Silentnight Healthy Growth Cosmo Eco Single Mattress
The Silentnight Healthy Growth Cosmo Eco is a single-size mattress built around an open coil spring system, which means a traditional, slightly bouncy feel with a Medium/Firm rating.
- Foam-free & hypoallergenic
- Medium-firm feel suits growing sleepers
- 60-night trial & 5-year guarantee
£259
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Silentnight Healthy Growth Cosmo Eco Mattress
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Mattress details
Mattress
Silentnight Healthy Growth Cosmo Eco Mattress
Size
Firmness
Medium Firm
Construction
Open Coil Spring
Eco-Friendly
Depth (cm)
23
Layers
3
Layer Details
Sleep surface
A quilted sleep surface fabric, which gives a soft, cushioned first touch before you reach the support beneath. Silentnight describes it as sumptuous, though the overall feel remains Medium/Firm.
Comfort layer
Breathable EcoComfort Fibres with an airflow border, which means air can circulate through the mattress rather than trapping warmth. A sensible choice for children, who often sleep warm.
Support system
An open coil traditional spring system with interconnected springs. Because the springs are linked, the whole surface responds together, giving an even, slightly bouncy Medium/Firm support.
Layer details from silentnight.co.uk product page, September 2026.
Key benefits
- Fits the smallest bedrooms: At 3ft wide it slots into box rooms and loft conversions; we suggest allowing at least 2.1m x 2.8m of floor space around it.
- Works with raised frames: At 23cm deep it suits bunk beds, cabin beds and mid sleepers, though you should check the frame's guardrail height against a 23cm mattress before buying.
- Foam-free for growing sleepers: No foam and no FR chemical treatments, which will reassure parents furnishing a child's first proper bed.
- Breathable where children need it: EcoComfort Fibres and an airflow border let warmth escape, which matters in a small room where a bed sits close to a radiator or under a sloped ceiling.
- Cheap, easy bedding: Standard single sheets and a 135 x 200cm single duvet fit, and both are the most widely stocked bedding of any UK size.
- Guest-room sensible: The Medium/Firm open coil feel suits occasional adult guests, and a single leaves room for a desk in a spare room that doubles as an office.
This size suits you if...
You're buying for a child or teenager moving into a full-size bed, and you want a foam-free, hypoallergenic mattress at a sensible price. It also fits if you need a mattress for a bunk or mid sleeper frame, or you're kitting out a guest room or a student flat where the frame is provided and the mattress isn't.
Consider another size if...
You share the bed, or you're a larger adult wanting a soft, contouring feel for full-time use. This mattress is only made as a UK single, so couples will need a different model in a UK double or larger.
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FAQ's
Will the Silentnight Healthy Growth Cosmo Eco single fit a bunk bed?
In most cases, yes. A UK single at 90 x 190cm is the standard bunk and mid sleeper footprint, and at 23cm deep this mattress sits within the range most raised frames accept. Do check your frame's maximum mattress depth first, since guardrails need to sit comfortably above the sleep surface.
How much floor space does a UK single mattress need?
We suggest allowing at least 2.1m x 2.8m for a UK single, which gives you room to walk alongside the bed and open drawers or a wardrobe. In a child's room that leaves useful space for toy storage and a desk, which is a large part of why the single remains the default children's size.
Is the UK single Cosmo Eco long enough for a teenager?
At 190cm, or 6ft 3in, the single is long enough for almost all teenagers and adults, so a child won't outgrow it in length. Width is the real limit: 3ft suits one sleeper only, so it carries most children comfortably from their first big bed through their teens.
Can an adult sleep on the Silentnight Healthy Growth Cosmo Eco single?
Yes, for one person. The 90cm width is the standard UK single-sleeper size and the Medium/Firm open coil support suits most adults for occasional or full-time solo use. Heavier adult side sleepers may find the interconnected springs a little too firm, since they don't contour the way pocket springs do.
What bedding do I need for the Cosmo Eco in a UK single?
Standard UK single fitted sheets, sized for a 90 x 190cm mattress, and a single duvet at 135 x 200cm. Both are the cheapest and most widely available bedding of any UK size, which keeps ongoing costs down, a small but real advantage when you're buying for a child who will go through plenty of sheet changes.