Planning a home renovation involves more than just picking out paint colors. If you are looking to brighten a dark room, adding a Velux skylight is one of the most effective ways to transform your living space. However, choosing the right size is critical for both aesthetics and energy efficiency. Use our calculator below to determine the ideal glass area for your room.
How to Use the Velux Skylight Calculator
Our calculator is designed to help homeowners and contractors determine if their selected Velux skylight configuration provides enough natural light for a specific room. The general rule of thumb used by architects and lighting experts—often referred to as the "15% Rule"—suggests that the total glass area should be at least 15% of the floor area of the room.
Understanding the 15% Rule
While 10% is the absolute minimum for basic visibility, aiming for 15% to 20% creates that "wow" factor associated with modern, sun-drenched homes. If your room has few or no vertical windows, you should lean toward the higher end of that scale.
Factors Influencing Your Skylight Choice
When using the Velux skylight calculator, keep the following environmental factors in mind:
- Room Orientation: North-facing roofs receive consistent, cool light. South-facing roofs receive intense, direct sunlight and heat gain, which might require Velux blinds to manage temperature.
- Ceiling Height: Higher ceilings allow light to spread further. In rooms with very high vaulted ceilings, you may need larger units to ensure the light reaches the floor level effectively.
- Roof Pitch: The angle of your roof affects how much light is captured. A steeper pitch generally allows for better self-cleaning of the glass but may change the internal light distribution.
Types of Velux Skylights
Once you have determined the square footage required, you need to choose the mechanism that fits your lifestyle:
1. Fixed Skylights (FS)
Ideal for areas where you only need light, not ventilation. These are common in high-ceilinged hallways or dining rooms where air circulation is already managed by HVAC systems.
2. Manual "Fresh Air" Skylights (VS)
These open with a control rod to allow hot air to escape. They are perfect for kitchens and bathrooms where moisture and odors need to be vented out.
3. Solar Powered "Fresh Air" Skylights (VSS)
The gold standard of Velux products. These feature a solar panel that charges a battery-operated motor. They require no wiring, include a rain sensor that closes the unit automatically at the first drop of rain, and often qualify for federal tax credits.
Installation and Flashing
No matter what the calculator says about the size, the installation is what ensures the longevity of your roof. Velux offers specific flashing kits for different roofing materials (shingle, tile, or metal). Using the official Velux flashing kit is the only way to secure the "No Leak Warranty," which covers both the product and the installation for 10 years.