Clean the window frame and glass
Measure the window dimensions
Apply weatherstripping around movable sashes
Seal gaps with caulk around the frame
Install shrink film over the interior side of the window
Use insulating window curtains or thermal drapes
Add a draft stopper at the bottom of the window
Use rope caulk for temporary gap sealing
Install interior storm windows
Replace damaged or worn seals
Close and lock the window tightly
Cover the window at night to reduce heat loss
Open coverings during the day for sunlight
Use reflective window film for heat control
Check for air leaks regularly and reseal as needed