Energy efficiency in sustainable buildings: a systematic review with taxonomy, challenges, motivations, methodological aspects, recommendations, and pathways for future research by Hafez, Fatma S., Sa'di, Bahaaeddin, Safa-Gamal, M., Taufiq-Yap, Y.H., Alrifaey, Moath, Seyedmahmoudian, Mehdi, Stojcevski, Alex, Horan, Ben, Mekhilef, Saad