Blackout blind for Velux windows: the roof window guide
Roof windows (Velux, Roto, Fakro) receive solar radiation almost vertically, making them 2 to 3 times hotter than a wall window in summer. The blackout solution depends on the type of window: a blind integrated into the frame for the sloped window itself, and a custom-made high-density curtain for vertical windows (dormer windows, gables, mansard windows) which also equip most attic rooms.
This guide compares solutions by window type, with their real performance, their limitations, and the optimal combination for sleeping and keeping cool in an attic bedroom.
Why attic bedrooms are the hardest to treat
An attic bedroom combines problems that lower floors do not have:
- The roof window receives sunlight vertically: a wall window receives radiation at an oblique angle. A roof window receives almost perpendicular radiation, especially in summer when the sun is high. The solar energy captured per m² is 2 to 3 times higher.
- Hot air rises and accumulates under the roof: by natural convection, the hottest air in the dwelling concentrates under the eaves. In summer, the temperature at ceiling level can exceed the floor temperature of the same floor by 5 to 8 °C.
- The roof heats up and radiates heat: the roof absorbs solar radiation all day and radiates heat in the evening. Even after sunset, the room remains hot as the roof continues to radiate.
- Light enters as early as 5:30 am in summer: a roof window has no obstruction (no building opposite, no trees). Light intensity reaches 10,000 to 50,000 lux from 6 am.
Result: attic bedrooms are the hottest in summer (35 °C and above in the evening) and the brightest in the morning. Blackout and thermal protection are not a luxury; they are a condition for sleeping.
Two types of attic windows, two different solutions
Most attic bedrooms have two types of windows, and each requires a tailored solution:
| Window type | Position | Blackout solution | Kurtens solution |
|---|---|---|---|
| Sloped roof window (Velux, Roto, Fakro) | In the roof slope, inclined | Blind integrated into the frame (with side guides) or exterior sunshade blind | Not suitable (a curtain cannot remain flush against an inclined surface) |
| Vertical window (dormer, gable, mansard, bull's-eye) | In a vertical wall, like a classic window | Custom-made blackout curtain on a wall rod | Suitable: custom-made Kurtens curtain (620 g/m², 100%*, 7 °C*, 22 dB*) |
Important note: a classic curtain cannot be placed directly on a sloped roof window. The fabric would fall forward and not stay against the glass. This is why roof windows require a blind with a side guiding system that keeps the fabric flat against the frame. Vertical windows (dormers, gables) are treated exactly like any wall window: a curtain on a rod.
Solution for sloped roof windows: integrated blind
Integrated blackout blind (Velux, Roto, Fakro)
The manufacturer's blackout blind is directly attached to the roof window frame, with side guides that keep the fabric flat against the glass regardless of the inclination. This is the only solution that guarantees blackout without light leakage on a sloped window.
Advantages: perfect fit to the frame, no lateral light leakage thanks to the guides, cord or remote control operation, integrated and discreet aesthetics.
Limitations:
- Thin fabric (100 to 200 g/m²): blocks light but does not insulate from heat. In summer, solar radiation heats the thin fabric, which radiates heat into the room. Blackout is good, thermal insulation is almost nonexistent.
- Fragile mechanism: the spring or cord is the weak point. Lifespan of 5 to 8 years, repair sometimes impossible (parts unavailable for older models).
- Price: 80 to 200 euros for manual version, 200 to 400 euros for motorized version. Price quickly increases with options.
- No acoustic performance: the thin fabric does not reduce the noise of rain on the Velux (50 to 70 dB, very annoying at night).
Exterior sunshade blind
The sunshade is installed on the exterior of the roof window and blocks solar radiation before it reaches the glass. This is the most effective solution against heat because it prevents the greenhouse effect (heat never penetrates between the glass and the room).
Advantages: blocks 75 to 90% of solar heat before the glass. Significant reduction in temperature in attic rooms in summer.
Limitations: does not block 100% of light (it is a dimming blind, 80-90%, not a blackout). Exposure to weather (reduced lifespan). Price: 150 to 350 euros.
Solar film on the Velux glass
A solar film adhered directly to the glass rejects 40 to 70% of solar radiation. It is an effective complement to the integrated blind: the film permanently deals with heat (even when the blind is open), and the blind deals with light when you close it.
Cost: 15 to 50 euros per window. Limitation: reduces light all year round (including in winter when natural light is welcome). May void the glazing warranty on some models.
Solution for vertical attic windows: custom-made curtain
Dormer windows, gables, mansard windows, and wall windows in attics are treated like any classic wall window. This is where the custom-made Kurtens curtain is perfectly suited:
- 100% blackout*: the 620 g/m² multi-layer fabric blocks all light, including sunrise at 5:30 am in summer. Zero halo on the edges thanks to custom sizing (15-20 cm lateral overlap).
- Thermal insulation up to 7 °C*: the curtain creates an air gap of 5 to 10 cm between the glass and the fabric, slowing down thermal exchange. On an exposed west-facing gable window (overheating at the end of the day), the effect is immediate.
- 22 dB sound attenuation*: reduces external noise entering through vertical windows (traffic if the room is on an upper floor, neighborhood).
Custom-made Kurtens blackout curtains are manufactured to the exact dimensions of your dormer or gable windows, to the nearest centimeter, up to 270 cm in height. For correct measurement, consult the size guide.
Comparison of solutions by window type
| Solution | Sloped window (Velux) | Vertical window (dormer/gable) | Blackout | Thermal | Acoustic | Cost |
|---|---|---|---|---|---|---|
| Integrated blackout blind | ✅ Suitable | Not relevant | 95-100 % | Low (~150 g/m²) | 0-3 dB | 80-400 € |
| Exterior sunshade blind | ✅ Suitable | Not relevant | 80-90 % (dimming) | Good (before glass) | 0 dB | 150-350 € |
| Solar film on glass | ✅ Suitable | ✅ Suitable | 20-40 % | Good (40-70 %) | 0 dB | 15-50 € |
| Kurtens custom-made curtain | ❌ Not suitable | ✅ Perfectly suitable | 100 %* | 5-7 °C* | 22 dB* | 80-350 € |
The optimal combination for an attic bedroom
An attic bedroom often has both a Velux and a vertical window (dormer or gable). The optimal combination treats each window with the appropriate solution:
- On the Velux: solar film + integrated blackout blind. The film blocks 40-70% of heat permanently (even with the blind open). The blind blocks light when you sleep or nap. Cost: 95 to 250 euros.
- On the vertical window: custom-made Kurtens thermal blackout curtain. Blocks 100% of light*, insulates against cold/heat (7 °C*), and reduces noise (22 dB*). Cost: 80 to 350 euros.
- Night ventilation: open the Velux at night (hot air exits through the top) and the vertical window (cool air enters through the bottom). This natural draft is particularly effective in attics because the height difference between the two windows creates an air current. Free.
This combination keeps an attic bedroom 8 to 12 °C below what it would be without protection, for a total investment of 175 to 600 euros. For more information on anti-heat solutions, consult our article bedroom too hot in summer: 5 solutions.
Rain noise on a Velux: what to do?
Rain noise on a roof window is a specific problem for attics. The impact of raindrops on the sloped glass can reach 50 to 70 dB, enough to wake a sleeper (WHO recommends less than 30 dB for sleep).
The integrated blind does not help: its thin fabric (100-200 g/m²) only attenuates 0 to 3 dB of rain noise.
The Kurtens curtain on the vertical window helps indirectly: it reduces the overall ambient noise in the room by 22 dB* by blocking noises entering through the vertical window (traffic, neighborhood). When background noise decreases, rain noise seems louder, but the total sound level in the room is lower.
For rain noise on the Velux itself: the most effective solution is an exterior roller shutter (blocks noise before the glass, 10-15 dB reduction). If a shutter is not possible, an exterior sunshade blind made of thick fabric partially dampens the impact of drops (5-8 dB).
*Data from tests conducted under optimal conditions.
Frequently asked questions
Can a curtain be installed on a sloped roof window?
No, a classic curtain cannot remain flush against a sloped surface: the fabric falls forward due to gravity. Sloped roof windows (Velux, Roto, Fakro) require a blind with side guides that keep the fabric against the frame. However, vertical attic windows (dormers, gables, mansard windows) are treated exactly like a classic window with a curtain on a rod.
Does the Velux blackout blind insulate against heat?
Very little. The integrated Velux blackout blind uses a thin fabric (~150 g/m²) that blocks light but not heat. Solar radiation heats the thin fabric, and the heat is transferred into the room. To block heat before the glass, an exterior sunshade blind (75-90% heat blocked, 150-350 euros) or a solar film adhered to the glass (40-70%, 15-50 euros) are more effective.
How to reduce heat from a Velux in summer?
The most effective combination: solar film on the glass (blocks 40-70% of heat permanently, 15-50 euros) + integrated blackout blind (blocks direct light) + night ventilation (open the Velux at night when the outside air drops below 25 °C). The exterior sunshade blind (150-350 euros) is the premium solution as it blocks 75-90% of heat before it reaches the glass.
How to blackout a dormer or gable window in an attic?
Dormer windows, gables, and mansard windows are vertical windows: they are treated like any classic window with a curtain on a rod. A high-density custom-made blackout curtain (620 g/m²) blocks 100% of light*, insulates against cold and heat (7 °C*), and reduces noise (22 dB*). Custom sizing is particularly important in attics as dimensions are often atypical.
How to reduce rain noise on a Velux?
Rain noise on a Velux can reach 50-70 dB. The integrated thin fabric blind only attenuates 0-3 dB. The most effective solution is the exterior roller shutter (10-15 dB reduction by dampening the impact of drops before the glass). An exterior blind made of thick fabric offers partial attenuation (5-8 dB). For vertical windows in the same room, a Kurtens curtain (22 dB*) reduces other noises and improves overall acoustic comfort.
What budget to blackout an attic bedroom?
For a room with 1 Velux + 1 vertical window (common configuration): solar film on the Velux (15-50 euros) + integrated Velux blackout blind (80-200 euros) + custom-made Kurtens curtain on the vertical window (80-350 euros) = 175 to 600 euros total. This combination treats light, heat, and noise on both types of windows, with the right solutions for each.
Velux blind or custom curtain: which to choose?
Both, but not for the same window. The integrated blind is the only option for the sloped roof window (a curtain cannot be installed there). The custom-made curtain is the best option for vertical windows (dormers, gables) because it offers triple performance (100% blackout*, 7 °C thermal*, 22 dB acoustic*) that the integrated blind does not. In an attic bedroom, the two solutions complement each other.
More curtain tips
Explore our latest articles
