Cold air pouring off a double hung window in winter is almost never the glass. It is the gaps around the moving sashes. The good news is that those gaps are the easy part to fix, and you can do the whole job yourself with a screwdriver and a draught sealing kit. This guide walks through sealing a double hung sash window from start to finish, with a full video of the job and written steps you can follow at your own pace.
What you are sealing and why
A double hung window has two sashes that slide past each other. Every place a sash can move is a place air can get through. There are four gaps worth sealing on a typical window.
- The two sides (stiles). Each sash runs up and down in a channel against the beads. Old channels are usually loose enough to rattle, which means they are loose enough to leak.
- The bottom rail. Where the bottom sash sits down on the sill.
- The top rail. Where the top sash meets the head of the frame.
- The meeting rails. The middle join where the two sashes overlap. This one is often the worst offender and the one people forget.
Seal those four and you close off the draught without touching the glass, the cords or the weights. The window still opens and shuts exactly as it did before. If you want the background on why old sashes leak in the first place, we cover it in why your double hung windows rattle, whistle and let the cold in.
Watch the full job first
It helps to see the whole job before you start your own. This video runs through a complete double hung window from the first bead to the final test.
Tools and parts
You do not need much. Most of the parts come in one kit.
- Draught Sealing Kit Double Hung Window, which holds the brush seals and meeting rail seal for one window
- Extra lengths of draught seal carrier track if you are doing several windows and want spare carrier on hand
- A flat screwdriver or a thin chisel to lift the staff beads
- A utility knife
- A tape measure and a pencil
- A fine tooth saw or good scissors to cut the seal and carrier to length
One thing to know before you lift any beads. Paint on an old window can contain lead, especially on anything painted before the 1970s. Wear gloves while you work, keep the dust down, and wash your hands before you eat or drink. It is a simple habit and worth getting into.
Step by step
Remove the staff bead
The staff beads are the thin timber strips on the inside face of the frame that hold the bottom sash in its channel. Run your knife down the paint line where the bead meets the frame so you do not tear the paint. Then work the screwdriver or chisel in behind the bead and ease it off gently along its length. Take your time and lever from several points rather than forcing one end. Once the beads are off, the bottom sash comes forward and you can reach the sides and the meeting rail.
Fit the carrier and brush seal
The seals sit in a slim carrier track that runs the length of the sash channel. Measure the channel, cut the carrier to length, and fix it so the brush sits lightly against the side of the sash. The aim is contact, not a hard press. The brush should touch all the way along and still let the sash slide freely. Do both sides. When you slide the sash up and down it should feel snug rather than sloppy, with no rattle.
Seal the meeting rails
Bring the two sashes to their normal closed position and look at the join in the middle. The meeting rail seal fits so the top and bottom sashes press against a seal instead of against bare timber. Cut it to the width of the sash and fit it to the rail. This is the seal that stops the whistling draught in the middle of the window, so do not skip it.
Rehang and test
Refit the staff beads by pushing them back into place. If they were pinned, tap the pins back gently. Now run the window through its full travel. The bottom sash should slide up and down smoothly, the top sash should still move, and both should close against the seals with light resistance. Hold your hand near the edges on a windy day and you should feel the difference straight away.
How long it takes
Your first window will take an hour or two while you get the feel of lifting beads and cutting seal to length. By the second or third window you will be much quicker, often half an hour each. It is a good weekend job for a run of windows in one room, and none of it needs power tools.
If you would rather understand the different seal types before you commit, the draught seals that actually work guide compares them. And if you are weighing up doing it yourself against bringing someone in, we lay out both sides in should you DIY or call the pros.
FAQ
Will draught proofing stop my sash windows from opening?
No. The seals are designed to let the sash slide while it moves and press closed when it is shut. Fitted correctly the window works exactly as before, just without the draught and the rattle.
Do I need to take the whole window apart?
No. You only lift the inner staff beads to reach the channels and the meeting rail. The cords, weights and glass all stay where they are.
What do I need to buy for one window?
The Draught Sealing Kit Double Hung Window covers a single window with the brush seals and the meeting rail seal. For a run of windows, keep some spare carrier track handy so you are not stopping halfway to reorder.
Can I still get the window painted or serviced later?
Yes. The seals sit in a carrier that can be lifted out if you ever need to strip and repaint the sashes, then refitted afterwards. Nothing you do here is permanent.
My window is painted shut. Can I still seal it?
You will want to free it first so the sashes move properly, otherwise the seals have nothing to work against. Once it slides again you can seal it the same way.