Thermal analysis of IFC building models using voxelized geometries

Multi-disciplinary three-dimensional representations of building designs are available in BIM. However, thermal analysis often remains a manual task due to disparities in modelling: In IFC, buildings are decomposed into sets of elements with individual solid volumes. Thermal analysis requires interfaces between pairs of adjacent spaces.
In this work, we present an end-to-end solution for thermal analysis on IFC building models. We derive thin-walled thermal interfaces from architectural building models using voxelization. Neighboring spaces (separated by wall volumes in IFC) are touching after aligning to the voxel grid. The resulting mesh is converted into OSM files for OpenStudio/EnergyPlus.
This paper provides an implementation, discussion and initial validation. The algorithm depends on a minimal amount of information and favors robustness over accuracy, algorithms on voxels are robust. It is suitable for early design feedback and partial or imperfect scan2bim models.

Transcript

1. Thermal analysis of IFC building models using voxelized geometries Thomas Krijnen and Tamer El-Diraby - Theohar Konomi - Ahmed Attalla
2. Presenter • Thomas Krijnen • Post-doctoral researcher @ TU Delft, NL • Founder AECgeeks • Maintainer IfcOpenShell.org • ✉ thomas@aecgeeks.com • 🐤 @aothms • 🖵 speakerdeck.com/aothms
3. Rationale. Current IFC export architecture slow release cycles diffuse focus repeated effort no alternatives
4. Rationale. Envisioned IFC export architecture fast release cycles focus reduced effort choice
5. “ Unix philosophy Write programs that do one thing and do it well. Write programs to work together. Write programs to handle text streams, because that is a universal interface. ” Douglas McIlroy, Peter H. Salus
6. Buildings as decompositions of solid volume products
7. Thin-walled thermal interfaces http://nrel.github.io
8. Geometry https://doc.cgal.org u (periodic) ⟶ v ⟶ 0 2π 0 1 2 3 4
9. Process outline BIM input Grid overlay
10. Process outline Space voxelization Discontinuities mesh
11. Process outline Simplified mesh Associated semantics and projected sub-surfaces (windows, walls)
12. Original IFC wall and infill elements
13. Original IFC space geometries
14. Voxelized space volumes (now touching)
15. Exported model in Open Studio
16. Statistics Voxel space volume 58071.25 (464570 × 0.53) IfcSpace volume sum 47257.91 One-sided thermal interface sum 36640.25 IfcWall area sum (length x height) 16683.05 IfcSlab area sum (volume / thickness) 20315.27 IfcWall + IfcSlab area sum 36998.32 Number of IfcSpaces 218 Number of unique boundary sides 208
17. Synthetic model
18. Effect of surface increase due to staircases
19. Future work: automated detection of spaces (a) voxelized IFC geometries (b) exterior (c) interior as negation of b (d) spaces obtained as c - a a) b) c) d)
20. Side step: other voxel use cases x y Door direction check Distance from exterior door Headroom check Safety barriers check
21. Conclusion IFC as a driver for innovation in modular tools A robust, but less accurate, approach for thermal analysis on building models is presented Voxelization as a “low tech” solution to computational geometry problems in our industry