Experimental and three dimensional numerical work was performed to evaluate the average heat transfer coefficients for forced convection heat transfer from the surface of a rectangular flat plate model collector flush mounted on the roof of a model residential house. Examined parameters are the roof tilt angle, windward and leeward orientations. Experiments were carried out for mass transfer using the naphthalene sublimation technique. The final results were presented in terms of heat transfer parameters using the analogy between heat and mass transfer. Numerical study was performed using Ansys Fluent 6.3. Results of experimental study are in good agreement with that of numerical study. It is observed that heat transfer coefficient decreases very slowly with increasing angle of attack and it can be stated that angle of attack does not have a strong effect on heat transfer coefficients in the range investigated. It is also observed that heat transfer coefficients on the leeward orientation are lower than those of the windward orientation. Flow separation was observed on collector surface in leeward orientation.