Blood vessels inspire HVAC plant loops
In vasoconstriction, thermal regulation happens through heat transfer between blood vessels and skin, these being the internal and peripheral tissues. Thinking of blood vessels as pipes with a fluid flow transferring the thermal energy to where it is demanded in a building, the smaller the diameter of the pipes, the less fluid will flow, and thus, the less heat will be taken away through conduction and convection, due to the temperature difference between the pipes and the adjacent surfaces.
Such pipes could be used in any thermal transfer system such as a roof mounted solar collector, a geothermal ground heat exchange system, or as a dynamic thermal barrier in walls.
An equivalent design solution might be creating a mesh of capillary pipes that can change their diameter embedded between the materials used for either external or internal surfaces. Having flexibility in narrowing the fluid channels is expected to decrease heat loss through less fluid flowing in the pipes. Another possible design solution could be bio-inspired capillary HVAC plant loops.