Residential and commercial buildings account for 41% of total energy consumption in the United States. Optimizing energy consumption and designing more Energy Efficient Green Buildings is a promising approach to reducing energy consumption. Modeling and simulation play an important role in the design, control, and operation of building systems. They are particularly valuable in evaluating performance, Indoor Air-Quality (IAQ), comfort, as well as for HVAC control design. In this talk, I will discuss computational approaches to tackle problems associated with building systems. These include (a) Data-driven algorithms and methods for monitoring IAQ under uncertainty. (b) Data-driven surrogate construction and coupling with CFD solver for accelerating RANS turbulence modeling.