Solar Heat Sink Heating/Cooling
Stone or water, both are excellent at absorbing solar heat and then slowly releasing it after sundown as the conservatory cools. In the morning, as the sun starts to heat the conservatory, the stone and/or water absorb that heat to keep the temperature down. Use slab stone meant for outdoor paths as your conservatory floor. Or, create a 5’x5’x18″ water lily pond in your conservatory. Both will do an excellent job of slowly absorbing and then releasing the sun’s energy.
Worried about the pond’s humid air fogging up the glass? Keep fans on and active, this will even out the temperature throughout the conservatory and will prevent condensation on the interior glass.