The Part L calculation in Hevacomp V26 now includes an option to allow for additional flexibility when tracing rooms.
Typically Design Database rooms are entered using the internal edge of room surfaces. The NCM Modelling Guide requires the floor area to be calculated to the centreline of internal partitions.
The Centre line option (under the General > Other tab) caters for tracing rooms using either:
Partition Centre lines
Internal partition edges
Care should be taken in selecting the correct method as this will have implications on room areas.