A new structural model for a heterogeneous material with multiple continuous phases is proposed. The corresponding equation for effective thermal conductivity was derived using three methods. The new model is substantially different from the conventional five fundamental structural models (Series, Parallel, two forms of Maxwell–Eucken, Effective Medium Theory). The model has two applications. First, as a new fundamental structural model to produce composite models using the combinatory rules previously proposed by J.F. Wang, J.K. Carson, M.F. North, D. J. Cleland, A new approach to modelling the effective thermal conductivity of heterogeneous materials, International Journal of Heat and Mass Transfer, 49 (17–18) (2006) 3075–3083. Second, to narrow the bounds of the effective thermal conductivity for heterogeneous materials where the physical structure can be characterised into general classes.