When you are performing a load calculation, is it important to understand the full geometry and volume of a building. Much of Manual J is centered around heat loss and heat gain through conduction of walls, windows, doors, ceilings, and floors. We also need to understand the volume of the building for calculating air infiltration.
Areas that should be scanned
Any space that is either 1) served by equipment or 2) is within the conditioned part of the building regular occupied by people.
Living areas
Bedrooms
Bathrooms
Hallways
Large walk-in closets
Yes, even if the closest do not have supply serving them.
What about really small spaces? Learn more.
Handling below grade or basement spaces
Basement areas of a home should only be scanned if they are currently served by equipment (or you planning to) and temperatures are maintained at or near 70F in the winter and 75F in summer.
Partially conditioned basements
If only a portion of the basement spaces has finished living areas that are served by equipment, then only scan those areas and do not scan the unconditioned utility rooms or storage spaces that may be present in the basement.
Unconditioned basements
if the basement does not have living space and is not served by supply or distribution from the equipment, it is considered unconditioned space and should NOT be scanned. Loads related to the basement are handled by the floor assumptions on the first story of the building.