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Best Secondary Glazing Kit for a Sash Window: 5 Picks for Draughts, Condensation and Heat Loss
A secondary glazing kit for a sash window is the cheapest way to stop a single-glazed sash rattling, fogging up and bleeding heat all winter. This roundup covers five products that solve different problems: clear shrink film for a fast seasonal seal, putty and glazing sets for restoring old timber sashes, and a moisture-clearing kit for failed sealed units. The picks suit renters who cannot alter the window, period-home owners keeping original frames, and anyone on a tight budget. The overview table below shows every option at a glance.
The Picks at a Glance
| Product | Key Spec | Best Use | Price Tier |
|---|---|---|---|
| Clearviewkit 8 x Window Kit | 8-window kit, clears trapped moisture | Failed double glazing with fogging | Mid |
| Duck Brand Window Insulation Kit, 62 in x 420 in | Fits up to 10 windows | Fast seasonal draught seal | Budget |
| Sarco Window Glazing Set, Large Dual Glaze | Full putty-and-points restoration set | Historic timber sashes | Premium |
| DAP 12108 Latex Window Glazing | 10.1 oz white latex paste | Re-sealing loose panes | Budget |
| Duck Brand Window Insulation Kit, 62 in x 630 in | Fits up to 15 windows | Whole-house winter prep | Budget |
1. Clearviewkit 8 x Window Kit
Type: Moisture-clearing kit for failed double glazing
Coverage: 8 windows
Intended use: Clearing trapped moisture inside failed sealed units
Format: Multi-window kit
This kit targets a specific problem rather than general draughts: the cloudy, foggy haze that appears inside a sealed double-glazed unit once the seal has gone. It is not a film or a pane — it is a treatment kit for clearing that trapped moisture, sold in an eight-window pack so a whole elevation can be tackled in one go. The kit format makes it a practical buy for a household with several misted units rather than a single bad window.
It suits owners of failed double glazing who want to see out of the glass again without paying for full unit replacement. It is not for timber sash windows that need new putty, and it will not fix a broken frame or a cracked pane. The multi-pack sizing also means a household with only one fogged window pays for coverage it will not use.
Trade-off: This is a moisture treatment, not a true secondary glazing layer, so it adds no insulation value to the window.
Check the current price on Amazon
2. Duck Brand Window Insulation Kit, 62 in x 420 in
Type: Shrink-film secondary glazing kit
Material: Crystal clear rolled shrink film
Coverage: Fits up to 10 windows
Installation: Indoor, cut to size
Included: Window tape
This is the classic renter-friendly approach: a roll of crystal-clear shrink film cut to size and fixed to the inside of the frame with the included tape, then tightened with heat. The clear film keeps daylight coming through while creating a still air pocket in front of the glass, which is exactly what takes the edge off a draughty sash. The 62 in x 420 in roll covers up to 10 windows, and it ships as the single most popular pick in this roundup.
It suits renters, students and anyone who cannot make permanent changes to a sash window, as well as homeowners sealing a spare room for the winter. It is not for anyone wanting a rigid, reusable pane, and it is not a long-term solution — the film is a seasonal layer. Sashes that are painted shut or have deep mouldings can make a clean tape line difficult.
Trade-off: The film is single-season in practice, so the cost repeats every autumn and the window cannot be opened without cutting the seal.
Check the current price on Amazon
3. Sarco Window Glazing Set, Large Dual Glaze
Type: Complete window glazing restoration set
Size: Large, dual glaze
Included: Glazing putty, whiting powder, glazing points, window opener, flexible and stiff putty knives
Intended use: Restoring historic windows
This is the only pick here that addresses the sash window itself rather than adding a layer over it. The set bundles glazing putty, whiting powder, glazing points, a window opener and two putty knives — flexible and stiff — so a full re-glaze of a timber sash can be done without sourcing each part separately. The dual-glaze sizing points to larger or multi-pane sashes, and the window opener helps free sashes that have been painted shut.
It suits owners of period and historic homes who want to keep original frames and restore them properly instead of covering them with film. It is not for anyone in a rental, and it is not a quick fix — re-glazing is a hands-on job with drying time between stages. The premium price only makes sense if several windows need attention.
Trade-off: The kit assumes the buyer already has the skill and time to re-glaze, and the outlay is hard to justify for a single small window.
Check the current price on Amazon
4. DAP 12108 Latex Window Glazing
Type: Latex glazing compound
Material: Latex paste
Color: White
Size: 10.1 oz
Intended use: Sealing glass into window frames
A single tube of white latex glazing compound for bedding and sealing glass into a frame. Latex paste is the forgiving choice for a first attempt at glazing: it tools smoothly, cleans up with water before it sets, and takes paint once cured. The 10.1 oz size is enough for small repairs — a cracked or crumbling putty line, or one or two panes on a sash.
It suits DIYers patching a sash window rather than rebuilding it, and anyone who already owns the knives and points. It is not a complete kit — glazing points, a putty knife and the technique still have to come from elsewhere. Anyone tackling a full set of sashes will need several tubes, which erodes the low unit price.
Trade-off: One tube covers only minor repairs, and latex compound is less durable than traditional linseed putty on exposed exterior faces.
Check the current price on Amazon
5. Duck Brand Window Insulation Kit, 62 in x 630 in
Type: Shrink-film secondary glazing kit
Material: Crystal clear rolled shrink film
Coverage: Fits up to 15 windows
Installation: Indoor, cut to size
Included: Window tape
The same clear shrink film and tape system as the ten-window kit, on a longer 62 in x 630 in roll rated for up to 15 windows. For a whole house of single-glazed sashes, buying the larger roll once is cheaper per window than stacking smaller kits, and the roll can be cut down to fit narrow or unusually shaped sashes. Installation is indoor-only, so no ladder work is needed.
It suits homeowners sealing an entire floor or house before winter, and anyone who has used the smaller kit and knows the film works. It is not for a single window, where the leftover film will sit unused, and it is not reusable in the way a rigid panel is. Sash windows with deep reveals may need extra tape to get a reliable seal.
Trade-off: The large roll only pays off across many windows, and the film still has to be replaced each season.
Check the current price on Amazon
Before You Buy
- Approach: Decide whether the window needs a layer over it (shrink film) or repair to the frame and putty itself — the two solve different problems.
- Material: Clear film preserves daylight but is seasonal; latex compound and putty are permanent repairs that need prep and drying time.
- Size: Match the kit’s window count to the actual number of sashes; a multi-window roll is poor value for one fogged unit.
- Compatibility: Shrink film needs a clean, dry frame and flat taping surface; deep mouldings and painted-shut sashes make sealing harder.
- Included accessories: Film kits should include tape; glazing jobs need points and knives, which only the full Sarco set supplies.
- Care: Latex glazing cleans up with water before curing; shrink film should be cut, not torn, and removed carefully to protect paint.
- Storage: Leftover film roll and spare tape store flat and keep for the next season; opened glazing compound does not.
Frequently Asked Questions
-
Does a secondary glazing kit work on a sash window?
Yes — shrink film taped to the inside of the frame creates a still air pocket in front of the glass, which cuts draughts and heat loss. The sash can still be opened, but the seal has to be cut and redone. -
What is the difference between shrink film and glazing putty?
Shrink film adds a temporary clear layer over an existing window. Glazing putty and compound reseal the glass into the frame itself, fixing the cause of draughts rather than covering it. -
Can a renter use these kits?
Shrink film kits are the rental-safe option because they attach with tape and peel away. Re-glazing a sash is a permanent alteration and generally needs the owner’s agreement. -
How many windows does one kit cover?
The two Duck Brand rolls are rated for up to 10 and up to 15 windows respectively, while the Clearviewkit covers 8. Film can be cut smaller, but it cannot be stretched to cover more windows than the roll allows. -
Which kit clears fogging inside failed double glazing?
The Clearviewkit is the only pick aimed at trapped moisture inside failed sealed units. Film and putty do not address fogging between panes. -
Is a full glazing set worth it for one window?
Usually not. The Sarco set earns its price across several historic sashes; for a single small repair, a tube of latex compound is the more sensible spend.
Bottom Line
For most sash-window owners, the Duck Brand Window Insulation Kit, 62 in x 420 in is the best secondary glazing kit for a sash window: it is cheap, needs no tools beyond scissors, keeps the glass clear, and comes off in spring without damaging the frame. Households sealing a whole house should size up to the 15-window roll, while period-home owners restoring original sashes should go straight to the Sarco set. Check the current price on Amazon before the cold sets in.