Despite its location and simple yet elegant beauty, the Underground-Vampire Facility, or U-Vamp, floor is the most important within any vampire coven. Located three floors below the ground, a full two floors below the lower floor of HCC Mansion, this is where everything medical takes place. The reason it is so important is because of the vampire's change from living to undead. If for any reason this change is prolonged or timed too close to the rising of the sun, the vampire must be taken deep underground and kept there until their transformation is complete. An IV is also often used for hydration, medical, and nutrition purposes during this time. This is crucial for their survival as this is the only way to ensure they are not "affected" by the rising sun during this very vulnerable process.
Being affected by the rising sun basically means that the energy of the sun that spreads through the planet as soon as it rises has touched them. Because it is the sun's invisible energies that we are unable to feel, thereby meaning they do not have to be in the sun's light in order to be affected by it. Normally, vampires are not affected by the rising sun any more than humans and many magical species are affected by the onset of nighttime. However, during their change from living to undead, the vampire is in a kind of death state and therefore are just as affected by the sun's energies as any other dead vampire. In other words, it would turn their body to ash. Therefore, being affected by the rising sun during this change is a guaranteed death sentence for them, hence this floor's high importance. Finally, it is very common for U-Vamps to have live plants so that the air is constantly being renewed despite them being so far underground.