The rule is OK.
You can write it with a long dash which is equivalent of English "is" and represent an intonational pause in Russian:
Этот дом -- новый. = This house is new.
Это -- новый дом. = This is a new house.
If you can replace "this" with "it" or "this object" than it should be "это" only.
Этот дом -- новый. = Thisobjecthouse is new.
Это -- новый дом. = This object is a new house.