Single-glazed thermal curtain: how to compensate for insufficient insulation

Single glazing is still very common in old homes, secondary residences, and some protected Haussmannian buildings. Its thermal performance is significantly inferior to that of modern double glazing: it lets in much more cold in winter and heat in summer. Replacing windows with double glazing often costs several thousand euros and is not always possible, especially in rental properties or listed buildings.

The thermal curtain offers an immediate and accessible solution to compensate for this structural weakness. Without any work or authorization, it creates an additional textile barrier that significantly reduces temperature exchange through the window.

Why does single glazing lose so much heat?

Single glazing consists of a single pane of glass, compared to two for double glazing with an insulating air gap between them. This structural difference has a direct impact:

• High thermal transmittance coefficient: single glazing allows about 5 to 6 times more heat to pass through than high-performance double glazing.
• Cold wall effect: in winter, the inner surface of the glazing cools significantly, creating a feeling of cold even when the ambient air is heated.
• Lack of acoustic insulation: single glazing also provides poor sound insulation, a problem often combined with heat loss.

Single-glazed thermal curtain: what it can truly compensate for

A thermal curtain does not replace a window change, but it compensates for a significant part of its weaknesses. By creating an additional air gap between the cold glazing and your interior, it limits heat exchange through convection and radiation.

Specifically, on a single-glazed window, a well-installed thermal curtain can:

• Reduce the feeling of a cold wall near the window.
• Decrease drafts felt in winter.
• Limit heat loss at night, when temperature differences are most significant.
• Provide a noticeable gain of 5 to 7 degrees depending on the models and installation conditions.

Thermal curtain for old homes: how to choose well?

Weight and lining: the priority criteria

For single glazing, opt for models with a thick, quilted lining. Quilting traps more air and improves insulating performance compared to a simple lined fabric. Our models achieve a thermal gain of 5 to 7 degrees thanks to this construction.

Height and width: covering the entire glazing

On single glazing, every centimeter not covered by the curtain is a zone of heat loss. The curtain must:

• Touch the floor to block upward drafts.
• Extend at least 15 cm beyond each side of the window frame.
• Completely cover the height of the glazing, from the top of the frame to the floor.

Our recommended models for single glazing

• Fleece thermal curtain: diamond quilting, combined thermal and acoustic insulation, ideal for old homes combining cold and noise.
• Anthracite grey thermal curtain: neutral color that fits into all interiors, effective thermal insulation.
• Blue thermal curtain: high blackout of 70 to 90%, ideal for single-glazed bedrooms.
• Taupe 3-in-1 curtain: combined thermal, acoustic, and blackout insulation for the most exposed windows.

Discover our entire collection of anti-cold thermal curtains, particularly suitable for single glazing and intense cold situations.

Single-glazed thermal curtain: should drafts also be addressed?

The thermal curtain reduces heat loss through the glazing itself, but a single-glazed window often also suffers from worn seals that let air through. For complete insulation, the thermal curtain works in conjunction with self-adhesive insulating seals placed on the frame, a low-cost solution that addresses both problems together.

To correctly orient the lining of your curtain according to the season, consult our guide on which way to put a thermal curtain.

FAQ: thermal curtain and single glazing

Can a thermal curtain really compensate for single glazing?

It does not replace double glazing but compensates for a significant part of its weaknesses, especially the feeling of a cold wall and drafts. The observed thermal gain is 5 to 7 degrees depending on the models and installation conditions.

Should single-glazed windows be replaced rather than installing a thermal curtain?

Replacing glazing remains the most effective long-term solution, but it represents a significant cost and is not always possible in rental properties or listed buildings. The thermal curtain offers an immediate and accessible improvement while waiting or as a complement.

What weight should be chosen for single glazing?

Prioritize models with a quilted lining rather than a simple lined fabric. Quilting traps more air and significantly improves insulating performance on a poorly insulated window like single glazing.

Does the thermal curtain also work against noise with single glazing?

Yes, partially. Single glazing insulates poorly against both cold and noise. Our models combining thermal and acoustic insulation, like the fleece thermal curtain, address both problems in a single installation.

How long before seeing a difference?

The effect is immediate from the first closing of the curtains in the evening. The feeling of a cold wall near the window quickly decreases, and the impact on the heating bill is measured over a full season.

To go further:

• Our collection of anti-cold thermal curtains
• Which way to put a thermal curtain: the complete guide
• Why put a curtain in front of an entrance door