▁evaluate ▁the ▁energy ▁efficiency ▁of ▁a ▁new ▁or ▁an ▁existing ▁building . ▁The ▁comparison ▁is ▁generally ▁done ▁for ▁energy ▁requirements ▁for ▁he ating ▁and ▁cool ing ▁of ▁ind oor ▁space . ▁The ▁energy ▁is ▁the ▁main ▁criter ion ▁considered ▁by ▁any ▁international ▁building ▁energy ▁rating ▁scheme ▁but ▁there ▁are ▁some ▁other ▁important ▁factors ▁such ▁as ▁production ▁of ▁green house ▁g ases ▁emission , ▁ind oor ▁environment ▁quality , ▁cost ▁efficiency ▁and ▁thermal ▁comfort , ▁which ▁are ▁considered ▁by ▁some ▁schemes . ▁Basically , ▁the ▁energy ▁rating ▁of ▁a ▁resident ial ▁building ▁provides ▁detailed ▁information ▁on ▁the ▁energy ▁consumption ▁and ▁the ▁relative ▁energy ▁efficiency ▁of ▁the ▁building . ▁Hence , ▁H ER s ▁inform ▁consum ers ▁about ▁the ▁relative ▁energy ▁efficiency ▁of ▁homes ▁and ▁encou rage ▁them ▁to ▁use ▁this ▁information ▁in ▁making ▁their ▁house ▁purchase ▁decision . ▁There ▁are ▁many ▁energy ▁rating ▁tools ▁by ▁which ▁one ▁can ▁calculate ▁the ▁energy ▁performance ▁of ▁a ▁building . ▁Basically ▁all ▁these ▁tools ▁involve ▁a ▁numerical ▁description ▁or ▁prepare ▁a ▁computer - based ▁model ▁for ▁the ▁rating ▁of ▁a ▁building ▁against ▁standard ▁occup ancy ▁and ▁activity ▁templates . ▁So , ▁H ERS ▁uses ▁a ▁computer - sim ulation ▁based ▁methods ▁for ▁assess ing ▁the ▁energy ▁efficiency ▁of ▁buildings ▁under ▁standard ▁conditions ▁and ▁its ▁potential ▁for ▁improvement . ▁ ▁House ▁energy ▁rating ▁scheme ▁H ERS ▁is ▁a ▁standard ized ▁scheme ▁for ▁evaluation ▁of ▁a ▁home ' s ▁energy ▁efficiency ▁and ▁expected ▁energy ▁costs . ▁Basically ▁a ▁H ERS ▁represents ▁the ▁guid eline ▁of ▁a ▁House ▁energy ▁rating .