or dedicated layers for a correct analysis of interstitial condensation;
• finishes and coatings (internal and external): besides their aesthetic function, they protect the internal layers. In an IFC file, the distinction between finish and structural element is vital for the quantity take-off, allowing for separate calculations of square meters of plaster versus cubic meters of masonry;
• anchoring systems and substructures: especially in ventilated facades, managing these elements in the BIM model requires a balance between geometric detail (LOD – Level of Development) and file heaviness. Often, a geometrically simplified representation rich in metadata is chosen.

In this regard, I recommend reading the in-depth article “Wall Stratigraphy: what it is and how to calculate it” which explains in detail everything you need to know about this topic.

What is stratigraphy and why is it essential in building envelopes?

In the context of BIM design and IFC file management, the term “stratigraphy” (or Material Layer Set in IFC technical language) does not simply refer to the graphical representation of a sectioned wall. It is, in every respect, the technological identity card of the building element.

Stratigraphy is the logical and sequential organization of the different materials that make up an envelope element (walls, floors, roofs). Its essential nature lies in the fact that it transforms a generic geometric volume into a real building component. Without a correctly defined stratigraphy, a wall in the BIM model is just an empty parallelepiped; with stratigraphy, it becomes a system capable of interacting with the environment.

Why is it so critical?

1. accuracy of the quantity take-off (QTO): if the stratigraphy is defined correctly, the software can query the model to know exactly how many cubic meters of insulation are needed, separating them from the cubic meters of bricks. An error here translates directly into budget errors;
2. energy analysis: energy calculation engines do not “see” the wall, but read the sequence of materials and their physical properties. An incorrect stratigraphy (e.g., inverted materials or missing thermal properties) invalidates any energy simulation;
3. IFC interoperability: when we export to IFC, the stratigraphy is translated into specific classes (IfcMaterialLayerSet). If this structure is disordered at the source, whoever receives the file (for example, the structural engineer or the mechanical engineer) will end up with unusable or geometrically inconsistent data.

What does stratigraphy include: layers and materials of the envelope

Entering into operational detail, a well-constructed stratigraphy is not a simple bullet list. Each “layer” within the wall or roof package must carry with it a specific set of attributes that define the behavior of the entire system.

When we analyze or create a stratigraphy, we are managing three levels of information for each individual layer:

Material identity

It is not enough to call a layer “Insulation.” It is necessary to specify whether it is Rock Wool, XPS, or EPS. In BIM, this means associating the layer with a specific material present in the software library, which in turn has a graphic fill for sections and a texture for 3D renders.

Geometric properties (fixed vs variable thickness)

Each layer has a thickness. However, the fundamental distinction is between layers with fixed thickness (such as a drywall panel or thermal insulation) and layers with variable thickness (such as sloped screeds or finishing pours). Correctly defining this property is vital for managing slopes in roofs or connections between irregular walls without “breaking” the model.

Physical-technical properties

This is where BIM shows its true power. Each material within the stratigraphy must include the parameters for calculation:

• thermal conductivity (λ), for calculating the U-value;
• density (ρ), for calculating mass and thermal inertia;
• vapor diffusion resistance factor (μ), essential for verifying whether the wall “breathes” or if condensation will form;
• specific heat capacity (c), to evaluate heat storage.

Managing stratigraphies with BIM software

To get a complete BIM model with all relevant information, it’s important to correctly set up your building’s the material layers. But let’s take a look at how easy it is to create new Material Layer compositions with Edificius, or maybe even customize those already present in the rich catalogue proposed by the software.

Before we begin, let me remind you that:

• if you already have the software and can’t see these features, simply upgrade to the latest version which is completely free and follow these simple steps:
  • access your my.accasoftware.com personal area;
  • use the “Updates from internet” feature that you can find in the “menu” or on the software’s home screen.
• if you don’t have the software yet, download the free version of Edificius now.

Add, delete, modify, or move material layers

To create customized Material Layers that fit your specific case, you can easily modify existing material layers or add new ones with Edificius.

Let’s see how to proceed to add, delete, modify or move the material layers in a simple and fast way.

First, enter the editor (wall, ceiling, roof, etc.) by selecting the element of interest and then the BIM library object editor command () that you can find in the “Properties” section on the right of the screen.

When the screen opens, click on the "Edit" command on the toolbar. At this point, access the new window where, by individually selecting the elements present in the material layer, you can change the properties in the appropriate fields.

In this section you can:

• add new layers to the right or left of a selected layer ();
• assign a material to an existing layer ();
• move a layer to the right or left ();
• delete a layer ().

As soon as you have finished with these changes, you can also:

• view the temperature diagram ();
• view the pressure diagram ();
• view the entire material layer with and without the hatch patterns ().

Now you can click on the "Finish" command to confirm and save all changes made.

Material Layer Envelope Management with a BIM Software | How to modify the material layering

Material Layers hierarchy

Once the material layer has been created and assigned to the building, you can dedicate yourself to the management of details, to make your work precise and, of course, coherent with reality.

For example, you can control the intersections of the various materials and make sure that there is continuity betwenn layers of the same type. The image below illustrates how to manage the building envelope layers correctly at the intersection points between two perimeter walls.

Managing wall material layers

With Edificius, to obtain correct intersections between the different materials and the different material layers (as in the image above), you can assign each layer with a different priority by creating a real hierarchy between the different 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 select the “layer type” (surface finishes, insulation, structure, etc.) and, if necessary, activate the “core” tick. This last aspect allows you to give continuity to each element within it and not to be “interrupted”, at the intersections between casings, by elements that do not belong to the core.

For a better understanding, simply follow these steps:

• materials that have the active tick on their “core” material do not intersect with materials not belonging to the core of other envelopes. This means it can continue without interruptions until it meets a possible connection with other elements of the same priority level;
• the priority increases from the “finish” up to “structure”. These layers are assigned with a value that you can display in the properties window under the heading “Priority” (the higher the value, the higher the priority);
• the “+” and “-” symbols, present in “layer type”, increase or decrease the priority degree of a given layer, assigning an increase or decrease in the score visible in the properties.

Managing Material Layers with BIM Software | Material layering Priority

This methodology allows you to correctly represent the intersections between the different layers of material of the various elements.

Material layers view

Imagine that you have associated all the material layering with the wrappings and want to display them in your model.

With Edificius you can view the material layers:

• in the 3D view – after selecting the “Plan view” object from the 3D view, activate the “Preview” option, from the toolbar, and the “Envelope Material Layer” check box, in the properties;
• in the drawing models – check the “material layer” in the properties window.

With this new function, you can now view all the changes made to the material layers in real time and always keep track of your design choices.

Manage wall material layers with BIM software

To learn more, I recommend watching this video that illustrates all the essential steps to create a material layer composition with Edificius.

FAQ about stratigraphies

What is a building envelope?

The building envelope is a complex and dynamic system that acts as a filter between the internal and external environment. It is not just the skin of the building, but a set of elements that ensure thermal insulation, protection from weather agents, moisture control, acoustic insulation, and aesthetic coherence with the architectural design.

Why is a building envelope fundamental in modern design?

The building envelope is fundamental because it decisively contributes to energy efficiency and living comfort, which today represent essential regulatory and design requirements. A properly designed envelope reduces energy consumption and improves the quality of indoor environments.

How does a building envelope integrate with BIM modeling?

In BIM, the building envelope becomes a smart object rich in data. In addition to geometry, parametric information such as thermal transmittance, surface mass, vapor resistance, and structural behavior are associated, allowing for energy simulations, preventive analyses, and correct interoperability through the IFC format.

What are the main components of a building envelope in BIM?

The main components of the envelope include the structural layer or core layer, thermal insulation, vapor barriers and retarders, internal and external finishes, as well as anchoring systems and substructures, particularly in ventilated facades.

What is stratigraphy in a building envelope?

Stratigraphy is the logical and sequential organization of the materials that make up an envelope element such as walls, floors, and roofs. In BIM, it represents the technological identity card of the building element and transforms a generic geometry into a real and analyzable component.

Why is stratigraphy essential in BIM design?

Stratigraphy is essential because it directly affects the accuracy of the quantity take-off, energy analyses, and IFC interoperability. An incorrect stratigraphy can generate budget errors, unreliable energy simulations, and problems in data exchange between different disciplines.

What information should a correct BIM stratigraphy include?

A correct BIM stratigraphy includes the precise identity of materials, geometric properties such as fixed or variable thickness, and physical-technical properties, including thermal conductivity, density, vapor resistance factor, and specific heat capacity.

How are stratigraphies managed with BIM software like Edificius?

With Edificius, it is possible to create, modify, delete, and move material layers through the envelope editor. The software also allows for visualizing temperature and pressure diagrams, controlling material priorities, and properly managing intersections between envelope elements.

What is the purpose of the material hierarchy in stratigraphies?

The material hierarchy serves to correctly manage intersections between different envelopes. By assigning priorities and defining the core, it is possible to ensure the continuity of structural layers and accurately represent the construction reality.

How to visualize stratigraphies in a BIM model?

Stratigraphies can be visualized both in the 3D view, by activating the preview and the envelope stratigraphy option, and in graphic tables through properties. This allows for real-time control of design choices and modifications made.