How to choose bedroom curtains - what truly matters for sleep and light

Bedroom curtains are usually chosen based on color and style. Rarely based on what they actually do for your sleep.

But if you wake up in the morning before you want to, if you have trouble falling asleep in the summer when it's still light outside, or if your room is too warm at night – curtains are one of the first environmental factors to check. Not because they are a miraculous solution, but because light and temperature in the bedroom have a documented physiological effect on sleep.

This article explains what truly matters when choosing bedroom curtains, without oversimplifying and without ignoring the nuances.

Why bedroom light matters

Your body regulates sleep partly through melatonin – the hormone that signals it's time to rest. Melatonin production is directly controlled by light: it increases with darkness, and decreases when your eyes perceive light, even at low intensities.

A study published in the Journal of Clinical Endocrinology & Metabolism showed that exposure to low-intensity artificial light – on the order of 5-10 lux, equivalent to a nightlight or the light from a streetlamp filtering through a thin curtain – can suppress melatonin production in sensitive individuals. Another study, published in PNAS by researchers from Northwestern University, showed that a single night spent with moderate light exposure (100 lux) increased heart rate, activated the sympathetic nervous system, and increased insulin resistance the next morning.

The sensitivity threshold is lower than most people intuitively realize. You don't need the light on in the room – the light filtering through a thin curtain from a brightly lit street is enough.

This doesn't mean everyone needs complete darkness to sleep well. But if your sleep is sensitive, if you wake up with the first rays of light, or if you live in an urban area with light pollution, the opacity of your curtains matters.

Degree of opacity – what it means in practice

Curtains and drapes fall into three functional categories:

1. Sheer - allow diffused light to pass through, provide privacy during the day but do not block nocturnal light. Ideal for living rooms or offices, less suitable as a sole solution for bedrooms if you are sensitive to light.
2. Room darkening - significantly reduce light, but do not eliminate it completely. Suitable for bedrooms where total darkness is not needed, or as an outer layer combined with a more opaque curtain.
3. Blackout - block 85-99% of external light through the fabric panel. Important to know: even blackout curtains allow light to enter through the side and top edges if not installed correctly. Mounting them on a track that extends 10-15 cm beyond the window frame on each side significantly reduces this problem.

For young children's bedrooms or for light sleepers, complete opacity makes a real difference. For adults with solid sleep, room-darkening curtains are often sufficient.

Material matters beyond aesthetics

Choosing the material for bedroom curtains is not just a visual decision – it has practical implications for light, temperature, and maintenance.

Linen – breathable and with a natural aesthetic

Linen has a natural weave with greater porosity compared to conventional cotton, which gives it excellent breathability. Linen curtains filter light in a diffused, warm way – they don't block light completely, but create a tranquil atmosphere. They are ideal for bedrooms where you want filtered natural light in the morning, not complete darkness.

From a thermal perspective, linen is good at temperature regulation – it allows air to circulate, preventing the room from overheating in the summer. In winter, a denser linen curtain adds a layer of thermal insulation to the window.

It wrinkles visibly – just like linen bedding – but for curtains, this is considered an aesthetic characteristic, not a defect. It washes easily and becomes softer with each wash.

Cotton – versatile and easy to maintain

Cotton is the most versatile material for curtains. It comes in various weights – from light, sheer muslins to dense fabrics that effectively filter light. The degree of opacity depends directly on the weight and density of the fabric, not necessarily the material itself.

Heavier cotton curtains offer decent thermal insulation and good light filtering. They are easy to wash, resistant to frequent use, and compatible with almost any decor style.

Hemp – durable and natural

Textile hemp has properties similar to linen – breathable, resistant, with a distinct natural texture. It is less common in curtains but is gaining ground as a sustainable material. Like linen, it softens with each wash and wrinkles naturally.

What to avoid in the bedroom

Curtains made of pure polyester or synthetic materials with chemical finishes may be suitable in other rooms, but in the bedroom – where you spend 7-8 hours in direct proximity – the quality of the material deserves consideration. Flame retardant finishes or anti-wrinkle treatments applied to synthetic materials can release volatile organic compounds (VOCs) at higher temperatures, and bedrooms tend to retain heat more than other rooms.

Room temperature and curtains

The optimal temperature for sleep is, for most adults, between 16°C and 19°C. Curtains contribute to temperature regulation in two ways:

Summer - a curtain that blocks direct solar radiation significantly reduces the room temperature during the day. Natural linen and cotton, in light colors, reflect some of the solar heat and allow air to circulate better than dense synthetic materials.

Winter - a layer of textile material at the window reduces heat loss through convection. Heavier curtains, falling to the floor and mounted close to the ceiling, create a more efficient thermal barrier than short curtains or those mounted only on the window frame.

Length and mounting – details that make a difference

Length: Curtains that fall to the floor or even slightly puddle on it create better thermal and acoustic insulation than short ones. Visually, long curtains also make the room appear taller.

Track mounting: Mount the track 10-15 cm higher than the window frame and 15-20 cm wider on each side. This ensures the curtain completely covers the window when drawn and reduces light entering through the edges – more important than the opacity of the material itself.

Number of panels: Two panels that overlap in the center block light better than a single one, regardless of the material.

Morning light – friend or foe

A less discussed aspect: morning light is not necessarily something to be completely blocked.

Exposure to natural light in the morning – within the first 30-60 minutes after waking up – helps reset the circadian rhythm and stimulate morning cortisol production, which contributes to alertness throughout the day. Research suggests that people exposed to more natural light in the morning tend to fall asleep more easily in the evening and have a more stable circadian rhythm.

Therefore, if you wake up naturally around the time you need to be active, a sheer or room-darkening curtain might be more suitable than a completely opaque one – it allows light to enter gradually, without the harshness of an alarm clock in complete darkness.

If, on the contrary, you wake up too early due to light (especially in summer, when sunrise is early), or if you work shifts and sleep during the day, complete opacity is a justified investment.

How to decide what suits you

A few practical questions before buying:

How sensitive are you to light during sleep? If you wake up at the first rays of light or if street light bothers you, prioritize opacity. If you sleep well even with filtered light, you have more freedom of choice.

How is the window oriented? An east-facing window receives direct light early in the morning – opacity is more important here. West-facing, evening light can be a problem in summer. North-facing, the light is diffused all the time – you can opt for lighter materials.

What is the urban context? Lit streets, advertisements, car headlights – external light pollution makes opacity more relevant than if you live in a quiet area.

What aesthetic do you want? Natural linen and cotton create a warm, organic atmosphere, suitable for bedrooms with Scandinavian, boho, or rustic styles. They are also materials that improve with time – just like bedding, they become softer and more beautiful with each wash.

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Sources:

• Obayashi K et al. Impact of Dim Light at Night on Urinary 6-Sulphatoxymelatonin Concentrations and Sleep in Healthy Humans. PMC7588991. ncbi.nlm.nih.gov
• Cain SW, Filtness AJ et al. Enhanced preference for high-fat foods following a simulated night shift. PNAS / Northwestern University sleep & light research referenced via ublockout.com
• Wahl S et al. Systematic review of light exposure impact on human circadian rhythm. PubMed 30311830. pubmed.ncbi.nlm.nih.gov

 

At Foxenia, we produce curtains and drapes from cotton, linen, and hemp – natural materials, without chemical treatments, that regulate light and temperature naturally. If you want to explore the available options, see our collection of curtains and drapes. And if you've read about how to care for natural fiber bedding, the same principles apply to curtains.