They need to

Most of all the house loses heat due to old windows. They need to be replaced with new ones with double -glazed windows, and if it is not affordable homeowner, then you can try, and overhaul the old. Glass must be put on a window putty, or applied silicone sealant for this. Then sequent or pump the gaps between the wall of the house and the window frame, and also do not forget at the site of the window sill mount. For this purpose, you can purchase an installation foam.