Mua máy sưởi cho phòng ngủ. Mua chăn điện dùng trên giường. Đắp thêm chăn. Treo rèm cửa dày hơn. Che phủ sàn (và tường). Sử dụng vật liệu cách nhiệt tốt hơn.

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
Obviously, if you don't already have a heater, you may want to consider buying one. Plug-in heating devices, which can usually be found at most department stores, are available in a wide range of sizes and power levels, making them a reasonable solution for any size room (and any budget).  Keep in mind that space heaters tend to use a lot of electricity. While you may be able to make up the difference by turning off your central heating, frequent space heater use can affect your utility bill. Al