Insulation kit for casement windows that prevents the return of hot air expelled by portable air conditioning. Easy to install, it achieves greater energy efficiency in the operation of our device and optimal air conditioning. It is compatible with all models of portable air conditioners with a hot air extraction pipe for casement windows. Sealed and insulated: keeps the hot air exit that all portable air conditioners generate out of the window sealed. It prevents the return of that hot air as well as the entry of insects, dust or dirt. Increased efficiency: achieving good indoor air conditioning in which the air in our room remains fresh and clean. Easy assembly and disassembly: without the need to drill holes or use certain tools, fitting stably to the air extraction tube. Waterproof: it can still be installed even on rainy days, preventing the entry of humidity, dust and pollen or small insects such as mosquitoes. Dimensions: the bag measures 400x300cm, the sealing cloth measures 40