How Many Skylights Should I Install (And What Size)?
Adding skylights to your home is one of the most impactful ways to introduce natural light, enhance design, and boost energy efficiency. But how many skylights do you need? And what size should they be?
This guide answers those questions with real examples, expert insights, and a free tool — the Skylight Cost Calculator — to help you estimate the right size, quantity, and budget for your home.
How Do I Determine the Number of Skylights I Need?
There’s no one-size-fits-all answer — it depends on your room type, size, and how much daylight you want.
General Rule of Thumb:
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✅ 10–20% of the floor area should be glazed (skylights or windows) to ensure optimal daylight.
For example:
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A 20m² kitchen = 2–4m² of skylight area
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A 10m² bathroom = 1–2m² of skylight area
Factors to Consider:
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Ceiling height
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Room function (kitchen, bedroom, hallway, etc.)
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Orientation of the roof (south-facing = more light)
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Thermal efficiency and ventilation needs
“Natural light is not just aesthetic — it impacts mood, energy use, and even sleep quality. Start with the room’s purpose, then size up from there.”
— Lee Dobson, Daylighting Consultant, Glasgow
Should I Install One Large Skylight or Multiple Smaller Ones?
Both approaches are practical, but their effects differ.
One Large Skylight:
✅ Cleaner design Aesthetic
✅ Fewer structural changes
✅ More uninterrupted light
❌ Can cause overheating in summer
❌ Harder to ventilate if non-opening
Multiple Smaller Skylights:
✅ Even distribution of light
✅ Better ventilation if some are open
✅ More flexibility with layout
❌ Higher install cost
❌ More internal framing
Room-by-Room Recommendations
| Room Type | Suggested Setup | Typical Sizes |
|---|---|---|
| Kitchen | 1 large or two small fixed frameless units | 1000x2000 or 2x 1000x1000 |
| Living Room | 1 large or modular frameless unit | 1200x2400 or 1500x1500 |
| Bathroom | 1 smaller triple-glazed fixed unit | 600x900 or 800x800 |
| Loft/Attic | 2 opening roof windows for ventilation | 780x1180 or 940x1400 |
Use the Skylight Cost Calculator
Need help deciding?
🧮 Skylights.co.uk have developed a free Skylight Cost Calculator that helps you:
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✅ Input room dimensions
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✅ Choose roof type (flat or pitched)
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✅ Select opening or fixed design
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✅ Compare frame vs frameless options
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✅ Get instant cost estimates
“We used the calculator to plan our extension. It gave us confidence in both the design and the budget.”
— Sarah, Brighton
Try it here →
Frameless vs Framed Skylights: Which Performs Better?
| Feature | Framed Skylights | Frameless Skylights |
| Aesthetics | Visible frame | All-glass, seamless finish |
| Light Transmission | Slightly reduced | Maximum daylight entry |
| U-value | ~1.3–1.4 W/m²K | ~0.9–1.1 W/m²K (triple-glazed) |
| Leak Resistance | Relies on seals/flashing | Factory-sealed, bonded glass |
| Maintenance | Higher due to framing | Low maintenance |
Frameless models from Skylights.co.uk are especially recommended for flat or low-pitch roofs, where visual impact and efficiency are paramount.
FAQs
Typically 10–20% of the floor area. For example, a 20m² space might benefit from 2–4m² of skylight.
They can, especially on south-facing roofs. Use solar-control glass and triple glazing to reduce heat gain.
Yes — frameless fixed skylights from Regal Glass Group are compatible with low-pitch roofs using proper upstand kerbs.
Usually not — but check with PlanningPortal.gov.uk for conditions on listed or conservation properties.
Any unit over 2500mm long may require structural support. The calculator can help guide you in selecting the correct size.
Final Thoughts
✔️ Let light lead your design choices — but size smart.
✔️ Use our Skylight Cost Calculator to find your perfect match.
✔️ Explore frameless options from Skylights.co.uk for a modern, low-maintenance style.
✔️ When in doubt, work with your architect or installer to tailor the layout and size.
