SBEM has an upper limit on the number of surfaces it can handle and this limit can be exceeded for very large buildings. To help get round this problem you can use the option 'Lump similar partitions' found on the Advanced tab of the Model options dialog. This can reduce the number of surfaces used in SBEM allowing calculations to complete. DesignBuilder users have successfully modelled huge tower blocks with many hundreds of zones using this method.
If you still have this problem after lumping similar partitions then you will need to simplify the model further:
1. Combine as many adjacent zones as possible using NCM zoning rules.
2. Use 'Lump similar zones' and ensure as much as possible that similar zones are exactly the same in layout to ensure the lumping process can work.
3. You may be able to merge stacked lift shafts, circulation areas, service areas etc using holes and merge zones connected by holes.
4. Once you have merged as much as possible try again.
5. If there is still a problem, you should be able to get a reasonable idea of how close you are to the limit by progressively deleting blocks/partitions until the calculations complete successfully.
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