Thermal blackout curtain vs. simple blackout curtain: a comparison
A simple blackout curtain blocks light. A thermal blackout curtain blocks light AND insulates against cold and heat. The performance difference is measurable: a simple blackout (150 to 300 g/m²) provides only 1 to 2 °C of thermal gain, while a multi-layered thermal blackout (500 g/m² and more) achieves 5 to 7 °C* of gain between the window and the room.
This guide compares the two types of curtains based on concrete criteria: thermal performance, blackout, sound insulation, price, and durability. The goal is to help you invest in the right product according to your actual needs.
What is the difference between a thermal blackout and a simple blackout?
The difference is not in the ability to block light (both block 95 to 100%). It is in the fabric construction and the performance it allows:
- Simple blackout curtain: a standard fabric (polyester, thick cotton) covered with an opaque coating (often a white or black acrylic coating on the back). The coating blocks light. The fabric has no particular insulating properties. Typical density: 150 to 300 g/m².
- Thermal blackout curtain: a technical multi-layered assembly (dense decorative fabric + high-density fleece + insulating/blackout membrane). Each layer has a function: the fabric absorbs, the fleece insulates, the membrane blocks light and radiation. Typical density: 400 to 620+ g/m².
The weight difference is telling: a simple blackout of 150x230 cm weighs 500 g to 1 kg. A Kurtens thermal blackout of the same dimensions weighs approximately 2.1 kg. This additional mass is what creates the thermal and sound barrier.
Detailed comparative table
| Criterion | Simple blackout | Multi-layered thermal blackout |
|---|---|---|
| Blackout | 80-100% (variable, often overestimated) | 100%* (multi-layered structure, no coating) |
| Thermal gain | 1-2 °C | 5-7 °C* |
| Sound attenuation | 3-7 dB (hardly noticeable) | 18-22 dB* (comparable to a closed door) |
| Density | 150-300 g/m² | 500-620+ g/m² |
| Construction | 1-2 layers + opaque coating | 3+ technical layers (fabric + fleece + membrane) |
| Blackout durability | Coating cracks in 2-4 years (washing, UV) | Structural, does not degrade with washing |
| Custom-made | Rarely (standard sizes) | Yes (to the nearest cm at Kurtens) |
| Price | 15-60 € | 80-350 € |
| Lifespan | 2-5 years (fragile coating) | 10-15 years |
Thermal performance: the gap that changes everything
The difference of 1-2 °C (simple blackout) vs 5-7 °C (thermal blackout) is not a technical detail. It's a difference you feel physically:
- 1-2 °C gain: imperceptible. The sensation of cold in front of the window persists. The heating continues to compensate. No measurable impact on the energy bill.
- 5-7 °C gain: the sensation of a "cold wall" in front of the window disappears. The room temperature is more homogeneous. The heating works less. The estimated savings are 25 to 120 euros per year depending on the glazing and heating method (source: calculations based on ADEME data, 10-15% of heat loss through windows).
In summer, the difference is just as significant. A simple blackout blocks light but lets 80 to 90% of solar heat pass through (the thin fabric heats up and radiates heat into the room). A thermal blackout blocks light AND 60 to 80% of solar heat thanks to its mass and insulating layers.
Blackout: why the coating ages poorly
Low-priced simple blackout curtains use an opaque coating applied to the back of the fabric to block light. This technique poses a durability problem:
- Cracking: after 10 to 20 washes, the coating begins to crack. Micro-holes appear and let light filter through. The blackout gradually decreases from 100% to 90%, then 80%.
- Peeling: the coating peels off the backing fabric, creating uneven areas that let light through in places.
- Odor: some acrylic coatings emit a chemical odor, especially in summer when the curtain heats up in the sun.
A multi-layered thermal blackout curtain does not rely on a surface coating. The blackout comes from the very structure of the fabric: the internal membrane blocks light mechanically, not chemically. It does not crack, peel, or lose performance with washing. It is a structural blackout, not a surface treatment.
Sound performance: the invisible bonus
A simple coated blackout curtain attenuates 3 to 7 dB of noise: barely perceptible to the human ear. The fabric is too thin and too light to significantly absorb sound waves.
A multi-layered thermal blackout curtain of 620 g/m² attenuates up to 22 dB*: street noise goes from clearly audible to discreet background noise. This is the difference between a curtain that blocks light and a curtain that blocks light, cold, AND noise.
For a bedroom facing a busy street, this triple performance is crucial. A single curtain solves three problems instead of stacking a blackout + a thermal + a soundproof (more expensive, bulkier, less effective than the integrated multi-layer). To learn more about soundproofing, consult our article soundproof curtain: is it really effective?
In which cases is a simple blackout sufficient?
A simple blackout remains a good choice in specific situations:
- Seldom used guest room: if the room is only occupied a few nights a month, investing in a thermal blackout is not justified. A simple blackout for 30 euros does the job for darkness.
- Room already well insulated with shutters: if you have shutters that you close every evening and high-performance double glazing, the curtain only needs to block residual light (shutter halo). A simple blackout is sufficient.
- Very tight budget, temporary solution: a simple blackout for 20 euros can help for a summer or winter before investing in a durable technical curtain.
In which cases is a thermal blackout essential?
- Master bedroom (daily use): you sleep in this room 365 nights a year. Thermal insulation (stable all night), blackout (deep sleep), and soundproofing (fewer awakenings) impact your daily health. The investment is fully justified.
- Baby's room: infants are sensitive to temperature (WHO recommends 18-20 °C for babies' sleep), light (10-20 lux are enough to wake them), and noise (sound peaks = awakenings). The thermal blackout curtain addresses all three.
- Housing without shutters: the curtain fully replaces the function of the shutter (darkness + insulation). A simple blackout only does half the job.
- Window exposed to cold (north, wind) or heat (south, west): the thermal gain of 5-7 °C makes a measurable difference in comfort and energy bills.
- Bedroom facing the street: the 22 dB* soundproofing transforms sleeping comfort. A simple blackout only attenuates 3-7 dB, insufficient to filter traffic noise.
The 10-year calculation
| Criterion | Simple blackout (renewed) | Kurtens thermal blackout |
|---|---|---|
| Initial price | 30 € | 150 € (custom-made average) |
| Lifespan | 2-4 years (coating degrades) | 10-15 years |
| Cost over 10 years | 75-150 € (3-5 replacements) | 150 € (no replacement) |
| Heating savings over 10 years | 0-50 € (negligible thermal gain) | 250-1 200 € (25-120 €/year) |
| 10-year balance | Net cost: 25-150 € | Net profit: 100-1 050 € |
Over 10 years, a thermal blackout costs the same (or even less) than a renewed simple blackout, while generating 250 to 1,200 euros in heating savings. It's an investment, not an expense.
Discover our custom-made thermal blackout curtains: 620 g/m², 100%* structural blackout, thermal insulation up to 7 °C*, 22 dB* sound attenuation. 7 colors, manufactured to exact dimensions, free delivery in 2 to 3 weeks. To compare blackout levels, consult our guide blackout vs. light-filtering vs. opaque. To choose a color, consult the color guide.
*Data from tests conducted under optimal conditions.
Frequently Asked Questions
What is the difference between a blackout curtain and a thermal blackout curtain?
A simple blackout blocks light thanks to an opaque coating on a lightweight fabric (150-300 g/m²). It insulates neither against cold (1-2 °C) nor noise (3-7 dB). A multi-layered thermal blackout (500-620+ g/m²) blocks light by its structure (no coating), insulates against cold (5-7 °C*) and noise (22 dB*). It's three functions in one curtain instead of one.
Does a blackout curtain insulate against cold?
A simple blackout (150-300 g/m²) insulates very little: 1-2 °C gain, imperceptible. For real thermal insulation, a high-density multi-layered thermal blackout (500+ g/m²) is needed, which achieves 5-7 °C gain*. Density and multi-layered construction make all the difference. The real insulation threshold is 500 g/m².
Does the coating of a blackout curtain last over time?
The coating (opaque coating) of a low-end blackout curtain degrades in 2 to 4 years: cracks after 10-20 washes, peeling, gradual loss of blackout. Multi-layered thermal blackout curtains do not use coating: the blackout comes from the fabric's structure (internal membrane), which does not degrade with washing or UV exposure.
Is a thermal blackout curtain more expensive than a simple blackout?
At purchase, yes: 80-350 euros versus 15-60 euros. Over 10 years, the cost reverses. A simple blackout lasts 2-4 years (3-5 replacements = 75-150 euros). A thermal blackout lasts 10-15 years (no replacement = 80-350 euros). Adding heating savings (25-120 euros/year), a thermal blackout generates a net profit of 100 to 1,050 euros over 10 years.
Can you have a light-colored thermal blackout curtain?
Yes. The blackout of a technical multi-layered curtain does not depend on the color but on the internal structure (blocking membrane). A Kurtens cream beige curtain blocks exactly as much light (100%*) as a gray curtain. All 7 colors offer the same thermal, blackout, and sound performance*. You choose the color based on aesthetic criteria only.
Is a simple blackout sufficient for a baby's room?
For darkness alone, a good 100% simple blackout may be sufficient. But babies are also sensitive to temperature (WHO recommends 18-20 °C) and noise (sound peaks wake them up). A multi-layered thermal blackout addresses all three problems: total darkness (100%*), stable temperature (7 °C gain*), and noise reduction (22 dB*). For daily use over several years, the investment is justified.
How to recognize a true thermal blackout curtain?
Check three criteria: grammage (minimum 500 g/m² for real insulation), detailed multi-layered construction (not just "blackout fabric"), and measured performance (communicated gain in °C and attenuation in dB). If the seller advertises "thermal blackout" without this data, it's probably a simple coated blackout with a marketing label. Kurtens curtains display 620 g/m², 7 °C*, and 22 dB* documented.
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