The transition from laminar (smooth) to turbulent (disordered) flow in a pipe remains one of the oldest outstanding problems in fluid mechanics. In a vertically-aligned pipe, under the influence of heating, the opposite process has been observed, i.e. turbulence may be partially or fully suppressed by buoyancy forces. As the suppression of turbulence leads to severe heat transfer deterioration, this phenomenon is undesirable in both heating and cooling applications, such as nuclear reactor cooling systems and geothermal energy capture. In this talk, I will present our recent efforts in modelling and understanding the transitions to and from turbulence in a vertical heated pipe, focusing on the competition between shear- and buoyancy-driven instabilities and the resulting suppression or enhancement of coherent structures. Using tools from dynamical systems theory, stability analysis and optimisation, I will show how we can capture and optimise the transitions between different flow states under varying heating conditions. Connections to turbulence control strategies in ‘ordinary’ (isothermal) pipe flow will also be discussed, where, in contrast, turbulence suppression is typically highly desirable, as it leads to drag reduction and lower energy consumption.