Modeling Buildings in TRNSYS (TRNSYS3D, TRNBuild, Type 56) - TRNSYS Forum

SketchUp to TRNBuild import issue

Mariem S — Fri, 03 Apr 2026 14:26:04 +0000

Hello everyone,
I’m trying to model a simple zone using SketchUp and then import it into TRNBuild, but I’m running into an issue.
Here’s what I did:
-Created a simple parallelepiped geometry in SketchUp
-Exported the model as an *.idf file
-Imported the file into TRNBuild

After importing, the zone appears to exist, and I can see 9 walls listed (not 6). However, all the surface areas are showing as 0 m².
I’ve attached screenshots for reference.
Has anyone encountered this issue before or knows what might be causing it? Any help would be greatly appreciated!
Thank you in advance.

Mariem

TRNBUILD.jpg

Window frame

SilviaC — Sun, 29 Mar 2026 00:47:52 +0000

Hi everyone,

What is the best way to model the window frame?

I remind these recommendation reported in manuals/slides, which appear to be contradictory:

It is better to model the window frame as a Wall and set FFRAME = 0.
the frame should be defined in TRNBuild (see slide attached)

Does “model the window frame as a Wall” mean that the frame has to be modelled in SketchUp/TRNSYS3D and then assigned the construction type Wall in TRNBuild, while the window frame fraction of the window, again in TRNBuild, should be set to 0?

If drawing the frame in SketchUp/TRNSYS3D is indeed necessary, what is the correct way to do it geometrically? I understand that it should obviously not be modelled as shown in the slide where the framed window is marked as “Doesn’t work in TRNSYS,” but I am unsure what the recommended workflow is.

I sincerely thank you in advance for your support

Warm Regards,

Silvia

slide.png

Effective convective heat transfer coefficient, identical boundary conditions.

Alex Sz — Thu, 12 Mar 2026 14:11:11 +0000

Dear TRNSYS-Team and -users,

I am currently working with Type 56 and have two questions regarding the treatment of heat transfer in TRNBuild / Type 56.

1)
First, regarding the convective heat transfer coefficients:
In the Construction Types, I specify constant convective heat transfer coefficients for the front and back surfaces,
for example 9.72 and 72 kJ/h·m²·K.
However, in the Type 56 outputs, the reported values for the "effective" convective heat transfer coefficient are different from the input values.

This raises a few questions for me:
What exactly is the difference between the input convective heat transfer coefficient and the output “effective” convective heat transfer coefficient?
Is the effective value directly used in the simulation, or is it only a reported/post-processed output quantity?
Is it recalculated during the simulation depending on surface temperature, air temperature, or other boundary conditions?
-Because when i applied different room air temperatures it did not change. It seems to be purely dependent on the surface Area proportions?
Which physical or scientific model is implemented here?

I would have expected the effective convective coefficient to remain equal to the prescribed input value if a constant coefficient is defined.
Since this is apparently not the case, I would like to better understand the underlying formulation in Type 56.

2)
My second question concerns the definition of the category “Boundary” or “Boundary conditions”, especially when it is set to “identical”.
What exactly does “identical” mean in this context?
Does it mean that the heat fluxes on one side of the construction are mirrored to the adjacent side of the neighboring zone,
i.e. that convective and/or radiative heat exchange is transferred consistently between both zones?
Or does it mean that a temperature boundary condition is imposed on the other side?
I could also not find an unambiguous explanation of this point in the Trnsys-Documentation/ Literature.

Any clarification on either of these topics, or references to documentation or publications, would be greatly appreciated.

Best regards,
Alex Sz

zone temperauter and active layer

tagreedwael — Wed, 10 Dec 2025 14:51:48 +0000

hello, i have a questio about the image provided in the question

is it normal when the haeting and cooling settings in the TRNbuild is off to show results like this? by the way i want cooling for summer and heating for winter and as you can see the thermostat only worked for the cooling mood and the active layer is varying with the temperautre only during winter. and the the zone temperautre and the extrnal is kind of close to each other,

can you tell me if it's normal or not? and shoudl the heating and cooling settings be on when i want to fine the energy consumption of the building?

hope you can clarify for me some points, Thaks

Screenshot-2025-12-10-174039.png

Issue with new window creation

Marpin — Tue, 09 Dec 2025 09:06:44 +0000

Hello,

Using Window 7.8, I created a double glazing window . After importing it in TRNSYS, I get the followng error :

*** Fatal Error at time : 0.000000
Generated by Unit : 39
Generated by Type : 56
Message : iniglasdata: value negative or greater then 1 for visual absorption was found after fitting for Window-ID 3 : abs_vis= -.0000000230 at angle = 90

Could you please help me on this error and how to make this window work. The glazing is 6mm Planbiel Grey / 22 mm Argon 90% / 4mm Planibel Clearlite.

Attached is the file I'm loading in type 56 and getting an error from TRNSYS.

Thank you.

thermostat connection

tagreedwael — Mon, 08 Dec 2025 14:18:46 +0000

hello, i'm having a promblem with making the thermostat work, after connecting it to an equation of an (ON and OFF) like the one in the picture. it still shows a zero value. how can i make it work with connecting it to the three of these ( type56, type941, equation).

thanks!

Screenshot-2025-11-28-150315.png

Error when importing .idf file in simulation studio

S_K_J — Thu, 04 Dec 2025 11:56:07 +0000

Hi, I have defined a single building with 5 thermal zones and i have assigned the interior walls as adjacent walls and properly assigned the boundary condition as respective adjacent zones. when i upload the idf file in simulation studio it shows that atleast 2 surfaces are required per zone for 1 zone. But in the model each zone consists of 6 surfaces. How can i resolve the issue?

Thanks in advance

type 941 (air to water heat pump)

tagreedwael — Sat, 08 Nov 2025 11:43:49 +0000

hello there,

wanted to ask about the connection between these five materials,

1-multizone-building (type 56)

2-water pump type( which one is the best? i'm working on type 3b is it ok? )

3-air to water heat pump (type 941)

4-thermostat (type 166)

5- active layer as an input (mass flow rate and temperature type 14h)

how can i connect these to make a full hydronic loop?

Thanks!

conversion from kJ/hr to W or kW for mass flow rate of an active layer

tagreedwael — Mon, 03 Nov 2025 20:16:48 +0000

hello, wanted to ask about conversion of mass flow rate, what is the equation that i should put?

i have six zones and each zone have an active layer, i wrote this equation but it gives me an error

and also, should i connect it to the input of the mass flow and then to the plotter?

what should i do? i'm new to this

Screenshot-2025-11-03-231409.png

zone temperature

tagreedwael — Sat, 01 Nov 2025 18:01:12 +0000

Hello, I'm having trouble with controlling the air temperature in the zone, I added an active layer with temperature of 30 degrees as an input, and the heating in TRNbuild is 20, but the temperature of the zone keeps getting higher than the set points, I can not control it, What should i do to do?

Screenshot-2025-10-31-165304.png