Choosing the correct Velux window size is an important step when planning a loft conversion, attic room, or roof upgrade. The right window size allows more natural light into your space, improves ventilation, and makes the room feel open and comfortable. If the size is chosen incorrectly, the room may remain dark, feel too hot or cold, or require extra roof work. It explains how to choose the correct Velux window sizes in a clear and simple way.
Why Choosing the Right Velux Window Size Is Important
Velux windows are installed directly into the roof, which means size affects both performance and appearance. A well-sized window improves daylight, airflow, and energy efficiency. It also fits properly between roof rafters, reducing installation time and cost.
A window that is too small may not provide enough light, while a window that is too large can cause heat loss and structural problems. Selecting the correct size helps create a balanced and comfortable living space.
What is Velux Window Size Codes?
Velux does not use standard width and height labels. Instead, each window has a unique size code that identifies its dimensions.
What Velux Size Codes Mean
Velux size codes include letters and numbers. The letters indicate the window type, while the numbers represent the size. For example, a code like MK04 refers to a medium-sized window, while SK08 indicates a larger window. These codes make it easier to replace old windows or order new ones without confusion.
Knowing the correct code is especially useful when replacing an existing Velux window, as it allows for a perfect fit without changing the roof structure.
Measuring the Roof Opening Correctly
Accurate measurement is one of the most important steps in choosing the correct Velux window size. Measurements should be taken carefully to avoid installation issues.
How to Measure Properly
Measure the width and height of the roof opening from inside the frame. It is also important to measure the distance between the rafters, as Velux windows are designed to fit common rafter spacings. Most roofs have standard rafter gaps, which makes installation easier when the correct window size is selected.
Double-checking measurements can prevent costly mistakes and delays.
Consider the Size and Function of the Room
The room where the Velux window will be installed plays a major role in deciding the correct size.
Small Rooms
In small spaces such as bathrooms, storage lofts, or narrow hallways, a smaller Velux window usually provides enough light and ventilation. Installing a large window in a small room can make the space feel unbalanced.
Large Rooms
Larger rooms like loft bedrooms, living areas, or home offices often require bigger windows or multiple Velux units. This ensures that natural light spreads evenly across the room and reduces the need for artificial lighting during the day.
Natural Light Requirements
One of the main reasons for installing a velux window sizes is to increase natural daylight. The amount of light needed depends on room size and layout.
Daylight Planning
As a general guide, the window area should be around ten to twenty percent of the floor area. This ratio helps create a bright and comfortable environment without overheating the room. Taller windows allow more daylight to enter, especially in rooms with sloped ceilings.
Choosing the Correct Window Height
The height of the Velux window affects both ease of use and light entry.
Ideal Window Position
The bottom of the window is usually placed around ninety to one hundred and ten centimetres from the floor. This height allows easy operation and provides a good outside view. Taller windows improve daylight and make the room feel more open and spacious.
Roof Pitch and Angle Considerations
Roof pitch is another important factor when choosing a Velux window size.
Why Roof Pitch Matters
Each Velux window is designed to work within a specific roof pitch range. Steeper roofs allow better light entry, while lower pitches may need special flashing to prevent water issues. Always check the roof pitch before finalising the window size to ensure proper performance and weather protection.
Ventilation Needs of the Room
Different rooms have different ventilation requirements, which can influence window size choice.
Rooms That Need Better Airflow
Kitchens, bathrooms, and bedrooms benefit from good ventilation. Choosing a slightly larger Velux window or one with better opening functionality helps remove moisture, heat, and stale air. Proper airflow improves indoor comfort and reduces condensation problems.
Single or Multiple Velux Windows
In some cases, one window may not be enough to light the space properly.
When Multiple Windows Are Better
Wide or long attic spaces often benefit from two or more Velux windows installed side by side. This allows daylight to spread evenly and creates a balanced look. Using multiple medium-sized windows can sometimes be more effective than installing one very large window.
Building Regulations and Safety Requirements
Local building regulations may affect which Velux window sizes you can install.
Important Regulations to Consider
Some rooms, especially loft bedrooms, require windows that meet emergency escape size standards. There may also be rules related to ventilation, fire safety, and energy efficiency. Checking these requirements before choosing a window size helps avoid legal and installation problems.
Energy Efficiency and Insulation
Velux window size can affect how well your home retains heat.
Balancing Size and Efficiency
Larger windows may lose more heat, especially in colder months. Choosing energy-efficient glazing, such as double or triple glazing, helps reduce heat loss. The correct balance between window size and insulation ensures comfort throughout the year.
Replacing an Existing Velux Window
Replacing an old Velux window is usually easier than installing a new one.
Matching the Existing Size
Most older Velux windows have a size code on the frame. Choosing the same size allows for a simple replacement without altering the roof opening. This saves time, reduces cost, and ensures a clean finish.
Common Mistakes to Avoid
Many homeowners make mistakes when choosing Velux window sizes. These include guessing measurements, ignoring roof pitch, or choosing a size based only on price. Taking time to plan properly helps avoid these issues and ensures long-term satisfaction.
Final Thoughts
Choosing the correct Velux window size is about more than just fitting a window into the roof. It affects natural light, ventilation, comfort, and energy efficiency. By carefully measuring your roof, considering room size, checking roof pitch, and planning for daylight needs, you can select a Velux window that enhances your living space.
A well-chosen Velux window adds value to your home, improves indoor comfort, and creates a brighter and healthier environment for years to come.