Draft-proofing window inserts

What it is

Old or single-glazed windows can leak a surprising amount of heat and let cold draughts pour in, and a removable insert that seals the window from the inside can cut that loss dramatically for a fraction of the cost of new glazing. Draft-proofing window inserts are clear or framed panels fitted into a window opening from inside to create an insulating air gap, reducing heat loss and draughts without replacing the window itself. They are a practical, money-saving home project that improves comfort and lowers heating bills, and many versions are removable for summer or for windows you still want to open.

The appeal is real comfort and energy savings for modest effort and cost. A trapped layer of still air is an excellent insulator, so an insert that creates a sealed air gap in front of the existing glass noticeably reduces the cold radiating in and stops draughts, making a room warmer and cheaper to heat. Compared with the expense of replacing windows or fitting secondary glazing professionally, a DIY insert is dramatically cheaper and often achievable in an afternoon.

There are several approaches at different effort levels. The simplest is heat-shrink window film, a clear plastic taped around the frame and shrunk tight with a hairdryer to create a sealed air gap, nearly invisible and very cheap. More substantial are rigid inserts, a clear acrylic or framed panel cut to fit snugly inside the window reveal, held by friction or magnetic strips, which are reusable season after season. Choosing the right method for your windows and how often you open them is the main decision.

The honest trade-offs are that film inserts are single-season and block the window from opening, while rigid inserts cost more and need accurate measuring and cutting. But all are far cheaper than new glazing, the materials are widely available, and for warmer rooms and lower bills without major work, draft-proofing inserts are one of the most cost-effective home improvements going.