Heat pumps need 2 stages for Arctic application.The single stage ones reach unity gain at minus 20-30F, depending on design. A 2 stage has 2 compressors and expansion links, choosing 2 types of active working fluid(often 2 freons will work). There are assorted gasses etc. Most domestic heat pumps use one working fluid, and are used with high quality conventional foam or fiberglass insulation up to 12 inches thick with hermetically sealed buildings and counter current air exchangers to maintain internal oxygen levels without losing heat to the outside. North/South pole and far north mining/exploration sites use these, although some ultra high efficiency homes do this to allow occupants/lights/etc to be the sole heat source = $$ Rabbit hole #1 = https://www.swep.net/refrigerant-handbook/refrigerant-handbo...

And then there is 'super insulation' - far better than foam, layers of mylar vacuum coated with Aluminium and wrapped 10-30 layers deep with a small amount of Cab-O-Sil that props the layers a little apart to make the mean free path - very mean indeed and the whole thing at a high vacuum, sealed after a heat soak steady pump-out below mylar melt of course = the modern Dewar. Biggest loss via the filler path as it slowly boils off. Helium is valuable, so it is trapped and recycled. Had a summer job at a cryogenic cooler maker, waaay back, probably better now. Rabbit hole #2 = https://ntrs.nasa.gov/api/citations/19750005989/downloads/19...

And Rabbits run in threes = https://en.wikipedia.org/wiki/Multi-layer_insulation