Thermal Lag - T0

In this article we’ll discuss thermal lag, an important value to take under consideration when analyzing walls and, more in general, building structures. We’ll use our thermal bridge FEM software, Mold Simulator Dynamic, to compute thermal lag in accordance with EN ISO 13786.

In case of simple structures (i.e. a set of homogeneous layers) thermal lag can be analytically evaluated using EN ISO 13786 formulae, but in more general situations a FEM simulation is required.
Thermal lag represents a structure’s thermal mass in terms of time; to make it simple, it’s how long it takes to the heat wave to pass through a building structure.

 

Thermal Lag - T0Thermal Lag - T1
T0: time when temperature is at its maximum on external surface. A sinusoidal heat wave is applied to external surface.T1: time when temperature is at its maximum on internal surface. The heat wave has been delayed and faded.

Thermal lag = T1 – T0 in hours

To have a better understanding of this subject please download this sample for Mold Simulator Dynamic:

You need Mold Simulator Viewer (free) to open it.

Thermal Bridge - Real

In this brief tutorial we’ll show you how to computer linear thermal transmittance of a typical thermal bridge: a junction between a wall and a floor. We’ll use Mold Simulator as FEM software for its analysis.

Thermal bridge

Thermal Bridge

The structure is in contact with external environment (on the left) and internal environment (on the right).
In this case, the thermal bridge is caused by floor; a way to evaluate it is to compute its linear thermal transmittance, ψ (psi) in W/mK.

Linear thermal transmittance
This value represents the difference between the theoretical configuration (just a wall) and the real one (a wall with an intersecting floor).

Theoretical configurationReal configuration
Thermal Bridge - TheoricalThermal Bridge - Real
Wall length (l): 1.1 m
Wall transmittance (U): 1.0980 W/m²K (computed simply considering wall’s material properties)
Thermal conductance (L2D): U x l = 1.2078 W/mK
Wall length (l): 1.1 m
Wall transmittance (U): 1.2548 W/m²K (FEM simulation with Mold Simulator)
Thermal conductance (L2D): U x l = 1.3803 W/mK (FEM simulation with Mold Simulator)

Thermal bridge ψ = 1.3803 – 1.2078 = 0.1725 W/mK
You can watch an interactive presentation of this tutorial downloading the project:

You need Mold Simulator Viewer (free) in order to view it.

Isotherms

This is the second part of a tutorial about window transmittance computation using Frame Simulator, our FEM simulator available for Windows and Mac OS X. For the first part, please see Window Transmittance – part 1.

In this tutorial we’ll use the following abbreviations:

  • LMB = left mouse button click;
  • MMB = middle mouse button click;
  • RMB = right mouse button click.

Borders definition
Please click “Boundary” tab and select “Internal”; now click on Assign boundary strip button and LMB over one of the lines in contact with intern environment. Similarly, select “External” please click Assign boundary strip button and LMB over one of the lines in contact with extern environment.
In current project, borders should look in this way:

Boundary

Moreover, please make sure to have selected Heat flow direction down flow direction in “Lines” tab.

Simulation
Please click “Simulation” tab and wait that the software performs all the necessary computations. At this point, you can select different types of view: heat flow, temperature, isotherms, etc.
The values required by ISO 10077-2 standard, window transmittance and Lf2D, are shown in “Results” table.

Isotherms

As you have seen, the way to window transmittance following ISO 10077-2 standard is extremely easy with Frame Simulator. We’re planning some more tutorials and articles, so stay tuned!

We’re extremely pleased to announce that we’ve released Mold Simulator for Mac OS X! Finally a new Mac FEM software for thermal bridge analysis. On Mold Simulator page you’ll also find the new 2.0.8 version.

Wooden Frame

The purpose of this tutorial is to introduce the basic functions of Frame Simulator, through a step by step development of a simple project regarding a wooden frame. The main result we want to get is to compute window transmittance applying ISO 10077-2.
Here you are the project:


Wooden Frame
Typical wooden frame of a window.

  • “ITERNAL” is the frame’s part in contact with intern environment;
  • “EXTERNAL” is the frame’s part in contact with extern environment;
  • “EPDM” has a conducibility of 0.25 W/(mK);
  • “Wood” has a conducibility of 0.13 W/(mK).

Window Transmittance

Insertion of project in Frame Simulator
In this tutorial we’ll use the following abbreviations:

  • LMB = left mouse button click;
  • MMB = middle mouse button click;
  • RMB = right mouse button click.

1 – Lines insertion
Please run the software. The main interface is composed by tabs representing the various phases of project insertion and by a viewport showing frame’s 2D section.
First of all you need to insert the lines composing the frame; this can be done using the tools in the “Lines” tab or you can simply import a DXF file. This should be the result:


Lines
Lines of wooden frame
ISO 10077-2 standard reports a series of rules:

  • Glazing must be replaced with an insulation panel at least 190mm long;
  • The end of the insulation panel must be in contact with an adiabatic surface.

2 – Areas properties insertion
At this point you have to insert the properties of all the areas. Please click on “Areas” tab to enter in areas insertion mode.
Click “Fill area” button and select material type (Standard, Adiabatic, Insulation, Transparent, Glazing gas). In case of standard material, please insert conducibility and emissivity. Usually emissivity is 0.9, except for special materials. LMB in the middle of the areas that you want to create with specific properties.
Areas should look like the following picture:


Areas
Areas of wooden frame
This is the end of the first part of this tutorial on window transmittance; stay connected to see how it ends.

We’re pleased to announce the release of Frame Simulator 2.0.7. Major changes are:

  • isotherms labels in views of section’s portion;
  • information about version used for a project;
  • merge project: keep vertices selected of new project;
  • ability to stop PSLG Boundary and PSLG fill algorithms;
  • rendering settings reset button;
  • hide data area.

Please visit Frame Simulator | Windows Transmittance page for more information.
Subscribe to our brand new YouTube channel to view the latest video tutorials!

Mold Simulator Viewer 2.0.6 is out; please go to Mold Simulator page to download it.

Frame Simulator Viewer 2.0.6 is out; please go to Frame Simulator page to download it.

The brand new EN ISO 10077-2 has just been released and Frame Simulator 2 has been adapted to fully satisfy it. Please go here to get the latest certification together with the new viewer version.