Setting: the same one as this question and this question; TL;DR, life is common throughout the Universe, it just tends to blow itself up before it figures out FTL travel and upgrades to Kardashev 2, which turns out to be very rare; hence, there are a few civilizations alive in every galaxy at a given time, but there is only one civilization that had the exact right course of events to actually come up with FTL. They're fine interacting with other species and would like to build cities or space stations that can house multiple different species at the same time, as is a staple of science fiction: Captain Legallydistinct never has any problem going down to an alien planet's surface and meeting up with the locals at a party, and the humans suggest at the Interstellar Conferences that we should work towards being able to have safe interspecies parties just like in Galaxy Journey.
Here I will enumerate some of the species that I'm dealing with (using pseudonyms, because I haven't exactly come up with English transliterations for their names yet):
- Humans. We are quite versatile and can live in areas that get as cold as 0 ºC or as hot as 20 ºC on a regular basis (for this question's purposes, I will operate under the assumption that that temperature range is "comfortable" for humans who have endured the unimaginable hardships of space travel). We also prefer 1 g, but there is some thought that we could survive in 1.5 or even 2 gs of gravity for short periods of time, and I'm sure nobody would be offended to have to spend time in 0.2 g and be able to fly around with cardboard wings (again, I will assume that that range is roughly comfortable, so humans' gravity range is 0.2 to 2 g). We can’t go too low for too long, though - our bones begin to atrophy and our heart begins to shut down.
- Dragons: the one species who has figured out how to build an energy-efficient and actually-functional warp drive, and the one who brought all the other species together. They have radically-different chemistry based on silicon, making them less fleshy than rocky, but they're still just as motile and intelligent (if not far more intelligent) as humans. They come from a world where the average temperature is around -100 ºC and the gravity is around 0.15 g, and without constant life support, they can't stand temperatures above -50 °C without getting heatstroke and promptly dying, but they can get as cold as -200 °C by slowing down their metabolisms and going into a sort of stasis until it warms up again. They can deal with surface gravities up to about 0.5 g before the square-cube law kicks in and they can’t hold themselves up anymore. They drink a mix of silane chemicals, and breathe methane; their chemistry doesn’t like oxygen or water but neither are toxic to a dragon.
- Elves: another carbon-based species born on a moderately Earth-like planet with gravity around 0.7 g and temps around -70 °C (I said Earth-like, not Earth-identical), the elves are a thick-furred bipedal species that have learned to use electricity generated by their photovoltaic fur to power much of their musculature instead of biochemical energy. They drink water and breath oxygen like humans, but can’t deal with temperatures hotter than 0 °C - their thick fur can be used as a high-surface-area radiator to keep them from passing out in very high temperatures, but at a certain point they overheat and, not being able to sweat, suffer heatstroke and die. They can deal with a human’s gravity of 1 g easily, and their resilient bones can let them survive in 0 g for as long as necessary; their circulatory system, which has to constantly pump blood to the radiator-like furred skin to keep them from overheating even under ambient temperatures, has to keep running all the time, even in zero g.
- Dwarves: carbon-based lifeforms that hail from a super-Earth orbiting a much brighter star, leading to surface temperatures upwards of 80 °C and gravities of around 2.5 g. They can put up with temperatures as high as 120 °C, as much life on their planet has evolved to due because its eccentricity carries it much closer to the sun during the summer, resulting in large temperature fluctuations over the course of a year. They can also withstand temperatures as cold as 40 °C, but below that point, their biochemistry starts to shut down and they suffer rapid decomposition - not exactly good. They can deal with high and low gravity as well, being a hardy species.
Obviously, there are some issues here. Some species would freeze to death in Death Valley, while others would die of heatstroke in Antarctica, while the dragons (who have established FTL travel and are pretty much the only way to get all four species together until an enterprising human steals their tech) would be crushed under high gravity as they suffocate.
Humans, elves, and dwarves have all figured out advanced computing, so they can just render holograms of each other in their ships and have the super-mega-genius equivalent of a video call, but the dragons are embarrassed to admit that, on account of their hyperintelligence, they never bothered to develop computers powerful enough to render holograms since all the calculations a computer would do they can do in their heads, and there aren’t cats on their world and there is therefore no impetus to create high-quality GPUs to stream videos of them. As such, the dragons not wanting to just wait around in silence having taxied everyone else within comms range, we need another solution.
So: what’s a convenient, casual solution that these four species could implement to allow them to have casual in-person conversations with each other without promptly overheating, freezing, being crushed, and/or asphyxiating? Putting on spacesuits and exoskeletons to withstand different gravities, atmospheres, and temperatures doesn’t exactly count, since that’s not what any of these species would consider to be “casual”. The result I’m aiming for is an explanation as to how a dragon, a dwarf, a human, and an elf can all walk into the same room without spacesuits on and not instantly be killed by something (since that happens fairly often in my world).