Within the scope of environmental modelling, convective heat transfer between a vegetal structure and its surrounding medium remains to be adequately described. However, for some applications, such as forest fire modelling, convective heat transfer is one of the factors responsible for vertical fire transitions, from ground level to the tree crowns. These fires are the most dangerous because their rates of spread can reach high speeds, around 1 m per second. An accurate characterization of this transfer is therefore important for fire propagation modelling. This study presents an attempt to formulate an analytical modelling of the convective heat transfer coefficient inside vegetal structures generated using an Iterated Function Systems (IFS) which only depends on the IFS parameters (parameters helpful to generate vegetal structures). The results obtained using this formula are compared with previously computed numerical results to evaluate their accuracy. The maximal discrepancies were found to be around 6% which proves the efficiency of the present model.