Draught Proofing

Ill-fitting, draughty windows can cause even more heat loss and discomfort than single glazed panes. Luckily, effective draught-proofing is an easy DIY job.  With a bit of practise, draught-proofing an entire sash window can take just a matter of minutes.

The best way to draught-proof many windows is to use the kind of draught proofing tape which is self-adhesive across half of its width. The other half protrudes to cover up gaps that allow draughts. As it's translucent, when in place the tape is unobtrusive. You can buy the necessary materials here.

The following guidelines are for wooden sash windows, but the process for other types of window is very similar.

Generally, you need to draught-proof three areas of a sash window:

  • The centre rail where top and bottom (or left and right) sashes meet.
  • The bottom of the bottom sash and top of the top sash.
  • The sides of the sashes.

Each needs to be draught-proofed slightly differently. The centre rail and the bottom of the bottom sash are usually the quickest, and also the most important, bits to draught-proof. Try doing these first, then do more only if necessary.

Before you begin, it's vitally important that you clean relevant surfaces. Self adhesive tapes hate dust or dirt and they also hate moisture, so before applying the tape, it is very important to:

  • Clean relevant surfaces with a damp cloth
  • Dry thoroughly
  • Spray the surfaces with rubbing alcohol, which is very good at removing oily marks and dries without leaving a residue
  • Dry thoroughly once more, then leave surfaces for a few minutes so that any residual moisture evaporates

Ideally, undertake draught proofing on a dry day, when there's no chance of moisture condensing onto the surfaces the tape is to stick to.

Centre rails: these can be a major source of draughts, especially if the sash closer does not draw sashes together effectively when closed. This area can also often be very moist if panes suffer from condensation, which can stop the tape from sticking effectively. If you can, ensure you have installed a Gecko Pane first to reduce pane condensation.

Middle of closed window
End of middle of closed window close up

Clean as advised, paying particular attention to where the sash meets the frame at the sides, as these areas can be particularly dirty. Cut a length of tape for each side of the sash closer. Cut them slightly longer than you need initially, then trim to the exact size. Affix the tape to the edge of the top sash, such that the tape overlaps the bottom sash by around 5mm. Trim off any excess. Repeat for the other side of the closer. Press down firmly all along the tape, especially at tape end points.

Try not to open the window for the next 24 hours to give the adhesive time to cure. Finally, gently open the window by raising the bottom sash then close it again to trap the draught proofing strip between the sash centre rails and close off any gaps.

Top and bottom edges: For the bottom sash, open the window by raising the bottom sash. Clean the horizontal bottom edge of the window frame (not the sash) as advised. Cut a length of tape slightly longer than the edge to be draught-proofed, then trim to the exact size. Apply the tape to the window frame such that it overlaps the edge of the window frame by about 10mm. Trim off any excess tape. Press down firmly all along the tape, especially at tape end points. 

End of the bottom of the window closeup
Middle of the bottom of the window

Close the window. The protruding edge of the draught-proof tape will close off any gaps. Try not to open the window for the next 24 hours to give the adhesive time to cure. The pictures below show that the bottom (and side) draught proofing tapes are unobtrusive once fitted.

Bottom of window when closed

Sides (bottom sash): Clean the edge of the window frame on either side where it meets the bottom sash as advised. Cut a length of tape slightly longer than the sash being draught-proofed, then trim to the exact size. Starting at the top of the sash, affix the tape to the edge of the window frame such that the protruding edge of the tape butts up against the sash, curving round to cover the gap between sash and frame. Press down firmly all along the tape, especially at tape end points. Try not to open the window for the next 24 hours to give the adhesive time to cure.

End of bottom sash edge
Bottom sash edge

Sides (top sash): As the frame next to top sashes is often curved, you usually have to affix the draught-proofing tape to the sash, not the frame. Clean the edge of the sash on both sides where it meets the frame as advised. Cut a length of tape slightly longer than the sash being draught-proofed, then trim to the exact size. Starting at the top of the sash, affix the tape to the edge of the sash such that the protruding edge of the tape curves round and butts up against the frame, covering the gap between sash and frame. You need to be careful that the tape doesn't protrude too much, or it will foul the bottom sash when you open the window. Press down firmly all along the tape, especially at tape end points. Try not to open the window for the next 24 hours to give the adhesive time to cure.

The end of the top edge
Edge of the top of the window