The single family home building type is disabled by default as it depends on the location and energy code.
So please follow these steps:
Enter your location
Based on your location the energy code drop down will change
Choose "Single Family Home - California Title 24 2016" or "ASHRAE Residential 2018" energy code respectively and the building type single family home will be automatically selected.
With these settings the other building types will be disabled, you will have to change the energy code to reset it.