Can anyone guide me on how to do a basement swimming pool?

Hi Jack,

Hevacomp will allow you to import the basement floor using a negative Finished floor level, eg:

Then, when entering your rooms, there is a Swimming Pool room type available  as below:

Finally, you may need to create surfaces to your requirements, for example by including a soil layer as below:

There may still be a solar component included in your gains results, so if you wished to exclude this you would need to export the report and manually remove it.