building vs heating system

building and heating system both are nouns.

Word	Noun	Adjective	Verb	Adverb
building	Yes	No	No	No
heating system	Yes	No	No	No

building (noun)	heating system (noun)
the act of constructing something	utility to warm a building
the commercial activity involved in repairing old structures or constructing new ones
a structure that has a roof and walls and stands more or less permanently in one place
the occupants of a building