The room is chilly with the heat on since there’s a window next to the sofa. The frame seems OK. It does open well. Nothing to peel. Pulling out a window that still functions seems less disruptive than replacing only the glass.
For homeowners comparing options through Horizon Windows, can you put triple glazing in double glazing frames is worth asking before anyone orders new units. Sometimes the existing frames can stay. Sometimes the glass is only half the problem.
Why Is Replacing Just the Glass Tricky?
An ordinary double glazed unit has two panes and one insulating gap. Triple glazing adds another pane and a second gap, making conventional units thicker.
A double glazed frame may hold glass around 24 to 28 mm thick. Many triple glazed units measure around 36 to 44 mm. Those extra millimetres have to go somewhere and the frame’s glass recess may simply be too narrow.
Horizon has a double and triple glazing comparison covering the different specifications. What the brochure cannot show is whether the beads and seals on a particular ten-year-old window will accept a different unit.
What Does the Installer Need to Look At?
A standard double glazed unit has two panes and one gap. The third pane and second gap in triple glazing increases the thickness of standard units.
Glass around 24 to 28 mm thick may be held in a double glazed frame. Many triple glazed units are roughly 36-44mm. Where do those additional millimeters go? Well, perhaps the frame’s glass recess is a little too small.
Horizon provides a comparison of double and triple glazing specs. What the brochure can’t tell you is whether the beads and seals on a specific 10-year-old window will accept a different unit.
What Does The Installer Have To See?
Seals, Recess and The Beads
The strips that hold the glass in its frame are known as the glazing beads. They seem trivial until someone attempts to put in thicker glass and discovers the old strips won’t clip back into place.
There must be area enough for the seals to operate as they should. A compressed gasket or badly seated bead is not a harmless cosmetic concern, particularly in a period of wind-driven Irish rain.
Another problem with older frames is that the correct replacement beads may not be available. That may kill a potential glass business.
Even if you have a new bead, it has to be putting the right amount of pressure. If the fit is difficult, you might get another leak instead of better insulation.
The Hinges And The Sash Opening
One item is a definite time frame. Another is a huge casement window hung on two hinges.
Additional weight usually signifies an additional pane. Heavier glass might make things worse if the sash already rubs its frame or needs a hard push to lock. Order only if satisfied with the hinges, locking points and strength of the sash.
A bathroom window may pass such tests while a wide bedroom opener would not — even if they both come from the same original installation.
Would A Slim Triple Glazed Unit Work?
Perhaps. Triple glazing is not usually the hefty 40mm unit people think of.
Horizon is a specialty 20mm triple glazed product with krypton gas filled cavities. It is a reminder that since many older windows were put up, glass construction has changed.
But 20 mm on the standard doesn’t automatically imply it fits. The fitter must check the manufacturer’s fitting specifications, proper packers, glazing beads and edge support. The glass must also fit within the size and weight limitations of the aperture.
And a fair assessment of thin three-pane unit performance is also needed. It does not inherently mean it’s better than every current double glazed unit simply because it has more glass.
If this cannot be proven, there is no reason for improvising with the thinner product.
Will The New Glass Solve The Cold Spot?
For example, if you’ve got a chilly window, better insulating glass may make a huge impact. The internal surface is often warmer and this might make the chair next to it more pleasant on cold nights.
Condensation is not that easy. Warm glass may minimize water on the room-facing pane, but interior humidity and ventilation are still important. Moisture between the panes is usually a sign that the original sealed unit has failed.
That instruction on triple glazing and condensation makes that a distinction worth studying before you buy a replacement.
A draft blowing through a bad gasket or a sash that does not close evenly calls for further repair. New expensive glasses will not fill a gap around the frame.
When Does a Whole New Window Make More Sense?
Keeping a good frame can save disruption. There is less work around the plaster, tiles and window boards, all of which may still be in excellent condition.
But a frame that has warped or started leaking is already asking for attention. New glass does little for ageing hinges, tired gaskets or damaged corners.
Choosing new uPVC Windows means the frame, glazing and hardware can be specified together instead of trying to match new components to a discontinued profile.
There is also modern double glazing to consider. A good low-E unit with suitable spacers may offer a worthwhile improvement without the cost or complications of three panes.
What Should Be Written Into the Quote?
A glass-only estimate can look appealing beside the price of a whole window. The comparison is meaningless until both cover the same work.
The written quote ought to say:
- What glass thickness the frame can accept
- Whether existing beads and seals can be reused
- If the hinges can take the new weight
- Whether the quoted U-value is for the glass or complete window
- What installation work and warranty are included
One window in the house may be worth reglazing while the next needs replacing. A whole-house quotation should explain that difference.
If the fitter cannot identify the frame system, the answer should not be a guess. Made-to-measure sealed units are not something a homeowner wants to pay for twice.
Conclusion
Some double glazed frames can take a triple glazed unit. Others are short of space, too worn or simply unsuitable for the added weight. A proper inspection decides which situation applies.
Horizon Windows’ Triple Glazing options offer a reference for comparing a complete replacement when changing the glass alone would involve too many compromises.