What percentage of roof should be skylights?

A general rule is 5-15% of the floor area. For living rooms, aim for 10-15% for bright natural light. For bedrooms, 5-10% is sufficient to avoid overheating. Never exceed 15% or you'll have serious cooling costs.

How big should a skylight be?

Common residential skylights range from 2x2 feet (4 sq ft) to 4x4 feet (16 sq ft). For a 200 sq ft room, you'd want 10-20 sq ft of skylight, which is 1-2 medium-sized units (e.g., two 2x4 skylights = 16 sq ft total).

Do skylights make rooms hotter?

Yes, especially south-facing ones. Low-E glazing and shades help, but oversized skylights in hot climates can add significant AC costs. North-facing skylights provide more even light with less heat gain.

Are tubular skylights worth it?

Tubular skylights (sun tunnels) are great for small spaces like hallways and bathrooms. They're cheaper, easier to install, and don't cause heat issues. However, they don't provide ventilation or a view like traditional skylights.

☀️ Skylight Size Calculator

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☀️ Skylight Sizing Guidelines

Skylights can transform a dark room into a bright, welcoming space. However, sizing is critical—too small and you won't notice a difference; too large and you'll overheat in summer.

The 5-15% Rule

Industry standard: skylight area should be 5-15% of the floor area.

5-8%: Bedrooms, bathrooms (subtle ambient light)
8-12%: Kitchens, home offices (functional brightness)
12-15%: Living rooms, art studios (maximum daylight)

Orientation Matters

North-facing: Best for consistent, cool light (ideal for offices). No direct sun in the US means no glare.
South-facing: Maximum light but significant heat gain. Requires Low-E glazing and shades.
East-facing: Morning sun (great for breakfast nooks). Minimal heat impact.
West-facing: Afternoon sun (can be intense). Consider shades or smaller sizes.

💡 Expert Tip from Tom Bradford, Skylight Installer:

"The biggest regret I see is oversizing south-facing skylights. A 4x8 skylight in a hot climate can add $300/year to your AC bill. If you're in Arizona, go smaller or choose north-facing. Also, always pay for Low-E coating—it blocks heat but keeps the light."

⚠️ Common Mistakes

1. Ignoring Roof Pitch: On steep roofs (>8:12), skylights appear smaller from inside. You might need to go one size larger than calculated.

2. Skipping the Shade: A skylight without a shade is a liability. Even in cold climates, summer sun can be brutal. Invest in cellular shades or exterior blinds.

3. DIY Installation: Skylights are the #1 source of roof leaks. Unless you're an experienced roofer, hire a pro. One leak can cause $10,000 in water damage.

Reviewed by Tom Bradford

Certified Skylight Installer, 15 years experience with VELUX and residential roofing.

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