Does your apartment have a balcony??! But to achieve comfort in the apartment, you should take care of its insulation. This will lead not only to an increase in temperature in the apartment, but also significantly increase the quadrature. To achieve a high-quality result, use modern materials (besides, installing them will allow you to save a few centimeters due to its compactness). We recommend using penofol, its surface is covered with an aluminum film, and for the second layer, use penoplex. These materials are not hazardous to health.
Work should start from the floor, it should be covered with heat-insulating material, then with a bar with a section of 40 by 40 mm in increments of half a meter. Do not forget to fill all the gaps tightly with insulation to achieve the greatest effect. Then the second layer of bars is laid (perpendicular). It is worth sticking the same penofol on the walls, gluing it gently from the side of the aluminum film, this will allow you to achieve the best result and heat preservation. The crate is fixed with dowels and self-tapping screws. All this can be sewn up, both with a fairly cheap clapboard, and with plastic or wooden panels.