Hi everyone,

I am trying to simulate some buildings using Archsim. The zone settings give us the chance to specify two parameters: Roof tilt angle and External floor tilt angle.

How does EnergyPlus read these two parameters? For example, if I have a tilted roof, isn't necessarily anymore to draw it in Grasshopper and E+ will treat it automatically based on the angle I give it? and what if I don't have a tilted roof (which is my case)? Once I put the angle to zero, Archsim doesn't recognize any roof at all!

As for the external floor tilt angle, I don't understand what it means, with the same problem when I put it to zero, there is no facades or floors recognized by Archsim.

I will really appreciate any help from you.


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This is also a question we are facing. We have a simple rectangular body defining our building. The selection of roof and floor tilt angles does not seem intuitive, and we can't find any explanation of these parameters in documentation. When we set  the 'roof tilt angle' to zero, ARCHSIM seems to incorporate the roof surface of our zone as part of the facade (which does also include the body's four vertical walls correctly. To get our simulation to work, we have to rely on the default ARCHSIM values of 45 deg. for roof tilt angle and 135 degrees for external floor tilt angle, but we are not sure why.

It would seem these two parameters are also relatively new as they did not seem to exist in the version of ARCHSIM used for Solemma's video tutorials.


Hi Adam,

Thank you for replying. As you said, I had to used the default values to run my simulations with no idea how this affects the results.

I hope someone from Archsim's team could clarify this question.

Hi again,

I have created different simulations and changed the roof tilt angle and floor tilt angle values (in a way that Archsim does not incorporate the roof and the floor as part of other surfaces). I got the same results whatever the values are. I have checked the idf files and found that the roof and the floors are always planar with 4 vertices (since my buildings have simple rectangular shape). In other words, the roof tilt angle and floor tilt angle are not recognized by EnergyPlus and thus it doesn't matter what their values are (at least for now).

Hope I could help.


Hi Alaa,

I can confirm this too with our work on similar models.

It seems that, provided you don't set any of the tilt angle parameters to 'zero', then they generally have no effect on E+ outputs.


The tilt angles in Archsim help the program to auto-identify which surface should be given the roof or slab constructions that you specified. The default is everything that has a tilt larger than 45deg will be recognized as facade. If the tilt is flatter then it will become a roof or slab. 

Below you see two zones with different roof tilt angles. The settings are at their 45deg default. If the roof becomes too steep then it is recognized as facade. 

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