In addition, energy saving is not reliable because of the contract period. Rent contract may be terminated in several years, which means the occupier can only obtain for several years rather than for the whole life cycle of a building. Specifically, the duration of reaping profit may be shorter than payback time. Given that most investors are often reluctant to take challenges (Rhoads, 2010), they tend to assign more weight to certain cost in the short term than to uncertain profit in the long term. The key information can be summarized as follows: