How Flame Retardant Blackout Linings and Fleece Linings Reduce Heat Loss and Improve Comfort

With energy prices still high and insulation becoming a priority for homes, hotels and commercial buildings, choosing the right curtain lining has become one of the simplest ways to improve comfort and reduce heating demand. Independent laboratory tests commissioned by Direct Fabrics show that our specialist flame retardant linings significantly reduce heat transfer through windows, with results ranging from 36 to 41 percent depending on the fabric combination.

This article breaks down the findings, explains the difference between standard blackout lining and acoustic blackout fleece lining, and shows how each option performs in real world environments.

Independent Testing: Up to 41 Percent Reduction in Heat Transfer

The laboratory evaluated several pairings of our flame retardant linings with our popular dimout and blackout fabrics. All combinations achieved strong insulation performance, with reductions in heat transfer falling within a tight 36 to 41 percent range.

Measured results:

• 41 percent reduction – Blackout Living plus Mimas Dimout
• 40 percent reduction – Blackout Living plus Horizon Blackout
• 38 percent reduction – Blackout Living plus Werrigbone Dimout
• 38 percent reduction – Acoustic Thermel Blackout plus Mimas Dimout
• 36 percent reduction – Acoustic Thermel Blackout plus Horizon Blackout
• 38 percent reduction – Acoustic Thermel Blackout plus Werrigbone Dimout

These results confirm that professional curtain linings offer genuine, measurable insulation benefits that meaningfully reduce heat loss through glazing.

Standard Blackout Lining vs Blackout Fleece Lining

One of the most interesting outcomes is the comparison between our flame retardant blackout lining and our acoustic fleece blackout lining.

Standard Flame Retardant Blackout Lining

Available at:
• 137 cm width: https://www.direct-fabrics.co.uk/flame-retardant-blackout-lining.html
• 274 cm width: https://www.direct-fabrics.co.uk/flame-retardant-blackout-lining-274cm.html

This lining achieved slightly higher thermal performance in the laboratory tests. As a simple, dense FR blackout lining, it provides:

• Very good heat retention
• A slimmer profile
• Clean drape
• High blackout performance

Acoustic Blackout Fleece Lining

Available at:
• https://www.direct-fabrics.co.uk/acoustic-blackout-insulation-curtain-lining.html

The fleece lining performed slightly lower in flat laboratory tests. The reason is straightforward:

The test was conducted with fabrics laid perfectly flat, which compresses the fleece and removes the natural air pockets that normally enhance insulation.

Real World Performance Will Be Higher for the Fleece

In real installations, curtains hang with folds and natural air channels. Fleece lining performs better when it can trap air within its fibres. For this reason, we expect its real world thermal performance to improve noticeably beyond the laboratory result.

Additional Benefit: Acoustic Performance

The fleece blackout lining offers something the standard blackout lining cannot: meaningful acoustic improvement.

Independent acoustic testing demonstrates:

• Up to 9 dB reduction in sound transmission
• Noticeable reduction in echo and reverberation
• Improved comfort in bedrooms, offices, hotels and apartments
• Better noise absorption due to the depth and structure of the fleece

If a customer wants thermal plus acoustic improvement in a single product, the fleece blackout lining is the superior option.

All Linings Are Fully Flame Retardant

Both the standard blackout lining and the fleece blackout lining are certified flame retardant. This makes them suitable for:

• Hotels
• Schools
• Care homes
• Hospitals
• Offices
• Commercial premises requiring BS-compliant FR fabrics

The FR treatment does not reduce thermal performance. It maintains safety without compromising insulation.

Which Lining Should You Choose?

Choose Standard Blackout Lining If:

• You want maximum thermal performance in a slim profile
• You want a cost-effective blackout solution
• Clean drape and crisp appearance are priorities
• Acoustic improvement is not required

Choose Acoustic Blackout Fleece Lining If:

• You want both heat retention and sound reduction
• You want a thicker, more luxurious curtain
• You need improved echo control
• The property suffers from drafts or external noise
• You want a softer, padded feel with strong insulation potential in real use

Key Takeaways

• Independent testing shows 36 to 41 percent reduction in heat transfer
• Standard blackout lining performed slightly better in flat tests
• Fleece blackout lining is expected to perform better in real installations due to natural air gaps
• Fleece lining provides up to 9 dB acoustic reduction, which standard blackout lining does not
• All tested linings are flame retardant and suitable for commercial projects
• Combining blackout or fleece lining with fabrics like Mimas Dimout delivers some of the strongest results