4. Seal windows
Do-it-yourself: A thrifty treatment for thin glass windows is to line them with bubble wrap: mist your windows with water and push the bubbled side of the sheet against the pane. No glue needed-simply re-mist and reattach if the plastic loses adhesion.
Big fix: Adding storm windows to existing frames is one way to boost heat retention. Replacing them entirely with Energy Star-certified windows, double- or triple-glazed and filled with insulating argon or krypton gas, keeps them sealed year-round.