There would be no gaps, and the windows would slide up and down with zero friction.
When first fitted, your sash window would have been pretty efficient.
However, in the real world, your sash window fits badly.
Years of use have caused wear on the moving parts.
Staff beads have been adjusted to close up the gaps, while still allowing the windows to slide freely.
Cold air and noise enter through the gaps - shown in blue below.
The lower pane is most frequently used, and is therefore the most worn part of the window.
By fitting the RUMPLE, the window frame is pressed against the parting bead.
This closes the gap and prevents air and noise from entering your home.
The Rumple fixes on to the staff bead.
By turning the threaded screw, the window is pushed lightly against the parting bead of the window, eliminating drafts and rattles.
Materials are easily sourced for pennies, and you may find that you have many of them in your toolbox already.
Step 1: Materials
Modesty Block - AKA
Knock Down Block
Knock Down Fittings
Cabinet Fixing Block
Machine Screw – Pan Head M5x 30mm
M5 Tap from Tap & Die set
25mm Drywall screw
Step 2: Preparation:
You need to machine a thread into the modesty block.
Very easy – run the M5 Tap into the block using the drill.
You need to cut the machine screw to the right length using a hacksaw
You need to cut a slot into the screw so that you can turn it with a screwdriver.
Step 3: Assembly
Step 4: Fitting.
Position the Rumple 3 inches from the top of the lower pane.
Drill pilot holes into the staff bead.
Screw the Rumple into the staff bead.
Push the window against the parting bead with one hand while turning the adjusting screw until it just catches.
Do the same on the other side of the window.
Stand back and admire your work.
Step 5: Benefits
Then you notice that the room is quieter.
When it gets cold, you will find that drafts have been reduced.
Rumples are pretty easy to make, but if you want to buy readymade rumples, send me an email at firstname.lastname@example.org
I will sell them on eBay