Short Answer
vyzn calculates according to SIA 380/1 (via the Enerweb engine) using only the data stored in the model. Thermal bridges and shading are not automatically approximated from the 3D geometry – we are deliberately transparent about this. For both, however, there are proven ways to enter the values simply and traceably.
Why It Matters
If your model does not contain thermal bridges, they are not included in the calculation. The same applies to shading: without your input, the shading factors are not passed to the calculation – the result is computed without this reduction, with full solar gains, and therefore tends to be too favourable. It is therefore worth addressing both points deliberately.
How It Works in vyzn
Thermal bridges
If your model does not contain thermal bridges, you have two proven options:
- Flat-rate surcharge (type "Pauschal"): You enter a percentage surcharge that is applied as a lump sum – ideal for early phases without detailed knowledge.
- "Detect automatically" function in the thermal bridges section: It derives linear thermal bridges from the window and door openings in your model and calculates the length from the opening dimensions: the perimeter from width and height; if only the area is available, the perimeter is approximated. It applies a default psi value of 0.12 W/(m·K), the position "Aussen" (outside) and the b-value "Standard". You can then review and adjust each automatically generated thermal bridge individually.
For point thermal bridges (chi value, type "Punktuell") and individual psi values, you maintain the values manually.
Shading
Shading is entered per window via the three SIA 380/1 shading factors:
- FS1 – horizon
- FS2 – overhang
- FS3 – side fin
vyzn does not perform a geometric shading calculation from the building volume (neighbouring buildings, sun position). We therefore recommend deliberately setting the FS factors where shading is relevant.
Frequently Asked Questions
Does vyzn derive thermal bridges or shading automatically from the 3D geometry?
No. vyzn only calculates with the data stored in the model. For linear thermal bridges, however, the "Detect automatically" function can derive values from the window and door openings.
What happens if I do not enter any shading factors?
The factors are not passed to the calculation – the result is computed without this reduction, i.e. with full solar gains and therefore tending to be too favourable.
Can I edit the automatically detected thermal bridges?
Yes, you can review and adjust each automatically generated thermal bridge individually.
Which approach suits my planning phase?
For early phases without detailed knowledge, the flat-rate surcharge is suitable; later on, automatic detection or detailed input makes sense. If you like, we can look at your specific model together and decide on the best approach.
Update (version 1.8.5)
As of version 1.8.5, automatic thermal-bridge detection can also be filtered by perimeter insulation, making it easier to select the relevant thermal bridges.