The purpose of this article is to introduce an Eilenberg-Moore spectral sequence converging to the cohomology algebra of a function space with an adjunction space as its source. Computability of the spectral sequence is shown by determining explicitly the mod cohomology algebra of the function space of maps from a non-orientable surface to the classifying space of a simply connected Lie group whose homology is -torsion free. Let be an orientable -dimensional manifold. Applying the spectral sequence obtained from a Heegaard splitting of the manifold , we also prove that is a direct summand of .