Would like to insulate a room so I won't freeze my ass off in the "spring city's" winter. Where to buy? Found some on taobao but can't post link. Would like to buy locally.

We are in Shangri-la and I recently helped someone here buy and install fiberglass insulation. I ordered through Taobao, but selected a seller in Kunming. You can probably do the same and then get their phone number or find out where they are located and go there to pick it up. I imagine many of the large home repair markets around Kunming would have some.

Most insulators in the USA now use a piped-in instant hardening foam. Faster, easier, less stressful than fiberglass or it's former incarnation - abestos. Dunno the brand - but if you're here long-term and it's your own place - look into this as an alternative to fiberglass insulation - it's actually kind of as nasty as asbestos.

Not here long term. Renting. Looking for insulation styrofoam. Can't post link from taobao but I used it in Nanjing.

I'm interested in this topic. Where is the insulation going? On the walls or on the ceiling? If using fibreglass, are you anchoring 2x4s to the walls and covering with sheets of drywall?

FG could also be used under solid wood floors, as these are usually attached to battens which are fixed to the floor. The FG could be rolled out between the battens .

I am renting. Looking for cheap styrofoam insulation come in 3-5cm sheets.

Have you any idea how much that will cost you? The areas of wall will be significant. It will also be unsightly and a fire hazard.

The building management may also stop you, because of the fire hazard. It is something I would never even consider because of the fire hazard.
There are other ways to survive the winter. The big issue when things are cold for a long time is damp, and when they are damp you feel the cold more. Walmart now has electric blankets in stock, these are now made to export standards and are safe, and will keep the damp out of your bed and bedding. The oilfilled radiators also work well in taking the chill off of a room, and take the damp out of your clothes. Thermal underwear, long johns etc. I would not have worn them before I came to China,but I do now, you can buy these in any large supermarket and in Metro.

It is your choice in the end, but IMHO using styrofoam is maybe not the best choice.