Modeling methodologies often allow simplifications of systems. For example, water heating distributions systems can be modeled with a simple heat loss factor for the distribution system and simplified schedules for when hot water will be flowing through the distribution system. This can under- or over-estimate the amount of heat that is moving from the hot water distribution system into the conditioned space, which can result in an inaccurate impact on space heating and cooling loads. And this impact will be much larger in some building types such as high-rise multifamily than in other types with much smaller hot water loads such as retail.